Development of Marine Energy
in New Zealand
Prepared for
Electricity Commission
Energy Efficiency and Conservation Authority
&
Greater Wellington Regional Council
30 June 2008
© Power Projects Limited
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CONTENTS
PART 1:
DEVELOPMENT OF MARINE ENERGY IN NEW ZEALAND .................. 3
1.1
Introduction and Purpose of Study .......................................................... 3
1.2
Layout of the Report.................................................................................. 4
PART 2:
2.1
MARINE ENERGY TECHNOLOGIES ....................................................... 5
Marine Energy Sources ............................................................................. 5
2.1.1
2.1.2
2.1.3
2.1.4
2.1.5
2.1.6
2.1.7
2.2
Wave Energy Devices................................................................................ 8
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
2.2.7
2.3
Classification ........................................................................................ 8
Energy Distribution in Waves ............................................................... 9
Oscillating Water Column Devices ..................................................... 10
Overtopping Devices .......................................................................... 11
Surge Devices .................................................................................... 12
Attenuator Devices ............................................................................. 12
Point Absorber Devices ...................................................................... 13
Tidal Energy Devices............................................................................... 15
2.3.1
2.3.2
2.3.3
2.3.4
2.3.5
2.3.6
2.3.7
2.3.8
2.3.9
2.3.10
2.3.11
PART 3:
Wave Energy ........................................................................................ 5
Tidal Energy ......................................................................................... 6
Heat (Ocean Thermal Energy Conversion) .......................................... 6
Osmotic Power ..................................................................................... 7
Marine Biomass .................................................................................... 7
Offshore Winds ..................................................................................... 7
Products of Marine Energy ................................................................... 8
Classification ...................................................................................... 15
Barrages ............................................................................................. 15
Impoundments & Constrictions........................................................... 16
Tidal Fences ....................................................................................... 17
Horizontal Axis Turbines..................................................................... 18
Shrouded Turbines ............................................................................. 19
Open Ring Turbines ........................................................................... 19
Pressure Devices ............................................................................... 20
Vertical Axis Turbines ......................................................................... 20
Oscillating Hydrofoils .......................................................................... 21
Marine Energy Devices in New Zealand ............................................ 22
DEVELOPMENT OF MARINE ENERGY................................................. 23
3.1
Introduction .............................................................................................. 23
3.2
Targets and Forecasts............................................................................. 23
3.2.1
3.2.2
3.2.3
3.3
Renewable Energy and Electricity Policy Targets .............................. 24
Specific Marine Energy Uptake Targets ............................................. 24
Developers’ Commercialization Strategies ......................................... 25
Funding Mechanisms .............................................................................. 25
3.3.1
3.3.2
Capital Grant Programmes ................................................................. 26
Renewables Obligations ..................................................................... 26
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3.3.3
3.4
Regulatory Mechanisms.......................................................................... 27
3.4.1
3.4.2
3.4.3
3.5
PART 4:
4.1
WAVE & TIDAL ENERGY RESOURCE ASSESSMENT ........................ 30
Introduction .............................................................................................. 30
5.1
Wave Energy Potential Locations .......................................................... 36
6.1
Southland ........................................................................................... 50
Tidal/Ocean Current Arrays in Foveaux Strait and Cook Strait .......... 51
Summary of Tidal/Ocean Current Device Array Sites ........................ 53
GROWTH OF THE MARINE ENERGY INDUSTRY ................................ 54
International Growth ................................................................................ 54
6.1.1
6.1.2
6.2
National & Regional Distribution of Potential Locations ..................... 46
Specific Tidal & Ocean Current Sites..................................................... 47
5.4.1
5.4.2
5.4.3
PART 6:
Wave Farm Arrays at Selected Sites.................................................. 43
Summary of Wave Device Array Locations ........................................ 45
Tidal & Ocean Current Energy Potential Locations.............................. 46
5.3.1
5.4
National & Regional Distribution of Potential Locations ..................... 36
Specific Wave Energy Sites .................................................................... 42
5.2.1
5.2.2
5.3
SeaFlow 300 kW Tidal Stream Generator .......................................... 35
SeaGen 1.2 MW Tidal Stream Generator .......................................... 35
POTENTIAL MARINE ENERGY PROJECTS IN NEW ZEALAND ......... 36
5.1.1
5.2
Pelamis P750 ..................................................................................... 32
Scaled 1.5 MW Pelamis or Attenuator................................................ 33
Generic 750 kW Point Absorber Device ............................................. 33
Tidal & Ocean Current Device Modelling............................................... 34
4.3.1
4.3.2
PART 5:
Marine Energy Resources and Extractable Reserves ........................ 30
Potential Marine Energy Projects ....................................................... 30
Wave Device Modelling ........................................................................... 31
4.2.1
4.2.2
4.2.3
4.3
Supply Chain Maturity ........................................................................ 28
Strategic Partnerships ........................................................................ 29
Investor Confidence............................................................................ 29
Summary................................................................................................... 29
4.1.1
4.1.2
4.2
Marine Energy Testing Centres .......................................................... 27
Permitting for Prototype/Demonstration Projects ............................... 28
Space/Resource Allocation Regimes ................................................. 28
Industry Developments ........................................................................... 28
3.5.1
3.5.2
3.5.3
3.6
Feed-in Tariffs .................................................................................... 27
International Forecasts for Marine Energy Development ................... 54
Comparison with Growth of the Wind Industry ................................... 57
Status of Marine Energy in New Zealand............................................... 58
6.2.1
6.2.2
Domestic Deployment Projects .......................................................... 58
Crest Energy Project .......................................................................... 59
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6.2.3
6.2.4
6.2.5
6.2.6
6.2.7
6.2.8
6.3
Forecast Growth of Marine Energy in New Zealand ............................. 62
6.3.1
6.3.2
6.3.3
PART 7:
Neptune Power Project....................................................................... 59
Power Generation Projects Proposal ................................................. 59
WET-NZ R & D Programme ............................................................... 59
Tidal Flow Seamills Project ................................................................ 60
Natural Systems Limited Project ........................................................ 60
Domestic Marine Energy Project Timetables ..................................... 61
Marine Energy Projects and Deployments in New Zealand ............... 62
Forecasts for Total Marine Energy Capacity ...................................... 62
Forecasts for Uptake of Marine Energy in New Zealand .................... 63
GREATER WELLINGTON REGION CASE STUDY ............................... 64
7.1
Introduction .............................................................................................. 64
7.2
Wave Energy Resources ......................................................................... 64
7.3
Tidal & Ocean Current Energy Resources ............................................ 64
7.4
Constraints on Marine Energy Projects................................................. 67
7.4.1
7.4.2
7.4.3
7.4.4
7.4.5
7.4.6
7.4.7
7.4.8
7.4.9
7.5
Operative Policies and Regulations.................................................... 68
Neptune Power Consent Area and Export Cable Route .................... 69
Cook Strait Submarine Cable Protection Zone................................... 71
Marine Reserves ................................................................................ 73
Areas of Significant Conservation Value ............................................ 74
Environmental Issues ......................................................................... 75
Fishing ................................................................................................ 77
Navigation........................................................................................... 77
Other Exclusions ................................................................................ 78
Summary................................................................................................... 79
BIBLIOGRAPHY ....................................................................................................... 80
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APPENDICES
APPENDIX A: CONTRACT, METHODOLOGY AND FORECASTS ............................ I
A.1
Contract and Working Arrangements ...................................................... i
A.2
Methodology and Data Sources................................................................ i
A.2.1 Forecasting ............................................................................................ ii
A.2.2 Cost Estimates ...................................................................................... ii
A.2.3 Acknowledgements .............................................................................. iii
APPENDIX B: MODELLING SINGLE POINT ABSORBERS....................................... I
B.1
Introduction ................................................................................................ i
B.2
Resonance ................................................................................................. ii
B.3
Power Train Efficiency ............................................................................. iii
B.4
Device Rating............................................................................................ iii
B.5
Assumptions............................................................................................. iv
B.6
Results ...................................................................................................... iv
B.7
Comparison with Published Pelamis Results ....................................... vi
APPENDIX C: “MARINE ENERGY RESOURCES: OCEAN WAVE AND TIDAL
CURRENT RESOURCES IN NEW ZEALAND”................................ I
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FIGURES
Figure 2.1: Energy Distribution in Waves .................................................................................. 9
Figure 2.2: The LIMPET OWC Device on Islay, West Coast of Scotland ............................... 10
Figure 2.3: Oceanlinx Prototype under Test at Port Kembla, NSW, Australia ........................ 11
Figure 2.4: ~1/4-scale Wave Dragon in Nissum Bredning, Denmark...................................... 11
Figure 2.5: Aquamarine’s Oyster Surge Device Design.......................................................... 12
Figure 2.6: The Pelamis P750 Prototype in Leith, Edinburgh (workers show scale) .............. 13
Figure 2.7: 40 kW PowerBuoy Ready for Deployment............................................................ 14
Figure 2.8: 1/4-scale WaveBob Prototype in Galway Bay, Ireland ......................................... 14
Figure 2.9: Si-hwa Tidal Power Plant, Korea (Artist’s impression).......................................... 16
Figure 2.10: TidalElectric's 3-pool Tidal Impoundment Proposal ............................................ 17
Figure 2.11: The 300 kW SeaFlow Prototype at Lynmouth, Devon ........................................ 18
Figure 2.12: SeaGen Deployed in Strangford Lough, Northern Ireland; April 2008 ................ 19
Figure 2.13: OpenHydro’s Open-Centre Turbine at EMEC, May 2007 (© PPL) ..................... 20
Figure 2.14: Enermar's Kobold Turbine, Straits of Messina, Italy (© PPL) ............................. 21
Figure 4.1: Pelamis P750 Power Matrix (OPD, 2004)............................................................. 32
Figure 4.2: Scaled 1.5 MW Pelamis Power Spectrum ............................................................ 33
Figure 4.3: Generic 750 kW Single Point Absorber................................................................. 34
Figure 4.4: Artist's Impression of SeaFlow Device .................................................................. 35
Figure 5.1: National Mean Significant Wave Height (1997-2007) ........................................... 37
Figure 5.2: National Mean Spectral Wave Power (1997-2007)............................................... 38
Figure 5.3: Mean Power Output from a 750 kW Pelamis device (1997-2007) ........................ 39
Figure 5.4: Mean Power Output from a 1.5 MW Pelamis device (1997-2007)........................ 40
Figure 5.6: Mean Power Output from a 750 kW SPA device (1998-2007) ............................. 41
Figure 5.6: Location of Sites of Specific Wave Power Evaluation........................................... 42
Figure 5.7: Depth-averaged Tidal Current Speeds for Mean Springs Flows........................... 47
Figure 5.8: Selected Modelling Locations in Cook Strait......................................................... 48
Figure 5.9: Selected Modelling Location in Foveaux Strait ..................................................... 49
Figure 5.10: Depth-averaged Tidal Current Speeds for Mean Springs for Southland ............ 50
Figure 6.1: Marine Energy Uptake Forecast for United Kingdom (BWEA, 2006).................... 54
Figure 6.2: Forecast Worldwide Marine Energy Capacity Growth (SE, 2005) ........................ 55
Figure 6.3: International Growth in Wind Energy Capacity (WWEA) ...................................... 57
Figure 6.4: Growth of Wind Energy Capacity in New Zealand (Clark, 2008) .......................... 57
Figure 6.5: WET-NZ’s Point Absorber Wave Energy Converter ............................................. 60
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Figure 7.1: Bathymetry of Cook Strait ..................................................................................... 65
Figure 7.2: Depth-averaged Mean Spring Tidal Currents in Cook Strait................................. 66
Figure 7.3: Maritime Constraints in the Cook Strait CMA........................................................ 72
Figure 7.4: Kapiti Marine Reserve (source: GWRC) ............................................................... 73
Figure 7.5: Final Area of Wellington South Coast Marine Reserve......................................... 74
Figure 7.6: Approaches to Wellington – LINZ Chart NZ463.................................................... 78
TABLES
Table 2.1: Marine Energy Sources and Products...................................................................... 5
Table 2.2: Simplified Classification of Wave Energy Converters .............................................. 8
Table 2.3: Simplified Classification of Tidal Energy Converters.............................................. 15
Table 2.4: Potential of Marine Energy Converter Technologies in New Zealand.................... 22
Table 3.1: Total Renewable Energy or Electricity Targets by Country.................................... 23
Table 3.2: Marine Energy Targets and Forecasts by Country................................................. 25
Table 4.1: Summary Estimates of Wave and Tidal/Ocean Current Reserves ........................ 31
Table 5.1: Proposed Wave Farm Arrays ................................................................................. 43
Table 5.2: Annual Production from a 50 x Pelamis P750 Array .............................................. 44
Table 5.3: Annual Production from a 50 x 1,500 kW Pelamis Array ....................................... 44
Table 5.4: Annual Production from a 50 x 750 kW SPA Array ................................................ 45
Table 5.5: Proposed Tidal/Ocean Current Arrays ................................................................... 52
Table 5.6: Proposed 50 x 300 kW Seaflow Tidal Current Arrays ............................................ 52
Table 5.7: Proposed 50 x 1.2 MW SeaGen Tidal Current Arrays ........................................... 52
Table 6.1: Examples of Device Developers with Multiple International Projects..................... 56
Table 6.2: Current Marine Energy Projects in New Zealand ................................................... 58
Table 6.3: Proposed Development of Neptune Power Project................................................ 61
Table 6.4: Proposed Development of Crest Energy Project.................................................... 61
Disclaimer
POWER PROJECTS Limited (hereinafter referred to as the "Consultant") warrants that any
estimates, opinions, conclusions or recommendations presented in this report are reasonably
held or made as at the time provided. The recipient accepts and acknowledges however, that
neither the Consultant nor its advisors, agents, officers or employees make any
representation or warranty as to the accuracy or reliability of any estimates, opinions,
conclusions, recommendations (any or all of which may change without notice) or other
information which has been provided and, to the maximum extent permitted by law, the
Consultant disclaims all liability and responsibility for any direct or indirect loss or damage
which may be suffered by any recipient through relying on or use of any estimates, opinions,
conclusions, recommendations or other information provided by the Consultant.
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Executive Summary
The Electricity Commission (EC), Energy Efficiency and Conservation Authority
(EECA) and Greater Wellington Regional Council (GWRC) want to address the
potential development of marine energy generation in New Zealand. This study
reviews the current state of domestic and international marine energy technologies
and their development and deployment. New wave and tidal/ocean current energy
resource assessments have been undertaken by integrating new mapping of the
resources with the performance characteristics of modelled wave and tidal/ocean
current devices to derive the potential electricity generation from device arrays at
promising sites.
The pace of domestic marine energy activity has picked up since 2006 with the
deployment of the first experimental wave energy converter (WET-NZ device), the
grant of the first consents for an in-stream tidal prototype (Neptune Power) and the
award of $1.85 million from the Marine Energy Deployment Fund (MEDF) to Crest
Energy for its proposed tidal stream project in Kaipara Harbour, subject to grant of a
resource consent for the project.
The pace of international marine energy precedes domestic developments. Verdant
Power has installed and operated six 35 kW tidal turbines in the East River of New
York since 2007. Ocean Power Technologies has had a 40 kW PowerBuoy working
continuously off the New Jersey coast for over 2 years now. More recently, the first
full-scale tidal stream demonstrator, the Marine Current Turbines’ SeaGen device
was deployed in Strangford Lough, Northern Ireland, in April 2008. Pelamis Wave
Power is now forecasting that its long-awaited Pelamis deployment of 3 Pelamis
devices at Aguçadoura, off Portugal, will occur in the third quarter of 2008.
To assess the potential for marine energy in New Zealand four tasks have been
carried out in the analysis reported here:
1. All marine energy technologies have been reviewed with a focus on
devices, which may have particular application in New Zealand waters.
Wave and tidal/ocean current devices have the best potential.
2. Factors that affect the pace of development and uptake of marine energy
technologies, including Government initiatives, industry activity and
investor interest have been reviewed.
3. Marine energy resources and reserves have been calculated by devising
power spectra for three generic wave devices and two generic tidal/ocean
current devices. These spectra have been applied to an extensive
modelling study of the national and wave and tidal/ocean current
resources to define areas of interest. Nominal arrays of both wave and
tidal/ocean current devices have then been modelled to determine the
capacity (in MWs) and annual electricity production (in GWh/year) for six
wave sites around the country and six tidal sites in two locations.
4. A case study has been undertaken on the Wellington Coastal Marine
Area, where national-scale modelling indicates excellent tidal and
potential wave sites. A review of the potential constraints on a marine
energy project in the Wellington CMA complements the wave and tidal
resource assessments.
Of all the marine energy sources, wave and tidal/ocean current energy have the best
potential for providing power to New Zealand in the future. Wave devices seek to
harness either breaking waves or open-ocean swells, whilst tidal devices extract
energy from either tidal rise and fall or tidal currents. Ocean thermal energy, osmotic
power and marine biomass may have future potential but technologies to harness
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these energy sources are at an early stage of development.
offshore wind is beyond the scope of this study.
The potential for
Many wave device designs are under development and there is, as yet, no
convergence on a common design. Five generic designs are maturing and are
reviewed here. Two of these – attenuator devices (like the well-known Pelamis
device) and point absorber devices (like the WET-NZ device) have been evaluated
for their potential use at six New Zealand sites.
Whilst there are many different tidal device designs, the fastest to mature is probably
the horizontal axis turbine – like a submarine wind turbine. Tidal rise and fall
technologies are simple – barrages or impoundments – but there are very few sites
where such technologies could be deployed in New Zealand. Two different but
related generic horizontal axis turbines have been analyzed in this study.
The development of marine energy depends not only upon the ingenuity and
capabilities of device developers but also upon an array of external factors, including
national targets for uptake of renewables (including marine), government assistance,
funding mechanisms, industry developments and investor confidence. The New
Zealand Government has begun to support marine energy but specific support for
new renewables is limited. Policy instruments, such as renewables obligations, feedin tariffs and regulatory assistance, have stimulated marine energy device
developments and deployments in the United Kingdom, Portugal, Denmark, Canada
and the United States.
The international and national growth of wind energy has been reviewed as a
template for the potential growth of marine energy. Current development of marine
energy is lagging behind forecasts of only 7 – 8 years ago. However, developers
with maturing technologies are beginning to permit multiple sites so very rapid growth
may occur, as new technologies mature to commercial status. Two domestic marine
energy developers have announced aggressive development plans, which are at
odds with the observed development of the wind industry here. Although New
Zealand will see the first demonstration projects in the next 3 – 5 years and the first
commercial deployment in 3 – 7 years.
The Wellington Coastal Marine Area (CMA) has been the subject of a detailed case
study, which shows that it has exceptional tidal/ocean current resources but limited
wave resources (as confirmed by the site modelled off the Wairarapa coast). The
policy environment in the Wellington CMA is described and the terms of the Neptune
Power consent are instructive for future developments.
Environmental
considerations and competing uses, such as fishing and navigation, will need to be
considered by project developers and there is an absence of useful data, such as
marine mammal interactions with marine energy devices, whale migration routes and
shipping movements. Further work will be required to measure and map these
issues and to address and other environmental issues.
In summary, mapping and modelling undertaken in this study indicates that marine
energy can make a significant contribution to New Zealand’s future electricity supply.
Over 7,000 MW of wave energy reserves may be available, sites are abundant and
geographically dispersed. The potential for tidal/ocean current energy is smaller
(<1,000 MW) but some specific sites with real potential have been identified, noting
also that harbours and inland passages were not mapped and modelled in this study.
Site selection is critical and more detailed mapping will be required to identify sites of
interest. Device selection and micro-siting of individual devices will also be critical for
optimizing power production from device arrays at favourable locations. Such work is
beyond the scope of this study but will be required to ensure that New Zealand and
project developers make optimal decisions about marine energy investments.
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PART 1: DEVELOPMENT OF MARINE ENERGY IN NEW ZEALAND
1.1
INTRODUCTION AND PURPOSE OF STUDY
The Electricity Commission (EC), is seeking advice on the potential development of
marine energy generation in New Zealand to assist with planning for future
transmission and generation investments. The Modelling Team has requested a
report comprising three parts:
1. Review of current marine energy technologies both overseas and in New
Zealand.
2. A timetable for the maturing technologies to penetrate the New Zealand
generation market.
3. A short list of potential marine energy schemes, including location,
timeframe, capital cost estimates, installed capacity (MW) and electricity
production (GWh).
No study of this kind has been undertaken in New Zealand before. Although recent
and current work has focussed on evaluating the potential of New Zealand’s wave
and tidal stream resources, there have been no published attempts to assess
potential schemes or to calculate an actual national contribution by marine energy to
the future generation portfolio.
The domestic marine energy sector is a very dynamic one. During the course of the
research for this report, five key events have occurred:
1. The first resource consent for a tidal stream prototype project was granted
(10 April 2008; Section 6.2.3).
2. Consent hearings for resource consents for a utility-scale tidal stream
project were held (26 - 30 May 2008; Section 6.2.2).
3. The first award under the Marine Energy Deployment Fund (MEDF) was
made (29 May 2008; Section 3.3.1)
4. The second round of funding under the MEDF was foreshadowed (as
above)
5. The first wave device prototype was deployed in Wellington Harbour (5
June 2008; Section 6.2.5).
Beyond these projects, however, there has been very little public information
released by other device/project developers. Thus any review of the contribution and
timetable for development of national resources must be speculative. However, this
proposal is aimed at extending knowledge of the national marine energy potential by
going beyond resource evaluations. Coupling national and regional modelling of
wave and tidal-stream resources with the potential energy production from three
example devices, in analysis of some site-specific deployments, will enable
extrapolation of regional and national deployments.
The Commission has recently commissioned other organizations to undertake similar
studies in wind and hydro projects and conducted similar work internally on
geothermal developments. However, in all three cases, mature wind, hydro and
geothermal technologies and well-researched resources have led to publicly
available listings of potential generation projects. The scope for the work reported
here did not allow the development of a rank-ordered listing of potential marine
energy project developments, ranked by their unit cost of electricity. The aim is to
approximate the development of marine energy by the evaluation of potential sitespecific wave and tidal-stream projects and extrapolate these projects to the regional
and national scales.
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1.2
LAYOUT OF THE REPORT
This report is laid out in six parts. Following this introduction, the contents of the
following parts are as follows:
Part 2
This part is a review of the development status of wave and tidal stream
energy converter devices both in New Zealand and overseas. The focus
is on the current status of devices, their performance characteristics,
where such data are available and projects in which they are being
deployed. The review discusses generic marine energy converters and
gives examples of the most mature technologies, i.e., those that have
already been deployed, at least, at prototype level.
Part 3
This part sets out the issues affecting the timing of development of
current technologies and their deployment in New Zealand. These
include government targets and forecasts, whether mandatory or
aspirational, developers’ commercialization strategies, funding and
regulatory mechanisms and industry developments.
Part 4
This part is a review of the wave and tidal/ocean current energy resource
assessments. It describes the resource modelling undertaken in this
study in the layperson’s terminology, although those interested in the
technical details of the modelling will want to read the two Appendices B
& C on wave modelling and MetOcean Solutions’ report.
Part 5
Drawing on the three previous parts, the results of modelling some
specific areas for potential wave and tidal/ocean current are described in
detail. Modelling involved the application of the generic devices (based
on real examples) to the resource forecasts derived for each area. Five
wave and one tidal/ocean current areas have been evaluated.
Part 6
International forecasts for the development of the international marine
energy industry have been made by a number of overseas
organizations. These forecasts are compared with the demonstrated
growth of the international wind industry. Within New Zealand six
projects, which have been publicized, are discussed here. This section
ends with a forecast for the uptake of marine energy in New Zealand.
Part 7
This part presents the results of the evaluation of the wave and
tidal/ocean current potential of the Wellington Coastal Marine Area. This
is followed by a review of the constraints on any potential marine energy
projects in the Wellington CMA. The constraints include operative
policies and regulations, existing marine energy projects, submarine
cables, marine reserves and conservation areas, fishing, navigation and
other exclusions.
This part serves as a case study for project
developers, not only in the Wellington CMA but nationally,
acknowledging that constraints faced by marine energy project
developers will differ from site to site.
Declaration of Interest
Power Projects Limited is a co-founder and current participant in the Wave Energy
Technology – New Zealand (WET-NZ) R & D programme. This is a consortium R & D
programme with Industrial Research Limited and the National Institute of Water and
Atmospheric Research. Over the last four years the consortium has developed a point
absorber device, which has been deployed in Pegasus Bay off Christchurch and, more
recently, Evans Bay in Wellington harbour. Power Projects Limited has used only what
information has been released in the public domain to describe the WET-NZ programme in
this report. See Section 6.2.5 for more detail about the programme.
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PART 2: MARINE ENERGY TECHNOLOGIES
2.1
MARINE ENERGY SOURCES
There are a number of different potential ways of extracting energy from the oceans.
None has yet achieved the status of commercial viability internationally, although
most have been under consideration and development since the oil price shocks of
the 1970s. Not all of these potential energy sources will have application in New
Zealand, because resource and environmental issues will have an impact.
There are seven principal marine sources, from which energy could be extracted.
Internationally, all of these sources are currently being investigated to differing
degrees but technologies – at various stages – are being developed to harness them
(Table 2.1). By far the biggest international investments are going into developing
conversion technologies for wave and tidal stream energy, although planning
pressure is driving increasing consideration of offshore wind in North European
Atlantic coast settings.
Energy Source
Conversion Technology
Products
Waves
Open ocean swells
Point absorbers; Attenuators
Breaking waves
Oscillating water columns
(OWCs); Overtopping devices
Tides
Tidal rise and fall
Barrages; Impoundments
Tidal/ocean currents
Turbines; Reciprocating
devices
Heat
Ocean Thermal Energy
Conversion (OTEC)
Osmotic power
Reverse osmosis
Marine biomass
Farming and harvesting
Offshore winds
Offshore wind turbines
Electricity
Hydrogen
Biofuels
Heat
Potable water
(& combinations of
above)
Table 2.1: Marine Energy Sources and Products
2.1.1
Wave Energy
Wave energy can be separated into two potential extractable sources: open ocean
swells and breaking waves. Open ocean swells result from the aggregated effects of
wind currents blowing across the surface of the ocean, particularly in major storms.
Swells result from the constructive interference of waves resolving into larger waves
with bigger amplitudes (i.e., wave height) and longer wavelengths (i.e., longer periods
between wave peaks). Breaking waves result from the incidence of these ocean
swells on the seabed, as waves approach the coast.
Anyone flying into Wellington airport from the south will have noticed the
‘herringbone’ patterns created by two or more swell directions in the open sea some
kilometres south of the airport. As the swells approach the coast they suffer friction
with the shallowing ocean bottom, which causes the swells to rotate into a single
direction roughly parallel with the coast. With increasing shallowness, wave heights
increase and increasing friction causes the waves to topple over, finally breaking on
the beach.
Devices, which extract energy from waves, are called ‘oscillating water column’
devices (OWCs) or ‘overtopping’ devices (see Sections 2.2.3 and 2.2.4). Both are
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sometimes lumped together as ‘terminator’ devices. Devices, which extract energy
from open ocean swells, are classified as either ‘attenuator’ devices or ‘point
absorber’ devices (see Sections 2.2.6 and 2.2.7).
2.1.2
Tidal Energy
Like wave energy, tidal energy can be split into two basic forms: tidal rise and fall and
the resultant tidal stream or ocean currents arising from that rise and fall and
modifications by weather conditions. Tidal rise and fall is controlled by the relative
position and gravitational attraction of the moon and, to a lesser extent, the sun on
the world’s oceans. The tides follow a diurnal cycle slightly longer than a normal day,
and a seasonal cycle, which gives rise to neep and spring tides. Tidal currents arise
to accommodate the diurnal rise and fall, although local weather effects and local
seabed topography can modify them. Whilst the astronomical control on tidal rise
and fall enables an extended forecast of high and low tides, this certainty does not
extend to tidal stream currents because of the weather effects. For example there
are diurnal tidal effects in Cook Strait, which can be forecast, i.e., tide tables.
However, resultant currents can be severely affected by local weather conditions to
the extent that, in severe storm conditions, the tide does not ‘turn’, as would be
expected (Stevens et al., 2006).
Conversion technologies, which can harness electricity from tidal rise and fall and
from tidal currents, are quite different. There are two basic tidal rise and fall
technologies, although their conceptual operation is similar. These are tidal barrages
and tidal impoundments. Tidal barrages are essentially barriers across rivers,
estuaries or bays, which disrupt the normal tidal rise and fall, holding back the rising
or falling water such that water level on one side of the barrier or impoundment is out
of synchronization with the water level on the other side. As the point of maximum
difference is reached the barrage or impoundment mechanism is opened, allowing
flow across it. The flowing water is used to generate electricity and can be utilized on
both the ebb and the flood tide.
Tidal barrages are an ancient technology. There is evidence of small tidal barrages
being used to generate rotary motion for corn grinding in post-Roman times and the
oldest tidal-powered corn mill (Eling Mill near Southampton) has been continuously
operational since the 9th Century.
The only modern era marine energy device of any scale is the Rance River barrage
on the estuary of that river near St. Malo in northern France. This barrage became
operational in 1967 and has a generation capacity of 240 MW. Originally it only
operated on the ebb tide but was converted to both ebb- and flood tide operation in
1997. There are two other smaller working examples at Annapolis Royal (20 MW) in
Nova Scotia and Kislaya (0.4 MW), near Murmansk, Russia.
2.1.3
Heat (Ocean Thermal Energy Conversion)
The thermal energy of ocean water can be converted into electrical energy by a
process called ocean thermal energy conversion (OTEC). OTEC is based upon heat
exchange between deep ocean water, pumped to the surface, and warm shallow or
surface water. The process requires a significant heat difference between these two
sources of water. Such differences occur in tropical latitudes either side of the
Equator, somewhat distorted by major ocean currents such as the Gulf Stream.
However, outside the Tropics the temperature difference is too small to enable
sufficient electricity to be produced economically from the heat exchange process.
OTEC projects have been trialled in Hawaii and a 30 kW device OTEC plant is being
tested in Japan. Mexico is considering the installation of some large-scale OTEC
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plants to produce both electricity and potable water. OTEC installations are unlikely
to be economic in New Zealand and are not considered further in this report.
2.1.4
Osmotic Power
Energy can be extracted from ocean water through the salinity difference (or
gradient) between salty seawater and freshwater. Statkraft, the Norwegian electricity
transmission grid operator and utility, has recently embarked on a research project to
build the world’s first osmotic power device (Statkraft, 2006). The prototype develops
only 35 kW, so commercial development of osmotic power is probably a considerable
time from commercial development. Osmotic power is not a commercial prospect for
New Zealand at present or in the mid-term future.
2.1.5
Marine Biomass
Early interest in marine biomass was demonstrated in the 1970s by proposals to
‘farm’ kelp on the Pacific coast and to harvest and process it to produce oil. The
concept was researched but no trials were conducted and commercial development
did not proceed. Since then other marine biomass projects have been or are now
under consideration, including the harvesting and processing of marine algae to
produce bio-fuels. Such projects could be attractive to New Zealand because of its
very large Exclusive Economic Zone (potentially the 4th largest in the world).
Marine biomass would provide a fuel, most likely restricted to transport applications.
It is unlikely that it would be economic to produce the bio-fuel, only to further convert
it to electricity for wider uses. For this reason and for the very early stage of
development, marine biomass is not considered further in this report.
2.1.6
Offshore Winds
In European Atlantic and North Sea coast countries, offshore wind farms have been
developed since 1991 (Vindeby, Denmark) and the United Kingdom (Blyth Harbour,
2003). Currently the largest offshore wind farm is Horns Rev off the north coast of
Denmark (80 x 2 MW Vestas V-80 turbines), although a 341-turbine array, called the
London Array, is under construction in the North Sea, roughly 70 km ENE of London.
The London Array will eventually have the same capacity as the Huntly Power
station, i.e., 1,000 MW. However, a slightly larger project has already been proposed
off the North Devon coast. If built, the Atlantic Array will have 350 turbines with a
generation capacity of 1,500 MW (providing power to over 1 million homes).
Most offshore wind projects are based upon effectively adapting onshore wind
turbine generators for offshore use and developments are limited to shallow water
applications. The drivers for offshore applications are better wind resources
(smoother flows with less damaging turbulence), decreasing onshore space for
projects and, perhaps most importantly, reduced difficulty in planning consents
caused by local opposition.
New Zealand has not yet reached the capacity of its onshore wind opportunities – as
indicated by the nearly 4,000 MW of onshore wind projects that have been built (322
MW by end-2007) or proposed to date. However, opposition to onshore wind farms
has grown and consenting is becoming more difficult and costly. Unfortunately, New
Zealand’s coastline does not shelve like the North Sea coast and any future offshore
wind projects in New Zealand may have to be close to shore, somewhat negating the
benefits of offshore sites. It is worth noting, however, R & D is under way on floating
wind turbine generators, which, if successful, would free New Zealand developers to
locate their arrays further offshore (Economist Technology Quarterly, 7 June 2008).
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2.1.7
Products of Marine Energy
A range of potential products can be produced using marine energy generation,
including electricity, hydrogen (by on-site electrolysis), heat, bio-fuels (of various
types) and potable water (Table 2.1). The vast majority of devices are being
designed with electricity as the intended end product. Some devices, such as the
Australian CETO will deliver both electricity and potable water, whilst Oceanlinx is
intending to build both electricity-producing and water-producing designs, following
its successful prototype deployment at Port Kembla, south of Sydney.
2.2
WAVE ENERGY DEVICES
2.2.1
Classification
Although fewer than tidal stream devices, an impressive number of wave energy
design concepts is currently under development. The European Marine Energy
Centre currently lists 51 wave energy device developments (EMEC, 2008). Even this
number is probably an under-estimate, as the authors of this report are aware of
devices not listed in the compilation. Despite the number of wave energy devices
that have been proposed, there is no commonly agreed standard classification. The
classification listed below breaks devices down on three criteria:
1. Environmental location of the device,
2. Intended operational water depth, and
3. Physical construction or energy extraction methodology (Table 2.2).
Other classifications are possible. For instance, oscillating water column and
overtopping devices are sometimes called ‘terminator’ devices, because they resist
the waves to absorb energy, whilst attenuator and point absorber devices can be
classified as ‘compliant’ devices.
Location
Onshore
Water Depth
(m)
0
Nearshore
1 - ~25
Classification
Oscillating
Water Column
Overtopping
Oscillating
Water Column
Surge devices
Overtopping/
terminator
Attenuator
Attenuator
Attenuator
Point Absorber
Offshore
~25+
Point Absorber
Point Absorber
Point Absorber
Point Absorber
Point Absorber
Manufacturer
Device
PICO plant, Azores
Tapchan, Norway
Oceanlinx
Oceanlinx
Aquamarine
Oyster
Wavedragon
Wavedragon
Pelamis
WavePower
C-Wave
Raft designs
Ocean
Power
Technologies
AWS II
Finavera
Renewables
Wavebob
Carnegie Corp.
WET-NZ
Pelamis
C-Wave
Martifer
PowerBuoy
AWS II
AquaBuOY
Wavebob
CETO II
“WaveWobbler”
Table 2.2: Simplified Classification of Wave Energy Converters
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Note that the listing of devices in the previous table indicates that the devices are in
active development. It is clearly not an exhaustive listing, nor is it intended that they
devices listed are representative, other than of their generic classes.
2.2.2
Energy Distribution in Waves
Energy in waves takes two forms: potential energy and kinetic energy. Kinetic
energy is the physical energy created by the position of the water mass, relative to
the energy collector. Potential energy is due to gravity and its extraction involves the
movement of the water from a higher to a lower potential energy position, usually
converting the potential into mechanical energy in the process. The most obvious
form of potential energy is the extraction of energy from the rising and falling of
passing waves (Figure 2.1).
Figure 2.1: Energy Distribution in Waves
Kinetic energy is the energy produced by movement. Although waves appear to
have a linear unidirectional movement, the particle motion in waves is approximately
circular – the waves are notionally rotating cylinders moving to the shore. This
circular motion is the reason why breaking waves at the beach appear to push and
pull, as much as lift and drop, swimmers in the surf. Extraction of kinetic wave
energy is achieved by using devices, such as turbines, which partially – but not
completely – resist the circular wave motion. Surfers hitting the perfect wave are
extracting both kinetic and potential energy on their graceful journeys to the beach.
The energy contained in waves can be resolved into three motion vectors:
1. Heave – the vertical component of motion
2. Surge – the horizontal component of motion
3. Pitch – the rotational component of motion
Wave energy converter designs are based upon extracting energy from one or more
of these components of motion. Some devices are designed to extract energy from
one particular vector, e.g., heave or surge, whilst others seek to extract energy from a
combination of these vectors.
Wave/swell environments are extremely complex, since a sea state is composed of
local and immediate wind-sea interactions, old-wind seas generated some hours ago
and long period swells from distant storms of several days. All of these may arrive
from different directions and lead to very complex sea-states. Extracting energy from
this complex sea-state, incident on a wave energy converter, is thus a complex
problem.
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In the following sections, devices are described in their respective environmental
position, i.e., relative to the coastline: onshore – nearshore – offshore.
2.2.3
Oscillating Water Column Devices
The structure of an oscillating water column device (OWC) is a fixed volume
chamber, open below the water surface but closed above, except for a single outlet.
The chamber is located either on the beach (or cliff) or nearshore, where waves are
breaking. The basic operational principle is that the breaking wave causes a rise of
water level within the chamber, which compresses the air above the water surface
and forces it out of the single outlet and, in so doing, turns a turbine. As the wave
recedes, the water level in the chamber drops and air is sucked back into the
chamber. With the right configuration the turbine will continue to rotate. Energy is
thus extracted from both rising and falling waves.
The first OWC device was the Pico Plant in the Azores, which was first
commissioned in 1973.
It suffered frequent operational problems and was
abandoned during the 1990s. The plant has been significantly refurbished since
2000, although operation is still discontinuous (Neumann et al., 2007).
Two other devices, Wavegen’s LIMPET device and Australian Oceanlinx device
(formerly Energetech) are both OWC devices, which have been discontinuously
operational since 2000. The key differences between the devices are that firstly,
Wavegen’s LIMPET is coast-attached (Figure 2.2), whilst the Oceanlinx device is
Figure 2.3).
Figure 2.2: The LIMPET OWC Device on Islay, West Coast of Scotland
Secondly, LIMPET uses a fixed blade turbine, called a Wells Turbine, which rotates
in the same direction, regardless of the direction of the air current, whilst the
Oceanlinx turbine establishes the unidirectional turbine rotation by rapidly variable
pitch blades, which change direction as the air direction changes.
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Figure 2.3: Oceanlinx Prototype under Test at Port Kembla, NSW, Australia
2.2.4
Overtopping Devices
Overtopping devices are relatively simple devices, based upon a low-head hydro
design. Water from advancing waves is captured in a reservoir slightly above sea
level, held and returned to the sea through conventional low-head hydro turbines,
which generate power.
The earliest overtopping device was a tapered channel (Tapchan) excavated into
cliffs in Norway. Breaking waves accelerated up the tapered channel and slopped
over into a lower reservoir before being fed back to the sea. More recently, a couple
of nearshore, bottom-sitting Danish devices, called WavePlane and Wave Dragon,
have been proposed and are under development. Wave Dragon has had a measure
of success and full-scale deployments are planned (Figure 2.4).
Figure 2.4: ~1/4-scale Wave Dragon in Nissum Bredning, Denmark
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2.2.5
Surge Devices
Surge devices generally sit on the seabed in a nearshore setting and extract energy
from the surging of passing waves (surge is the horizontal component of the wave
motion). Surge devices consist of a base, which sits or is anchored to the shallow
seabed, to which is attached by a hinge mechanism an arm or a baffle, which pivots
in response to the surging movement of passing waves. There are at least three
such devices under development, including Oyster (Figure 2.5), WaveRoller and
BioWave. Development of a fourth surge device, EB Frond is currently on hold.
Figure 2.5: Aquamarine’s Oyster Surge Device Design
A variant of this surging design is a pressure-sensitive device, which reacts to
pressure changes of passing waves, rather than kinetic movement. The prototype
design of the CETO device was a pressure-sensitive design but this device has been
redeveloped as a more conventional point absorber design (Section 2.2.7).
2.2.6
Attenuator Devices
An attenuator device is essentially a floating device, which works in parallel to the
wave movement direction and effectively rides the crests and troughs of swell waves.
Movement along the length of the device can be controlled to produce energy. They
are probably the most common device design. Because the devices have to span
the wavelength (i.e., the distance between two swell crests), they are usually very
large (Figure 2.6).
Since the cross-sectional area of the device orthogonal to the swell crests is
relatively small, the device experiences lower forces than a terminator device (such
as an OWC or overtopping device). Attenuator devices can look markedly different
but their basic principle of energy extraction is the same. The most well known
attenuator device is Pelamis, the P750 prototype version of which is shown in the
figure below. Three of these devices have been sold to a Portuguese utility, Enersis,
and are in the process of being deployed at a site of the Portuguese coast, called
Aguçadoura. The deployment was due in 2006 but has been delayed due to
problems, reportedly with the device mooring system. Pelamis Wave Power is also
constructing devices for Scottish Power Renewables for a deployment of 4 x 750 kW
devices at the European Marine Energy Centre (the Orcadian Wave Farm) and a
further deployment of up to 7 x 750 kW devices at the proposed Wave Hub facility in
Cornwall (the West Wave project).
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Figure 2.6: The Pelamis P750 Prototype in Leith, Edinburgh (workers show scale)
A power spectrum published by the developer of this device has been used in the
resource modelling (Section 4.2.1).
There are also a number of different floating ‘raft’ designs undergoing testing, e.g., the
Portuguese Martifer raft. However, development of raft designs has slowed relative
to other design concepts.
2.2.7
Point Absorber Devices
Perhaps the second most common generic device design – after the attenuator
devices – are point absorbers. Point absorbers have a physical analogy to
conventional maritime navigation buoys. They are usually largely submerged, axisymmetric and anchored to the seabed.
Point absorbers essentially have two key parts – a large spar, which either sits on the
seabed or floats in the water column below the level of wave particle motion and a
surface or near-surface float, which reacts to passing wave crests and troughs. As
such point absorbers extract the heave component (i.e., the vertical motion) of wave
kinetic energy, although newer devices are being built which strive to extract energy
from all three modes – heave, surge and pitch).
The devices have a small cross-section relative to an advancing wave front and thus
do not extract as high a proportion of the passing energy as attenuator or terminator
devices. However, their relative small areal footprint lends them particularly well to
deployment in arrays and, as we shall see, most developers plan that individual
devices will have low unit generation capacities (100 kW to 1 MW) but achieve utility
scale by deployment in arrays. A high proportion of current academic research on
point absorbers is dedicated to establishing array designs.
The most developed point absorber is the PowerBuoy developed by a New Jersey
company, Ocean Power Technologies (OPT). Early versions of this device have
been deployed since 1994 and the company is now involved in a number of
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deployment projects. The company was listed on the Alternative Investment Market
of the London Stock Exchange (AIM) and, more recently, listed on the NASDAQ in
2007.
The PowerBuoy device is fairly representative of the generic concept of point
absorber device geometry – a central axi-symmetric spar with a separate float
(Figure 2.7).
Figure 2.7: 40 kW PowerBuoy Ready for Deployment
Another device currently under development is the Irish WaveBob device. This
device has been trialled at the Galway Bay wave testing centre over the last two
years and the company has recently opened an office in the United States as it looks
to expand operations there. Again the WaveBob device comprises a central spar
linked, in this case, by hydraulic arms to a separate float (Figure 2.8). Wavebob
differs from the PowerBuoy in that the former is an entirely floating device, slackmoored to the seabed, whilst the PowerBuoy has a central spar, which rests on the
seabed. The device has been significantly modified suffering damage in 2007.
Figure 2.8: 1/4-scale WaveBob Prototype in Galway Bay, Ireland
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2.3
TIDAL ENERGY DEVICES
2.3.1
Classification
A large number of tidal energy design concepts is currently under development.
Putting aside barrages and impoundments, one compilation of devices (including
tidal fences) indicated that over 70 tidal/ocean current devices were under
development (Hales, pers. comm.). The European Marine Energy Centre lists 52 tidal
current device developments (EMEC, 2008).
Both numbers are probably a
significant under-estimate, as neither includes device developments in New Zealand
(of which there are at least eight) and possibly many other countries.
Despite the number of designs that have been proposed for tidal and current energy
converters, there is no commonly agreed standard classification. The classification
listed below breaks devices down on two criteria:
1. The source of the tidal energy to be harnessed,
2. The physical construction or energy extraction methodology (Table 2.3).
Conversion Technology
Tidal Rise and Fall
Barrages
Impoundments
Fences
Tidal/Ocean Current Devices
Horizontal Axis Turbines
Shrouded HA Turbines
Pressure Devices
Vertical Axis Turbines
Oscillating Hydrofoils
Manufacturer
Examples
Various
Tidal Electric
Blue Energy
Rance River
None
None
MCT
SMD Hydrovision
OpenHydro
Lunar Energy
HydroVenturi
Various
Engineering Business
SeaGen, SeaFlow
TidEL
EMEC deployment
RTT 1000
Prototype trial, UK
Various prototypes
Stingray
Table 2.3: Simplified Classification of Tidal Energy Converters
2.3.2
Barrages
Barrages are effectively low-head hydroelectric devices, which harness the artificial
phase difference created between the rising and falling tides on the seaward side of
the barrage and water being either impounded or excluded from the landward side of
the barrage. Tidal barrages comprise a series of gates, which are open during the
flood tide and close at high water. As the tide falls on the seaward side of the
barrage, the gates are opened and the conventional hydroelectric generators are
used to generate electricity.
Presently, the largest working example is the 240 MW tidal barrage on the Rance
River in Northern France (PPL, 2005), although there are also smaller operational
schemes in eastern Canada (Annapolis Royal: 20 MW) northwestern Russia
(Kislaya: 0.5 MW). China also has five small barrages, associated with irrigation
schemes, with a cumulative total of 4 MW.
Tidal barrages continue to be developed. The world’s largest scheme – 254 MW at
Si-hwa in South Korea - is currently under construction and is due to be
Figure 2.9). At least two other major barrage projects – at Garolim and Inchon Bay are under consideration or development in South Korea.
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Figure 2.9: Si-hwa Tidal Power Plant, Korea (Artist’s impression)
The UK Government has also revived a 30-year old plan to build a barrage across
the tidal estuary of the River Severn between Wales and England. A recent review
by the Sustainable Development Commission has shown that this huge scheme –
8,500 MW – may be viable (SDC, 2007). The UK Department of Business,
Economic and Regulatory Reform is conducting further evaluation to establish the
potential of Severn Estuary barrage.
Tidal barrages have high initial capital costs but are cheap to operate as there are no
fuel costs and the main structure requires relatively little maintenance. Silting behind
the barrage and the potentially serious environmental change caused upstream of
the barrage can be problematic for consenting.
In New Zealand a number of tidal barrage proposals have been made, particularly in
the five major harbours on the west coast of the North Island (Hokianga, Kaipara,
Manukau, Aotea and Raglan harbours). However, the average tidal range (2 – 3 m)
is small, there are significant potential environmental challenges, not least of which is
the presence in some of these harbours of the rare Hector’s and very rare Maui’s
Dolphins. Conflicting uses, such as commercial, customary and recreational fishing,
are likely to make barrages a difficult, if not unattractive, option in New Zealand. For
these reasons, tidal barrages will not be considered further in this report.
2.3.3
Impoundments & Constrictions
Tidal impoundments are man-made enclosures, which entrap rising flood tides,
restrict their exit at high tide to create an artificial hydraulic head, which can be used
to generate electricity. TidalElectric has proposed a 432 MW tidal impoundment off
the North Wales/Liverpool Bay coast (PPL, 2005). This scheme involves building an
impoundment wall in shallow offshore conditions and creating three compartments,
which will be drained separately to smooth the power flow (Figure 2.10).
Impoundments require relatively shallow water offshore, since the principal
component is a sea wall, requiring large volumes of material to be dumped and
worked into the impoundment. Such structures will be critically sensitive to water
depth, as it will control the volume of material required. Since most of New Zealand’s
coasts are reasonably steeply shelving, there are few, if any, locations where
impoundments would be practical. The relatively low tidal range is also a negative
factor as the natural tidal range controls the maximum hydraulic head that can be
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achieved within the impoundment. For these reasons, tidal impoundments will not be
considered further.
Figure 2.10: TidalElectric's 3-pool Tidal Impoundment Proposal
Tidal constrictions occur across natural harbours with narrow mouths. The large
natural harbours of the west coast of the North Island (see maps in Part 5 of this
report) are good examples. The natural constrictions at their mouths cause
acceleration of tidal stream velocities and cause significant head differences between
the harbour water level and the open sea level (effectively a phase difference
between the harbour and the ocean).
Woodshed Technologies has proposed harnessing this phase difference with their
Tidal Delay® technology, not by placing devices in the harbour mouth but by laying
or burying water pipes across narrow isthmuses between the harbour and the open
sea. The pipes will be full of water and will act as siphons. Turbines within the pipes
will generate electricity from the two-way flow of water as the tides rises and falls.
Woodshed Technologies became a public unlisted company in Australia in January
2008 and has a project, through its wholly-owned UK subsidiary, CleanTechCom
Limited, with another UK company to establish a trial Tidal Delay® project across the
Churchill barriers between the southern Orkney Islands.
2.3.4
Tidal Fences
Tidal fences are man-made structures across narrow harbour mouths or similar sites,
where tidal flows are constricted and the tidal stream velocities are accelerated.
Rather than blocking or constricting the tidal flows, tidal fences contain vertical axis
turbines (although horizontal axis turbines would be possible) and capture energy
from the passing tidal stream. They are thus essentially passive devices, which have
limited effects on the natural tidal flows. They also offer the opportunity for roads to
be carried across the tidal fence.
The best example is a tidal fence is the Canadian Blue Energy range of devices.
Their Ocean Turbine is based upon a Davis Hydro turbine design, which is a vertical
axis turbine with vertical blades. The blades rotate in a single direction, regardless of
tidal flow direction. The turbines are housed in large concrete caissons, which are
moored to the seabed and can be joined to form a ‘fence’ across a river or estuary
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mouth. Because they do not constrict flow (except coincidentally), the implications
for upstream siltation are much less serious than for barrages. The Ocean Turbine
has been proposed at a range of scales and six prototypes have been trialled but no
commercial version has yet been built. The company is currently working to build a
20 kW demonstration device, although no date has been set for deployment.
Tidal fences are discounted for early New Zealand deployment for similar reasons to
tidal barrages and impoundments – conflicting uses in harbour mouths (shipping and
fishing access) and difficulties of getting consents in what will be very
environmentally sensitive areas.
2.3.5
Horizontal Axis Turbines
EMEC lists over 70 active projects to develop tidal devices, which include 21
horizontal axis devices, although both numbers are probably under-estimates.
Although there are significant differences in details this class of device is
conceptually similar to the standard wind turbine generator, i.e., a single monopole
tower with an upwind rotor and turbine, connected through a gearbox to a horizontal
axis generator.
There are a number of horizontal axis tidal stream turbines under development.
The best known and most advanced of which are:
1.
2.
3.
4.
Marine Current Turbines’ SeaFlow (Figure 2.11) and SeaGen (Figure 2.12)
SMD Hydrovision’s TidEL device
Clean Current Power Systems (Canada)
Hammerfest Strøm (Norway)
Note this grouping does not include other variants on horizontal axis turbines,
including shrouded turbines (see next section) or ring turbines, like the OpenHydro
device (see Section 2.3.7).
Marine Current Turbines is the clear industry leader in terms of ocean deployments.
It has had a 300 kW prototype, called SeaFlow, installed off Lynmouth in Devon, UK,
since 2003 (Figure 2.11). This device has been used in the tidal stream resource
modelling (Section 4.3.1).
Figure 2.11: The 300 kW SeaFlow Prototype at Lynmouth, Devon
More recently, MCT has successfully installed the first utility-scale tidal stream
turbine in Strangford Lough, Northern Ireland. The SeaGen device incorporates two
600 kW generators, powered by two 16 m twin-bladed turbines, mounted on a cross
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arm, attached to a bottom-resting monopole tower. The device was finally installed in
April 2008 (Figure 2.12). The device is presently being commissioned and is due to
feed electricity into the Northern Ireland grid in August-September 2008. This is thus
the largest grid-connected tidal stream device yet deployed. A hypothetical version
of this device has been used in the resource modelling (Section 4.3.2).
Figure 2.12: SeaGen Deployed in Strangford Lough, Northern Ireland; April 2008
2.3.6
Shrouded Turbines
There are a number of devices that use shrouds (i.e., Venturi tubes) to accelerate the
natural flow, because the available energy in a tidal stream flow is proportional to the
cube of the velocity of the flow. The most commonly cited of these devices is the
Lunar Energy device, which is based on a Scottish design (Rotech RTT). Crest
Energy originally intended to deploy this device in its project (see Section 6.2.2).
Other shrouded devices include the Underwater Electric Kite and the ‘TNEI’ device.
The TNEI device is of interest in New Zealand because Neptune Power has
proposed it as the device it will utilize for its proposed project in Cook Strait, for which
it submitted an initial resource consent application in August 2007. Neptune Power’s
proposed project is described in more detail in Section 6.2.3.
2.3.7
Open Ring Turbines
Open ring turbine designs have been proposed but only two are presently under
development. These are the Clean Current Turbines device and the OpenHydro
device or “Open-Centre Turbine”, which was deployed and is currently under test at
the European Marine Energy Centre in Orkney. In both cases the device consists of
an open-centred ring blade system with a separate generator on the circumference of
the ring of blades. The centre of the ring is open and large enough to allow the
unimpeded passage of fish and possibly small marine mammals. In the case of the
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OpenHydro prototype, the device can be raised and lowered into the current. When
viewed at EMEC in May 2007, the device was awaiting commissioning (Figure 2.13).
Figure 2.13: OpenHydro’s Open-Centre Turbine at EMEC, May 2007 (© PPL)
In 2007 OpenHydro announced that it had won a tender to supply its Open-Centre
Turbines to a project underwritten by the Nova Scotia Government, followed shortly
by another announcement that it will also supply the technology to Alderney
Renewable Energy in the UK Channel Islands. The Canadian development will be at
a new tidal testing centre being established in the Bay of Fundy by Nova Scotia
Power.
The OpenHydro device is interesting in the New Zealand context because it is the
newly chosen technology of Crest Energy for its proposed project in Kaipara Harbour
(Section 6.2.2).
2.3.8
Pressure Devices
There is one pressure device, called the HydroVenturi device, which is under
development in the United Kingdom. The device is a submerged Venturi tube laid on
the seabed or in the water column. The Venturi tube accelerates flow within it in
exchange for a decrease in hydrodynamic pressure. The current small-scale
prototypes have been trialled in rivers. Other pneumatic pressure devices are being
developed.
2.3.9
Vertical Axis Turbines
The second largest group of devices, after horizontal axis devices, are vertical axis
devices. These devices are based on the “Darrieus” rotor design for wind turbines,
although such wind turbines are no longer under development. There are a number
of such devices, including the Kobold Turbine, currently deployed in Sicily (Figure
2.14), Edinburgh Designs’ variable-pitch blade design and the Blue Energy tidal
fence (see Section 2.3.4).
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Figure 2.14: Enermar's Kobold Turbine, Straits of Messina, Italy (© PPL)
There are at least two New Zealand-based projects, which were developing vertical
axis tidal turbines. One of these projects was never made public and is currently on
hold, whilst the other, Tidal Flow Seamills, is planning the deployment of a smallscale prototype device (see Section 6.2.6).
2.3.10 Oscillating Hydrofoils
There is a class of tidal stream devices, which seek to extract energy by use of
oscillating or reciprocating hydroplanes. The best known of these is Stingray, which
comprises a support base and a single hydroplane (although multi-plane devices
were contemplated). Unlike all of the tidal devices listed above, which are passive in
operation, the Stingray required active control. The device operates by active control
of the angle of attack of the hydroplane, which caused it to rise or fall due to pressure
from the passing current (Power Projects, 2005). The rise and fall of the hydroplane
caused a pumping action in a connecting hydraulic arm, which drove a turbine and
generator.
The UK designer of Stingray, the Engineering Business, successfully tested a 150
kW version of the device in Yell Sound in the Shetland Isles. However, despite
attracting some Government R & D funding, the company announced in 2005 that it
was discontinuing development of the device.
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2.3.11 Marine Energy Devices in New Zealand
There is a wide range of options for extracting energy from waves, tides and ocean
currents. Although there are some generic designs for extracting energy, most of the
technologies are immature and there remains significant divergence in design. There
is as yet no common design, as there is for wind turbine generators. Indeed there is
unlikely to be a single design for marine energy converters, because there are so
many different forms of marine energy extraction and an even greater number of
mechanisms to extract that energy.
Some devices extract products other than electricity. They are not considered further
here. Some extraction methodologies will most likely remain inappropriate for New
Zealand conditions – OTEC, tidal barrages – and they are not considered further.
Others are at an early stage – osmotic power and marine biomass – and commercial
developments of other technologies may precede them.
Wave and tidal/ocean current devices have the best potential to contribute to New
Zealand’s medium-to-long-term electricity portfolio. It would not be appropriate or
without risk to select specific manufacturers’ technologies but the potential of generic
technologies for deployment in New Zealand can be ranked (Table 2.4).
Conversion
Technology
Energy Source
Comment
Waves
Breaking Waves
Onshore Oscillating Water
Column
Likely in new breakwater designs
Nearshore Oscillating Water
Column
Possible but difficult to consent
Overtopping Devices
Possible but difficult to consent
Surge Devices
Possible but limited by steeply
shelving coastline
Attenuators
Possible but navigation problems
for large arrays
Point Absorbers
Probable widespread deployment
of arrays
Open Ocean Swells
Tidal/Ocean Currents
Tidal Rise and Fall
Barrages
Prohibitively expensive; potentially
impossible to consent
Impoundments
Very unlikely due to steep
shelving coastline
Fences
Unlikely due to competing uses;
very difficult to consent
Horizontal Axis Turbines
(including shrouded & opencentred turbines)
Current Devices
Probable widespread deployment
of arrays
Vertical Axis Turbines
Possible, subject to successful
design
Pressure Devices
Possible
Oscillating Hydrofoils
Technology problematic
Table 2.4: Potential of Marine Energy Converter Technologies in New Zealand
NOTE: Devices in bold red are considered most likely to be deployed in NZ
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PART 3: DEVELOPMENT OF MARINE ENERGY
3.1
INTRODUCTION
This section describes and discusses factors that control and influence the
international and domestic development of marine energy. Because marine energy
technologies are not yet commercially competitive with the lowest cost forms of
energy – gas, wind and hydro, the role of Governments is critical in establishing
targets, regulatory interventions and providing funding to encourage R & D, earlystage deployments and pre-commercial developments.
3.2
TARGETS AND FORECASTS
Most developed countries’ Governments have set targets for uptake of renewable
energy or, more specifically, generation of electricity from renewable sources to give
their investors (including Governments’ own investments) guidance on their preferred
direction for energy investments. The targets may be statutory, mandatory or
aspirational; short-term targets tend to be statutory or mandatory, whilst longer-term
and usually much higher targets tend to be aspirational (Table 3.1).
Country
2010-15
Australia
-
China
-
Denmark
-
France
-
Ireland
Target: 13.2%
of electricity
2015-2020
Target: 20% of
electricity
Target: 20% of
total energy
Target: 30% of
total energy
Target: 20% of
total energy
Target 33% of
renewable
energy by 2020
2020+
Source
-
Govt. target
-
Govt. target
-
Govt. target
-
Govt. target
-
Govt. target
-
-
Target: 90% of
electricity by
2025
Govt. target
Portugal
Target: 45 % of
electricity by
2015
-
-
Govt. target
Scotland
Target: 18% of
electricity by
2010
Aspiration: 40%
electricity by
2020
Forecast: over
50% of electricity
Forecast: 17 % 30 % of all energy
by 2050
Scottish
Executive
New Zealand
Spain
Basque Region
Sweden
United Kingdom
5 MW of marine
renewables by
2010
Target: 6.66%
of electricity
Target: 10% of
renewable
energy by 2010
Target: 15% of
renewable
energy by 2020
-
-
USA
Regional energy
strategy
-
-
Govt. target
Govt. target
25% of
electricity by
2025
Industry
aspiration
Table 3.1: Total Renewable Energy or Electricity Targets by Country
Key: Total energy targets, total electricity targets, aspirational targets, forecasts
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Relatively few countries to date have set specific targets for marine energy but those
that have tend to be the ones that have had the longest developments in or biggest
commitment to investment in marine energy. A growing number of countries are
making forecasts of, if not setting targets for, the likely contribution of marine energy
to electricity or total energy supply, e.g., the Basque region in Spain.
3.2.1
Renewable Energy and Electricity Policy Targets
Most developed countries have now established renewable energy or renewable
electricity targets as part of wider packages to reduce GHG emissions and increase
uptake of renewables. The European Union has set a binding target on its 27
members of 20% of energy consumption to come from renewable sources by 2020
and has agreed individual targets with each of its member nations, ranging from 10%
to 49% (REN21, 2008). The following focusses on nations active in developing
marine energy.
The UK has set a target of 10% renewable energy by 2010 and had originally set an
‘aspirational’ goal of 20% renewable electricity generation by 2020. However, this
was scaled back in October 2007 to 15%. The Scottish Executive has set a more
aggressive target than the British Government for Scotland – an 18% target by 2010
(apparently already achieved), to be followed by a target of 40% of electricity
generation from renewable sources (most likely, new wind, hydro but including
marine) by 2020. In 2007 Ireland set itself a target of 15% of renewable energy use
by 2010 and 33% by 2020 with a strategic goal to accelerate uptake of renewable
energy.
The Chinese Government’s declared target is to supply 10 per cent of energy (60
GW) from renewables by 2010 and 120 GW by 2020. About 50 GW of the 2010
target is expected to come from small hydro and 10 GW from wind and biomass.
China is at the same early stage as New Zealand in developing its marine energy
potential.
As part of the New Zealand Energy Strategy the Government has set a target of 90%
renewable electricity generation by 2025, although it has not set any technologyspecific targets.
3.2.2
Specific Marine Energy Uptake Targets
Despite the large number of countries with renewable energy targets, few have set
specific marine energy targets (Table 3.2).
Perhaps most aggressively Portugal has an ‘indicative’ target of 50 MW of installed
wave power by 2010 but this may have been an aspiration, rather than a formal
target (EREC, 2004). Either way, the delays to installation of the Pelamis devices at
Aguçadoura and other device installations are likely to mean that this target will not
be met. The 550 MW target by 2020 may not be easily achieved in light of these
recent delays.
The Spanish renewable energy association (APPA) has indicated that there are
13,000 MW of potential marine energy around Spain’s coasts and has proposed a 50
MW target for new marine energy projects (APPA, 2007). There are currently five
wave projects in development: 3 x OWC projects, one OPT PowerBuoy project
(Santoña) and one Pelamis project (Muxia). Two of these projects are within the
Basque region, which has a regional energy strategy target of 5 MW of wave power
installed by 2010.
Despite the advanced state of regulatory thinking and commitment to marine energy
by the United Kingdom, it has not set any firm targets for uptake of marine energy.
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Country
2020
2050
Source
Ireland
Forecast: 84 MW
installed
Target: 500 MW
installed
New Zealand
1 - 2% of electricity
-
Energy Outlook
to 2030
Portugal
Target:
550 MW installed
-
Government
Target
Scotland
Forecast: 10% of
Scotland’s electricity
production
-
Marine Energy
Group Report
(2004)
Spain
Basque Region
5 MW off Basque
coast by 2010
-
Basque Region
Energy
Strategy
United
Kingdom
Forecast: 3% of UK’s
electricity
Forecast: 485
MW
Installed
Target: 20% of
UK’s electricity
Ocean Energy
in Ireland – SEI
– 2005
Carbon Trust
Report (2006)
Table 3.2: Marine Energy Targets and Forecasts by Country
Key: Total energy targets, total electricity targets, aspirational targets, forecasts
The UK Government has forecasted that marine energy could supply up to 3% of
electricity supply by 2020 (as part of its overall target of 15% of energy supply from
renewable energy resources). It also has an aspirational target for marine energy to
supply 20% of electricity by 2050. As part of its proposed targets, Ireland has
proposed a target of 500 MW of installed ocean energy capacity by 2020 with an
interim target of 75 MW by 2012, underpinned by investment to accelerate
technology developments and solutions to infrastructural and economic issues.
3.2.3
Developers’ Commercialization Strategies
Developers’ appetite for investment may depend on individual countries’ resources
and general environment but their individual commercialization strategies are also
important.
Marine energy device developers adopt a range of different
commercialization strategies, of which the end-members are:
1. Pure device developers (e.g., Pelamis Wave Power, Marine Current
Turbines)
2. Pure project developers (e.g., international energy companies, such as
Chevron and Total, and major European utilities, such as Scottish Power
and EdF), which invest in projects, utilizing more than one technology
Between these end-members are device developers, who also invest in their own
deployment projects (e.g., Ocean Power Technologies, Finavera). As marine energy
technologies mature, the industry is likely to see increasing participation by investors,
such as international energy companies and utilities, which have little direct
involvement in specific technologies. These organizations will probably accelerate
the pace and spread of project developments.
3.3
FUNDING MECHANISMS
Most developed countries also have supportive policies in place to promote the
uptake of renewable energy to meet the targets set out in the previous section.
There are a number of different mechanisms, which promote renewable energy or,
more particularly, individual forms of renewable energy.
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The three most common mechanisms are:
1. Government-funded capital grant programmes
2. Renewables obligations
3. Feed-in tariffs
The following sections focus on the best-known schemes and those that specifically
promote uptake of marine energy technologies. Other support mechanisms, such as
production tax credits, net metering and direct investment loans have not been
applied to marine energy technologies. Some Governments have a portfolio of
funding mechanisms from R & D funding to feed-in tariffs to stimulate both
‘technology push’ and ‘market pull’.
3.3.1
Capital Grant Programmes
The British Government introduced capital grant schemes to provide incentives for
marine energy deployments in their waters.
The UK’s Marine Renewables
Deployment Fund (MRDF) was established in February 2006 and offered ₤ 42 million
(NZ$ 111 million) for deployments in UK waters. Developers complained that the
funding process was arduous and the criteria for funding were too severe, particularly
the requirement that devices had to demonstrate 3 months’ continuous deployment
to qualify for funding. This qualification was relaxed to 3 months’ cumulative
deployment. However, at the time of writing only two projects had applied for funding
from the MRDF and none had been awarded funds (RAB, 2008).
The Scottish Executive had a similar scheme of capital grant awards totalling ₤ 13
Million (NZ$ 34 million), called the Wave and Tidal Energy Support scheme
(WATES). The WATES scheme opened between October 2006 and in February
2007 gave varying amounts to 9 projects to establish deployments – largely at the
European Marine Energy Centre – in 2008.
In New Zealand the Minister of Energy introduced the New Zealand Marine Energy
Deployment Fund (MEDF) on 17 October 2007. The MEDF is designed to
encourage device developers to deploy devices in New Zealand waters. The fund is
$ 8 million, nominally $2 million per year for 4 years. The criteria for awards are
somewhat less onerous than the UK’s MRDF scheme. Two bids were received by
the closing date of the first round on 29 February 2008 (NZ Government 2007d). The
Minister announced the first award ($ 1.85 million), to Crest Energy on 29 May 2008
(subject to grant of a resource consent for the project). He also confirmed that the
second round would open on 31 July 2008 and close on 24 November 2008. The
next awards are likely to be announced in May 2009.
The Fund will award up to $2 million per annum for three further years to co-fund
prototype deployments in New Zealand waters. The awards are relatively small in
terms of the costs of deployments but they are clearly attractive to developers, who
must at least match the financial contribution from the MEDF. The Fund is clearly
stimulating both interest in New Zealand from overseas and deployment activities.
3.3.2
Renewables Obligations
Also called renewable portfolio standards (RPSs), renewables obligations are
requirements on electricity generators to supply electricity from specified renewable
energy resources. ROs are essentially used by Governments to promote the
development and uptake of specific technologies, e.g., wind and marine, which
cannot compete initially with established forms of fossil fuel generation. Generating
companies acquire Renewable Obligation Certificates (ROCs) for electricity produced
from eligible wave or tidal energy generators or, alternatively, pay a higher buy-out
fee. In the UK the Government pays ₤ 0.34/MWh of electricity produced and the
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generator acquires one (ROC) for each MWh generated. From April 2009, marinegenerated electricity will get two ROCs at prices set according to generation market
electricity prices.
Scotland has advanced further with a specific scheme for the uptake of marine
energy, called the Marine Supply Obligation (MSO), which was introduced in April
2007. Qualifying generation capacity must demonstrate a minimum period of
operation, a capacity factor and an availability factor. The MSO will pay ₤17.5p/kWh
(NZ$ 46c/kWh) for wave-generated electricity and ₤10.5p/kWh (NZ$ 28c/kWh) for
tidal stream-generated electricity. There is a capacity limit of 75 MW of generation
that will be supported under this scheme. Projects are already being commissioned
to take advantage of this scheme, e.g., Wavegen’s new proposal in Siadar Bay on the
Isle of Lewis in Scotland.
3.3.3
Feed-in Tariffs
Since feed-in tariffs were introduced in the US in 1978, they have been effective in
increasing interest, investment and innovation in new technologies. They have been
particularly effective in promoting wind and solar projects but they are being applied
to marine projects too. A similar feed-in tariff in Germany for solar PV installations
and wind generation has made it the biggest user of both within 10 years.
With respect to marine energy feed-in tariffs, the best known are the schemes for
marine energy in Portugal, Spain, Ireland and Scotland. Portugal has by far the most
generous feed-in tariff for marine energy deployments: € 23c/kWh for the first 12 MW
of wave energy generation installed for 10 years. As a result there are now at least
four projects under development, all of which involve overseas device developers,
deploying in Portuguese waters.
In Spain until 2004 marine energy projects could receive the same feed-in tariff as
onshore wind installations but, in that year, the Spanish Government introduced a
specific feed-in tariff for wave and tidal energy (and geothermal energy) of €
6.89c/kWh for the first 20 years, followed by a € 6.51c/kWh for subsequent years.
For the first 15 years a specific tariff can be fixed for each installation. There are now
at least three major projects, involving overseas device developers, now being built in
Spain.
Ireland has a Renewable Energy Feed in Tariff (ReFIT) in 2006 with different values
of support for different renewable technologies. It offers a € 22c/kWh tariff for marine
energy-generated electricity.
3.4
REGULATORY MECHANISMS
In addition to funding mechanisms, Governments have taken a number of other steps
to promote marine energy through regulatory interventions.
These include
establishment of marine energy centres, reduced permitting requirements for
demonstration zones and space/resource allocation regimes. In reality there is
something of a continuum between these regulatory initiatives.
3.4.1
Marine Energy Testing Centres
The United Kingdom established the first marine energy testing centre, the European
Marine Energy Centre (EMEC), in the Orkney Isles in 2004. It now has a hierarchy of
testing centres, ranging from the New and Renewable Energy Centre (NaREC) - for
testing scale prototypes, to EMEC - for full-scale prototype testing in open-sea
conditions and WaveHub - a new facility of the Cornish coast for supported
commercial projects involving multiple devices. Other countries have followed the
UK’s lead: wave and/or tidal testing centres are now under development on the
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Pacific and Atlantic coasts of Canada and the United States. Smaller-scale testing
centres, in more sheltered locations, have been in established at Nissum Bredning in
Denmark (see Figure 2.4) and Galway Bay, in the lee of the Aran Islands, off the
west coast of Ireland (see Figure 2.8).
3.4.2
Permitting for Prototype/Demonstration Projects
The United Kingdom has established a protocol for permitting of demonstration
projects, which is used at EMEC and elsewhere (DTI, 2005). Marine energy testing
centres have reduced permitting requirements, insofar as ‘blanket’ consents may
have been granted to a centre for deployment with developers having to supply
information to consenting authorities on effects specific to their devices, rather than
full consents. They may have coincidentally reduced the competition for deployment
sites at other locations.
3.4.3
Space/Resource Allocation Regimes
In the United States, the Federal Energy Regulatory Commission (FERC) introduced
a reduced permitting scheme in 2007 for temporary demonstration projects. This
scheme is a hybrid between a demonstration project permitting regime and a
space/resource allocation regime. Developers can apply for a FERC consent, which
would be a ‘fast-track’ process relative to conventional permitting, although the
developers still have to secure State permits before projects can proceed.
At present the FERC scheme appears to be the only dedicated marine energy
space/allocation regime. Such a regime may be appropriate for marine energy
projects in New Zealand to avoid the unregulated ‘land grab’ that occurred with
respect to aquaculture in the early 2000s and led to the current moratorium on
aquaculture developments. A planned approach to marine energy developments, in
much the same way as the oil and gas exploration permitting regime works, would
ensure orderly and viable developments take place.
3.5
INDUSTRY DEVELOPMENTS
Industry developments depend on the maturity of the current industry and the ability
and willingness of existing suppliers to other industries coming together to form a
supply chain for a new marine energy industry. A key feature of development of such
an industry in the UK has been the formation of strategic partnerships between
developers and their suppliers and investors.
Lastly, the pace of industry
development will be controlled by the confidence of private investors to participate in
the industry, taking a lead from Government investment.
3.5.1
Supply Chain Maturity
There is currently no marine energy supply chain in New Zealand, since no projects
of any significant scale have yet been proposed.
However, the necessary
components of a supply chain are in place – working in other industries – and will be
brought to bear on marine energy quickly, if economic and profitable opportunities
exist. However, New Zealand does not have the benefit of over-supplied industries,
such as the offshore oil and gas industry in the UK, looking for future opportunities in
related fields.
New Zealand has the key components of a marine energy supply chain, running from
entrepreneurial project developers to buyers of marine-generated electricity.
However, that supply chain may have little depth, i.e., very limited number of
suppliers in one ‘link of the chain’. It may also have some gaps, particularly in terms
of engineering facilities and equipment. Such a gap – in steel-rolling capacity – was
identified when wind project developers sought to fabricate wind turbine towers in
New Zealand.
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AWATEA has recently completed a consortium-funded study, undertaken by Power
Projects Limited, looking at the current status of the marine energy supply chain in
New Zealand. The study has two outputs – a supply chain ‘gap’ analysis and a
Supply Chain Directory of current companies, consultants and organizations, which
are or could contribute to a strong domestic supply chain. The Supply Chain
Directory was published and distributed on 29 May 2008. The Gap Analysis report
will be completed in July 2008.
3.5.2
Strategic Partnerships
One of the hallmarks of mature marine energy projects in the United Kingdom is that
the lead developer engages with a wide range of potential investors, suppliers and
supporters-in-kind. At one stage in 2006 the Ocean Power Delivery (now Pelamis
Wave Power) website listed 29 consortium partners in the project, making
contributions from R & D to equipment supply.
By contrast most current domestic marine energy projects have a single entrepreneur
or partnership without the depth of investors, suppliers and supporters-in-kind, which
will be necessary to make their first deployments possible. The WET-NZ R & D
programme is unusual in having three contributing parties in the consortium.
3.5.3
Investor Confidence
As noted in the previous section, successful projects require a range of participants,
beyond the initial entrepreneur/investor. Although New Zealand has yet to see the
range of participants involved in domestic projects, they will clearly be necessary to
make deliver successful results.
It is encouraging to see international oil and gas companies (energy companies),
investing in marine energy projects. For example, Total is a joint venture partner with
Ocean Power Technologies in project developments in Spanish and French waters,
whilst Chevron’s technology venture company has invested recently - in Wavebob.
Several major European generation, transmission and distribution utilities, such as
Vattenfall, Statkraft, E.On and RWE, have invested in projects, particularly in
Scotland. The venture capital community has been a small contributor, particularly to
the Pelamis project. To date interest amongst energy companies and utilities in New
Zealand’s marine energy projects (see next section) has not extended to any public
investment in projects.
3.6
SUMMARY
Ultimately the widespread deployment of marine energy technologies will depend on
developers being successful in reducing capital costs and operating costs, so that the
unit cost of electricity from a marine energy converter is competitive with lower cost
forms of energy, such as gas-fired Combined-Cycle Gas Turbines, geothermal and
wind power. Otherwise, marine energy will have but niche application.
Whilst international energy developments, such as the persistent high price of oil,
international efforts to set a price for carbon and the establishment of national and
international emissions trading mechanisms, will promote renewables, the unit cost of
marine energy will fall only through continuing deployments and economies of scale
in commercial production.
Governments, including that of New Zealand, have done much to provide incentives
for marine energy, including capital grant programmes (such as the MEDF in New
Zealand), renewables obligations, feed-in tariffs and introduction of regulatory
assistance. Continuing developer commitment and growing investor confidence will
provide the remainder of the momentum to encourage the development of marine
energy both in New Zealand and overseas.
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PART 4: WAVE & TIDAL ENERGY RESOURCE ASSESSMENT
4.1
INTRODUCTION
Whilst a number of public and unpublished projects have identified potential areas for
marine energy projects in New Zealand, there has been no attempt to quantify the
resources available for commercial extraction.
4.1.1
Marine Energy Resources and Extractable Reserves
There is some confusion in publications as to whether figures cited for particular
areas represent the natural wave or tidal/ocean power available (albeit expressed as
MW of potential electricity generation) or whether they represent the harnessable
energy that can be commercially extracted. Whilst it is relatively easy to make rough
assessments of the naturally available power, it is much more difficult to make
assessments of the extractable energy.
For example, it has been proposed that the tidal flows into and out of Kaipara
Harbour are equivalent to 11,000 MW of potential electricity. However, Crest
Energy’s proposal to install only 200 MW of tidal stream generators in the main body
of the channel leading to the harbour mouth clearly demonstrates that the extractable
energy is a small fraction of the potential energy. Similarly, there has been a
estimate that the tidal/ocean currents in Cook Strait could contain 13,000 MW of
potential electricity generation. Mapping undertaken in this project shows that the
areas where currents reach sufficient speeds to be attractive for generation are a
much smaller part of the Strait and, even there, water depth and competing uses may
be a constraint on areally extensive generation schemes.
4.1.2
Potential Marine Energy Projects
Previous reports on marine energy in New Zealand have taken different approaches
to determining the potential for marine energy projects. PB Power reviewed the
status of marine energy technology developments and tried to derive both unit device
and array sizes (PB Power, 2006). They also reviewed the available marine energy
resources but made no attempt to combine technologies and resources to assess
potential target areas or project sizes.
Sinclair Knight Merz (SKM) undertook a number of Regional Renewable Energy
Assessments, available on the EECA website (SKM, 2006-08), which used simple
‘rules of thumb’ to derive potential marine energy reserve sizes within each studied
region. SKM took the approach of assessing the regional potential wave and tidal
energy resources and then trying to assess the potential of a small range of marine
energy technologies within each region. By and large their studies did not identify
specific projects or sites, where projects might be conducted.
Venture Southland undertook a review of the energy potential of the Southland
region, including wave and tidal energy, but no estimates of the potential resources
or reserves were calculated (Venture Southland, 2003). Power Projects Limited
estimates that the potential wave energy reserves off the coast of Southland could
exceed 2,000 MW with more than 100 MW of tidal/ocean current potential. Together
these studies indicated a combined potential for marine energy around the coast of
New Zealand in excess of 8,000 MW, just short of the current national electricity
generation capacity (Table 4.1).
These numbers should be treated with great caution. They are not based on a
detailed economic evaluation, since the cost of mature wave and tidal energy
generation technologies has yet to be established. The best conclusion that can be
drawn is that wave and tidal energy reserves are likely to exceed the country’s
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requirements for electricity derived from these sources. The country will continue to
have a wide ranging portfolio of generation assets, which will include marine energy,
if the price of marine energy generation technologies can be brought down
sufficiently to be competitive with other forms of generation (e.g., wind, hydro and
geothermal).
Source
Wave
Tidal
(MW)
(MW)
~2,500
>40
~2,500
>30
Wellington CMA
?
>300
Southland
~2,000
>100
>7,000
>500
Location
Regional Renewable
Energy Assessments
SKM (2006 – 08)
This report
Power Projects Ltd
North Island
(ex. Wellington CMA)
South Island
(ex. Southland)
TOTAL
Table 4.1: Summary Estimates of Wave and Tidal/Ocean Current Reserves
Note:
the numbers above should be cited with great caution, taking
account of the summary nature of the calculations.
A three-stage approach has been used in the analysis reported here:
1.
New modelling of wave and tidal/ocean currents around New Zealand,
including site-specific analysis of six potential wave sites and two
potential tidal/ocean current sites. The new modelling is based upon
hindcast data, validated against a number of wave buoy and measured
tidal/ocean current data.
2.
Development of power spectra for three notional wave devices and two
notional tidal/ocean current devices. Devices chosen were modelled on
the existing or generic devices.
3.
Application of the power spectra to the wave and tidal resource at the
specific sites to derive electrical production data.
The aim of the analysis reported here was not to identify specific sites at which
projects could be undertaken with specific technologies: that will be work undertaken
– in much more detail – by project developers as part of a full commercial proposal
for their projects, ahead of submitting consent applications to the appropriate regional
and local authorities. The present study therefore seeks to link high-graded areas
with potential technologies without going to the next level of detail – to determine an
economic value for a project proposed in each area.
4.2
WAVE DEVICE MODELLING
It is essential to understand the performance characteristics of any wave energy
converter (WEC), in order to characterize the power produced by the device. More
technical detail on wave device modelling can be found in Appendices B & C at the
end of this report. The following is a layperson’s summary.
There are a variety of different wave energy conversion methods and different device
designs under development, as described in Sections 2.2 and 2.3. These come in a
range of sizes and generation capacities. Performance characteristics are generally
more difficult to characterize than for other forms of renewable energy, because the
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power produced by a wave energy converter is generally dependent on multiple
parameters.
Raw wave power - the energy flux within a wave field - is proportional to the wave
period (T) and the square of the wave height (Hsig2). The significant wave height
(Hsig), which is the statistical average of the highest 1/3rd of the incident waves, is
used in place of average wave height.
Raw wave power (in kW/m of wave-front) can be found approximately from the
following formula:
P=
ρg 2 2
kW
2
H sig T ≈ (1.0 3 )H sig
T
32π
m ⋅s
Similarly, the power captured by the action and operation of a device is also
dependent on both the wave height and the period. In an ideal world technology
developers would publish accurate performance characteristics that had been
thoroughly calibrated through testing and operational experience. In the real world
most WEC developments are not sufficiently advanced to derive these performance
characteristics. In any event, most WEC developers are either unable or unwilling to
release this information.
4.2.1
Pelamis P750
One developer that has previously published data for their WEC is Pelamis Wave
Power, which published a ‘power matrix’ for the Pelamis P750 device in 2004 in one
of their marketing documents (Figure 4.1). Unfortunately, the matrix is probably now
slightly out-of-date and has not been updated. Although this published ‘power matrix’
serves as a useful template for the industry, it remains one of the only data sets on
any WEC currently in the public domain. The ‘Power Matrix’ approach can also be
misleading in that it provides little information about the response of the device to
spectral shapes, spreads or directions of wave propagation.
The Pelamis power matrix has been used in this study to assess the wave energy
potential of selected sites around the coast of New Zealand. These sites are thus
identified as particularly appropriate, although not exclusively so, for use with the
Pelamis P750 device and its successive modifications.
Figure 4.1: Pelamis P750 Power Matrix (OPD, 2004)
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4.2.2
Scaled 1.5 MW Pelamis or Attenuator
A scaled ‘commercial’ version of the Pelamis power matrix was produced by
University of Edinburgh to anticipate changes in the overall structure and
performance as it developed towards full commercial realisation (Figure 4.2; Scottish
Executive, 2006). This matrix was also applied in the analysis of the chosen sites
around the coast of New Zealand.
Figure 4.2: Scaled 1.5 MW Pelamis Power Spectrum
These figures are superficially similar but note that the axes are different:
1. The ranges and scale intervals of the X axes are different
2. Y axis values (ordinate) are inverted in Figure 4.2. More importantly, the
statistical measure Hrms is used in place of Hsig, although Hsig is widely
regarded as the industry standard. Note: Hrms = Hsig divided by √2.
4.2.3
Generic 750 kW Point Absorber Device
An extensive literature search did not identify any other published power matrices for
offshore WEC devices. To fulfill the scope of the study, and to better represent the
spread of technologies under development, a generic Point Absorber device was
modelled resulting in the matrix shown in Figure 4.3.
The methodology behind this approach is somewhat simplistic but functional. It
involves a basic interpretation of wave power theory, as developed by Falnes (2002b
& c) and others, and was not intended to be comprehensive or device specific.
Further details are beyond the scope of this report but are available in Appendix C.
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Wave height (Hrms, m)
3
-
-
-
-
-
-
-
-
-
750
750
750
695
598
515
444
383
2.75
-
-
-
-
-
-
-
-
750
750
750
738
637
548
472
407
351
2.5
-
-
-
-
-
-
-
750
750
750
750
671
579
498
429
370
320
2.25
-
-
-
-
-
-
750
750
750
750
694
604
521
449
386
333
288
2
-
-
-
-
-
750
750
750
750
699
616
536
463
399
343
296
256
1.75
-
-
-
-
710
750
750
731
679
612
539
469
405
349
300
259
224
1.5
-
-
-
546
609
645
650
627
582
524
462
402
347
299
257
222
192
1.25
-
-
347
455
507
537
542
522
485
437
385
335
290
249
214
185
160
1
-
73
222
364
406
430
433
418
388
349
308
268
232
199
172
148
128
0.75
-
41
125
273
304
322
325
313
291
262
231
201
174
150
129
111
96
0.5
-
18
55
135
203
215
217
209
194
175
154
134
116
100
86
74
64
0.25
-
5
14
34
70
107
108
104
97
87
77
67
58
50
43
37
32
0
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Wave energy period (s)
Figure 4.3: Generic 750 kW Single Point Absorber
4.3
TIDAL & OCEAN CURRENT DEVICE MODELLING
Modelling of tidal/ocean current devices is different from modelling for wave devices
as the time component of the resource is of a different scale. Tidal stream devices
operate, using the same principle as wind turbine generators – generating power
directly from the water current. The recoverable tidal stream power is limited by:
1. Characteristics of the site (water depth, vertical flow profile, turbulence)
2. Environmental conditions (impact of the device on the tidal stream)
More detail on the modelling of tidal/ocean current devices can be found in Appendix
C at the end of the report. A layperson’s summary follows here.
The focus in tidal/ocean current device modelling is on assessing the instantaneous
power that can be extracted from the currents incident on the device and then
assessing the recoverable power derived from the device, acknowledging the various
losses in transferring the kinetic energy in the current to electrical power produced by
the generator.
The losses include:
1. Coupling of the device’s active surfaces, e.g., blades, with the current flow,
swept area of the blades
2. Mechanical inefficiencies in the turbine, drive train, generator and power
conditioning equipment.
These losses are additive: small losses in one component (say 5%) mount up, so
that total efficiencies may be as low as 40%, i.e., only 40% of the power available in
the tidal stream is converted to electrical power. There are also likely to be periods
when current flows are too low to turn the blades (i.e., below the ‘cut-in speed’ of the
device) and periods when the tidal flow exceeds the rated power of the device, so the
device produces at its capacity, rather than that of the available current.
Tidal current velocity is critical in site selection because the power available varies as
the cubic function of the current velocity. Put simply, a doubling of the current
velocity causes an eight-fold increase in the available power.
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Two generic tidal stream generators have been modelled in this study. The
performance derives from power spectra, which are based on, but are not identical
to, the following:
4.3.1
SeaFlow 300 kW Tidal Stream Generator
The Marine Current Turbines’ SeaFlow generator has been deployed off Lynmouth in
Devon since 2003 (see Section 2.3.5). It has a twin-bladed (11 m diameter)
horizontal axis upstream rotor, driving a turbine generator, mounted on a monopole
tower, which has been drilled into the seabed (Figure 2.11). The generator can be
raised from and lowered into the tidal current flow and is capable generating 300 kW.
4.3.2
SeaGen 1.2 MW Tidal Stream Generator
Marine Current Turbines’ SeaGen Generator is the pre-commercial successor to
SeaFlow (see Section 2.3.5). It was deployed in Strangford Lough, Northern Ireland,
in April 2008 and is currently being commissioned. It differs significantly from its
predecessor, principally in having two turbines mounted at each end of hydrofoil,
which can be raised and lowered on the monopole tower. The twin-bladed rotors (16
m diameter) drive two retractable 600 kW-rated turbines (Figure 4.4).
Figure 4.4: Artist's Impression of SeaFlow Device
NOTE: there was no intention in the modelling that these specific devices were being
actively considered for deployment – they were merely used to derive generation
performance estimates.
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PART 5: POTENTIAL MARINE ENERGY PROJECTS IN NEW ZEALAND
Part 4 reviewed the definitions of wave and tidal/ocean current energy resources and
described the methodology for determining potentially extractable resources by
modelling three wave and two tidal stream devices. The next step is to integrate the
performance characteristics of the chosen devices with resource assessments at
selected locations to calculate their generation potential.
5.1
WAVE ENERGY POTENTIAL LOCATIONS
Mapping the wave and tidal/ocean current resources around the New Zealand coast
is a major undertaking. Characterizing the wave environments and potential
resources is complex and time-consuming. The MetOcean Solutions Limited report
(Appendix C) contains a detailed technical explanation of the mapping and
assessment of national, area and site-specific wave resources and presents a wider
range of maps and tables than is contained here. What follows is a summary of the
modelling and mapping with a simplified interpretation in layperson’s terms.
There is a generally accepted ‘rule of thumb’ for wave energy projects, which will
assist an understanding and evaluation of the maps of the wave resources that
follow. A mean spectral wave power of greater than 20 kW/m in an area indicates
potential for wave energy projects there. The actual requirements of a particular site
are clearly much more detailed.
The maps presented here are based on a 10-year hindcast (1998-2007) and
comprise two maps that characterize the resource:
1. Mean significant wave height – this parameter is approximately the mean
(Figure 5.1)
2. Mean spectral wave power – the flux of potential energy associated with the
wave spectrum (Figure 5.2)
There are also three further maps, which integrate the power spectra from the three
wave devices to derive the potentially extracted power from each device. These
maps are:
3. Mean power output from the modelled 750 kW Pelamis device (Figure
5.3)
4. Mean power output from the modelled 1,500 kW variant of a Pelamis
device (Figure 5.4)
5. Mean power output from the modelled 750 kW single point absorber
(Figure 5.5).
These maps are representation of the power that could be extracted by a single unit
of each of three modelled wave devices at any point on the map. it is very unlikely
that single devices will be deployed for commercial applications, other than as early
stage prototypes.
5.1.1
National & Regional Distribution of Potential Locations
The following maps demonstrate that there is a wide range of potential locations for
wave device deployments. The same is not true for tidal/ocean current device
deployments (see Section 5.3.1). For waves, almost any location on west- or southfacing coasts will have significant potential for wave projects. A range of west, south
and east coast locations have been modelled to demonstrate the potential variability
of electricity production around the New Zealand coast.
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Figure 5.1: National Mean Significant Wave Height (1997-2007)
Mapping of the wave energy resources around New Zealand shows that most of the
New Zealand CMA (and EEZ) has waves with a mean significant wave height of
more than 2 m (Figure 5.1). There is a general gradient of declining wave height
from southwest to northeast. Wave heights exceed 2 m very close to west- and
south-facing coasts. Close to the coast and on north- and east-facing coasts, where
the main islands provide some shelter from the prevailing south-westerly swell and
wave directions, nearshore significant wave heights are less than 2 m.
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Figure 5.2: National Mean Spectral Wave Power (1997-2007)
The mean spectral wave power is a measure of the wave energy flux at any location
(Figure 5.2). Mean spectral wave power is measured in units of kW per metre of
wave front (kW/m). It is also common to cite the mean spectral wave power, usually
measured from a wave buoy, for any measured location. Note that the figures on this
map have been validated against six wave buoy locations: the hindcast data are an
accurate reflection of the measured wave resource (see Appendix C, Section 3.4, for
validation details).
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Figure 5.3: Mean Power Output from a 750 kW Pelamis device (1997-2007)
Note: colour scale is specific to this map
Figure 5.3 is the integration of the mean spectral wave power and the power
spectrum from the 750 kW Pelamis device (Section 4.2.1). The interpretation of this
map is that the contour values (measured in kilowatts) define the mean
instantaneous power output from a single 750 kW Pelamis device at any point on the
map. A single Pelamis device located off southwest Fiordland would, on average,
produce in excess of 300 kW continuously. The same device located just outside the
Manukau Harbour would produce an average output of c. 100 kW.
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Figure 5.4: Mean Power Output from a 1.5 MW Pelamis device (1997-2007)
Note: colour scale is specific to this map
Figure 5.4 is the integration of the mean spectral wave power and the power
spectrum from the scaled-up 1.5 MW Pelamis device (Section 4.2.2). The contour
values (measured in kilowatts) define the mean instantaneous power output from a
notional 1.5 MW Pelamis device at any point on the map. A single 1.5 MW Pelamis
device located off southwest Fiordland would produce an average in excess of 1.3
MW continuously. The same device located just outside the Manukau Harbour would
produce an average output of c. 1 MW.
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Figure 5.5: Mean Power Output from a 750 kW SPA device (1998-2007)
Note: colour scale is specific to this map
Figure 5.5 is the integration of the mean spectral wave power and the power
spectrum from the 750 kW SPA device (Section 4.2.3). The contour values
(measured in kilowatts) define the mean instantaneous power output from the SPA
device at any point on the map. A single SPA device located off southwest Fiordland
would produce an average in excess of 600 kW continuously. The same device
located just outside the Manukau Harbour would produce an average output of c. 500
kW.
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5.2
SPECIFIC WAVE ENERGY SITES
Six sites have been analyzed in detail to assess the potential electricity generation
potential of wave device array deployment at each of the sites. The sites were
chosen to represent the range of wave climates around New Zealand:
1. All modelled sites were 6 km from the coast, a reasonably small distance
for a submarine export cable but sufficiently far offshore not to
inconvenience most competing users (i.e., not ordinarily visible from the
coastline)
2. Sites had a range of water depths from 23 to 65 m
3. Sites were selected for their proximity to onshore transmission
grid/distribution network access and proximity to potential load centres.
The sites chosen were all open-ocean locations offshore from Port Waikato, Taranaki
(near Cape Egmont), Gisborne, Wairarapa (near Riversdale), Westport and
Southland (near Orepuki) (Figure 5.5).
Figure 5.5: Location of Sites of Specific Wave Power Evaluation
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5.2.1
Wave Farm Arrays at Selected Sites
Summary statistics of the wave climates at each site have been produced from the
wave hindcast data. These statistics have then been used to calculate the annual
electricity production from a wave farm array at each site. Each modelled wave
device has been applied to each site so that there are eighteen different potential
wave farm arrays.
To assess the power output of each wave farm arrays, the following assumptions
about the layouts of each of the arrays have been made:
1. Each wave farm will comprise fifty wave energy converters
2. The rated capacity of the arrays of Pelamis P750 and 750 kW SPA
devices will be 37.5 MW, whilst the 1.5 MW Pelamis array will be 75 MW.
Keeping the number and capacity of the arrays the same at each site allows a
comparison of the space requirements of the arrays at each site (Table 5.1). Clearly,
any project developer would determine the capacity and number of devices at any
site as part of their economic evaluation of the project.
The density of packing of wave energy devices in an array is an area of active
research and the only current array in the world is three CETO II devices moored
outside Fremantle Harbour. Carnegie Corporation claims that they will ultimately
achieve 8 MW/km2 for the CETO II device. However, it should be noted that these
devices have very low rated capacity, 300 MW, compared with the devices modelled
here. The optimal layout and packing density of devices, and wake and other effects
between devices are still uncertain. The following assumptions regarding packing
density and related effects have been made:
1. 1,500 kW Pelamis packing density: 12.5 per km 2 (Scottish Executive,
2006)
2. Pelamis P750 packing density: 15 per km2 (scaled, after Scottish
Executive, 2006)
3. 750 kW SPA device packing density: 25 per km2, on the basis that these
devices have a much smaller footprint than Pelamis devices.
4. A (pessimistic) power loss of 5% through array effects, although others
use a figure of only 1% (Scottish Executive, 2006).
5. The capacity factor (annual mean yield / nameplate capacity) is calculated
and not assumed.
Rated
Capacity
Sea Room
MW
Km
Pelamis P750
37.5
3.33
15.0
11.25
1,500 kW
Pelamis
75.0
4.00
12.5
18.75
750 kW SPA
37.5
2.00
25.0
18.75
Device
2
Packing
Density
Devices/km
Generation
Density
2
MW/Km
2
Table 5.1: Proposed Wave Farm Arrays
Combining these array designs with the power production for single devices,
calculated from the modelling, enables an assessment of the annual yield (in MW),
annual production (in GWh/year) and the capacity factor of each array.
For an array of Pelamis 750 devices, production is relatively low. This is because
individual devices never achieve their rated 750 kW capacity, even at the most
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energetic location in Southland (Unit Power column, Table 5.2). As a result annual
mean yields are substantially lower than the 37.5 MW nameplate capacity. More
tellingly, the calculated capacity factor is low and very low in the more sheltered
locations (11 – 29%). These are very modest values, since the calculations have not
assumed any availability factor – the devices are continuously available. However,
the evaluation is based upon the device developer’s published power spectrum and,
for that reason, is regarded as reliable.
Location
Unit Power
Array
Capacity
Annual
Mean Yield
Capacity
Factor
Annual
Production
kW/unit
50 x 750 kW
MW/year
%
GWh/year
Port Waikato
129
37.5
6.1
16
53.7
Taranaki
149
37.5
7.1
19
62.0
Gisborne
88
37.5
4.2
11
36.6
Wairarapa
109
37.5
5.2
14
45.4
Westport
158
37.5
7.5
20
65.7
Southland
228
37.5
10.8
29
94.9
Table 5.2: Annual Production from a 50 x Pelamis P750 Array
By contrast the power produced by an array of 50 of the modelled 1,500 kW Pelamis
device is very high. Annual mean yields are in the range 38.7 to 64.3 MW per annum
(Table 5.3). Capacity factors are therefore very high (52 – 86%), probably
unrealistically high. Even if an availability factor (85 - 95%; EPRI, 2003) were
included in the calculation, it would be unlikely to reduce capacity factors to the
figures of between 20% and 40% cited or assumed in other analyses (e.g., EPRI,
2003). The likely source of the over-estimation error is the modelled power
spectrum, which effectively allows the modelled device to generate high levels of
power in a wide range of conditions.
Location
Unit Power
Array
Capacity
Annual
Mean Yield
Capacity
Factor
Annual
Array
Production
kW/unit
50 x 1,500
kW
MW/year
%
GWh/year
Port Waikato
1,236
75.0
58.7
78
514.3
Taranaki
1,275
75.0
60.6
81
530.5
Gisborne
815
75.0
38.7
52
339.1
Wairarapa
999
75.0
47.4
63
415.7
Westport
1,316
75.0
62.5
83
547.6
Southland
1,354
75.0
64.3
86
563.4
Table 5.3: Annual Production from a 50 x 1,500 kW Pelamis Array
The power output from an array of 50 x 750 kW SPA devices has a range of annual
mean yields between 17.6 and 30.5 MW per annum (Table 5.4). This yield translates
to a range of capacity factors between 47% and 81%. Though more moderate than
the figures for the 1,500 kW Pelamis array, these capacity factors are still much
higher than would be expected. Again, source of the over-estimate is most likely the
modelled power spectrum derived for this device.
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Location
Unit Power
Array
Capacity
Annual
Mean Yield
Capacity
Factor
Annual
Array
Production
kW/unit
50 x 750 kW
MW/year
%
MWh/year
Port Waikato
551
37.5
26.2
70
229.3
Taranaki
572
37.5
27.2
72
238.0
Gisborne
371
37.5
17.6
47
154.4
Wairarapa
441
37.5
21.0
56
183.5
Westport
592
37.5
28.1
75
246.3
Southland
643
37.5
30.5
81
267.6
Table 5.4: Annual Production from a 50 x 750 kW SPA Array
5.2.2
Summary of Wave Device Array Locations
Wave spectra derived from 10-year hindcasts have been integrated with model
power spectra for three generic device types. Some significant conclusions emerge
from the calculation of output power from arrays of fifty of the devices:
1. Regardless of the selection of the device, the six locations produce unit
power in the same order: Southland, Westport, Taranaki, Port Waikato,
Wairarapa and Gisborne. Clearly, choice of location is the critical factor in
likely power production.
2. Modelled arrays at Southland, Westport, Taranaki and Port Taranaki
produce comparative amounts of power, whilst the Wairarapa and
Gisborne produce less but remain potential sites.
3. Not surprisingly, the larger the capacity of devices, the higher the unit
power output. The 1.5 MW unit generators produce substantially more
power than the 750 kW devices.
4. The 750 kW attenuator devices produce between one-quarter and onethird of the power of the point absorber devices and between one-tenth
and one-sixth of the output power of the 1.5 MW attenuator devices. This
is the result of the 750 kW attenuator devices rarely achieving their peak
output. They perform best in more energetic conditions, which rarely
occur.
5. The 1.5 MW devices generate approximately 100% more unit power at
the Southland location than they would at the Gisborne location
6. The 750 kW point absorber devices generate about 73% more power at
Southland compared with the Gisborne location.
7. The 750 MW attenuator devices generate 150% more power at the
Southland location than at Gisborne but overall production is low.
8. The 1.5 MW attenuators and 750 kW devices extract a greater proportion
of energy in normal, rather than extreme conditions.
Note that the conclusions here are based on modelled power spectra and the results
are valuable for comparative, rather than absolute, purposes. The very high (and
probably unrealistic) capacity factors calculated from this analysis indicates that
further work is required to refine the analysis. Improved power spectra, based on
real performance measurements, would enable more reliable estimates of power
output but device developers do not routinely make these publicly available.
The analysis does show that the characteristics of the wave conditions at each site
have significant effects on the output power, whilst the selection of device types is
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key decision in determining the likely power production from each array. Selection of
device type would be critical in the less productive east coast locations but device
survival (and capacity factor) are likely to be bigger issues at the more energetic
locations.
5.3
TIDAL & OCEAN CURRENT ENERGY POTENTIAL LOCATIONS
The maps presented in this section are the depth-averaged mean Spring tidal flows,
derived by combined the principal lunar semidiurnal constituent (M2) with the S2
solar constituent. This is a good approximation of the mean of the highest flows that
occur on a monthly basis.
There are two ‘rules of thumb’, which will assist an understanding and evaluation of
the maps of the tidal resource in following sections:
1. All in-stream tidal devices have a ‘cut-In speed’, the point at which the
turbines will self-start and begin to generate power. A current speed of
0.7 m/sec is generally considered the cut-in speed for most horizontal axis
in-stream current devices (Scottish Executive, 2006).
2. However, mean tidal current speeds of less than 2 m/sec are unlikely to
contain much power and would be unlikely to support deployment projects
at the current state of technological development. A nominal minimum
figure of 1 m/sec is required to be attractive for potential deployments.
5.3.1
National & Regional Distribution of Potential Locations
Mapping shows that the depth-averaged current speeds for mean Spring flows over
most of the New Zealand CMA (and Exclusive Economic Zone) are very low, c. 0.3
(Figure 5.6). Since the cut-in speed of in-stream turbines is about 0.7 m/secs, there
are clearly few places, where tidal/ocean current projects will be possible.
The map does show that there are three open ocean areas of interest, namely:
1. Cape Reinga
2. Cook Strait
3. Foveaux Strait & south side of Stewart Island
At this regional scale of mapping, the well-known localised areas of tidal current flow
are not resolved. Locations such as French Pass and Tory Channel in the
Marlborough Sounds, and the large harbour and estuarine environments in the North
Island (e.g. Kaipara Harbour) do offer a potential tidal resource, albeit with a more
limited spatial extent (Bellve et al., 2008). However, these locations fall beyond the
scope of the present report, which considers the open-ocean resources only.
Note that the North Island west coast harbours have not been modelled and mapped
in detail, because they would require detailed bathymetric data. As we shall see, the
largest, the Kaipara Harbour, is already subject of consent applications for a tidal
current project (Section 6.2.2), which may limit the opportunity for other developers.
Cape Reinga was not studied in detail and is not considered further in this report,
because there is a clear lack of transmission and distribution infrastructure at the
northern tip of the Northland peninsula. It is also a considerable distance north of
any significant population or load centres.
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Figure 5.6: Depth-averaged Tidal Current Speeds for Mean Springs Flows
5.4
SPECIFIC TIDAL & OCEAN CURRENT SITES
The national mapping clearly indicates that the eastern side of Cook Strait, Foveaux
Strait and south of Stewart Island offer the best opportunities in terms of the mean
current velocities from the modelling. These areas were subject to more detailed
modelling and six sites, five on the eastern side of Cook Strait (Figure 5.8). One
promising site in Foveaux Strait south of Bluff was selected for detailed evaluation
(Figure 5.9). All six were analyzed, using the modelled in-stream turbines
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Figure 5.7: Selected Modelling Locations in Cook Strait
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Figure 5.8: Selected Modelling Location in Foveaux Strait
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5.4.1
Southland
Detailed mapping of the Southland region shows that there are three areas of
increased tidal/ocean current flows: the south side of the Bluff peninsula and the
northern and southern tips of Stewart Island (Figure 5.9). These last two are
interesting but of relatively little potential since they are some distance from
infrastructure or population. The area south of Bluff is a very attractive location –
close to the coast and approximately 6 kilometres from the Tiwai aluminium smelter.
The five sites within Cook Strait, which were analyzed, are also described here.
Figure 5.9: Depth-averaged Tidal Current Speeds for Mean Springs for Southland
Note: contour shown is 1 m/second speed contour
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5.4.2
Tidal/Ocean Current Arrays in Foveaux Strait and Cook Strait
As with the wave energy sites, six sites have been analyzed in detail to assess the
potential generation from deployments of tidal/ocean current device arrays. The sites
were chosen to represent the range of tidal/ocean current conditions in two areas:
Cook Strait and Foveaux Strait (Figure 5.8).
Some assumptions have been made about the layout of each of the nominal arrays
to enable an assessment and comparison of the power output of the arrays at each
site. For the purposes of this analysis, each array has been designed as follows:
1. Array comprises fifty tidal/ocean energy converters
2. The rated capacities of 50 x 300 kW SeaFlow device arrays (15 MW), and
3. The rated capacities of 50 x 1.2 MW SeaGen device arrays (60 MW)
The density of packing of the tidal/ocean current arrays is also a subject of active
research. The only in-stream array recently in operation is that of Verdant Power in
the East River, New York. However, these devices are relatively small (35 kW units)
and are not directly comparable with 1.2 MW units, such as SeaGen. Packing
densities in the literature range widely between 15 units/km2 (Scottish Executive,
2006) to 200 units/km2 (EPRI, 2003).
The EPRI figure, based upon 18 m diameter turbines and using separation distances
extrapolated from experience with wind turbines - namely lateral spacing of 9 m and
downstream spacing of 180 m (10 rotor diameters), uses a technique that accounts
only for the influence of neighbouring turbines upon others within the array. This
approach can often over-estimate the achievable packing density, as it takes no
account of the actual energy flux incident upon the array, i.e., it is possible to
conceive of an array that captures more energy than is actually available.
The amount of extractable energy at a particular tidal site is a contestable issue that
is receiving attention within academia. The Significant Impact Factor (SIF) is an
estimate of the fraction of the energy in a particular site that can be extracted, without
altering the underlying hydrodynamic characteristics of the site. Some authors (e.g.,
Couch & Bryden, 2004) estimate the SIF at 10%, whereas others (e.g., Salter, 2005)
suggest that it could be significantly higher. The Carbon Trust (Carbon Trust, 2005)
suggests a range of 10 - 50% and emphasizes that it will be unique to a particular
site.
A spacing model developed by the Energy Systems Research Unit of the University
of Strathclyde), taking into account the SIF, indicates a lateral spacing of 60 m and
longitudinal spacing of 250 – 1,000 m (Strathclyde University, 2008. This suggests a
narrower range of packing densities - between 12 and 48 units per km2.
The conservative figure of 15 units/km2 has been selected here but further research
on this subject is required.
There are also serious wake effects, caused by turbulence created by the devices
and this is also an area of active research. Two assumptions have been made:
1. A capacity factor of 40% has been assumed for both devices
2. A power loss of 5% due to wake effects has been used (Scottish
Executive, 2006)
3. Both devices have a packing density of 15 units/km2
The design of the arrays of the two devices is shown in Table 5.5.
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Rated Capacity
Packing
Density
MW
Devices/km
300 kW SeaFlow
15.0
15.0
3.33
1.2 MW SeaGen
60.0
15.0
3.33
Device
Sea Room
2
Km
2
Table 5.5: Proposed Tidal/Ocean Current Arrays
Combining the array design and power production for the SeaFlow device enables an
assessment of the annual yield in MW and annual production at each site (Table
5.6).
Location
Water
Depth
Unit Power
Array
Capacity
Annual
Mean Yield
Annual
Production
Figures 5.8
& 5.9
m
kW/unit
50 x 300 kW
MW/year
GWh/year
CS1
42
48.8
15.0
2.32
20.3
CS2
50
93.4
15.0
4.44
38.9
CS3
69
49.6
15.0
2.36
20.6
CS4
31
107.2
15.0
5.09
44.6
CS5
86
33.0
15.0
1.57
13.7
FX1
31
8.5
15.0
0.40
3.5
Table 5.6: Proposed 50 x 300 kW Seaflow Tidal Current Arrays
Similarly, combining the SeaGen device power production with the array parameters
for a 50-unit array and convolving them with the resource characteristics at the six
sites yields a wide range of results in terms of annual yield in MW/year and annual
production GWh/year (Table 5.7).
Location
Water
Depth
Unit Power
Array
Capacity
Annual
Mean Yield
Annual
Production
Figures 5.8
& 5.9
m
kW/unit
50 x 1.2 MW
MW/year
GWh/year
CS1
42
210.0
60.0
9.98
87.4
CS2
50
400.0
60.0
19.00
166.4
CS3
69
211.0
60.0
10.02
87.6
CS4
31
458.6
60.0
21.78
190.8
CS5
86
143.0
60.0
6.79
59.5
FX1
31
38.8
60.0
1.84
16.1
Table 5.7: Proposed 50 x 1.2 MW SeaGen Tidal Current Arrays
The tables clearly show that the Cook Strait arrays produce significantly more power
than the Foveaux Strait array, which probably reflects the relatively low current speed
at and small area of the Foveaux Strait site. Amongst the Cook Strait sites, CS2 and
CS4 are clearly much more productive than the other sites. Inspection of the maps
confirms that these sites have the highest current speeds and largest areal extent.
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The sites are somewhat areally restricted and the shoreward extensions of the areas
may be too shallow for larger turbines. A detailed study of each site would identify
the potential locations for turbines and thus the practical capacity at each site.
5.4.3
Summary of Tidal/Ocean Current Device Array Sites
Power spectra from two generic tidal/ocean current devices have been integrated
with 10-year hindcasts of current flows from six locations in Cook Strait and Foveaux
Strait. Unit power, annual mean yield and annual power production have been
determined for 50-unit arrays of two generic devices at each site. Some significant
conclusions emerge from the calculation of power outputs from the modelled arrays:
1. Output power varies considerably for each of the devices at each site.
There is about 13 times difference between the power output of the arrays
at the most energetic site (CS4), compared with the least energy sites
modelled here (CS4). Mean velocities at each site are a critical factor in
determining the output from arrays at each site.
2. Regardless of the selection of the device, the six locations produce unit
power in the same order: CS4, CS2, CS3, CS1, CS5 and FX1. The
choice of location is the critical factor in likely power output.
3. There is an obvious correlation between the sites with the highest mean
velocities and the power output from arrays at each site – compare CS2
and CS4 with the other Cook Strait sites in Figure 5.8.
4. The proposed location of the Neptune Power prototype turbine is
coincident with the weakest current location in this study – a good choice
for a first deployment. It would not be the preferred location for a
commercial deployment, when compared with the other Cook Strait
locations.
5. The Foveaux Strait location is much less productive than all the Cook
Strait locations but this is a logical conclusion from the lower mean current
velocity modelled at the site (compare Figure 5.8 and 5.9).
6. The larger 1.2 MW device array produces about 4 times more annual
electricity than the 300 kW device array. This is partly because the 1.2
MW device is a twin-turbine device and also because the larger diameter
blades (16 m versus 10 m) have more than double the swept area.
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PART 6: GROWTH OF THE MARINE ENERGY INDUSTRY
6.1
INTERNATIONAL GROWTH
6.1.1
International Forecasts for Marine Energy Development
In 2006 the British Wind Energy Association – despite its name, the UK trade
association for marine energy – produced the “Path to Power”, a policy review
document seeking to promote marine energy in the United Kingdom (BWEA, 2006).
The analysis undertaken for this study, undertaken in 2005, was based upon
scenarios forecasting the deployment of prototype devices (c. 1 MW), small arrays (c.
5 MW), large arrays (c. 30 MW) and, in due course, significant projects (>30 MW).
The results of the study indicated that the UK could potentially achieve marine
energy deployments totalling 3,000 MW by 2020. This assessment now looks too
optimistic. Present deployments in the UK are a long way short of the cumulative
total (50 MW) forecast for 2008 in the study (Figure 6.1). It also seems unlikely that
the UK will achieve a total of about 220 MW by 2012, even if the EMEC and Wave
Hub facilities are fully occupied by this time.
Figure 6.1: Marine Energy Uptake Forecast for United Kingdom (BWEA, 2006)
Just prior to the BWEA study, the Scottish Executive attempted to forecast the
development of marine energy both within Scotland and worldwide (Scottish
Executive, 2005). The analysis indicated very slow growth in the early 2000s but a
Figure 6.2). Almost 50% of the capacity growth was forecast to occur in the United
Kingdom and the growth of wave energy capacity was forecast to be about 60% of
the total. By 2009 the Scottish Executive expected marine energy capacity to reach
a cumulative total of 84 MW.
In the event, deployments of marine energy have been slower than forecast,
although it is true that the UK has had the highest proportion of deployments and
there have been more wave than tidal deployments. At the end of 2007 the
cumulative total of deployed capacity (not including devices which had been
previously deployed and subsequently removed or become non-operational) was 8
MW (IEA:OES, 2008). This figure will rise later this year due to:
1. Deployment of Marine Current Turbines’ 1.2 MW SeaGen tidal stream
turbine (Section 2.3.5), and
2. Belated deployment of the three Pelamis devices at Aguçadoura in
Portugal (Carcas, 2008).
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Figure 6.2: Forecast Worldwide Marine Energy Capacity Growth (SE, 2005)
Nonetheless, the total capacity of marine energy deployed and operational at the end
of 2008 will not be close to the 54 MW figure forecast by Scottish Executive (SE) in
2004. Worldwide deployments are lagging the SE estimates by about 3 years.
Part of the reason for the lag of deployments is over-optimistic development
timetables for device developments. A recent study in the UK has shown that device
developments tend to more complex than developers envisage (RAB, 2008). Delays
are caused because:
1. Prototype developments take longer than expected
2. By and large, each device is being developed in isolation and there
appears to be little collaboration and pooling of ideas
3. Unexpected events cause significant delays
4. Supply chain capacity is quickly exceeded, so equipment or materials are
not readily available.
Delays in UK-based projects since 2000 have averaged at least two years and over
eight years in one case.
Whilst the absolute figures may be over-estimated, the general trend is probably
reasonable (and similar to wind energy, see below). The increasing rate of device
deployments is driven by a number of factors:
1. A number of relative new companies have moved from start-up to device
deployments very quickly (e.g., OpenHydro: founded in 2005, first
deployment of a 250 kW generator in 2008).
2. Over the last few years some device developers have announced multiple
projects, even though they have yet to develop and deploy a mature
technology (Table 6.1).
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3. Device developers are planning multi-device arrays as their principal
mode of commercial deployment. Deployments, although constructed
incrementally, will be built on a utility scale.
Device developers are signing contracts for multiple international projects, securing
access to multiple sources of funding and supply chains, so that finance and
fabrication capacity are unlikely to be significant brakes on development in future.
The implication is that once developers can deploy a mature technology, the next
phase of growth of marine energy will be very rapid - only slowed by developers’
capacity to secure planning consents for deployment and to build multiple machines.
Taking a representative sample only, six of the more advanced device developers
have publicized projects at 21 locations, which could increase international marine
energy capacity by 634 MW by 2015. (There is little point trying to devise a
comprehensive listing, because many developers are commercially sensitive and
secretive about their plans, new devices may become available in the period to 2015
and there is no guarantee that the projects listed will proceed as proposed).
Projects
Developer
Pelamis
Ocean Power
Technologies
Location
Aguçadoura, Portugal
22.5
Orcadian Wave Farm
WestWave, Cornwall
Atlantic City
Hawaii
Santoña, Spain
Perth, Australia
3.0
5.0
0.04
1.0
1.4
100.0
Makah Bay, Washington
Finavera
(AquaBuOY)
100.0
Ucluelet, B. Columbia
Western Cape,
South Africa
Port Kembla, NSW
Portland, Victoria
5.0
WaveHub, Cornwall
Namibia
Hawaii
Lunar Energy
Republic of Korea
EMEC, Orkney Islands
OpenHydro
6 Developers
1.0
Coos County, Oregon
Rhode Island
Oceanlinx
Capacity (MW)
Bay of Fundy,
Nova Scotia
Alderney, Channel
Islands
21 Locations
Details
3 x 750 kW
Option to add 20 MW
4 x 750 kW
Up to 7 x 750 kW
40 kW prototype
Multi-unit array planned
Multi-unit array planned
10 MW array to grow to 100 MW
1 MW demonstration plant
deployed
FERC preliminary permit
received
Investigative Use permit granted
20.0
Multi-unit array
0.45
27.5
450 kW prototype
Multi-unit array planned
1.5 MW unit to be installed with
15-20 MW to follow
5 MW array
1.5 MW to be followed by 10 x
1.5 MW units
3 x 0.9 MW units
1 MW demonstration, followed
by 300 MW array by 2015
Prototype (250 kW) in place and
second device planned
1 x 1 MW unit under
construction
21.5
5.0
16.5
2.7
300.0
0.5
1.0
??
Multi-unit array (? x 1 MW units)
634.1 MW
Nominal date: 2015
Table 6.1: Examples of Device Developers with Multiple International Projects
Note: Rather than being exhaustive, this listing merely demonstrates the scale of
planned developments by only 6 developers
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6.1.2
Comparison with Growth of the Wind Industry
The growth of the international and domestic wind industry offers an insight into how
the marine energy industry may develop. Internationally, the wind industry grew
steadily once the monopole tower, 3-bladed upwind turbine became the de facto
standard in the 1980s. However, growth became exponential in the late 1990s and
2000s as wind turbine prices dropped and the unit cost of electricity became
competitive with gas- and hydro-generated electricity (WWEA; Figure 6.3).
Subsidies, such as feed-in tariffs, which were introduced in Spain and Germany as
incentives to encourage uptake of wind (and other forms of renewable energy), have
also accelerated uptake.
Figure 6.3: International Growth in Wind Energy Capacity (WWEA)
In 2000 global wind energy capacity was 18 GW; the forecast for 2010 is 160 GW –
an almost nine-fold increase in 10 years.
In New Zealand the growth of the wind industry was similarly slow to start but since
2004 has been even faster than the international rates (Figure 6.4).
Figure 6.4: Growth of Wind Energy Capacity in New Zealand (Clark, 2008)
Note: the notchy nature of above curve is because developments are shown in
the year they were commissioned
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In New Zealand the first 250 kW wind turbine generator was installed at Brooklyn in
1993, before the first 3.6 MW wind farm at Hau Nui in Wairarapa was commissioned
in 1996 (Clark, 2008). It was another four years before the second wind farm,
Tararua I (31.7 MW) became operational and 2004 before the first major wind farm,
Te Apiti (90.8 MW), provided power to the National Grid.
At the end of 2006, total domestic capacity was 160 MW but that doubled to 322 MW
at the end of 2007. A further 165 MW of capacity under is construction and due to be
commissioned in 2008 - 2009. Future growth is likely to be significant with 1,985 MW
seeking or granted consents to build (NZWEA, 2008). Wind energy capacity is
forecast to grow at between 150 MW and 200 MW per annum for the foreseeable
future (Clark, pers. comm.).
6.2
STATUS OF MARINE ENERGY IN NEW ZEALAND
6.2.1
Domestic Deployment Projects
Power Projects Limited is aware of at least 24 domestic marine energy projects that
have been proposed in the last four years. This is almost certainly an under-estimate
because project and device developers tend to work in secrecy. Six of the projects
do not involve deployment of devices and not all of the remaining 18 projects are still
active. The projects range from conceptual ideas to university research projects to
deployment projects like the WET-NZ R & D programme.
Of the 18 device projects, only six have been made public and can be discussed
here (Table 6.2). The 18 comprise six wave device projects and 12 tidal device
projects and they are evenly balanced between device developments and projects
proposing to import overseas technologies. All of these projects were in existence
before the Marine Energy Deployment Fund was announced but few would be ready
to apply for funding.
Name
Crest Energy
Neptune
Power
Power
Generation
Projects
WET-NZ
Tidal Flow
Seamills
Natural
Systems
Limited
Participants
Device/Site
Funding
Comment
Crest Energy
Open Hydro;
formerly Lunar
Energy device
Kaipara Harbour
Self-funded at
present with
MEDF funding to
come
Resource
consents
hearings held 29
May 2008
Neptune Power
TidEL device
originally; new
device with TNEI
Cook Strait
Self-funded at
present
Resource
consent granted
on 10 April 2008
Self-funded;
HERA
contributed to UK
visit in 2007
Project dormant
since UK visit in
June 2007
Government
funding through
FRST
Device deployed
since Dec 2006;
further funding
requested
Unknown
Project dormant
for at least one
year
Self-funded
Project on hold
pending further
progress in UK
device trials
Power
Generation
Projects
IRL, NIWA and
PPL
Tidal Flow
Seamills
Natural Systems
Limited
Pelamis
importation &
domestic
fabrication
WET-NZ’s own
device;
Pegasus Bay &
Wellington
Own vertical axis
turbine;
Karori Rip
HydroVenturi:
Canterbury
irrigation canals
Table 6.2: Current Marine Energy Projects in New Zealand
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6.2.2
Crest Energy Project
Auckland-based Crest Energy originally proposed to deploy the Lunar Energy tidal
stream turbine in the Kaipara Harbour in applications for resource consents
submitted to Northland Regional Council in July 2006 (Crest Energy, 2006). Crest
Energy planned to use 200 units in an extended array. However, new consent
applications were submitted in mid-2007 and parts of the original applications were
withdrawn. The new applications indicate that Crest Energy is now planning to
deploy the OpenHydro ring turbine device (Section 2.3.7) and will move to an
incremental development. Although Crest Energy’s decision to move to the
OpenHydro device may delay deployment of the Lunar Energy device in New
Zealand, the latter may eventually be deployed here in other projects.
Northland Regional Council finally held hearings on Crest Energy’s consent
applications in the week of 26 – 30 May 2008. A decision on the granting of the
consents is expected within 3 months. During the week of the hearings, the Minister
of Energy announced that Crest Energy would be awarded $1.85 million for the
deployment of the first three devices from the Marine Energy Deployment Fund,
subject to grant of a resource consent for the project.
6.2.3
Neptune Power Project
The Neptune Power proposal to establish a tidal stream project in Cook Strait
garnered a great deal of publicity in 2006 and 2007. In July 2007 Neptune submitted
a brief application for consents to establish a single trial turbine at a site near Karori
Rip off the south coast of Wellington (and slightly out of the main part of Cook Strait).
The site is probably close to the site envisaged for deployment by Tidal Flow
Seamills (see Section 6.2.6).
Neptune Power reviewed their plans at a workshop convened by the Electricity
Commission, where they unveiled ambitious plans to deploy 900 MW of tidal stream
devices off Cape Terawhiti by 2021 (Neptune Power, 2007, see next section).
On April 10 2008 Neptune Power was granted a non-notified consent to install a
single prototype device with an export cable connecting to the onshore Vector
distribution network (GWRC, 2008). The consent documents indicate that Neptune
Power plans to deploy its prototype device in late 2009. The proposed site for the
prototype deployment is somewhat east of the site proposed for the utility-scale
development.
6.2.4
Power Generation Projects Proposal
This project was first announced in the Business Section of the Sunday Star-Times in
mid-2004. The project at that time proposed to establish an array of Pelamis devices
on the west coast of the North Island. Power Generation Projects Limited (PGP)
sought support from the Heavy Engineering Research Association (HERA) and some
of its members accompanied PGP staff to the United Kingdom to meet Ocean Power
Delivery in mid-2007. PGP has made no public release on developments since that
time. The project was again featured in an article in the Business Section of the
Sunday Star-Times (on four projects) in May 2008 but the article did not report any
new developments in this project.
6.2.5
WET-NZ R & D Programme
The Wave Energy Technology – New Zealand (WET-NZ) project is a consortium R &
D programme funded by the Foundation for Research, Science and Technology.
The partners are two Crown Research Institutes, Industrial Research Limited and the
National Institute of Water and Atmospheric Research, together with Power Projects
Limited, the co-author of this report.
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The WET-NZ consortium has developed a point absorber wave device, a quarterscale version of which was deployed in Pegasus Bay off Christchurch in December
2006. The device has been significantly modified between open ocean deployments
during 2007-08 (Figure 6.5). The longest continuous deployment was for 35 days
and the device has survived a number of storms. In early 2008 a second version of
the device was fabricated to enable parallel testing to continue; the second device
has yet to be deployed. However, in May 2008 the original device was withdrawn
from Pegasus Bay, refurbished and redeployed at Evans Bay in Wellington Harbour,
where it was tested for about 30 days.
Figure 6.5: WET-NZ’s Point Absorber Wave Energy Converter
6.2.6
Tidal Flow Seamills Project
This project was first proposed publicly in 2004 but further developments have not
been forthcoming. The proposed new vertical axis turbine was to be installed near
the Karori Rip, a well-known tidal current off the south coast of Wellington. Power
Projects Limited understands that a small-scale version of the device has been
fabricated and Tidal Flow Seamills intends to test this device later in 2008.
6.2.7
Natural Systems Limited Project
Natural Systems Limited has acquired the New Zealand and South Pacific licence for
the HydroVenturi device.
Natural Systems’ focus is on small-scale hydro
opportunities on rivers and canals, rather than open ocean currents (Natural
Systems, 2006). It has a proposed prototype site on a Canterbury canal race.
It appears that the HydroVenturi technology is still at an early stage of development
and the company’s interest seems to be either in the UK or the US. The New
Zealand licence held by Natural Systems Limited will accelerate any deployments
here but the delays in device development and the focus on run-of-river or canal
applications may mean that it is some time before larger-scale tidal stream
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applications are realized. For these reasons the HydroVenturi Technology will not be
considered further.
6.2.8
Domestic Marine Energy Project Timetables
There are a number of marine energy project developers now active in New Zealand.
It is instructive to review the proposed development timeframes for the more
advanced of these projects.
Neptune Power has secured consents and is planning its first prototype deployment
by the end of 2009 (Section 6.2.3). The development of its commercial tidal stream
turbine project will then follow an incremental development schedule (Table 6.3, after
Neptune Power, 2007).
Date
2008
2009 – 2011
2011 – 2012
2013 – 2016
2017 – 2021
Proposed Activity
Units Installed
Consents granted for single
prototype deployment
Single twin-turbine prototype
First commercial stage
Second commercial stage
Third commercial stage
TOTAL
Capacity
(MW)
-
-
1
30
60
90
1
150
300
450
180
900
Table 6.3: Proposed Development of Neptune Power Project
Neptune’s proposal is extremely ambitious. It has taken the New Zealand wind
industry 14 years to move from one 225 kW turbine to 320 MW of wind capacity,
utilizing a mature and proven wind turbine technology. Neptune Power’s proposal is
to install greater total capacity, utilizing a new, as yet untested technology, in very
difficult marine conditions. It will be a very considerable challenge to deliver this
project to the timetable proposed by the developer.
Crest Energy has sought consents for its tidal stream project in the Kaipara Harbour
(Section 6.2.2). Its project plan has four incremental stages with progressive
increases in numbers of turbines. Note that the timetable shown takes the mid-point
of the forecast periods for each stage (Table 6.4, after Crest Energy, 2008). This
timetable is much more reasonable but is still a considerable stretch, given that Crest
Energy have yet to secure their consents for the first stage of development.
Undoubtedly, the MEDF grant they recently received will provide a stimulus to their
activities.
Date
2008
2010
2013
2016
2022
Proposed Activity
Units Installed
Consents applied for;
Granted and not appealed?
First commercial stage
Second commercial stage
Third commercial stage
Fourth commercial stage
TOTAL
Capacity
(MW)
-
-
20
20
40
120
20
20
40
120
200
200
Table 6.4: Proposed Development of Crest Energy Project
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6.3
FORECAST GROWTH OF MARINE ENERGY IN NEW ZEALAND
6.3.1
Marine Energy Projects and Deployments in New Zealand
There are some common features to the forecasts for deployment of marine energy,
the timetables put forward by marine energy project developers and the historical
development of wind energy, with which the development of marine energy may have
some corollaries.
1. Assessments made in the early 2000s have proven unduly optimistic.
Active device developments were advancing rapidly at that time but
subsequent progress slowed due to equipment problems, fabrication lead
times and deployment delays. None of the forecasts cited above
accurately predicted the present state of deployments
2. All the forecasts show slow early progress but an accelerating pace of
development post-2010. This acceleration – reflected as exponential
growth curves – matches the actual development of wind capacity quite
well. As a result the 2005 and 2006 forecasts become increasingly overoptimistic post-2010.
Whilst the forecast numbers may have proven over-optimistic, the forecast trends
may still be correct. Early forecasts may have predicted a ‘false dawn’ on the basis
of contemporaneous optimism. The start has been delayed, perhaps, but there is no
reason to think that marine energy could not eventually grow at the 25 - 35% annual
growth rates that the wind energy industry has experienced. The reasons why this
exponential growth may eventually occur are as follows:
1. A trend for device/project developers over the last two years to secure
multiple international project locations
2. Most projects are proposed as multi-unit project deployments
3. The size of proposed multi-unit arrays has increased
4. National testing/deployment centres is increasing, simplifying and
accelerating the time to deployment for devices under development.
The supportive actions in the New Zealand Energy Strategy (MED, 2007) will
accelerate activity here. Nonetheless, the optimism of international forecasts, made
over only 3 – 4 years ago, justifies a more measured forecast for the uptake of
marine energy in New Zealand. Potentially accessible marine energy resources in
New Zealand are large but the cost and difficulties of accessing and harnessing
those resources are very significant, particularly whilst marine technologies remain
immature and the supply chain has yet to develop.
6.3.2
Forecasts for Total Marine Energy Capacity
There have been a number of early-stage forecasts of the potential total capacity for
marine energy in New Zealand. Perhaps the most extensive study to date has been
done by Sinclair Knight Merz in a series of Regional Renewable Energy
Assessments (SKM, 2006 – 2008). The reports document the renewable energy
potential of regional council areas. The series is still incomplete because East Coast,
Wairarapa and Southland studies have not been published. However, the eleven
reports that have been produced have a cumulative total of over 6,000+ MW of wave
energy potential and low hundreds of MW of tidal energy. It would be reasonable to
assume that the total wave capacity would be less than 10,000 MW, since neither the
East Coast, nor Wairarapa will add significantly to the total. Contrary to the results
of the present study, SKM identify c. 1,000 MW of wave power on the Wellington
coast.
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SKM’s total figure is significantly lower than Carnegie Corporation’s 30,000 MW
forecast for wave potential (Carnegie Corporation, 2008). The latter may be a
provisional estimate based on very coarse grid mapping and is probably less reliable
than the SKM estimate. SKM’s forecasts for tidal/ocean current potential are much
lower – in the low 100s of MW. SKM recognizes little tidal/ocean current potential in
the Wellington region, which is contrary to the results of this study and certainly
contrary to Neptune Power’s previous suggestion that there is 12,000 – 13,000 MW
of tidal energy potential in the north-central and eastern part of Cook Strait.
In Power Projects’ view it is premature to attempt a total forecast for the capacity of
marine energy in New Zealand. The large range of estimates made by others
(<10,000 to 30,000 MW for wave) serves to demonstrate the difficulty of doing such
an assessment. In any event these are estimates of the potential resource and the
likely recoverable reserves, i.e., the total capacity of the economic projects, are likely
to be considerably lower than these very large figures.
Whilst these very large estimates may also serve to promote marine energy, they set
an unrealistic expectation of the likely size and timing of the contribution of marine
energy, which may ultimately discredit the nascent industry. A more measured
approach is justified: identifying regional wave and tidal/ocean potential, by
integrating resource data and device performance data to derive potential project
capacity (in MWs) and annual generation capacity (in GWh/year). In due course
project developers will do more detailed analysis matching device performance and
resource assessments on a site-by-site basis.
6.3.3
Forecasts for Uptake of Marine Energy in New Zealand
A number of New Zealand-based organizations have commented on the
development of marine energy technologies, suggesting that they lag behind wind
technologies.
In 2006 the New Zealand Business Council for Sustainable
Development cited dates of ‘demonstration use’ by 2025 and ‘early commercial use’
by 2050 (NZBCSD, 2006). Both sets of estimates are unjustifiably pessimistic and,
recent deployments have pre-empted these dates.
Meridian Energy cites a more optimistic figure of 10 - 25 years (Meridian Energy,
2008) and an overseas investor in marine energy technologies overseas, the Triodos
Bank, has suggested that technologies are only 5 years behind wind devices
(Triodos Bank, 2008). An estimate of 5 – 10 years is probably appropriate with New
Zealand gradually catching up with the leading countries (Scotland, Portugal, United
States and Canada), as domestic interest and investment grow.
With respect to contribution of marine energy to New Zealand’s energy supply
portfolio, the only published estimate was published in the “Energy Outlook to 2030”
(MED, 2006). In the ‘Renewables Scenario’ 200 MW of wave energy capacity was
due to be installed by 2030. This figure seems conservative by comparison with the
plans of the two current project developers.
Power Projects Limited believes that there will be at least three demonstration
projects in the water within the next 3 – 5 years and the first commercial deployment
can be expected within 3 - 7 years. Whilst the present slow pace of developments
here may continue for 3 – 5 years, there is likely to be exponential growth, once
domestic and international device prototypes mature into commercial products. The
pace of development lies partly in the hands of developers, working to reduce unit
costs of marine-generated electricity. However, the macro-economic environment
(ongoing high energy prices, concern about global warming, carbon pricing and
emissions trading) are likely to have a bigger impact in accelerating the development
and uptake of marine energy technologies overseas and here in New Zealand.
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PART 7: GREATER WELLINGTON REGION CASE STUDY
7.1
INTRODUCTION
Previous sections have covered the development of marine energy technologies and
presented the national and regional wave, tidal and ocean current energy resource
evaluation and mapping. Detailed studies of wave resources in six nationally
distributed areas and tidal/ocean current resources in the Southland Coastal Marine
Area (CMA) have been presented. In this final part of the report, a case study for the
Wellington region CMA is presented, covering mapping of the wave, tidal and ocean
current resources, combined with a review of constraints on activities in the CMA,
with particular respect to marine energy and local coastal uses and occupation.
7.2
WAVE ENERGY RESOURCES
It was originally intended that the wave resources of the Wellington CMA would be
evaluated. The proposed area was the same area as that chosen for the tidal/ocean
current study (Figure 5.8). However, early results indicated that the wave resources
in this area were very limited and further work was discontinued. As an alternative a
site on the lower Wairarapa coast was studied in detail instead and the results of the
analysis of this site are presented in Section 5.2.
7.3
TIDAL & OCEAN CURRENT ENERGY RESOURCES
The tidal & ocean current resources of Cook Strait have been widely recognized.
Although there are significant tidal/ocean current energy resources (over 13,000 MW
by some authors) attributed to the region, there has been little attempt to quantify the
recoverable reserves of energy that could be extracted from the tidal and ocean
currents passing through Cook Strait.
The Cook Strait is only 24 kilometres wide at its narrowest part, where it is aligned
approximately north - south (Figure 7.1). In this central region of the Strait, the
Terawhiti Sill is the shallowest part of the divide between the North and South
Islands, with the water depths only to around 240 m. To the north of the Sill, the
Narrows Basin is a broad channel that extends to 350 m deep, while to the south the
bathymetry is typically shallower (~140m), truncated by the cook Strait Canyon
(which is a westerly extension of the Hikurangi Trench. The complex bathymetry has
significant effects on the tidal flows through the Strait (Figure 7.1).
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Figure 7.1: Bathymetry of Cook Strait
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Figure 7.2: Depth-averaged Mean Spring Tidal Currents in Cook Strait
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One of the main reasons for strong tidal flows through Cook Strait is the phase
difference of the principal lunar semidiurnal constituent (M2). Essentially, the high
tide level on the Eastern side precedes the high tide on western side of the Strait by
around 5 hours. It is this difference in timing that leads to the high flows in the Strait,
not the water levels. Indeed, the tidal range in the Cook Strait is relatively modest
(~1 m) compared with most locations in New Zealand. Localized effects within the
Strait mean that the strongest tidal currents are adjacent to the Wellington Southern
coast, where there are clear zones of flow acceleration exceeding 1 m/sec.
Further, the effect of local bathymetry can clearly be seen in the acceleration of the
currents immediately west and south of the peninsula. There are at least four areas
(at least 2 km2 each), where currents may exceed 2.5 m/sec. However, local
turbulence will be a significant factor for tidal project developers in these zones of
high flow.
More details on the modelling and characterization of the tidal current resources in
Cook Strait can be found in Appendix C.
The results of the analysis of five sites in Cook Strait are presented in Section 5.4.2
to enable a comparison with the modelled site in Foveaux Strait.
7.4
CONSTRAINTS ON MARINE ENERGY PROJECTS
Many constraints may affect development of marine energy projects within the
Coastal Marine Area (CMA). These include regulatory requirements to obtain
resource consents, to meet environmental requirements (including monitoring), to
consult with affected and interested parties and to work with others undertaking
competing activities within the same space.
Regional and local authorities may have different requirements on project
developers, depending upon their operative plans (see below) and there may be
specific issues and requirements, with which any project developer will have to
comply. The following sub-sections relate to potential projects within the Coastal
Marine Area (CMA) administered by Greater Wellington Regional Council (GWRC).
A prospective marine energy project developer would do well to make early contact
with the relevant regional council responsible for the CMA, within which the
developer has identified a potential project site, to establish the specific
requirements.
No resource allocation regime for marine energy projects is in place in New Zealand,
the only requirement for device/project developers being that they must secure
consents under the Resource Management Act 1991 (RMA), for space occupation,
erection of structures, taking of energy and, possibly, discharges. The RMA process
is essentially an environmental management regime, operating on a ‘first come, first
served’ basis. The authorities, which grant consents under the RMA, cannot
consider the trade competition aspects of the proposals, nor can they consider the
financial and technical capabilities of project developers, unless there are related
potential environmental implications. The principal focus of the RMA is on
sustainable management of natural and physical resources, and “environment” has a
very broad definition under the RMA.
Before reviewing the actual constraints on marine energy projects, it is appropriate to
review the policies and regulations, operative in the Wellington CMA.
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7.4.1
Operative Policies and Regulations
A hierarchy of legislative and regulatory policies controls activities in the CMA. As
noted above the primary legislative instrument affecting marine energy projects is the
Resource Management Act 1991 (RMA) and later amendments. The next layers in
the hierarchy are the New Zealand Coastal Policy Statement (NZCPS) prepared by
the Minister of Conservation, Regional Policy Statement (RPS) and the Regional
Coastal Plan (RCP), both prepared by the regional council. Each document has to
‘give effect to’ the documents higher up in the hierarchy. The Act gives councils
functions, under section 30 of the RMA, for managing the CMA, with the Minister of
Conservation having a role. More recently, an amendment to section 7 of the RMA
requires consenting authorities to ‘give particular regard to’ the benefits to be derived
from the use and development of renewable energy. The current Labour-led
Coalition government is in the final stages of introducing a National Policy
Statement on Renewable Electricity Generation, which will be notified possibly in
July 2008 and in place by early 2009. This is intended to give councils and the
Environment Court specific guidance on how to deal with nationally significant
renewable energy projects.
The New Zealand Coastal Policy Statement 1994 (NZCPS), currently under
statutory review, established a requirement that particular scheduled activities which
have significant or irreversible adverse effects on the CMA are ‘restricted coastal
activities’, i.e., discretionary or non-complying activities and decided upon by the
Minister of Conservation. The erection of structures, which provide a significant
barrier to water movement, subject to specific limits, e.g., a marine energy converter,
could be a restricted coastal activity. The laying of submarine cables is not a
restricted coastal activity. The Proposed New Zealand Coastal Policy Statement
2008 was notified on 8 March 2008 and submissions closed on 7 May 2008. A
Board of Inquiry will hold public hearings in June – July 2008.
Below the NZCPS is the Wellington Regional Policy Statement (RPS), which aims
to maintain the quality of the Wellington region’s coastal environment. The objectives
and policies are intended to provide an overview of the resource management issues
of the region and policies and methods to achieve integrated management of the
natural and physical resources of the whole region. The RPS gives effect to the
intentions of the NZCPS with respect to activities in the CMA but the RPS also has
positive intentions with respect to marine energy. Noting the current high level of
dependency of the regional economy and communities on non-renewable sources of
energy and the ‘growing number of adverse effects’ that result from the production
and use of that energy, the RPS recognizes marine energy and seeks efficient use of
renewably generated energy, including marine energy.
A Draft Regional Policy Statement for the Wellington region 2008 was issued by
GWRC in early 2008. As required by section 59 of the RMA, the RPS aims to make
‘sustainable management’ the core for management of the natural and physical
resources of the region. This new draft statement specifically acknowledges the rich
renewable energy resources of the Wellington region and will provide direction on the
importance of renewable energy projects, albeit overlaid with considerations on a
case-by-case basis.
The Wellington Regional Coastal Plan (RCP) is the plan that gives effect to the
intentions and provisions of the RMA, NZCPS and RPS in the Wellington CMA,
seaward of Mean High Water Spring tides (MHWS). The present plan promotes
economic and social well being (arising from economic activity, such as electricity
generation), the development and use of appropriate structures in the CMA (e.g.,
would apply to a (marine) energy converter) and ensures that factors, such as the
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effects of waves and tides, sea level rise and coastal hazards on any man-made
structure, are taken into account. There are also policies, whose intent is to address
activities, whose adverse effects are short term, minor or reversible.
This hierarchy of legislative and regulatory instruments provides the basis on which
regional councils (and district councils for shore-based activities) can consider and
evaluate proposed developments, such as marine energy projects. Any developer
would be well advised to understand the constraints imposed by these instruments
not only on any proposed project. The recent award of a non-notified resource
consent to Neptune Power provides a useful case study of the outcome of a marine
energy project consent application.
7.4.2
Neptune Power Consent Area and Export Cable Route
Any marine energy device/project developer must secure consents from regional and
local councils under the RMA 1991, prior to undertaking any physical works. On 10
April 2008, GWRC granted the first (non-notified) consent for a domestic marine
energy project to Neptune Power. The consent has been granted for 10 years in an
area south of Red Rocks off the south coast of Wellington (Figure 7.3; page 72).
Neptune Power has consents to undertake three activities:
1. Place, use and maintain a prototype tidal stream generation turbine and
associated export cables,
2. To disturb the foreshore and seabed, and
3. To occupy the coastal marine area (CMA).
The consent also enables the developer to harness the energy.
Any device developer would need to seek such consents from the regional authority
responsible for the CMA (from high water out to 12 nm from the coast) where their
chosen site lies. There are likely to be further consent requirements for export cables
crossing the beach and for any onshore structures, e.g., a substation or monitoring
facility but these are sought from the local district or city council, Wellington City
Council in Neptune Power’s case. If the cable crosses a marginal strip administered
by DoC, a concession under the Conservation Act may be required.
These activities are ‘discretionary’ in the Wellington CMA, meaning that the activities
are not permitted as of right and the regional council applies its discretion in granting
a coastal permit for the activity. In Neptune Power’s case, the GWRC granted a
‘non-notified’ consent, meaning that public submissions and hearings were not
required. Neptune Power had been required to consult with a number of ‘affected
parties’, and to obtain their written approval under section 94 of the RMA, prior to
GWRC deciding whether or not to publicly notify the application.
Because marine energy deployments are new activities in New Zealand, there is little
information available on their environmental effects. GWRC took the approach that
empirical acquisition of such information, by permitting the deployment of a single
prototype turbine with substantial monitoring equipment, was required. Experience
gained with the prototype turbine will contribute to further consent applications for a
larger-scale multi-unit array, which is what Neptune Power is ultimately proposing
(Neptune Power, 2007).
The consent was granted with immediate effect for 10 years, although the device will
be deployed for only between 3 and 5 years. First deployment is quoted as late
2009. The location of the prototype device and the 11 kV export cable route (6 – 8
km) have been approved. The export cable will be armoured and buried by a subsea
cable plough.
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Neptune Power had to consult with a number of affected and interested parties as
part of their application. The identification of and consultation with affected parties is
good practice for any developer seeking a non-notified consent. Affected parties will
be different depending on the choice of site. Neptune Power consulted with the
following:
1.
2.
3.
4.
5.
Tangata Whenua (Wellington Tenths Trust and Ngati Toa Rangatira Inc.)
The Department of Conservation (DoC)
Wellington Harbourmaster
Cook Strait Commercial Fishing Association
CRA 4 Rock Lobster Industry Association Incorporated
None of these parties raised objections to the Neptune Power proposal.
Other interested parties, which were consulted by GWRC and/or Neptune Power
included:
•
•
•
•
•
Ministry of Economic Development
Energy Efficiency and Conservation Authority
Maritime New Zealand
Ngati Rarua Iwi
Transpower New Zealand (see next section)
Each party offered its views but the only consent condition arising was a requirement
for Neptune Power to provide the actual co-ordinates for their device and export
cable to Land Information New Zealand (LINZ) on deployment.
The resource consent granted to Neptune Power goes on to deal with a number of
environmental issues that arise from the placement and operation of the prototype
tidal stream turbine, effects on pelagic and benthic sea life and the seabed, the
effects of accidental movement and ongoing maintenance (including intermittent
removal) of the device.
As the first deployment project there is a substantial
requirement for monitoring of effects, including marine life (cetacean and marine
mammal) collisions, fish strikes, acoustic effects and electromagnetic fields.
The consent is conditional on Neptune Power and its contractors meeting a range of
specific conditions, relating to the:
•
•
•
•
•
•
Provision of an Operations and Maintenance Plan
Turbine and Mooring Structure
Operational, Maintenance and Monitoring
Monitoring and Reporting
Unintended Detachment
GWRC Review
The requirements on Neptune Power are extensive but no more onerous than for
other marine activities. Future device/project developers should be able to benefit
from Neptune Power’s experiences, assuming that they remain on track to be the first
project to deploy a tidal stream turbine in the CMA. Resource consent applications
are very good, but general, guides to the issues that marine energy project
developers will face in securing consents at their own chosen locations, e.g., Neptune
Power, 2007 & 2008; Crest Energy, 2006 & 2007; Willis and Handley, 2008.
It is important to note that the consents do not provide an exclusion zone on other
activities. Vessels can navigate over the top of the area that the turbine will be
located in and over the export cable route but there is clearly an issue for any vessel,
using trawling or dredging equipment.
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7.4.3
Cook Strait Submarine Cable Protection Zone
The first national grid power cables were laid across Cook Strait in 1964 and the
Submarine Cables and Pipelines Protection Act 1966 was passed to protect them.
There were subsequently a number of instances of cables being displaced, damaged
or even broken, probably as the result of trawling or small boat anchoring. The cost
of repair/replacement runs into millions of dollars, particularly as cable-laying vessels
are not readily available in New Zealand. In 2006 Transpower estimated that
replacement of a cable would cost more than $80 million, whilst repairing a power
cable would exceed $30 million (Transpower and Ministry of Transport, 2006). The
consequential effects of loss of transmission of both electricity and communications
would be severe and, potentially, even more expensive.
As a result of instances of damage to the cables, a general increase in fishing activity
and evidence of illegal fishing, the Act was amended in 1996 to increase substantially
the penalties for damaging the cables or carrying out illegal activities and a
Submarine Cable Protection Zone (CPZ) was created to protect the cables.
Presently the Cable Protection Zone is about 7 km wide but narrows sharply at each
end, where the submarine cables come ashore – at Fighting Bay in Marlborough and
Oteranga Bay on the Wellington coast (Figure 7.3).
The CPZ protects both Transpower’s high-voltage direct current (HVDC) power
cables and fibre optic communications cables owned by other companies. Although
both sets of cables have protective armoured coatings and are designed to withstand
normal seabed and tidal conditions, they are still vulnerable to damage. In some
cases the cables are suspended above the seafloor due to seabed irregularities.
All fishing/anchoring within the CPZ is prohibited with the exception of limited daylight
fishing (crayfish, paua, kina and set nets) within 200 m of the low water mark and
outside the marked landfalls at Fighting Bay and Oteranga Bay. Support boats must
not anchor or indirectly attach themselves to the seabed within the CPZ.
Transpower and the Ministry of Transport jointly manage the CPZ. Activity within the
CPZ is monitored by sea and helicopter surveys and Protection Officers have powers
to order vessels to leave the CPZ and to seize fishing equipment left there (e.g., nets
and cray pots). Vessels with partly deployed nets are considered to be fishing and
vessels, which accidentally drift into the CPZ, are still liable.
If a vessel is found to have partially deployed fishing or anchoring equipment over the
side, then the onus is on the vessel operator to prove that the vessel was not fishing
or anchoring – the reverse of the normal onus of proof under law. Penalties for
breaching the Act include $100,000 for fishing or anchoring, $250,000 for damaging
a cable and forfeiture of the vessel and other property.
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Figure 7.3: Maritime Constraints in the Cook Strait CMA
Note: discontinuities in the submarine cables indicate where the cables are buried
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7.4.4
Marine Reserves
Marine reserves are specified areas of the sea and foreshore that are managed by
the Department of Conservation to preserve them in their natural state as the habitat
of marine life for scientific study. Within a marine reserve, all marine life is protected:
fishing and the removal or disturbance of any living or non-living marine resource is
prohibited (except for permitted monitoring or research).
Marine reserves became possible under the Marine Reserves Act of 1971 (MRA),
largely in response to pressure from New Zealand’s scientific community – hence the
scientific bias in their establishment. Although reserves may now be established with
consideration for recreational and traditional use, the scientific emphasis remains.
However, there is a new Marine Reserves Bill before Parliament, which could change
the purpose from primarily scientific. Although anybody may propose a marine
reserve, it is an onerous process. In practice therefore, they are usually proposed by
the Minister of Conservation, universities, any body administering land, which has a
frontage on the sea or any body engaged in scientific study of marine life or natural
history. There are currently over thirty marine reserves, since the first was
established in 1975. However, the cumulative area of marine reserves around the
mainland territorial sea is small, amounting to less than the area of the smallest
National Park (Abel Tasman).
The principal permitted activities within a marine reserve are public observation of
marine life, navigation and anchoring. Fishing is not allowed, nor are discharges into
a marine reserve. Exploration and extraction of minerals, harbour works and any
marine energy project are also prohibited, unless they were explicitly allowed in the
original Order-in-Council, establishing the reserve. Within the Wellington CMA there
is one principal marine reserve – the Kapiti Island Reserve - and one proposed
reserve, the Wellington South Coast Marine Reserve.
Kapiti Marine Reserve
The Kapiti Marine Reserve links the Kapiti Island Nature Reserve and the Waikanae
Estuary Scientific Reserve on the adjacent mainland. The reserve extends either
side of Kapiti Island and all marine life, habitats, objects and structures within the
reserve are protected (Figure 7.4). The reserve was established in 1992.
Figure 7.4: Kapiti Marine Reserve (source: GWRC)
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Wellington South Coast Marine Reserve
The Ministers of Conservation, Fisheries and Transport have approved the
application for the Wellington South Coast reserve (sometimes referred to as the
“Kupe/Kevin Smith Marine Reserve”, although the name has not been formally
adopted). The reserve has been surveyed but it has yet to be gazetted and created
by an Order-in-Council. Over the years the proposal has progressed through DoC,
Ministry of Fisheries and Ministry of Transport department reviews and the presently
proposed reserve, which covers 840 hectares, includes all foreshore up to the
Figure 7.5). This is slightly smaller than the 969 hectares originally proposed.
Figure 7.5: Final Area of Wellington South Coast Marine Reserve
Although the reserve has not yet been gazetted, it would now be extremely unlikely
that any marine energy project would be allowed to proceed within the proposed area
of the reserve before its gazettal and it will be forbidden once the reserve is formally
declared. Note that Neptune Power’s export cable route runs along the western
boundary of the proposed reserve before coming ashore at the old quarry.
7.4.5
Areas of Significant Conservation Value
The Regional Coastal Plan defines Areas of Significant Conservation Value (ASCVs),
within with most activities are classified non-complying. Outside these areas,
activities such as marine energy deployments may be undertaken subject to
obtaining a consent from the regional council. The current and proposed marine
reserves were covered in the previous section but there are other ASCVs. With the
exception of the Bridge ASCV, which extends between Mana Island and the
mainland coast, the remainder of the ASCVs are limited to estuaries, narrow strips of
foreshore or reefs in separate and discrete locations around the coast (Figure 7.3;
page 72). As such they are unlikely to be interesting to or problematic for marine
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energy project developers, except potentially as crossing points for submarine export
cables.
7.4.6
Environmental Issues
A number of environmental issues will impact on future marine energy projects in the
Wellington CMA. These include, but are not limited to, the following:
1. Extreme weather conditions – Cook Strait and the south coast of
Wellington experience significant periods of extreme weather during winter
months. Maximum significant wave heights have exceeded 10 m in the
period 1998 to 2007, although periods of extreme waves do not persist for
long (see Appendix 3, table 6.16). Such waves are problematic for surfacepiercing or floating devices in terms of survival, general wear and tear and
access for repairs and maintenance. Submarine current conditions are
likely to be less variable and extreme. Nonetheless, all devices will need to
be designed to survive these conditions, whilst operating efficiently in a
range of normal conditions. Project developers will need contingency plans
to address issues such as anchors dragging and unintentional movement of
devices, particularly in light of the location of the HVDC cables entering
Cook Strait at Oteranga Bay. Lifting and movement of subsea cables will
also be potentially problematic.
2. Marine mammals and whale migration – whales, seals and dolphins
occupy or migrate through the Wellington CMA.
Common and dusky
dolphins are frequently observed in large numbers in the CMA and
occasionally in Wellington Harbour (DoC, 2008). Humpback, Bryde’s and
blue whales have all been sighted in Cook Strait and rarely in Wellington
Harbour (McComb, P., pers. comm., 2008). New Zealand fur seals are
known to have breeding sites in Cook Strait.
Whales migrate northwards along the east coast of New Zealand at all
times of the year, with some individuals passing through Cook Strait and
northwards up the west coast of the North Island. There has been a steady
increase in recorded numbers since 2000, possibly as the result of the
closure of the Perano Whaling Station in Tory Channel in 1964. Over 50
humpback whales were recorded passing through Cook Strait in the winter
of 2000 (Gibbs and Childerhouse, 2001). An annual two-week survey has
been conducted in successive seasons with 40 – 45 humpback whales
recorded during these surveys.
The Department of Conservation and Te Papa made whale and other
marine mammal sighting and stranding databases available but mapping of
migration routes would be valuable in assessing locations. Such data is not
available, so site-specific analysis is not possible (Bott, N., pers. comm.,
2008). Until such data is available, the whole of Cook Strait can be
regarded as a migration route for whales.
The effect of marine energy technologies on migrating whales is difficult to
assess and monitoring of deployments, such as the proposed Neptune
Power prototype, will provide the best evidence.
Other marine life – fish and other pelagic species are unlikely to be
affected by submarine, surface-piercing or floating devices. Fish tend to
congregate around marine structures and ‘fish strike’ is very rare. Whilst
concern has been expressed about the effects of rotating blades on
submarine tidal turbines, there is scant evidence from deployments of any
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detrimental effects to fish life, principally because the speed of rotation of
submarine turbines will be relatively slow (~20 revolutions per minute).
Fish and other pelagic marine life should be able to pass through the rotor
without damage. Device developers are mitigating any impacts by either
shrouding the turbine blades or alternatively utilizing open-ring turbines
(see Sections 2.3.6 and 2.3.7).
Whilst the East River of New York may not be the best analogue for the
Wellington CMA, Verdant Power has conducted an extensive monitoring
programme there, including a continuous, almost 3-dimensional sonar
survey (Corren, D., pers. comm., 2008). During the course of this survey,
fish and diving birds have been found to avoid the six in-stream tidal current
turbines and no collisions were observed. Further, as might be logically
expected, fish and other marine life tends to avoid the higher current
velocity flow regions, where the turbines are located, preferring the lower
velocity flow regions, thus naturally avoiding the turbines.
3. Energy extraction – removal of energy by device arrays will cause
downstream changes, though these may be negligible. Wave height
reductions may be up to 10 – 15% behind wave arrays but wave height is
restored by diffraction within 3 – 4 km downstream of the array (EPRI,
2004). Energy extraction by submarine tidal/ocean current turbines is likely
to be less serious, although the effects of turbulence may be greater. Since
Cook Strait currents are reportedly turbulent naturally, any increase in
turbulence may be minimal. Further research is required on this topic.
4. Sediment deposition and movement – energy extraction caused by the
presence of devices or by their energy extraction is likely to cause some
increase in sediment deposition and may affect natural movement patterns.
Again these effects may be minimal and monitoring, which will be required
as a resource consent condition, should provide evidence of any effects.
There will also be considerable environmental benefits from the deployment of
marine energy projects in the region:
1. Absence of visual and noise effects – marine energy devices,
particularly submarine tidal current turbines will have no visual or noise
impacts on humans. Effects on marine life are also likely to be negligible.
Even surface-piercing devices, such as wave point absorber or attenuator
devices are unlikely to be visible, if located sufficiently far offshore.
Although seawater in the region is not particularly turbid, except during
storms, most marine life does not navigate visually. Tidal/ocean current
turbines are unlikely to generate significant audible noise. Neptune
Power’s consent indicates that its prototype will generate less noise than
the Cook Strait ferries and in high current conditions, predicted noise levels
from the turbine will be less than ambient levels. Indeed, it may be
necessary to install ‘pingers’ to warn and discourage curious marine
mammals from venturing too close.
2. Offsetting thermal generation – if and when marine energy technologies
become commercially competitive, developers may favour them, seeking to
minimize or reduce their carbon footprints. The introduction of the
proposed emissions trading scheme and the Government’s stated
‘preference’ for renewable generation will favour marine energy
developments, over fossil fuel generation.
© Power Projects Limited
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30 June 2008
7.4.7
Fishing
Commercial, customary and recreational fishing are important activities in the
Wellington region.
Fishing activities range from recreational and customary
collection of paua, rock lobster and kina close to the foreshore to deeper-water
commercial fishing (i.e., less than 100 m, for hoki and other species) further out in the
CMA. The MRA, Fisheries Act and Submarine Cables and Pipelines Protection Act
exclude fishing activities from the CPZ, marine reserves and ASCVs.
General information on exclusion zones and fishing management areas for specific
species can be found on the Ministry of Fisheries’ NABIS on-line map database
(www.nabis.govt.nz). Further details on species-specific fishing exclusion zones can
be found in reports by the Department of Conservation (Froude, 2004), although the
Ministry of Fisheries administers the exclusion zones.
Fishing interests are likely to have concerns regarding both spatial exclusions around
marine energy projects and potential effects on fish stocks. It is likely that marine
energy projects will require navigation and fishing exclusion zones around them.
This exclusion may have an impact not only on fishing but on fishers’ access to more
distant grounds. There is also a perception that marine energy projects will add to
the cumulative impact of closures for other reasons (marine reserves, AICVs).
Fishers already face these exclusions as well as specific issues, such as Fisheries
Act regulations and a ban on vessels >45 m in length within 1 nm of the coast.
The New Zealand Seafood Industry Council (SeaFIC) advises that fishing activities
are likely in all areas of the CMA that are not subject to exclusions. The absence of
any indication of active fishing does not mean that areas where marine energy
projects may be proposed will not compete for space for fishing or navigation of
fishing vessels. Early direct contact with quota owners and other fishers will
determine definitively the location of areas that are most important for fishing in any
part of the CMA (or alternatively, less important). SeaFIC can direct marine energy
project developers to the appropriate quota owners and other fishers.
7.4.8
Navigation
Cook Strait and the south coast of Wellington are sea areas with constant coastal
shipping. Commercial and fishing vessels pass through Cook Strait and there is
almost hourly passages of the Cook Strait ferries between Wellington and the
entrance to Tory Channel. There are fewer vessel movements east of Wellington
Harbour, around Cape Palliser and off the Wairarapa coast but there is sufficient
activity for shipping navigation to be an issue for marine energy projects.
There are no designated shipping lanes in the Wellington region, although there is a
Voluntary Code For Vessels Carrying Oil Or Other Harmful Liquid Substances In Bulk
(Maritime NZ, 2006). The code has some advisory routes for entry into Wellington
Harbour. These are based on safe operational behaviours and general ‘rules of the
road’:
From the East: vessels must keep at least 5 nautical miles off Cape
Palliser and 3 nautical miles off Baring Head until due south of the harbour
entrance.
From the West: vessels must pass midway between the Brothers and
Fisherman’s Rock, then at least 4 nautical miles off Cape Terawhiti, thence
4 nautical miles off Karori Rock.
There is also a designated pilot boarding station for vessels requiring a pilot. The
relatively large number of ferries and other vessels not requiring pilots indicate that
© Power Projects Limited
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30 June 2008
vessels unfamiliar with the area should take care in the area of the harbour. There
are also advisory notes for vessels departing Wellington Harbour. More details can
be found in the Maritime NZ publication and the NZ hydrographic chart for Wellington
Harbour (Figure 7.6). Maritime NZ does collect ship route tracking data and they can
advise project developers on conflicting navigation uses.
For marine energy projects, it is obviously vital that developers avoid areas of
frequent shipping use. In law there is a presumption that any vessel can go
anywhere. In practice, the area is subject to the Greater Wellington Navigation and
Safety Bylaw, administered by the Greater Wellington Harbourmaster.
Figure 7.6: Approaches to Wellington – LINZ Chart NZ463
Copies of this and other hydrographic charts available at www.linz.govt.nz
7.4.9
Other Exclusions
There are a number of other Regional Coastal Plan constraints, which might have an
impact on marine energy projects in the Wellington CMA. These include the
following:
1. Mooring areas (Wellington and Porirua Harbours, Pauatahanui Inlet and
Island Bay)
2. Commercial developments (Wellington Harbour)
3. Aquifer zones (Wellington Harbour)
4. Water quality classes (nearshore areas managed for water contact
recreation, i.e., swimming or surfing, and shellfish gathering purposes)
Maps
of
these
areas
are
available
on
the
GWRC
website
(www.gw.govt.nz/section866.cfm) and they are shown in Figure 7.3 (page 72).
These areas are likely to present little or no difficulties to marine energy projects
since the majority of them lie within Wellington Harbour, Porirua Harbour,
Pauatahanui Inlet or very close to shore, in areas where marine energy projects are
unlikely to be developed, particularly in the first instance.
© Power Projects Limited
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30 June 2008
7.5
SUMMARY
The tidal/ocean current resources of the Greater Wellington CMA present an
attractive target for future marine energy investigations. Undoubtedly the mapping
presented here and the proposed deployment of the prototype tidal/ocean current
device by Neptune Power will raise interest in the Wellington CMA. The Wellington
CMA represents the best tidal/ocean current resource mapped in this study, taking
into account other factors such as access to transmission infrastructure and markets.
It is likely that other projects will be proposed here in due course.
Modelling of wave resources during the course of the present study indicates that
these are not so attractive. The results for the Wairarapa location are probably
analogous to the results that might have been obtained in Cook Strait or the south
coast of Wellington. It is likely that other areas will be developed first, before the
Wellington CMA becomes attractive.
Significant constraints to marine energy projects will have to be overcome or
addressed by project developers. These include intrinsic issues, such as site
selection, device survival and absence of information on environmental effects, and
extrinsic issues, such as competing uses, lack of information on shipping movements
and whale migration. However, there is an even-handed regulatory environment and
information gained from the Neptune Power prototype deployment will be directly
useful to both developers and regulators. The Wellington CMA is likely to be one of
the first areas to see larger-scale tidal/ocean current developments in New Zealand.
© Power Projects Limited
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30 June 2008
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Turning the Tide: Tidal Power in the UK. Sustainable
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Regional Renewable Energy Assessments. 12 Consultants’
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© Power Projects Limited
Page 84 of 84
30 June 2008
APPENDIX A: CONTRACT, METHODOLOGY AND FORECASTS
© Power Projects Limited
-A-
30 June 2008
APPENDIX A: CONTRACT, METHODOLOGY AND FORECASTS
A.1
CONTRACT AND WORKING ARRANGEMENTS
Dr. Bruce Smith of the Electricity Commission (EC) initially commissioned the
research work but once in progress, Power Projects Limited proposed a consortium
approach, including the Energy Efficiency and Conservation Authority (EECA). Once
agreed between the parties, PPL contracted for this work under EC contract T60.
Power Projects Limited then sub-contracted MetOcean Solutions Limited to
undertake the resource reviews, integration with device performance characteristics,
site-specific and regional marine resource mapping.
Dr. John Huckerby and Mr. David Findlay of Power Projects Limited in Wellington
undertook their share of the work between 14 February and 30 June 2008, whilst Dr.
Peter McComb, Dr. David Johnson and Dr. Brett Beamsley of MetOcean Solutions
Limited in New Plymouth and Raglan between 4 March and 30 June 2008. There
was close co-operation between the two companies to ensure that performance
information from individual devices was integrated with area-specific wave and tidal
resource assessments.
A.2
METHODOLOGY AND DATA SOURCES
Power Projects completed the overall report but specifically Parts 2 and 3 with
comments by MetOcean Solutions. Parts 2 and 3 use only publicly available sources
of information and knowledge by Power Projects Limited through its international
contacts and involvement with the International Energy Agency’s Ocean Energy
Systems Implementing Agreement (IEA:OES-IA). Power Projects has attended three
of the last four IEA:OES Executive meetings, contracted through the Aotearoa Wave
and Tidal Energy Association (AWATEA).
The IEA:OES-IA is dedicated to
disseminating an understanding of international developments in marine energy.
Various recent Government publications have been used, including:
•
•
•
•
Energy Outlook to 2030 (MED, 2006)
New Zealand Energy Strategies (NZ Government, 2007a & b)
Emissions Trading Scheme (NZ Government, 2007c)
Energy Data Files (MED, 2005 - 7).
International publications by the US-based Electric Power Research Institute (EPRI,
2003) and two UK-based organizations, the Carbon Trust (2006) and, most recently,
the Sustainable Development Commission (SDC, 2007) have proven very useful.
Finally a review by the Renewables Advisory Board in the United Kingdom provided
valuable evidence on the effects and benefits of UK Government funding for marine
energy projects there (RAB, 2008).
Part 4 summarizes the wave and tidal energy resource assessments that have been
undertaken in this study:
1. Quantifies the wave and tidal stream (both estuarine/harbour and open
ocean) resources, and
2. Specifically models two tidal stream areas and six wave energy areas,
chosen for a range of wave conditions,
3. Each one of the wave energy sites has been further analyzed by
simulating the installation of three generic wave energy converters or two
tidal stream energy converters to derive energy conversion and
production in each area.
© Power Projects Limited
- A-i -
30 June 2008
Appendices B & C describe the methodology and technical details of the resource
and device modelling, which underpin the resources assessments.
Part 5 was the most difficult to complete, because there is no current public inventory
of potential projects, as there are for wind, hydro and geothermal generation. It is
therefore not possible to analyze an existing inventory and make comparative
judgments about the potential of each project. With the exception of a small number
of proposed projects outlined in media articles, there has not been any systematic
review of the domestic potential for marine energy, other than ‘technically feasible’
resource assessments (e.g., SKM, 2006 - 2008).
Part 6 integrates marine energy converter information and areal resource
assessments with constraints facing any marine energy projects. The Wellington
CMA is used a case study to set out the opportunities for and constraints on any
intending marine energy project development in this area. The case study serves as
a general guide to the development of any marine energy project in New Zealand,
although the opportunities and constraints will differ between sites.
A.2.1 Forecasting
This report is also a speculative forecast of the future of marine energy in New
Zealand. As far as possible it is a factual and objective account of international and
domestic devices and deployments to date. Forecasting future developments is
obviously more difficult, with the possibilities ranging from a vibrant domestic industry
supplying local projects and exporting to international markets to a stillborn
renaissance, similar to the development of first-generation marine energy devices in
the 1970s. It is notable that the New Zealand Electricity Department and its
successor, the Electricity Corporation of New Zealand, conducted reasonably
extensive research on the potential for marine energy in the 1980s and early 1990s.
PPL has previously sought access to reports produced by these organizations but
access has been declined.
With respect to individual devices Power Projects Limited has based its conclusions
on future development and New Zealand deployment of these devices on the past
history and current status of device developments. Absence of or low ranking of any
device mentioned in this report is not intended to criticize or disadvantage these
devices. Devices and companies mature at changing rates and their relative
competitive positions change over time. The current clear leaders could be
overtaken as device designs converge to single niche designs, just as the designs of
the 1970s have been overtaken by Pelamis, SeaGen and the other devices
described here. With so many devices at such different stages of development, it is
impossible to forecast the future accurately.
Notwithstanding the above, Power Projects Limited is confident that marine energy
will become an important generation source in future. The first 2 kW device was
deployed in December 2006 (the WET-NZ device in Pegasus Bay in Christchurch)
and bigger devices are likely to be deployed as a result of encouragement from the
Marine Energy Deployment Fund (NZ Government, 2007d). The first device was
recently moved to Wellington Harbour (May 2008) and a second 2 kW device will
soon be deployed in Pegasus Bay.
A.2.2 Cost Estimates
Cost figures, including cost ratios, in this report are cited first as the cost or ratio cited
in each reference used (i.e., the overseas currency in money of the day terms). The
figures are then directly converted to New Zealand dollar (without any adjustment for
time) at the 2008 mid-month exchange rate for each currency (IRD, 2008):
© Power Projects Limited
- A-ii -
30 June 2008
NZ$ : US$
=
0.7540
NZ$ : ₤
NZ$ : Euro
NZ$ : AU$
=
=
=
0.3769
0.5385
0.8764
A.2.3 Acknowledgements
Power Projects would like to acknowledge the following:
•
MetOcean Solutions Limited for their excellent mapping work and close
co-operation in the production of this document
•
David Findlay for his work on the wave and tidal stream device modelling
•
The various device developers for the information that they provided via
their websites and presentations
•
At Greater Wellington Regional Council, Piotr Swiercynski (Policy Advisor)
and Mike Pryce (Wellington Harbourmaster) for advice and feedback on
the Wellington constraints to marine energy projects; Nick Page (GIS
Officer) for maps and constraints data in GIS format
•
Alan Sheppard and Nici Gibbs at the Seafood Industry Council for advice
on fishing issues in the Wellington CMA and further afield
•
Evan Perry of EMS and Andy Wilson of Vector for GIS information on the
Transpower Grid and Vector distribution network layouts, respectively
•
Steve Smith of Department of Conservation and Anton Van Helden of Te
Papa Tongarewa for information on whale migration, sightings and
strandings
© Power Projects Limited
- A-iii -
30 June 2008
APPENDIX B: MODELLING SINGLE POINT ABSORBER DEVICES
© Power Projects Limited
-B-
30 June 2008
APPENDIX B: MODELLING SINGLE POINT ABSORBERS
B.1
INTRODUCTION
The Pelamis P750 wave energy converter is only one of a wide variety of devices
currently under development. It is, however, the only one for which a power
spectrum has been published. In the absence of published data for other WECs, a
power spectrum for a generic single point absorber (SPA) was created to demonstate
how the performance from different devices might be compared. The power
spectrum, developed in the following section, is not intended to be representative of
any particular device, it is simply illustrative of the performance of a generic single
point absorber.
WECs convert the energy flux within an incident wave field into useful energy. Often
the most convenient form of ‘useful’ energy end product is electricity. However, in
order to produce electricity of acceptable quantity and quality, the device will have to
perform a sequence of energy conversions
The energy from the wave field interacts with a floating or active body (or bodies),
which dynamically responds and, consequently, stores mechanical energy. The
kinetic and potential energy in the waves, expressed as motion vectors of heave,
surge and pitch, can be converted to electricity via several intermediate steps, e.g.,
kinetic & potential energy to mechanical energy to magnetic energy to electrical
energy.
The wave power, or energy flux, in a wave field can be found from the equation:
Equation 1
P=
ρg 2 2
kW
2
H sig T ≈ (1.0 3 )H sig
T
32π
m ⋅s
Equation 1 gives a value of the energy flux per metre of wave front. A well-designed
wave energy device will aim to maximize its capture width and therefore its yield (i.e.,
its coupling efficiency to the wave). For a terminator device (such as an oscillating
water column device), the maximum theoretical energy capture is approximately
equal to the physical width of the device, measured perpendicular to the direction of
wave propagation. By contrast, however, Falnes (2002B & C) has shown that “the
maximum energy which may be absorbed by a heaving axi-symmetric body is equal
to the wave energy transported by the incident wave front of width equal to the
wavelength divided by 2π”. A single point absorber WEC is roughly equivalent to a
heaving axi-symmetric body. This result may be termed the maximum absorption
width dMAX.
Equation 1
Where λ is the wavelength, which is related to the period through the dispersion
relationship. For deepwater the dispersion relationship is given by:
Equation 2
gT 2
λ=
2π
Falnes also derived an equation for the upper bound of the Power-to-Volume ratio for
a WEC. This is summarized as:
Equation 3
© Power Projects Limited
P πρgH
<
V
4T
- B-i -
30 June 2008
where V is the volume of the absorber, and H and T and the wave height and period
respectively.
These equations can be combined to calculate a theoretical maximum power capture
for a particular axi-symmetric point absorber, moving in one degree of freedom (i.e.,
heave), given the volume of the device, the wave period and wave height,
substituting the significant wave height, Hsig for spectral sea states ().
Equation 4
PMax
ρg 3 H 2T 3
ρg 3 H 2T 3 VπρgH
IF
≤
3
128π 3
4T
≤ 128π
3 2 3
VπρgH IF ρg H T ≥ VπρgH
4T
4T
128π 3
The relationship represented by this equation is theoretical and, whilst it can be used
to demonstrate general trends, it is unlikely that a real device will ever approach this
sort of performance. The reasons for the disparity between theoretical and actual
performance are threefold:
1. Any device will suffer from inefficiencies at each energy conversion and
transmission stage and,
2. Point absorbers are essentially resonant devices, which - for optimum
3. Hydrodynamic performance - must fulfil a set of criteria defining their
dynamic interaction with the wave field.
4. Equation 6 (upper bound of the power-to-weight ratio) approaches
equality as the volume goes to zero. This is clearly unrealistic.
B.2
RESONANCE
Power is the product of force and velocity. For optimal power capture, one
requirement is that the force applied to the power take off device must be in phase
with the velocity of the device. When this condition is met the device resonates with
the wave field. A surface-piercing free-floating body is subject to a natural oscillation
in heave, whose period is governed primarily by the relationship between its mass
and its volume (hydrostatic spring). One condition for resonant behaviour is that the
natural period of the device is the same as that of the incident waves. This is a very
simplified discussion of an involved subject but it is sufficient for this analysis.
The relative absorbed-power response can be calculated from Equation 6.
Equation 5
RAPS =
1
1+ (ω 0 /2δ ) 2 (ω /ω 0 − ω 0 /ω ) 2
In the above equation, the parameters, ω and ω 0 refer to the incident frequency and
natural frequency of the device respectively. The system damping (from the power
take off system and viscous effects) is represented by the δ term.
Figure B1 shows how the response of a point absorber varies with the period of the
incoming waves. The value of the response has been non-dimensionalized. In this
instance the device has a natural period of 8 seconds and its response is narrow
banded, i.e., it exhibits reasonable performance across a narrow band of periods.
A curve similar to the one above was used to modify the ideal performance
characteristics and to take into account the frequency sensitivity of the device.
© Power Projects Limited
- B-ii -
30 June 2008
Figure B1: Typical Response for a Single Point Absorber
B.3
POWER TRAIN EFFICIENCY
Inefficiencies within the power take off system of the device will also vary depending
upon the operating conditions, for instance a hydraulic pump or motor as used in a
transmission system, will have an optimum operating point that will most likely
depend on both the pressure and the flow rate within the system. Its efficiency may
well drop off dramatically as it deviates from this point. Similarly other hydraulic
devices such as Pelton wheel turbines and electrical generators will have
performance characteristics that will vary with the operating conditions while
hydraulic transmissions will have a pipe loss that varies with the square of the flow
rate and the pressure component. Electrical conversion units such as generator
sets, transformers and power conditioning units will all demonstrate a power loss
(usually manifested as heat) whose magnitude will depend on the instantaneous
operating conditions.
The configuration of components within the power train, and the influence of the
performance characteristics of these components upon the performance of the
overall unit is, by its nature, device specific, and in the interests of maintaining a
generic approach, no attempt has been made here to include the sensitivity of the
power train efficiency to the wave height and period within the operating
characteristics of the generic point absorber. As a compromise a flat power train
efficiency, across both wave height and period, was used to imply the impact of these
inefficiencies while preserving the original trends.
Equation 6
B.4
Pmod = ηPTO * RAPS * PMax
DEVICE RATING
Finally, wave power machines must include the facility to ‘rate’ their developed power
in order to avoid overloading the electrical and mechanical components within the
drive train. This feature has been included within the generic point absorber model by
flattening off the power matrix above a rated value. See Equation 7.
© Power Projects Limited
- B-iii -
30 June 2008
Equation 7
B.5
P P
≤ Prat
Pmat = mod Mod
Prat Otherwise
ASSUMPTIONS
This approach assumes more than it can rely upon. It therefore can only be taken as
a first pass attempt to identify trends within the confines of basic wave power theory.
Assumptions taken include:
•
•
•
•
•
Linear wave theory, and the deepwater dispersion relationship
Flat efficiency characteristics for all power conversion and transmission
devices.
Strict resonant behaviour of the absorber device
Damping, and gross efficiency data.
Potential flow theory – no viscous hydrodynamic component.
These assumptions are justified by the nature of the report. The onus remains upon
device developers, and possibly the academic community, to produce verifiable
device characteristics, and, in the absence of these, a simplified attempt was made
to predict general trends and representative characteristic curves. It is understood
that a full study of these phenomena is beyond both the scope of this report.
A full analysis of the performance characteristics of a wave power device is an
involved process that will most likely require hydrodynamic analysis (using a potential
flow solver) to determine the hydrodynamic properties of the active body. It may also
require a more detailed computational fluid dynamic analysis of key elements, or
indeed the device itself. A separate mooring analysis is generally required to
account for the – often non-linear – interaction with the mooring attachment, and a
dynamic model of the power take off and control systems will all have to be
integrated holistically to allow for complete specification of the device performance.
Much of this work is numerical in nature, and sufficiently involved to require both
extensive computing resources and the judicious application of assumptions.
B.6
RESULTS
A number of figures are reproduced here showing the resulting power matrices for a
number of hypothetical point absorber devices. The input characteristics are shown
in Table B1 and Figures B2 to B4.
Banding
Rating (kW)
Natural Period (secs)
Damping
Volume (m3)
Efficiency (%)
Narrow
Medium
300
8
0.01
472
60
350
9
0.015
301
60
Broad
500
10
0.03
445
40
Table B1: Properties of Modelled Single Point Absorbers Wave Energy Converters
© Power Projects Limited
- B-iv -
30 June 2008
Figures B2 – B4: Power Matrices for Modelled Single Point Absorbers
© Power Projects Limited
- B-v -
30 June 2008
B.7
COMPARISON WITH PUBLISHED PELAMIS RESULTS
It is interesting to compare the power matrices produced through this method and
those generated thorough more sophisticated modelling and testing. To this end,
the published 750 KW Pelamis spectrum (Figure B5) is shown alongside several
attempted correlations (Figures B5 – B8).
Figures B5 – B8: Comparison of Pelamis spectrum with Modelled Spectra
Wide bandwidth devices most closely replicate the Pelamis spectrum (compare
Figures B5 and B8) but the exact matrices are difficult to match exactly. The stepped
effect in the high frequency, large wave-height area of each matrix, is present in the
published results and replicated in the present modelling. This stepped effect
corresponds to a high frequency breaking wave region, which is either unrealistic or
sufficiently detrimental to the performance of the device to require all developed
power to be shed (Table B2).
© Power Projects Limited
- B-vi -
30 June 2008
Rating (kW)
Natural Period (secs)
Damping
Volume (m3)
Efficiency (%)
Comparison 1
750
11
0.1
471
40
Comparison 2
750
11
2.0
402
35
Comparison 3
750
9
0.05
262
60
Table B2: Comparison of Properties of Pelamis P750 with Modelled Results
© Power Projects Limited
- B-vii -
30 June 2008
APPENDIX C: “MARINE ENERGY RESOURCES: OCEAN WAVE AND
TIDAL CURRENT RESOURCES IN NEW ZEALAND”
© Power Projects Limited
-C-
30 June 2008
MARINE ENERGY RESOURCES
Ocean wave and tidal current resources in New Zealand
Prepared for the Energy Efficiency and Conservation Authority and
the Electricity Commission of New Zealand
May 2008
Suite 3, 17 Nobs Line, PO Box 441
New Plymouth, New Zealand
T: 64-6-7585035 E: enquires@metocean.co.nz
New Zealand Marine Energy Resources
Report Status
Version
Date
Status
RevA
RevB
Rev0
Rev1
26/06/2008
29/06/2008
24/07/2008
22/08/2008
Draft
Draft for review
Updated draft
Approved for release
Approved
By:
McComb
Johnson
McComb
McComb
It is the responsibility of the reader to verify the currency of the version number of this report. This
report was prepared by D. Johnson, P. McComb, B. Beamsley and R. Zyngfogel.
The information, including the intellectual property, contained in this report is confidential and
proprietary to MetOcean Solutions Ltd. It may be used by the persons to whom it is provided for the
stated purpose for which it is provided, and must not be imparted to any third person without the prior
written approval of MetOcean Solutions Ltd. MetOcean Solutions Ltd reserves all legal rights and
remedies in relation to any infringement of its rights in respect of its confidential information.
© MetOcean Solutions Ltd 2008
MetOcean Solutions Ltd
ii
New Zealand Marine Energy Resources
TABLE OF CONTENTS
1
INTRODUCTION ........................................................................................... 1
1.1
1.2
2
Scope of work............................................................................................ 1
Report structure ......................................................................................... 3
METOCEAN DATA SOURCES .................................................................... 4
2.1
Numerical hindcasting ............................................................................... 4
2.2
Wave hindcasting....................................................................................... 8
2.2.1
Wave model ....................................................................................... 8
2.2.2
Boundary conditions .......................................................................... 8
2.2.3
Winds................................................................................................. 9
2.2.4
Validation .......................................................................................... 9
2.2.5
Spectral parameters .......................................................................... 10
2.3
Tidal current modelling............................................................................ 12
2.3.1
Current Model.................................................................................. 12
2.3.2
Boundary conditions ........................................................................ 13
2.3.3
Model output.................................................................................... 14
3
WAVE ENERGY DEFINITIONS AND CONVERSIONS.......................... 15
3.1
3.2
3.3
3.4
4
Energy of the wave field .......................................................................... 15
Wave energy flux..................................................................................... 15
Wave power devices ................................................................................ 17
Wave model validation for wave power ................................................... 22
TIDAL STREAM ENERGY DEFINITIONS AND CONVERSIONS ........ 26
4.1
4.2
4.3
4.4
Tidal flow energy..................................................................................... 26
Tidal stream devices ................................................................................ 27
Power recovery efficiency........................................................................ 27
Device specifics ....................................................................................... 30
5
WAVE ENERGY RESOURCE MAPS ........................................................ 31
6
WAVE ENERGY SITE ASSESSMENTS .................................................... 43
6.1
6.2
6.3
6.4
6.5
7
Locations ................................................................................................. 43
Summary statistics ................................................................................... 45
Wave height – period statistics................................................................. 45
Wave power persistence exceedence statistics.......................................... 46
Wave power variability ............................................................................ 46
TIDAL ENERGY RESORCES..................................................................... 63
7.1
7.2
7.3
7.4
New Zealand scale ................................................................................... 63
Cook Strait............................................................................................... 63
Foveaux Strait.......................................................................................... 63
Tidal power simulations........................................................................... 63
8
SUMMARY ................................................................................................... 72
9
REFERENCES .............................................................................................. 73
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LIST OF TABLES
Table 3.1
Table 3.2
Table 3.3
Table 3.4
Table 3.5
Table 4.1
Table 6.1
Table 6.2
Table 6.3
Table 6.4
Table 6.5
Table 6.6
Table 6.7
Table 6.8
Table 6.9
Table 6.10
Table 6.11
Table 6.12
Table 6.13
Table 6.14
Table 6.15
Table 6.16
Table 6.17
Table 7.1
The
750
kW
Pelamis
power
matrix
(http://www.pelamiswave.com/media/power-matrix.jpg). Values are in
kW. 19
Hypothetical 1500 kW Pelamis power matrix. Values are in kW...... 20
Hypothetical 750 kW SPA power matrix. Values are in kW.............. 21
Hypothetical 750 kW Single Point Absorber wave energy converter
characteristics ................................................................................... 21
Wave hindcast validation results....................................................... 25
Generic tidal device specifications.................................................... 30
Wave energy site assessment locations ............................................. 43
Mean site-specific statistics based on 10-years hindcast data............. 47
Median site-specific statistics based on 10-years hindcast data.......... 48
Site-specific statistics at the 99th percentile non-exceedence level based
on 10-years hindcast data.................................................................. 49
Joint probability distribution (parts-per-thousand) of significant wave
height and peak spectral wave period for the Southland assessment
location............................................................................................. 50
Joint probability distribution (parts-per-thousand) of significant wave
height and peak spectral wave period for the Westport assessment
location............................................................................................. 51
Joint probability distribution (parts-per-thousand) of significant wave
height and peak spectral wave period for the Taranaki assessment
location............................................................................................. 52
Joint probability distribution (parts-per-thousand) of significant wave
height and peak spectral wave period for the Port Waikato assessment
location............................................................................................. 53
Joint probability distribution (parts-per-thousand) of significant wave
height and peak spectral wave period for the Gisborne assessment
location............................................................................................. 54
Joint probability distribution (parts-per-thousand) of significant wave
height and peak spectral wave period for the Wairarapa assessment
location............................................................................................. 55
Southland wave power – annual persistence exceedence (%). ........... 56
Westport wave power – annual persistence exceedence (%).............. 57
Taranaki wave power – annual persistence exceedence (%). ............. 58
Port Waikato wave power – annual persistence exceedence (%). ...... 59
Gisborne wave power – annual persistence exceedence (%).............. 60
Wairarapa wave power – annual persistence exceedence (%)............ 61
Monthly wave height and spectral wave power statistics for the
Southland assessment location. ......................................................... 62
Tidal energy site assessment results. Devices 1 and 2 are specified in
Table 4.1, and the site locations are shown on Figures 7.7 and 7.8. ... 64
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LIST OF FIGURES
Figure 2.1
Figure 2.2
Figure 2.3
Figure 2.4
Figure 3.1
Figure 4.1
Figure 4.2
Figure 5.1
Figure 5.2
Figure 5.3
Figure 5.4
Figure 5.5
Figure 5.6
Figure 5.7
Figure 5.8
Figure 5.9
Figure 5.10
Figure 6.1
Figure 7.1
Figure 7.2
Figure 7.3
Figure 7.4
Figure 7.5
Figure 7.6
Figure 7.7
Figure 7.8
Regional-scale domain used for wave and tidal current modelling. ..... 5
The nested high-resolution Cook Strait domain for tidal current
modelling. .......................................................................................... 6
The nested high-resolution Foveaux Strait domain for tidal current
modelling. .......................................................................................... 7
Validation time-series comparing the MSL wave hindcast with
waverider buoy data collected at the Kupe Gas Field (35 km south of
Hawera). See Figure 3.1 for location................................................. 10
Location of the wave power validation sites...................................... 24
Incident power density as a function of current velocity.................... 26
Typical plot of turbine output power versus flow speed .................... 28
Mean significant wave height (1998-2007) ....................................... 33
Mean significant sea wave (T<10s) height (1998-2007).................... 34
Mean significant swell wave (T>10s) height (1998-2007)................. 35
Mean significant wave height squared (1998-2007) .......................... 36
The maximum significant wave height hindcast over 1998-2007 ...... 37
Mean wavelength (1998-2007) ......................................................... 38
Mean spectral wave power (1998-2007) ........................................... 39
Mean power output from a single 750 kW Pelamis device (1998-2007)
......................................................................................................... 40
Mean power output from a single 1500 kW Pelamis device (19982007) ................................................................................................ 41
Mean power output from a single 750 kW SPA device (1998-2007) . 42
Location of the wave power assessment sites .................................... 44
Depth-averaged tidal current speeds for the Mean Spring flows ........ 65
Depth-averaged tidal current speeds for the Highest Astronomical
flows ................................................................................................ 66
Depth-averaged tidal current speeds for the Spring Tide flows in the
Cook Strait, including the 1 m/s speed contour. ................................ 67
Depth-averaged tidal current speeds for the Highest Astronomical
Tidal flows in the Cook Strait, including the 1 m/s speed contour. .... 67
Depth-averaged tidal current speeds for the Spring Tidal flows in the
Foveaux Strait region, including the 1 m/s speed contour.................. 68
Depth-averaged tidal current speeds for the Highest Astronomical
Tidal flows in the Foveaux Strait region, including the 1 m/s speed
contour. ............................................................................................ 69
The output locations in the Cook Strait region for detailed tidal power
generation simulation. The Spring Tidal flows are also shown, along
with the 1 m/s speed contour and the 25 m water depth contour. ....... 70
The output location in the Foveaux Strait region for detailed tidal
power generation simulation. The Spring Tidal flows are also shown,
along with the 1 m/s speed contour and the 25 m water depth contour.
......................................................................................................... 71
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1
INTRODUCTION
The Energy Efficiency and Conservation Authority (EECA) and the Electricity
Commission (EC) of New Zealand have appointed Power Projects Ltd (PPL) to
provide a summary of the current marine energy developments and the
intermediate-range outlook for New Zealand. Specifically, the objective is to
provide advice on the potential development of marine energy generation to
assist with the planning for future transmission and generation investments.
MetOcean Solutions Ltd (MSL) has been subcontracted by PPL to provide an
assessment of the open-coast wave and tidal energy resources.
The aim of this report is to provide a framework to assess potential for
deployment of marine energy devices, prior to the industry maturing and
sufficient data becoming available for objective evaluation on generator
performance and operation criteria (including opex-capex issues). As improved
device and economic data becomes available, it is envisaged that this report will
provide a basis for subsequent analysis of the applicability of the improving
technology.
1.1
Scope of work
The scope of this report is to:
•
Identify the spatial distribution of the open-coast marine energy
resources in New Zealand (waves and tidal currents);
•
Provide a quantitative description of the open-coast tidal resources,
including a detailed examination of two primary locations (Cook Strait
and Foveaux Strait);
•
Provide a quantitative description of the open-coast wave energy
resources, including detailed examination of six example locations that
effectively bracket the typical wave energy range, and
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New Zealand Marine Energy Resources
•
Simulate the likely wave energy conversion using three generic wave
power devices (based on the manufacturer’s specifications where
available).
The scope is achieved using the following methods:
•
Undertake a region-scale 10-year numerical wave hindcast for New
Zealand waters;
•
Undertake depth-averaged tidal current modelling of New Zealand
waters, with detailed modelling of the Cook Strait and Foveaux Strait
regions;
•
Produce maps of the open-coast wave and tidal energy resources;
•
Produce maps of the wave statistics and power output from three generic
devices;
•
Undertake a time-series simulation of the wave power output from the
three devices at six discrete locations, and
•
Characterise the ocean current regime at potential Cook Strait and
Foveaux Strait tidal power locations and simulate the power output with
a generic current energy conversion device.
Specific deliverables include:
•
Summary maps of the open-coast tidal resource, wave climate, potential
wave power, and energy output for generic wave conversion devices.
•
Detailed analysis of two potential tidal energy regions and six wave
energy sites, considering probable power output and seasonal variability.
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New Zealand Marine Energy Resources
1.2
Report structure
This report is structured as follows. The data sources used to characterise the
wave and tidal resources are detailed in Section 2. Wave energy definitions are
presented in Section 3 and information on the conversion of tidal stream energy
is presented in Section 4. Wave energy resource maps are provided in Section 5,
and more detailed site assessments for wave power are included in Section 6.
Open ocean tidal energy resources for New Zealand are provided in Section 7,
including detailed assessments of Cook Strait and Foveaux Strait. The report
findings are summarised in Section 8 and the references cited are listed in
Section 9.
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2
2.1
METOCEAN DATA SOURCES
Numerical hindcasting
Metocean data for the marine energy assessment have been generated using a
numerical hindcasting technique, which recreates the time-series of wave
conditions and tidal flow conditions.
For the wave hindcasts in this study, a NZ wide domain was used (Fig. 2.1) with
a longitude/latitude grid with resolution of 0.05˚ by 0.05˚ (approximately 4.5
km by 5.4 km). Tidal current modelling was carried out on the NZ grid at a
resolution of 0.06˚ by 0.06˚ (approximately 5.6 km by 6.6 km) and on two
nested, high-resolution domains over the Cook Strait region (Fig 2.2) and the
Foveaux Strait region (Fig. 2.3); nested grid resolutions were 0.002˚ by 0.002˚
(approximately 170 m by 230 m) and 0.004˚ by 0.004˚ (approximately 340 m by
450 m), respectively.
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Figure 2.1 Regional-scale domain used for wave and tidal current modelling.
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New Zealand Marine Energy Resources
Figure 2.2 The nested high-resolution Cook Strait domain for tidal current modelling.
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Figure 2.3 The nested high-resolution Foveaux Strait domain for tidal current
modelling.
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New Zealand Marine Energy Resources
2.2
Wave hindcasting
2.2.1 Wave model
SWAN (Simulating Waves Nearshore) was used for all of the wave modelling.
SWAN is a third generation ocean wave propagation model, which solves the
spectral action density balance equation for wavenumber-direction spectra. This
means that the growth, refraction, and decay of each component of the complete
sea state, each with a specific frequency and direction, is solved, giving a
complete and realistic description of the wave field as it changes in time and
space. Physical processes that are simulated include the generation of waves by
surface wind, dissipation by white-capping, resonant nonlinear interaction
between the wave components, bottom friction and depth limited breaking. A
detailed description of the model equations, parameterizations, and numerical
schemes can be found in Holthuijsen et al. (2007). All 3rd generation physics are
included. The Collins friction scheme is used for wave dissipation by bottom
friction.
The solution of the wavefield is found for the non-stationary (time-stepping)
mode. Boundary conditions, wind forcing and resulting solutions are all time
dependent, allowing the model to capture the growth, development and decay of
the wavefield.
2.2.2 Boundary conditions
The wave spectra on the open ocean boundaries of the coarse domain were
obtained from the NOAA WAVEWATCH III (NWW3) solution. NWW3 is a
state-of-the-art wave generation, propagation and transformation model for
forecasting the evolution of directional wave energy spectra across the global
oceans.
Along the open boundaries of the model domain, the primary statistical
parameters of the incoming wavefield are interpolated from the NWW3
hindcast solution. Boundary spectra are then reconstructed by assuming a bimodal Ochi-Hubble shape.
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New Zealand Marine Energy Resources
Boundary conditions for the high resolution nested grid come directly from the
coarse domain.
2.2.3 Winds
The regional wind field is very important for wave generation. A spatially
varying wind field was specified from a blended global wind product developed
by MSL. These data are 10m wind velocity vectors in a 3-hourly gridded format
at a resolution of 0.25° of longitude and latitude. The wind field is a
combination of the 6-hourly Blended Sea Winds data1 and the winds from the
NWW3 hindcast. The blended data product combines the benefits of measured
satellite data with the temporal resolution and continuous coverage of the
modelled re-analysis.
2.2.4 Validation
The hindcast wave model outputs have been validated with wave buoy data
from numerous locations around New Zealand (ranging from 10-110m depths).
A validation plot for one of these locations is shown in Figure 2.4, in the highlycomplex western Cook Strait. In this region there are rapidly changing wave
conditions and strong gradients in local wave generation due to topographic
forcing of the winds between the North and South Islands.
The wave model validation process has been undertaken as part of the
engineering design specifications for the offshore oil industry, which have used
the MSL hindcast data in the development of the Kupe, Pohokura, Tui and
Maari Fields, plus applications in the Maui Field. Extensive peer-review of the
methods and outcomes has been undertaken by a range of international experts,
including marine warranty surveyors, design engineers and consulting
oceanographers. The hindcast data have also been applied to harbour design and
underkeel clearance applications, which have received peer-review by
international experts.
1
From NCDC, NOAA, Zhang (2006).
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New Zealand Marine Energy Resources
Figure 2.4 Validation time-series comparing the MSL wave hindcast with
waverider buoy data collected at the Kupe Gas Field (35 km south of
Hawera). See Figure 3.1 for location.
2.2.5 Spectral parameters
Directional wave spectra were output at hourly intervals over the hindcast run,
and 10 years of data were available for the present study (1998 – 2007). The
standard spectral wave parameters were derived as follows.
Given a directional wave spectrum S ( f ,θ ) , the 1-dimensional spectrum is
obtained by integrating over directions:
2π
S ( f ,θ )dθ
S( f ) =
(2.1)
0
From the computed spectral energy density S(f), the peak frequency fp and peak
energy Sp = S(fp) of the spectrum are located. Spectral moments
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New Zealand Marine Energy Resources
∞
f j S ( f ) df
Mj =
(2.2)
0
are computed, allowing further statistics to be defined:
significant height
Hs = 4 M0
(2.3)
mean period
Tm 1 = M 0 M 1
(2.4)
mean apparent period Tm 2 = M 0 / M 2
(2.5)
mean frequency
f mean = M 1 / M 0
(2.6)
mean crest period
Tcr =
M2 / M4
(2.7)
spectral width
M22
SW = 1 −
M0 M4
(2.8)
Tm2 is often used as a spectral approximation of the zero-down-crossing period
statistic Tz.
Directional moments are:
∞ 2π
Mc =
S ( f ,θ ) cosθ dθ df
(2.9)
S ( f ,θ ) sin θ dθ df
(2.10)
0 0
∞ 2π
Ms =
0 0
The mean direction is θ 0 = arctan
Ms
Mc
and the directional spread is ∆ = 2 −
(2.11)
2 M c2 + M s2
M0
.
(2.12)
The spectral peakedness parameter (Goda, 1970) is given by
MetOcean Solutions Ltd
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New Zealand Marine Energy Resources
2
Qp =
M02
2.3
∞
f S ( f ) 2 df .
(2.13)
0
Tidal current modelling
The MSL implementation of POM (Princeton Ocean Model) was used to
hindcast the tidal currents in the New Zealand region. POM is a primitive
equation ocean model that numerically solves for oceanic current motions. The
details of model implementation are described in Mellor (2004)2. POM has been
used for numerous scientific applications studying oceanic and shelf circulation.
2.3.1
Current Model
For the tidal simulations, POM was used in a vertically integrated twodimensional mode, solving the momentum and mass conservation equations
given by:
τ wx τ bx
∂u
∂u
∂u
∂η 1 ∂Pa
∂ 2u ∂ 2u
+u
+v
− fv = − g
+ AH
+
+
−
−
ρh ρh
∂t
∂x
∂y
∂x ρ ∂x
∂x 2 ∂y 2
τ wy τ by
∂v
∂v
∂v
∂η 1 ∂Pa
∂ 2v ∂ 2v
A
+ u + v − fv = − g
+
+
−
+
−
H
ρh ρh
∂t
∂x
∂y
∂y ρ ∂y
∂x 2 ∂y 2
∂η ∂(u[h + η ]) ∂(v[h + η ])
+
+
=0
∂t
∂x
∂y
(2.14 a,b,c)
where t is the time, u and v are the depth-averaged velocities in the x and y
directions respectively, h the MSL depth,
is the elevation of the surface, g the
gravitational acceleration, f the Coriolis parameter,
the density of water, and
Pa is atmospheric pressure. AH is a horizontal eddy viscosity coefficient,
calculated with a Smagorinsky parameterisation,
1
AH = C m ∆x∆y
2
2
∂u
∂x
2
∂v ∂u
+
+
∂x ∂y
2
∂v
+
∂y
2
1
2
(2.15)
The numerical model code is freely available as open source code.
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with Cm set at 0.2.
The surface and bottom shear stress,
w
and
b
are due to wind and bottom
friction. The bed shear stress is parameterised with a quadratic type friction law,
τ bx = C D
(u
2
)
+ v 2 u τ by = C D
(u
2
)
+ v2 v
(2.16 a,b)
that depends on an adjustable drag coefficient, CD ~ 10-3. Surface shear stresses
are set to zero for the tidal simulations.
The model equations are solved with finite differences and explicit timestepping, limited by a Courant condition. A time step of 8 s was used for the
regional grid, and a time step of 5 s for the nested fine-scale grid.
2.3.2
Boundary conditions
The same boundary conditions are applied at all open boundaries. For the
surface elevation, an Orlanski (1976) type radiation boundary condition is
applied, but with the normal component of the outgoing phase speed determined
as the normal projection of the full oblique phase speed. (NPO in Marchesiello
et al., 2001). For the normal component of depth-averaged velocity, u n , a
Flather (1976) type constraint is used,
u n = u nb +
g
η −η b
h
(
)
(2.17)
The boundary values of u nb and η b are known boundary values for the surface
elevation and depth-averaged current.
The TPXO7.0 global inverse tidal solution (Egbert and Erofeeva, 2002) was
used to prescribe the tidal elevation and current velocity around the coarse grid.
Elevations and velocities from the coarse domain solution were then used for
the boundaries of the fine scale grid.
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2.3.3
Model output
The 2D hydrodynamic model was run for a period of 40 days and then postprocessed to derive the primary nine tidal constituents (M2, S2, N2, K2, K1,
O1, P1, Q1, M4) for each node in the domain. The modelled open ocean tidal
flows have been validated at several sites in the offshore Taranaki region as part
of the engineering design studies for oil and gas projects. The constituents of
tidal elevation within the regional and high-resolution domains (i.e. Cook Strait
and Foveaux Strait) were also validated against the published tidal constituents
for discrete locations.
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3
3.1
WAVE ENERGY DEFINITIONS AND CONVERSIONS
Energy of the wave field
The total wave energy (Et) is given by;
1
Et = E p + Ek = ρgH 2
8
(3.1)
Where ρ is the density of seawater (~1025 kg.m-3), g is the acceleration due to
gravity (9.81 m.s-1) and H is the wave height.
The total wave energy (eqn. 3.1) is the energy per unit wave crest length,
averaged over the wavelength. An alternative energy estimate omits the 1/L
term (Komar, 1976), and is found by multiplying Et by the wavelength (L) to
define EL. According to linear theory,
L=
gT 2
tanh(kh)
2π
(3.2)
where T is the wave period, h is the water depth and k is the water wave
number.
3.2
Wave energy flux
The energy flux (measured in watts per unit of wave crest, W.m-1), is the rate at
which energy is being transmitted, and represents the power of the wave field.
The energy flux (P) is the average energy in the wave multiplied by the rate at
which that energy is propagating (i.e. the group velocity, Cg).
P = E × Cg
(3.3)
where
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New Zealand Marine Energy Resources
Cg =
2kh
1
C
1+
sinh(2kh)
2
(3.4)
and C is the wave celerity, given as
C=
gT
tanh(kh)
2π
(3.5)
From a spectrum of potential wave energy (i.e. measured or modelled), the
energy flux can be estimated through integration over the entire spectrum.
However, a wave spectrum is not always available so an alternative parametric
deep-water estimate (Pp) is often applied (Hagerman and Bedard, 2003);
Pp = 0.42T p H s
2
(3.6)
where Tp is the peak spectral wave period. This parametric estimate of the
available wave power (eqn. 3.6) provides a very similar result to the spectral
integration method in deep water. The spectral integration method is used in this
report to represent the available wave power for generation assessment.
The ability of a specific device to extract energy from a spectral sea state is
typically reported by the developers as a ‘power matrix’. This matrix provides a
power output for any combination of the wave height - wave period estimates.
Typically, the significant wave height (Hs) is used along with the wave energy
period (Te), where in deep water.
Te =
m−1
m0
(3.7)
In intermediate depths it is important to take account of the effect of depth on
wave group velocity. The most appropriate way to consider energy period is
from the conceptual definition as the period of the regular wave that has “the
same parametric height and the same power density as the sea-state under
consideration”. If the total power density and the parametric wave height (Hs)
are already known, this leads to,
MetOcean Solutions Ltd
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New Zealand Marine Energy Resources
Te =
64π P
.
ρg 2 H m 0 2
(3.8)
Alternatively, Burger et al (2005) derived the energy period (Te) based on the
Bretschneider spectrum, where
Te = 1.15.Tz , or
(3.9)
Te = 0.86.T p
(3.10)
where Tz is the zero down-crossing wave period and Tp is the peak wave period.
It is worth noting that the definitions and equations for wave power are depthintegrated, and provide a measure of total power that might be extracted by a
perfect device. However in reality a wave device usual operates at the surface or
in a discrete part of the whole water column, and could not recover all of the
available power.
3.3
Wave power devices
There are various types of possible wave power devices, including the point
absorber; surfacing following or attenuator; terminator (perpendicular to wave
propagation); oscillating water column; and overtopping device. Within this
range of devices, the power take-off mechanisms include: hydraulic ram,
elastomeric hose pump, pump-to-shore, hydroelectric turbine, air turbine, and
linear electrical generator.
The available power matrix data released by developers are typically derived
from tank testing or numerical modelling (or a combination of both), but to date
few (if any) have been validated with full-scale tests. The sea-states referred to
by the height and period parameters are therefore usually two-parameter
idealised models (such as the Bretschneider spectrum) combined with a simple
directional spreading function.
This report examines the possible power recoverable for three different wave
energy devices, based on their published power matrices;
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New Zealand Marine Energy Resources
•
750 kW Pelamis device. This device has 4 segments and 3 power
modules and, for wave events with Te > 13 s, the Te = 13 s power curve
has been applied. The power matrix is provided in Table 3.1, based on a
significant wave height and peak spectral wave periods.
•
Hypothetical modified 1500 kW Pelamis device. The University of
Edinburgh (2006) scaled up the Pelamis power matrix to represent
anticipated future machines. This matrix (Table 3.2) assumes a device
180 m in length, with 5 segments and 4 power modules, suitable for
water depths ranging from 50-150 m. For wave events with Te > 19 s,
the Te = 19 s power curve has been applied, while for events with H > 3
m, the H = 3 m power curve has been applied. RMS wave height is used
in this matrix.
•
Hypothetical 750 kW Single Point Absorber (SPA). This device has
the performance characteristics described in Table 3.3, and specification
listed in Table 3.4. For wave events with Te > 19 s the Te = 19 s power
curve has been applied, while for events with H > 3 m the H = 3 m
power curve has been applied. RMS wave height is used in this matrix.
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New Zealand Marine Energy Resources
The 750 kW Pelamis power matrix (http://www.pelamiswave.com/media/power-matrix.jpg). Values are in kW.
Sig. wave height (m)
Table 3.1
8
-
-
-
-
-
-
-
750
750
750
750
750
750
750
750
690
625
7.5
-
-
-
-
-
-
750
750
750
750
750
750
750
750
686
622
593
7
-
-
-
-
-
750
750
750
750
750
750
750
750
676
613
584
525
6.5
-
-
-
-
750
750
750
750
750
750
750
743
658
621
579
512
481
6
-
-
-
-
750
750
750
750
750
750
711
633
619
558
512
470
415
5.5
-
-
-
750
750
750
750
750
737
667
658
586
530
496
446
395
355
5
-
-
-
736
726
731
707
687
670
607
557
521
472
417
369
348
328
4.5
-
-
544
635
642
648
628
590
562
528
473
432
382
356
338
300
266
4
-
-
462
502
540
546
530
499
475
429
384
366
339
301
267
237
213
3.5
-
270
354
415
438
440
424
404
377
362
326
292
260
230
215
202
180
3
129
198
260
305
332
340
332
315
292
266
240
219
210
188
167
149
132
2.5
89
138
180
212
231
238
238
230
216
199
181
163
146
130
116
103
92
2
57
88
115
136
148
153
152
147
138
127
116
104
93
83
74
66
59
1.5
32
50
65
76
83
86
86
83
78
72
65
59
53
47
42
37
33
29
34
37
38
38
37
35
32
29
-
-
-
idle
idle
22
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
10.5
11
11.5
12
12.5
13
1
0.5
26
23
21
Wave energy period (s)
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New Zealand Marine Energy Resources
Hypothetical 1500 kW Pelamis power matrix. Values are in kW.
RMS wave height (m)
Table 3.2
3
-
-
-
-
-
-
-
-
-
1500
1500
1500
1500
-
-
-
-
2.75
-
-
-
-
-
-
-
-
1500
1500
1500
1500
1500
1453
-
-
-
2.5
-
-
-
-
-
-
-
1500
1500
1500
1500
1500
1470
1319
1192
-
-
2.25
-
-
-
-
-
-
1500
1500
1500
1500
1500
1450
1350
1175
1039
900
-
2
-
-
-
-
-
1500
1500
1500
1500
1500
1450
1320
1180
1008
865
750
635
1.75
-
-
-
-
1500
1500
1500
1500
1500
1440
1277
1119
971
845
724
607
490
1.5
-
-
-
1450
1500
1500
1500
1460
1444
1253
1071
915
782
651
540
450
361
1.25
-
-
650
1258
1470
1450
1467
1299
1136
968
826
688
567
462
378
314
251
1
-
95
427
871
1116
1170
1106
969
834
688
558
449
366
297
242
201
161
0.75
-
53
241
525
730
769
709
605
493
397
317
254
206
168
137
114
91
0.5
-
24
108
237
336
358
326
274
222
178
142
114
93
75
61
51
41
0.25
-
5
27
62
88
94
85
72
58
47
33
22
18
14
10
5
0
0
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Wave energy period (s)
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New Zealand Marine Energy Resources
Hypothetical 750 kW SPA power matrix. Values are in kW.
RMS wave height (m)
Table 3.3
3
-
-
-
-
-
-
-
-
-
750
750
750
695
598
515
444
383
2.75
-
-
-
-
-
-
-
-
750
750
750
738
637
548
472
407
351
2.5
-
-
-
-
-
-
-
750
750
750
750
671
579
498
429
370
320
2.25
-
-
-
-
-
-
750
750
750
750
694
604
521
449
386
333
288
2
-
-
-
-
-
750
750
750
750
699
616
536
463
399
343
296
256
1.75
-
-
-
-
710
750
750
731
679
612
539
469
405
349
300
259
224
1.5
-
-
-
546
609
645
650
627
582
524
462
402
347
299
257
222
192
1.25
-
-
347
455
507
537
542
522
485
437
385
335
290
249
214
185
160
1
-
73
222
364
406
430
433
418
388
349
308
268
232
199
172
148
128
0.75
-
41
125
273
304
322
325
313
291
262
231
201
174
150
129
111
96
0.5
-
18
55
135
203
215
217
209
194
175
154
134
116
100
86
74
64
0.25
-
5
14
34
70
107
108
104
97
87
77
67
58
50
43
37
32
0
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
idle
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Wave energy period (s)
Table 3.4
Hypothetical 750 kW Single Point Absorber wave energy converter characteristics
Natural Period (s)
Damping Coefficient
Efficiency (%)
Rating (kW)
Radius (m)
Stroke (m)
MetOcean Solutions Ltd
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0.06
80
750
6
3
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New Zealand Marine Energy Resources
3.4
Wave model validation for wave power
The MSL numerical wave hindcast model has been rigorously validated against
measured wave data from around New Zealand, at nearshore and offshore (continental
shelf) locations. However, the relationship between wave height and wave power is
non-linear, which means that small errors in the hindcast wave heights can lead to very
significant errors in the mean wave power assessment for a location. Also, the spatial
and temporal scale used in the numerical hindcasting process is important so that
topographic and bathymetric effects on the waves’ physics can be properly resolved.
The scale factor may be important when comparing the high-resolution outputs from the
MSL model with other wave hindcast results that have employed a coarser-scale
domain.
For the present assessment, a further regional validation process has been undertaken
specifically for the derived wave power values. This exercise has been undertaken using
waverider buoy data from six locations around New Zealand, as shown on Figure 3.1.
For this validation analysis, the deepwater parametric method (eqn. 3.6) was used to
estimate the wave power flux from both the measured and modelled wave data. This
method was used because wave spectra were not available from all the buoy sites.
The validation results (Table 3.5) clearly show that the wave model is accurately
representing the average energy flux for the wide range of locations tested. The
modelled results are all within 20% of the measured power values, and there are no
indications of systematic under-prediction or over-prediction throughout the range of
environments tested. This is a very robust validation, particularly considering the use of
a parametric technique that assumes a generic spectral shape.
A further validation was undertaken using the full wave spectral integration method,
using measured wave spectra from the offshore Maari Field in August - September
2003. During this period, the mean measured spectral wave power was 34.8 kW.m-1,
while the hindcast spectral wave power for the same period was 38.8 kW.m-1.
One of the most energetic coastal locations in New Zealand is the Southland region.
During 1989, Electricorp Production commissioned a wave energy assessment
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New Zealand Marine Energy Resources
involving wave data collection in 90 m water depth in the Western Foveaux Strait
(46.52083 S, 167.45833 E). Over the Autumn months of March-May 1989, the
averaged measured spectral wave power was 65.4 kW m-1 and the mean significant
wave height was 3.66 m (BTW, 1989). By comparison, the mean spectral power from
the MSL hindcast model for this same location during all the March-May periods over
1998-2007 was 73.7 kWm-1 and the mean significant wave height was 3.55 m.
In summary, the hindcast techniques that have been applied in this assessment have
received due scrutiny by international experts, and MSL hindcast wave data have been
used extensively for the engineering design criteria within New Zealand’s’ offshore oil
industry. Further, the site-specific validations for wave power clearly show that the
MSL hindcast method provides a reliable representation of the wave energy resource.
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New Zealand Marine Energy Resources
Figure 3.1 Location of the wave power validation sites
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New Zealand Marine Energy Resources
Table 3.5
Wave hindcast validation results
Data location
Data source
Duration
Kupe Field
MetOcean
Apr-Nov 2007
Maari Field
MetOcean
Sept-Dec 2007
Pohokura Field
MetOcean
Jun-Nov 2003
Baring Head
NIWA/GWRC
Jan-Dec 2007
Steep Head
NIWA/ECAN
Jan-Dec 2007
Steep Head
NIWA/ECAN
Mar-Dec 2003
Bay of Plenty
EBOP
Jun-Dec 2004
MetOcean Solutions Ltd
Measured
Modelled
Measured
Modelled
Measured
Modelled
Measured
Modelled
Measured
Modelled
Measured
Modelled
Measured
Modelled
Mean Hs
(m)
2.02
2.02
2.23
2.19
1.78
1.94
1.26
1.16
2.01
1.74
1.99
1.88
0.99
1.14
Mean Hs2
(m2)
5.05
4.88
6.2
5.67
3.99
4.38
2.13
1.88
4.69
3.71
6.20
4.11
1.36
1.81
Mean wave power
-1
(W m )
21281
22448
27106
27213
18039
20690
9060
8380
21847
17468
19442
18900
5094
5647
25
New Zealand Marine Energy Resources
4
4.1
TIDAL STREAM ENERGY DEFINITIONS AND CONVERSIONS
Tidal flow energy
The instantaneous power density (P) of a flowing fluid incident to an underwater
turbine is given as;
P
A
=
Water
1
ρU 3
2
(4.1)
where A is the cross-sectional area of flow intercepted by the device (i.e. the area swept
by the turbine rotor, m2) and ρ is the density of water (~1025 kg.m-3 for seawater) and U
is the current speed (m.s-1). Because the power density varies with the cube of the
current velocity (eqn. 4.1), it increases rapidly with current speed (i.e. Fig. 4.1).
Power densities of 500 - 1000 W.m-2 are available for flow velocities of between 11.3 m.s-1 (2-2.5 knots). In order to determine the power density distribution for a
particular site it is necessary to identify the velocity distribution and convert the velocity
distribution into a power density distribution; from which various descriptive statistics
can be derived (i.e. mean, median and percentiles of the power density distribution).
Figure 4.1 Incident power density as a function of current velocity
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New Zealand Marine Energy Resources
4.2
Tidal stream devices
There are two main categories of tidal devices; tidal barrages and tidal current turbines.
Barrages are not open-coast devices and are not considered further in this report.
Tidal stream devices operate using the same principle as wind turbines; generating
power directly from the water current, typically where the flows exceed 0.5 m.s-1. The
turbines can be orientated either horizontally or vertically and the systems can be either
floating or secured directly to the seabed.
The recoverable tidal flow energy is limited by the characteristics of the site (i.e. water
depth etc) as well as environmental considerations (i.e. the impact of a device on the
circulation patterns). Typically the usable cross-sectional area available is limited at the
top and bottom of the profile in order to facilitate navigational clearance requirements;
eliminating the upper 15-20 m in water channels maintained for ocean-going vessels
and 5 m elsewhere in order to provide clearance for shallow-draft vessels. At the
bottom the turbine should be above the low-speed benthic boundary layer, which is
approximately 1/10 of the low water depth (~MLWS). The maximum energy that can be
extracted is calculated from the power density multiplied by the usable cross-sectional
area between the top and bottom limits as described above.
4.3
Power recovery efficiency
The power recovery efficiency and turbine performance can be estimated by
considering the power conversion efficiency of each step of the extraction process,
beginning with the power of the flowing water stream and proceeding through the
turbine, drive train, generator and power conditions steps.
Turbine efficiency varies with the velocity of water flow. A plot of a turbines output as
a function of flow speed typically consists of three regions; i) zero to cut-in speed, ii)
cut-in speed to rated speed, and iii) greater than rated speed (Fig. 4.2)
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New Zealand Marine Energy Resources
Figure 4.2 Typical plot of turbine output power versus flow speed
In Region I, velocities are below the cut-in speed and the turbines’ blades do not create
sufficient lift to rotate the drive train so no power is generated. In Region III when
velocities exceed the rated speed of the turbine, power output is held constant, typically
at the turbine’s rated power, regardless of the velocity. Rated power output is
maintained by either applying a force to the rotor shaft or changing the pitch angle of
the turbine blades to generate less lift. In Region II (between the cut-in speed and the
rated speed) the turbine’s output depends on a chain of conversion efficiencies,
including the turbines power coefficient (Cp) and the power take-off efficiency (η), such
that;
Pelectric = P × C p × η
(4.2)
where P is the power density of the water passing through the area swept by the
turbine, i.e.
P=
1
ρU 3 A
2
(4.3)
Where A is the area swept by the turbine rotor.
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New Zealand Marine Energy Resources
The power coefficient (Cp) is the ratio of the actual power produced to the kinetic
energy of a stream tube the same diameter as the rotor, and is given as;
C p. =
Protor
π
8
2
ρD U
(4.4)
3
where D is the rotor diameter. During its field trials, the 11 m diameter single turbine
Seaflow tidal energy device had instantaneous Cp values ranging from 0.2-0.6. When
averaged, the values ranged between 0.38-0.45 depending on the current velocities. This
appears to be fairly standard for tidal energy devices. The power take-off efficiency (η)
is a function of the drive-train, generator and power conditioning of the unit, such that,
η = η dirve−train × η generator × η power _ conditioning
Cp
(4.5)
The power coefficient - This is the efficiency with which the turbine extracts
kinetic energy from the incoming flow. For water flowing through an unshrouded
turbine, maximum extraction efficiency occurs when the flow speed at the rotor face is
reduced by 1/3 relative to the free-stream velocity, which yields an optimal extraction
efficiency of 16/27(~59%, i.e. the Lanchester-Betz limit). Shrouded devices can achieve
higher efficiencies. Typical values of Cp for un-shrouded devices range from 0.2-0.6,
and average out at around 0.45, or 45%.
ηdrive-train The drive train efficiency. This is the efficiency with which the energy
extracted from the flow is delivered to the generator. Typical values range from 8096%
ηgenerator The generator efficiency. This is the efficiency with which the mechanical
energy input to the generator is converted to electricity. Losses are primarily due to
friction, and typical generator efficiency values range from 80-95%.
ηpower conditioning
The power conditioning efficiency. This is the efficiency with which
the electricity produced by the generator is conditioned to meet phase and voltage
requirements of the local grid interconnection point. Losses are primarily electrical
energy dissipated as heat, and typical power conditions efficiency values range from 9098%.
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New Zealand Marine Energy Resources
For typical component efficiencies, the overall efficiency would be within the range of
40%, which is the proportion of incident flow power converted into properly
conditioned electric power output.
4.4
Device specifics
For the purpose of this assessment, the time-series simulation of power generation has
considered two generic devices; an unshrouded turbine with a diameter of 16 m, and an
unshrouded turbine with a diameter of 10 m. The device specifics are listed in Table
4.1. Using these specifications, the generation of electrical power from the tidal stream
was simulated in the time-domain at 15-minute intervals over a one-year period. The
depth-average current speed was used directly for the simulation, rather than applying a
current profile, which is a reasonable assumption given that the turbines used in this
simulation occupy approximately the middle third of the water column. Site assessment
results are provided in Section 7.
Table 4.1
Generic tidal device specifications
Parameter
Turbine diameter (m)
Cut-in speed (m.s-1)
MetOcean Solutions Ltd
Device 1
16
0.7
Device 2
10
0.8
Rated speed (m.s-1)
2.5
2.5
Power coefficient (Cp)
0.45
0.50
Drive-train efficiency
0.90
0.92
Generator efficiency
0.90
0.95
Power conditioning efficiency
0.95
0.95
30
New Zealand Marine Energy Resources
5
WAVE ENERGY RESOURCE MAPS
A series of New Zealand-scale maps are presented to characterise the wave energy
resources. These maps are derived from the MSL 10-year wave hindcast, and provide
approximately 5 km spatial resolution.
The mean significant wave height is provided in Figure 5.1, showing a mean wave
height gradient from the southwest of New Zealand to the northeast. The mean heights
for an arbitrary sea fraction (T<10s) and swell fraction (T>10s) are presented in Figures
5.2 and 5.3, respectively. These maps are useful for characterising the mean sea state,
and clearly show that the northeast sector of New Zealand is sheltered from the
dominant Southern Ocean swells. Wave power is proportional to the square of the wave
height, and for reference purposes the mean significant wave height squared is
presented on Figure 5.4.
The maximum significant wave height over the period 1998-2007 is shown on Figure
5.5, providing an interesting pattern. While the mean wave energy is higher on the
South and West coasts, some of the largest wave heights were observed on the East
Coast of the North Island (from Wairapapa – East Cape). Isolated areas of high wave
heights, for example around the Coromandel, are signatures of a single isolated storm
event in the 10-year time-series.
Two figures that effectively characterise the New Zealand wave climate for potential
generation are the mean wavelength of the equivalent energy period (Fig. 5.6) and the
mean spectral wave power (Fig. 5.7). The mean wavelength plot shows the clear
differences between the swell-dominated West Coast (with wavelengths around 150 m)
and the sea-dominated East Coast (with wavelengths 50-100 m). The mean spectral
wave power (Fig. 5.7) indicates that a mean annual resource of at least 30 kW.m-1 is
available within about 15 km of the shoreline along most of the West Coast of New
Zealand, excepting the Western Cook Strait region and the North Taranaki Bight. The
most energetic location for wave power is the Southland coast, from Fiordland to the
west of Stewart Island. Along the East Coast of New Zealand, only the Catlins region in
South Otago has an equivalent resource to the West Coast. In the North Island, the
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New Zealand Marine Energy Resources
coastline from Wairarapa to East Cape is the next most energetic region, but with
around one third of the median energy of the typical West Coast locations.
The mean power output from the three wave power conversion devices (discussed in
Section 3.3) are presented in Figures 5.8 – 5.10. These data are derived from a 10-year
time-series simulation (1998-2007) and represent the mean output from a single device,
calculated for every node in the hindcast domain.
MetOcean Solutions Ltd
32
New Zealand Marine Energy Resources
Figure 5.1
MetOcean Solutions Ltd
Mean significant wave height (1998-2007)
33
New Zealand Marine Energy Resources
Figure 5.2 Mean significant sea wave (T<10s) height (1998-2007)
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34
New Zealand Marine Energy Resources
Figure 5.3 Mean significant swell wave (T>10s) height (1998-2007)
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35
New Zealand Marine Energy Resources
Figure 5.4 Mean significant wave height squared (1998-2007)
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36
New Zealand Marine Energy Resources
Figure 5.5 The maximum significant wave height hindcast over 1998-2007
MetOcean Solutions Ltd
37
New Zealand Marine Energy Resources
Figure 5.6 Mean wavelength (1998-2007)
MetOcean Solutions Ltd
38
New Zealand Marine Energy Resources
Figure 5.7 Mean spectral wave power (1998-2007)
MetOcean Solutions Ltd
39
New Zealand Marine Energy Resources
Figure 5.8 Mean power output from a single 750 kW Pelamis device (1998-2007)
MetOcean Solutions Ltd
40
New Zealand Marine Energy Resources
Figure 5.9 Mean power output from a single 1500 kW Pelamis device (1998-2007)
MetOcean Solutions Ltd
41
New Zealand Marine Energy Resources
Figure 5.10 Mean power output from a single 750 kW SPA device (1998-2007)
MetOcean Solutions Ltd
42
New Zealand Marine Energy Resources
6
6.1
WAVE ENERGY SITE ASSESSMENTS
Locations
Six coastal locations have been selected for detailed analysis of their wave power
potential (Table 6.1; Fig. 6.1).) These locations have been chosen to represent a range of
wave climates around New Zealand, within the realms of feasible grid connectivity. A
common distance of 6 km offshore has been selected at each site, providing a range of
water depths from 23-65 m. Wave and wave power statistics have been extracted for
these locations from the MSL New Zealand regional wave hindcast simulation.
Table 6.1
Wave energy site assessment locations
Station
Depth (m)
Distance offshore (km)
Latitude
Longitude
MetOcean Solutions Ltd
Southland
31
6
-46.401
167.677
Westport
65
6
-41.734
171.390
Cape Egmont
51
6
-39.287
173.682
Port Waikato
23
6
-37.440
174.635
Gisborne
39
6
-38.708
178.148
Wairarapa
62
6
-41.126
176.137
43
New Zealand Marine Energy Resources
Figure 6.1 Location of the wave power assessment sites
MetOcean Solutions Ltd
44
New Zealand Marine Energy Resources
6.2
Summary statistics
Summary statistics of the wave climate, wave energy and wave power for the mean,
median and 99th percentile level are presented in Tables 6.2, 6.3 and 6.4, respectively.
Of the sites examined, Southland is the most energetic and Gisborne is the least
energetic. The West Coast locations (Westport, Taranaki and Port Waikato) all show
very similar wave climate and wave power statistics. The Wairarapa location was
approximately 25% more energetic than the Gisborne site.
Notably, the East Coast occasionally experiences very energetic wave conditions (see
Fig. 5.5), so while the mean wave energy is lower than the West Coast, the East Coast
storm conditions have potential to be more severe, which has implications for the
engineering design basis for a wave farm. Further, these occasional energetic storms are
not a reliable wave power source, and the use of the median annual wave power
statistics (Table 6.3) is better statistic for inter-site comparisons. For example, based on
Table 6.3 the Wairarapa location has one third the energy resource of the typical West
Coast environment.
6.3
Wave height – period statistics
The wave climate may be characterised with a joint probability distribution of the
significant wave heights and peak spectral wave periods. These data are an essential
requirement for a wave power assessment, and they are presented as parts-per-thousand
in Tables 6.5 – 6.10. The data show that Southland and the West Coast locations are
dominated by 10-14 s wave conditions, while the East Coast locations (Gisborne and
Wairarapa) have slightly lower periods (8-12 s).
MetOcean Solutions Ltd
45
New Zealand Marine Energy Resources
6.4
Wave power persistence exceedence statistics
Persistence exceedence tables provide a useful method to examine the duration of the
energetic conditions, and these matrices are provided for each of the six assessment
sites in Tables 6.11-6.16. As an example interpretation: for the Southland location
(Table 6.11) for 12% of the year the wave power is >80 kW/m for periods of 48 hours
or more.
6.5
Wave power variability
The natural variability of incident wave power is an important consideration for the
planning of electricity generation. To understand the variability of wave power on a
daily basis, the hindcast wave power time-series was analysed for the standard deviation
from the daily mean, and then normalised to the mean to provide an estimate of the
percentage variability. Such variability estimates are provided for each of the six
locations (Table 6.2), and a more detailed monthly analysis is provided for the energetic
Southland location in Table 6.17. Typically, the daily power variability can be expected
to range from 25 - 40%.
MetOcean Solutions Ltd
46
New Zealand Marine Energy Resources
Table 6.2
Mean site-specific statistics based on 10-years hindcast data.
Station (6 km offshore)
Hs
Hs (swell, T>10s)
Hs (sea, T<10s)
Wavelength
Wave power
Mean daily power variability
Pelamis 750 kW generator
Hypothetical Pelamis 1500 kW generator
Hypothetical SPA 750 kW generator
Surface wave orbital velocity
Surface wave orbital velocity cubed
MetOcean Solutions Ltd
Units
m
m
m
m
kW.m-1
%
kW
kW
kW
m/s
m/s
Southland
2.91
2.05
1.95
132
53.7
29.4
228
1354
643
1.07
1.72
Westport
2.33
1.60
1.62
153
30.9
25.8
158
1316
592
0.76
0.65
Taranaki
2.26
1.51
1.60
150
29.7
27.0
149
1275
572
0.75
0.67
Port Waikato
2.15
1.49
1.46
129
27.4
26.4
129
1236
551
0.84
0.86
Gisborne
1.43
0.68
1.22
108
10.8
38.2
88
815
371
0.60
0.45
Wairarapa
1.72
0.89
1.42
119
13.7
35.1
109
999
441
0.67
0.55
47
New Zealand Marine Energy Resources
Table 6.3
Median site-specific statistics based on 10-years hindcast data.
Station (6 km offshore)
Hs
Hs (swell, T>10s)
Hs (sea, T<10s)
Wavelength
Wave power
Pelamis 750 kW generator
Hypothetical Pelamis 1500 kW generator
Hypothetical SPA 750 kW generator
Surface wave orbital velocity
Surface wave orbital velocity cubed
MetOcean Solutions Ltd
Units
m
m
m
m
kW.m-1
kW
kW
kW
m/s
m/s
Southland
2.79
2.02
1.79
138
40.8
216
1500
750
1.02
1.07
Westport
2.20
1.52
1.48
156
22.6
130
1467
627
0.71
0.36
Taranaki
2.13
1.45
1.46
155
22.2
116
1460
582
0.70
0.34
Port Waikato
2.04
1.45
1.33
132
21.3
104
1444
582
0.80
0.51
Gisborne
1.22
0.53
1.04
110
5.2
38
730
325
0.52
0.14
Wairarapa
1.53
0.74
1.26
123
7.3
76
1116
430
0.60
0.22
48
New Zealand Marine Energy Resources
Table 6.4
Site-specific statistics at the 99th percentile non-exceedence level based on 10-years hindcast data.
Station (6 km offshore)
Hs
Hs (swell, T>10s)
Hs (sea, T<10s)
Wavelength
Wave power
Pelamis 750 kW generator
Hypothetical Pelamis 1500 kW generator
Hypothetical SPA 750 kW generator
Surface wave orbital velocity
Surface wave orbital velocity cubed
MetOcean Solutions Ltd
Units
m
m
m
m
kW.m-1
kW
kW
kW
m/s
m/s
Southland
6.37
5.08
4.23
203
239.5
670
1500
750
2.17
10.17
Westport
5.22
3.90
3.84
256
141.3
590
1500
750
1.70
4.94
Taranaki
5.04
3.72
3.75
243
136.5
586
1500
750
1.71
4.97
Port Waikato
4.72
3.48
3.50
188
117.8
521
1500
750
1.81
5.91
Gisborne
4.23
2.70
3.60
202
80.0
530
1500
750
1.61
4.19
Wairarapa
4.73
3.13
3.84
233
96.6
590
1500
750
1.71
4.97
49
New Zealand Marine Energy Resources
Table 6.5
Location
Hs (m)
> 0 <= 0.5
> 0.5 <= 1
> 1 <= 1.5
> 1.5 <= 2
> 2 <= 2.5
> 2.5 <= 3
> 3 <= 3.5
> 3.5 <= 4
> 4 <= 4.5
> 4.5 <= 5
> 5 <= 5.5
> 5.5 <= 6
> 6 <= 6.5
> 6.5 <= 7
> 7 <= 7.5
> 7.5 <= 8
> 8 <= 8.5
> 8.5 <= 9
> 9 <= 9.5
> 9.5
Total
Joint probability distribution (parts-per-thousand) of significant wave height and
peak spectral wave period for the Southland assessment location.
Southland
0-2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
MetOcean Solutions Ltd
2-4
3.1
11.3
0.3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
14.7
4-6
1.4
4.7
16.7
10.7
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
35.5
6-8
1.2
3.8
2.8
5.1
8.5
7.9
2.9
0.6
0.1
0
0
0
0
0
0
0
0
0
0
0
32.9
Peak spectral wave period (s)
8-10
10-12 12-14 14-16
0.9
1.8
0.4
0
10.7
5.2
1.6
0.3
19.4
16.1
2.5
0.7
28.5
60
10
2.3
19.6
104.6
28.8
5
7.9
100.1
57.1
5.8
8.7
65.3
67.2
8.1
7.2
30.5
61.3
6.3
3.5
13.3
46.3
6.1
1.4
8.3
26.3
7
0.2
4.4
14.2
6.2
0.1
2.4
7.2
4.8
0
1.6
4
2.2
0
0.3
2.1
1.2
0
0.1
1.3
0.8
0
0.1
0.7
0.7
0
0
0.4
0.3
0
0
0.1
0.3
0
0
0
0
0
0
0
0
108.1 414.1 331.5
58.1
16-18
0.1
0.1
0.1
0.5
0.7
1.5
0.9
0.3
0.1
0.1
0.1
0
0
0
0
0
0
0
0
0
4.5
18-20
0
0
0
0
0
0.1
0.1
0
0
0
0
0
0
0
0
0
0
0
0
0
0.2
Total
8.9
37.7
58.6
117.1
169.2
180.4
153.2
106.2
69.4
43.1
25.1
14.5
7.8
3.6
2.2
1.5
0.7
0.4
0
0
1000
50
New Zealand Marine Energy Resources
Table 6.6
Location
Hs (m)
> 0 <= 0.5
> 0.5 <= 1
> 1 <= 1.5
> 1.5 <= 2
> 2 <= 2.5
> 2.5 <= 3
> 3 <= 3.5
> 3.5 <= 4
> 4 <= 4.5
> 4.5 <= 5
> 5 <= 5.5
> 5.5 <= 6
> 6 <= 6.5
> 6.5 <= 7
> 7 <= 7.5
> 7.5 <= 8
> 8 <= 8.5
> 8.5 <= 9
> 9 <= 9.5
> 9.5
Total
Joint probability distribution (parts-per-thousand) of significant wave height and
peak spectral wave period for the Westport assessment location.
Westport
0-2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
MetOcean Solutions Ltd
2-4
0.3
0.3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.6
4-6
0.4
3.9
4
1.7
0.3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
10.3
6-8
0.9
5.1
7.9
9.9
9.1
5.3
1.4
0.4
0
0
0
0
0
0
0
0
0
0
0
0
40
Peak spectral wave period (s)
8-10
10-12 12-14 14-16
0.4
0.2
0.1
0.2
12
7.5
1.5
0.7
33.2
65.6
12.7
2.5
34.5
132.6
54.6
5.9
25.7
95
94.1
11.1
14.7
54.8
78.4
10.9
10.3
25.4
50.3
9.6
5.8
10.4
22.7
10.1
2.9
6
8.8
6.5
1.3
3.8
3.9
3.7
0.5
2.5
1.7
1.3
0.1
0.9
0.7
0.9
0
0.6
0.4
0.3
0
0.2
0.7
0.2
0
0
0.3
0.1
0
0
0.4
0.2
0
0
0.1
0.1
0
0
0.1
0.1
0
0
0.1
0.1
0
0
0
0.2
141.4 405.5 331.6
64.7
16-18
0.1
0.1
0.5
1.8
1.6
0.9
0.3
0.2
0
0
0
0
0
0
0
0
0
0
0
0
5.5
18-20
0
0
0
0.1
0.1
0.1
0
0.1
0
0
0
0
0
0
0
0
0
0
0
0
0.4
Total
2.6
31.1
126.4
241.1
237
165.1
97.3
49.7
24.2
12.7
6
2.6
1.3
1.1
0.4
0.6
0.2
0.2
0.2
0.2
1000
51
New Zealand Marine Energy Resources
Table 6.7
Location
Hs (m)
> 0 <= 0.5
> 0.5 <= 1
> 1 <= 1.5
> 1.5 <= 2
> 2 <= 2.5
> 2.5 <= 3
> 3 <= 3.5
> 3.5 <= 4
> 4 <= 4.5
> 4.5 <= 5
> 5 <= 5.5
> 5.5 <= 6
> 6 <= 6.5
> 6.5 <= 7
> 7 <= 7.5
> 7.5 <= 8
> 8 <= 8.5
> 8.5 <= 9
> 9 <= 9.5
> 9.5
Total
Joint probability distribution (parts-per-thousand) of significant wave height and
peak spectral wave period for the Taranaki assessment location.
Taranaki
0-2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
MetOcean Solutions Ltd
2-4
0.9
1.2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2.1
4-6
1.3
4
4.7
2.8
0.1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
12.9
6-8
1.7
4.6
9
12.5
14.1
8.4
1.9
0.4
0
0
0
0
0
0
0
0
0
0
0
0
52.6
Peak spectral wave period (s)
8-10
10-12 12-14 14-16
3.2
1.3
0.4
0.3
11.6
13.9
3.1
0.8
29.2
74.9
17.3
2.8
28.2
117.7
72
8.8
18.4
79.1
104.3
13.1
15.8
40.1
79.2
12.6
13.5
17.9
46.3
12.4
7.5
7.5
19.6
9.9
4.1
5.6
7
6
1.2
3
2.8
3.2
0.3
1.8
1.1
1.4
0.1
1.2
0.7
0.4
0
0.5
0.4
0.2
0
0.4
0.4
0.1
0
0
0.3
0.1
0
0
0.1
0.1
0
0
0
0
0
0
0.1
0.1
0
0
0
0.1
0
0
0
0.1
133.1 364.9 355.1
72.5
16-18
0
0.3
0.8
1.9
1.8
0.5
0.3
0.2
0
0
0
0
0
0
0
0
0
0
0
0
5.8
18-20
0
0.1
0.1
0.1
0.2
0
0.1
0.1
0
0
0
0
0
0
0
0
0
0
0
0
0.7
Total
9.1
39.6
138.8
244
231.1
156.6
92.4
45.2
22.7
10.2
4.6
2.4
1.1
0.9
0.4
0.2
0
0.2
0.1
0.1
1000
52
New Zealand Marine Energy Resources
Table 6.8
Location
Hs (m)
> 0 <= 0.5
> 0.5 <= 1
> 1 <= 1.5
> 1.5 <= 2
> 2 <= 2.5
> 2.5 <= 3
> 3 <= 3.5
> 3.5 <= 4
> 4 <= 4.5
> 4.5 <= 5
> 5 <= 5.5
> 5.5 <= 6
> 6 <= 6.5
> 6.5 <= 7
> 7 <= 7.5
> 7.5 <= 8
> 8 <= 8.5
> 8.5 <= 9
> 9 <= 9.5
> 9.5
Total
Joint probability distribution (parts-per-thousand) of significant wave height and
peak spectral wave period for the Port Waikato assessment location.
Port Waikato
0-2
0.2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.2
MetOcean Solutions Ltd
2-4
3.2
5.4
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
9.6
4-6
0.3
2.9
8.5
3.8
0.2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
15.7
6-8
1.7
2.6
7.4
11
6.5
3.9
0.8
0
0
0
0
0
0
0
0
0
0
0
0
0
33.9
Peak spectral wave period (s)
8-10
10-12 12-14 14-16
2.1
0.6
0.3
0.2
13.4
15.3
4.2
1
26.4
83.4
23.1
4.4
20.4
131.8
88.2
12
11.3
71.6
128.3
16
9.3
28.2
86.9
17.7
6.5
11.1
38.9
16.6
3.4
5.6
13.7
10.2
1.6
4.6
4.6
5.4
0.4
2.8
2.3
2
0
1.5
0.9
0.7
0
0.8
0.4
0.4
0
0.2
0.6
0.2
0
0
0.3
0.2
0
0
0.2
0.1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
94.8
357.5 392.9
87.1
16-18
0.2
0.5
1.3
2.1
1.9
1
0.3
0.2
0.1
0.1
0
0
0
0
0
0
0
0
0
0
7.7
18-20
0
0.2
0.1
0.1
0
0.1
0.1
0
0
0
0
0
0
0
0
0
0
0
0
0
0.6
Total
8.8
45.5
155.6
269.4
235.8
147.1
74.3
33.1
16.3
7.6
3.1
1.6
1
0.5
0.3
0
0
0
0
0
1000
53
New Zealand Marine Energy Resources
Table 6.9
Location
Hs (m)
> 0 <= 0.5
> 0.5 <= 1
> 1 <= 1.5
> 1.5 <= 2
> 2 <= 2.5
> 2.5 <= 3
> 3 <= 3.5
> 3.5 <= 4
> 4 <= 4.5
> 4.5 <= 5
> 5 <= 5.5
> 5.5 <= 6
> 6 <= 6.5
> 6.5 <= 7
> 7 <= 7.5
> 7.5 <= 8
> 8 <= 8.5
> 8.5 <= 9
> 9 <= 9.5
> 9.5
Total
Joint probability distribution (parts-per-thousand) of significant wave height and
peak spectral wave period for the Gisborne assessment location.
Gisborne
0-2
0.2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.2
MetOcean Solutions Ltd
2-4
10.3
36.9
2.7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
49.9
4-6
1.9
11.8
17.1
6.4
0.6
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
37.8
Peak spectral wave period (s)
6-8
8-10
10-12 12-14 14-16
8
5.9
12
10.5
3.1
36.5
59.5
92.9
56.6
5.6
35.8
95.1
80.2
53.6
3.1
26.2
64.3
45.5
19.1
1.2
17.3
31.5
35.7
7.9
0.8
8.5
14.7
22.1
5.4
0.3
2.2
9.6
11.3
3.3
0.1
0.1
5.1
5
2
0.1
0
2.3
2.7
1.1
0
0
0.7
2
0.6
0
0
0.2
1.2
0.4
0
0
0
0.6
0.2
0
0
0
0.4
0.3
0
0
0
0.1
0.4
0
0
0
0.1
0.3
0
0
0
0
0.1
0.1
0
0
0
0
0.1
0
0
0
0
0.1
0
0
0
0
0
0
0
0
0
0
134.6 288.9 311.8 161.8
14.6
16-18
0.4
0.2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.6
18-20
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Total
52.3
300
287.6
162.7
93.8
51
26.5
12.3
6.1
3.3
1.8
0.8
0.7
0.5
0.4
0.2
0.1
0.1
0
0
1000
54
New Zealand Marine Energy Resources
Table 6.10 Joint probability distribution (parts-per-thousand) of significant wave height and
peak spectral wave period for the Wairarapa assessment location.
Location
Hs (m)
> 0 <= 0.5
> 0.5 <= 1
> 1 <= 1.5
> 1.5 <= 2
> 2 <= 2.5
> 2.5 <= 3
> 3 <= 3.5
> 3.5 <= 4
> 4 <= 4.5
> 4.5 <= 5
> 5 <= 5.5
> 5.5 <= 6
> 6 <= 6.5
> 6.5 <= 7
> 7 <= 7.5
> 7.5 <= 8
> 8 <= 8.5
> 8.5 <= 9
> 9 <= 9.5
> 9.5
Total
Wairarapa
0-2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
MetOcean Solutions Ltd
2-4
1.1
20.4
8.5
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
30
4-6
1.2
11.9
29.7
9.9
1.1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
53.8
Peak spectral wave period (s)
6-8
8-10
10-12 12-14 14-16
1
0.8
1.3
1.1
0.2
23.5
21.9
42.6
23.2
4.1
37.3
75.4
116.4
55.1
5.8
25.9
67.6
84
44.2
4.3
17.2
31.5
55.8
29.1
2.8
9.8
16.5
28.4
12.7
1.1
2.7
11.2
13.4
7.2
1
0.4
7.4
6.6
3.6
0.2
0.1
2.9
4.3
1.4
0.1
0
0.9
2.7
0.6
0.1
0
0.3
2.8
0.6
0.1
0
0.1
1.4
0.4
0
0
0
0.7
0.4
0
0
0
0.1
0.2
0
0
0
0
0.1
0
0
0
0.1
0.2
0
0
0
0
0
0
0
0
0
0.1
0
0
0
0
0
0
0
0
0
0.2
0
117.9 236.5 360.6 180.4
19.8
16-18
0
0.4
0.3
0.1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.8
18-20
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Total
6.7
148
328.5
236
137.5
68.5
35.5
18.2
8.8
4.3
3.8
1.9
1.1
0.3
0.1
0.3
0
0.1
0
0.2
1000
55
New Zealand Marine Energy Resources
Table 6.11 Southland wave power – annual persistence exceedence (%).
Spectral wave power
(kW.m-1)
>=0
>=20
>=40
>=60
>=80
>=100
>=120
>=140
>=160
>=180
>=200
>=220
>=240
>=260
>=280
>=300
>=320
>=340
>=360
>=380
>=400
>=420
>=440
>=460
>=480
>=500
MetOcean Solutions Ltd
Duration (hours)
> 12
100
75
50.12
30.91
19.41
12.54
7.98
5.38
3.65
2.37
1.56
1.02
0.68
0.55
0.39
0.27
0.22
0.17
0.12
0.08
0.04
0.04
0.02
0.02
0.02
0
> 24
100
73.84
47.93
28.55
17.27
10.65
6.65
4.19
2.47
1.56
1.03
0.59
0.38
0.26
0.16
0.12
0.1
0
0
0
0
0
0
0
0
0
> 36
100
72.16
44.88
25.34
14.9
8.55
5.05
3.2
1.59
0.84
0.4
0.32
0.22
0.16
0.1
0.04
0
0
0
0
0
0
0
0
0
0
> 48
100
70.44
41.46
22.4
12.09
6.73
3.73
1.86
0.98
0.49
0.21
0.19
0.12
0
0
0
0
0
0
0
0
0
0
0
0
0
> 60
100
68.56
38.05
19.64
9.75
5.1
2.5
1.22
0.55
0.1
0.09
0.07
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 72
100
66.38
34.56
16.41
7.77
3.96
1.33
0.31
0.19
0.1
0.09
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 84
100
63.99
31.48
14.32
5.33
2.54
0.9
0.31
0.1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 96
100
61.29
28.39
11.63
3.89
2.04
0.49
0.12
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 108
100
57.8
26.38
9.76
3.41
1.57
0.26
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 120
100
54.48
23.1
7.52
2.88
1.04
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 132
100
51.6
20.62
6.21
2.31
0.76
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 144
100
48.58
17.92
5.09
1.69
0.76
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 156
100
45.79
15.33
4.4
1.52
0.41
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 168
100
43.73
13.48
4.22
1.14
0.23
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
56
New Zealand Marine Energy Resources
Table 6.12 Westport wave power – annual persistence exceedence (%).
Spectral wave power
(kW.m-1)
>=0
>=20
>=40
>=60
>=80
>=100
>=120
>=140
>=160
>=180
>=200
>=220
>=240
>=260
>=280
>=300
>=320
>=340
>=360
>=380
>=400
>=420
>=440
>=460
>=480
>=500
MetOcean Solutions Ltd
Duration (hours)
> 12
100
54.69
22.7
10.04
5.04
2.63
1.5
0.79
0.5
0.36
0.24
0.22
0.2
0.16
0.12
0.09
0.07
0.07
0.05
0.05
0.04
0.04
0.04
0.04
0.04
0.02
> 24
100
52.61
20.67
8.37
3.56
2.01
0.91
0.39
0.23
0.13
0.11
0.07
0.07
0.07
0.06
0.03
0
0
0
0
0
0
0
0
0
0
> 36
100
50.37
17.35
6.41
2.63
0.98
0.4
0.15
0.09
0.05
0.04
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 48
100
46.99
14.32
5.02
1.48
0.33
0.06
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 60
100
43.42
11.14
2.79
0.49
0.09
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 72
100
39.46
9.07
2.11
0.34
0.09
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 84
100
34.57
7.28
1.38
0.34
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 96
100
32.06
6.15
0.97
0.13
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 108
100
28.76
5.09
0.62
0.13
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 120
100
26.27
3.91
0.49
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 132
100
23.64
3.17
0.34
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 144
100
20.77
2.53
0.18
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 156
100
19.2
1.84
0.18
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 168
100
17.34
1.84
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
57
New Zealand Marine Energy Resources
Table 6.13 Taranaki wave power – annual persistence exceedence (%).
Spectral wave power
(kW.m-1)
>=0
>=20
>=40
>=60
>=80
>=100
>=120
>=140
>=160
>=180
>=200
>=220
>=240
>=260
>=280
>=300
>=320
>=340
>=360
>=380
>=400
>=420
>=440
>=460
>=480
>=500
MetOcean Solutions Ltd
> 12
100
53.97
21.8
9.25
4.44
2.2
1.26
0.68
0.38
0.28
0.22
0.17
0.14
0.1
0.07
0.05
0.05
0.05
0.04
0.04
0.04
0.04
0.02
0.02
0.02
0.02
> 24
100
51.94
19.54
7.95
3.22
1.6
0.78
0.35
0.2
0.14
0.07
0.07
0.07
0.03
0.03
0.03
0
0
0
0
0
0
0
0
0
0
> 36
100
49.59
16.83
5.73
2.3
0.67
0.41
0.1
0.05
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 48
100
47.14
14.08
4.47
1.02
0.38
0.17
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 60
100
43.69
11
2.42
0.46
0.2
0.11
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 72
100
39.61
9.24
1.58
0.3
0.2
0.11
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Duration (hours)
> 84
> 96
100
100
35.33
32.31
7.15
5.82
0.95
0.85
0.12
0.12
0.11
0
0.11
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 108
100
29.97
5.12
0.85
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 120
100
27.7
3.94
0.46
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 132
100
25.36
3.05
0.17
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 144
100
23.61
2.25
0.17
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 156
100
21.19
1.73
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 168
100
20.07
1.55
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
58
New Zealand Marine Energy Resources
Table 6.14 Port Waikato wave power – annual persistence exceedence (%).
Spectral wave power
(kW.m-1)
>=0
>=20
>=40
>=60
>=80
>=100
>=120
>=140
>=160
>=180
>=200
>=220
>=240
>=260
>=280
>=300
>=320
>=340
>=360
>=380
>=400
>=420
>=440
>=460
>=480
>=500
MetOcean Solutions Ltd
> 12
100
52.52
19.47
7.54
3.12
1.46
0.74
0.46
0.27
0.16
0.12
0.08
0.05
0.02
0.02
0
0
0
0
0
0
0
0
0
0
0
> 24
100
50.95
17.5
6.11
2.35
0.89
0.4
0.18
0.11
0.03
0.03
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 36
100
48.81
15.08
4.78
1.41
0.47
0.19
0.04
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 48
100
46.01
12.26
3.3
0.58
0.27
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 60
100
42.43
9.96
1.54
0.27
0.16
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 72
100
39.09
7.48
1.31
0.2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Duration (hours)
> 84
> 96
100
100
35.73
32.41
5.68
4.62
0.52
0.52
0.11
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 108
100
30.3
3.69
0.39
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 120
100
28.21
3.29
0.14
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 132
100
25.9
2.7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 144
100
23.51
1.9
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 156
100
21.43
0.87
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 168
100
19.01
0.69
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
59
New Zealand Marine Energy Resources
Table 6.15 Gisborne wave power – annual persistence exceedence (%).
Spectral wave power
(kW.m-1)
>=0
>=20
>=40
>=60
>=80
>=100
>=120
>=140
>=160
>=180
>=200
>=220
>=240
>=260
>=280
>=300
>=320
>=340
>=360
>=380
>=400
>=420
>=440
>=460
>=480
>=500
MetOcean Solutions Ltd
> 12
100
13.22
4.08
1.5
0.79
0.51
0.31
0.25
0.16
0.14
0.12
0.09
0.05
0.05
0.02
0.02
0.02
0
0
0
0
0
0
0
0
0
> 24
100
11.01
2.94
0.97
0.43
0.24
0.17
0.13
0.04
0.04
0.03
0.03
0.03
0.03
0
0
0
0
0
0
0
0
0
0
0
0
> 36
100
8.94
2.25
0.58
0.14
0.05
0.04
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 48
100
7.49
1.51
0.18
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 60
100
6.19
0.81
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 72
100
5.28
0.58
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Duration (hours)
> 84
> 96
100
100
4.63
3.91
0.12
0.12
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 108
100
2.85
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 120
100
2.33
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 132
100
1.75
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 144
100
1.27
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 156
100
1.27
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 168
100
0.54
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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New Zealand Marine Energy Resources
Table 6.16 Wairarapa wave power – annual persistence exceedence (%).
Spectral wave power
(kW.m-1)
>=0
>=20
>=40
>=60
>=80
>=100
>=120
>=140
>=160
>=180
>=200
>=220
>=240
>=260
>=280
>=300
>=320
>=340
>=360
>=380
>=400
>=420
>=440
>=460
>=480
>=500
MetOcean Solutions Ltd
> 12
100
18.46
5.59
2.3
1.12
0.65
0.42
0.26
0.2
0.17
0.12
0.09
0.08
0.08
0.04
0.03
0.02
0.02
0.02
0.02
0.02
0.02
0
0
0
0
> 24
100
15.34
3.99
1.35
0.56
0.42
0.25
0.12
0.11
0.07
0.03
0.03
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 36
100
12.62
2.81
0.72
0.26
0.15
0.04
0.04
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 48
100
10.83
1.84
0.43
0.12
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 60
100
9.03
1.36
0.17
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 72
100
7.64
1.04
0.09
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Duration (hours)
> 84
> 96
100
100
6.55
5.51
0.77
0.77
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 108
100
4.43
0.65
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 120
100
3.65
0.51
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 132
100
3.35
0.37
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 144
100
2.88
0.21
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 156
100
2.53
0.21
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
> 168
100
1.78
0.21
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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New Zealand Marine Energy Resources
Table 6.17 Monthly wave height and spectral wave power statistics for the Southland
assessment location.
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
Mean Hs
(m)
2.49
2.67
2.87
3.12
3.20
3.21
2.96
3.05
3.13
3.00
2.76
2.45
2.91
MetOcean Solutions Ltd
Median Hs
(m)
2.41
2.56
2.63
2.96
3.13
3.01
2.92
3.02
3.07
2.93
2.70
2.37
2.79
Mean spectral wave
power (kW.m-1)
35.7
42.2
49.8
62.8
67.1
69.0
57.0
61.2
62.6
57.8
43.6
35.3
53.7
Median spectral wave
power (kW.m-1)
27.9
33.2
35.3
48.4
50.6
47.6
47.6
49.3
48.6
45.9
35.7
26.8
40.8
Mean daily wave
power variability (%)
29.4
28.6
27.3
28.7
29.5
28.9
27.1
30.4
32.9
31.2
28.7
30.5
29.4
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New Zealand Marine Energy Resources
7
7.1
TIDAL ENERGY RESORCES
New Zealand scale
The open-ocean tidal energy resources in New Zealand are represented in Figures 7.1
and 7.2. These plots show the depth-averaged flows associated with the Mean Spring
Tides (M2+S2) and the Highest Astronomical Tides, respectively. There are three
regions with accelerated flows; Cook Strait, Cape Reinga and the waters surrounding
Stewart Island. The tidal resources in Cook Strait and Foveaux Strait are further
considered in the following sections.
7.2
Cook Strait
The tidal energy resources within the Cook Strait are presented in Figures 7.3 and 7.4,
showing the depth-averaged flows associated with the Spring Tide (M2+S2) and the
Highest Astronomical Tide, respectively.
7.3
Foveaux Strait
The tidal energy resources within the Foveaux Strait are presented in Figures 7.5 and
7.6, showing the depth-averaged flows associated with the Spring Tide (M2+S2) and
the Highest Astronomical Tide, respectively.
7.4
Tidal power simulations
Tidal power simulations have been undertaken at six locations; five in the Cook Strait
and one in Foveaux Strait, as shown on Figures 7.7 and 7.8. At each location, the timeseries of the depth-averaged tidal flows (at 15 minute intervals) has been converted to
electrical power using the methods defined in Section 4. Two single-turbine tidal power
devices have been simulated, as described in Table 4.1. The results are summarized in
Table 7.1.
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New Zealand Marine Energy Resources
Table 7.1
Tidal energy site assessment results. Devices 1 and 2 are specified in Table 4.1,
and the site locations are shown on Figures 7.7 and 7.8.
Parameter
Mean power of the resource
Device 1
Rated time
Working time
Mean annual power
Mean annual production
Device 2
Rated time
Working time
Mean annual power
Mean annual production
MetOcean Solutions Ltd
Units
Wm-2
CS1
1,660
CS2
3,610
CS3
1,555
CS4
5,190
CS5
1,095
FX1
304
%
%
kW
MWh
4.3
63.6
105.0
919.3
14.9
79.6
200.0
1752.00
1.9
69.8
105.5
923.8
22.3
80.0
229.3
2009.1
2.0
56.5
71.5
626.1
0.0
45.7
19.4
169.8
%
%
kW
MWh
4.3
58.3
48.8
427.3
14.9
75.9
93.4
818.2
1.9
65.0
49.6
434.1
22.3
76.6
107.2
938.8
2.0
50.6
33.0
289.5
0.0
36.9
8.5
74.0
64
New Zealand Marine Energy Resources
© MetOcean Solutions Ltd. All rights reserved.
Figure 7.1 Depth-averaged tidal current speeds for the Mean Spring flows
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65
New Zealand Marine Energy Resources
© MetOcean Solutions Ltd. All rights reserved.
Figure 7.2 Depth-averaged tidal current speeds for the Highest Astronomical flows
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66
New Zealand Marine Energy Resources
Figure 7.3 Depth-averaged tidal current speeds for the Spring Tide flows in the Cook Strait,
including the 1 m/s speed contour.
Figure 7.4 Depth-averaged tidal current speeds for the Highest Astronomical Tidal flows in
the Cook Strait, including the 1 m/s speed contour.
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67
New Zealand Marine Energy Resources
Figure 7.5 Depth-averaged tidal current speeds for the Spring Tidal flows in the Foveaux
Strait region, including the 1 m/s speed contour.
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New Zealand Marine Energy Resources
Figure 7.6 Depth-averaged tidal current speeds for the Highest Astronomical Tidal flows in
the Foveaux Strait region, including the 1 m/s speed contour.
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New Zealand Marine Energy Resources
Figure 7.7 The output locations in the Cook Strait region for detailed tidal power generation
simulation. The Spring Tidal flows are also shown, along with the 1 m/s speed
contour and the 25 m water depth contour.
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New Zealand Marine Energy Resources
Figure 7.8 The output location in the Foveaux Strait region for detailed tidal power
generation simulation. The Spring Tidal flows are also shown, along with the 1
m/s speed contour and the 25 m water depth contour.
MetOcean Solutions Ltd
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New Zealand Marine Energy Resources
8
SUMMARY
An investigation of the open ocean marine energy resources in New Zealand waters has
been undertaken. The scope has utilised the following methods:
•
A region-scale 10-year numerical wave hindcast for New Zealand, with detailed
validation for wave statistics and wave power;
•
Depth-averaged tidal current modelling of New Zealand waters, with highresolution modelling of the Cook Strait and Foveaux Strait regions;
The specific deliverables that have been produced are:
•
Summary maps of the open-coast tidal resource, wave climate, potential wave
power, and energy output for generic wave conversion devices.
•
Detailed analysis of two potential tidal energy regions and six wave energy sites,
considering the environmental statistics, probable power output, daily and
seasonal variability and time-domain analyses.
The summary modelling results are:
•
There is a mean annual wave power resource of at least 30 kW.m-1 available
within about 15 km of the shoreline along most of the West Coast of New
Zealand, excepting the Western Cook Strait region and the North Taranaki
Bight. The most energetic wave power location is along the Southland coast,
from Fiordland to the west of Stewart Island. Along the East Coast of New
Zealand, only the Catlins region in South Otago has an equivalent resource to
the West Coast. In the North Island, the coastline from Wairarapa to East Cape
is the next most energetic region, with around one third of the median energy of
the West Coast.
•
There are three locations in New Zealand with an open-coast tidal resource;
Cook Strait, Cape Reinga and the waters surrounding Stewart Island. The mean
annual Cook Strait resource is as high as 5000 Wm-2, while the resource in
Foveaux Strait adjacent to Bluff is approximately 300 Wm-2.
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New Zealand Marine Energy Resources
9
REFERENCES
BTW (1989). Wave climate report Western Foveaux Strait. Report prepared for Electricorp
Production. Report Ref. 8645.
Burger M.F, Van Gelder P.H.A.J.M, Gardner F. (2005). Wave energy converter performance
standard "a communication tool. 6th European Wave and Tidal Energy Conference,
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Egbert, G.D., and S.Y. Erofeeva, (2002). Efficient inverse modeling of barotropic ocean tides,
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Flather, R.A. (1976) A tidal model of the northwest European continental shelf. Memoires de
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Goda, Y. (1970). Numerical experiments on wave statistics and spectral estimates. Report of
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for the long-term integration of regional oceanic models. Ocean Modelling, 3, 1-20
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model”.
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University,
Princeton,
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from:
http://www.aos.princeton.edu/WWPUBLIC/htdocs.pom/
Orlanski, I. (1976) A simple boundary condition for unbounded hyperbolic flows. Journal of
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Salter S.H. and Taylor J.R.M., (1984). Bending moments in long spines. Edinburgh
University Wave Power Project report submitted to the UK Wave Energy Steering
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Tolman, H.L. and D. Chalikov, (1996). Source terms in a third-generation wind-wave model.
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Tengku Andri