A SOPAC Desktop Study of Ocean-Based Renewable Energy Technologies

SOPAC Miscellaneous Report 701

A technical publication produced by the SOPAC Community Lifelines Programme Acknowledgements

Information presented in this publication has been sourced mainly from the internet and from publications produced by the International Energy Agency (IEA).

The compiler would like to thank the following for reviewing and contributing to this publication:

• Dr. Luis Vega • Anthony Derrick of IT Power, UK • Guillaume Dréau of Société de Recherche du Pacifique (SRP), New Caledonia • Professor Young-Ho Lee of Korea Maritime University, Korea • Professor Chul H. (Joe) Jo of Inha University, Korea • Luke Gowing and Garry Venus of Argo Environmental Ltd, New Zealand SOPAC Miscellaneous Report 701 Pacific Islands Applied Geoscience Commission (SOPAC), Fiji

• Paul Fairbairn – Manager Community Lifelines Programme • Rupeni Mario – Senior Energy Adviser • Arieta Gonelevu – Senior Energy Project Officer • Frank Vukikimoala – Energy Project Officer • Koin Etuati – Energy Project Officer • Reshika Singh – Energy Resource Economist • Atishma Vandana Lal – Energy Support Officer • Mereseini (Lala) Bukarau – Senior Adviser Technical Publications Ivan Krishna • Sailesh Kumar Sen – Graphic Arts Officer Compiler

First Edition October 2009

Cover Photo Source: HTTP://WALLPAPERS.FREE-REVIEW.NET/42__BIG_WAVE.HTM Back Cover Photo: Raj Singh A SOPAC Desktop Study of Ocean-Based Renewable Energy Technologies

SOPAC Miscellaneous Report 701

Ivan Krishna Compiler

First Edition October 2009

A technical publication produced by the SOPAC Community Lifelines Programme SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 4 List ofAcronyms ACP WB WEC VAT US$ USA USP UNELCO UN UNDP UNCTAD UK TFPM S.p.A SARA SSG SWEL SPR SPC SRP SOPAC SERI RITE RED REM PM PTO PNG PRO PIRE PIFS PIEPSAP PIC OWC OC-OTEC CC-OTEC OTEC NREL NaREC NIOT NELHA MHD MST MW MJ LFPM kW kVA IMF IEA GHG GEF GDP FJ$ FRP EMC EST EU EN EPA EPC DTI DECM DOE (USA) CO2 CAD$ CIRAD CWP CDM AWS ASTM ADB World Bank Wave EnergyConverter Value AddedTax United StatesDollar United StatesofAmerica University oftheSouthPacific Vanuatu’s PowerUtility United Nations United NationsDevelopmentProgramme United NationsConferenceonTradeAndDevelopment United Kingdom Transverse FluxPermanentMagnet Società perAzioni Scientific Applications&ResearchAssociates Seawave Slot-ConeGenerator SyncWave EnergyLatchingSystem SyncWave PowerResonator Secretariat ofthePacificCommunity Société deRechercheduPacifique Secretariat ofthePacificAppliedGeoscienceCommission Solar EnergyResearchInstitute Roosevelt IslandTidalEnergy Reversed ElectroDialysis Regional EnergyOfficialsMeeting Permanent Magnet Power Take-OffMechanism Papua NewGuinea Pressure RetardedOsmosis Pacific IslandRenewableEnergyProject Pacific IslandForumSecretariat Pacific IslandEnergyPolicyandStrategicActionPlan Pacific IslandCountry Oscillating Watercolumn Open CycleOTEC Closed CycleOTEC Ocean ThermalEnergyConversion National RenewableEnergyLaboratory New andRenewableEnergyCentre National InstituteofOceanTechnology Natural EnergyLaboratoryofHawaiiAuthority Magnetohydrodynamic Multi-Stage Turbine Mega Watt Mega Joule Longitudinal FluxPermanentMagnet Kilo Watt,ameasureofrealpower Kilo VoltAmpere,ameasureofapparentpower International MonetaryFund International EnergyAgency Greenhouse as Global EnvironmentalFacility Gross DomesticProduct Fiji Dollar Fibreglass ReinforcedPlastic European MarinenergyCentre Early StageTechnologies European Union European Norm Environmental ProtectionAgency Electric PowerCorporation,Samoa Department ofTradeandIndustry Direct EnergyConversionMethod Department OfEnergy-USA Carbon Dioxide Canadian Dollars Centre deco-opérationInternationaleenRechercheAgronomiqueDéveloppement Cold WaterPipe Clean DevelopmentMechanism Archimedes WaveSwing American StandardsandMeasurementsBureau Asian DevelopmentBank EU memberstatesinAfrica,CaribbeanandPacific A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Table of Contents

Executive Summary...... 9

1. introduction...... 1 0

2. Ocean Thermal Energy Conversion Technology...... 1 1 2.1 introduction...... 11 2.2 background and History of OTEC ...... 11 2.3 Technology Types...... 13 2.3.1 Closed-Cycle OTEC...... 13 2.3.1.1 Kalina and Uehara Cycles...... 15 2.3.2 Open-Cycle OTEC...... 17 2.3.3 hybrid OTEC System...... 19 2.4 Plant Design and Location...... 19 2.5 Other Uses of OTEC Technology...... 21 2.5.1 Air Conditioning...... 21 2.5.2 Chilled-soil Agriculture...... 21 2.5.3 Aquaculture...... 21 2.5.4 Desalination...... 22 2.5.5 hydrogen Production...... 22 2.5.6 Mineral Extraction...... 22 2.6 limitations of OTEC Technologies...... 22 2.6.1 Technical Challenges...... 22 2.6.2 engineering Challenges...... 24 2.6.3 Disadvantages of OTEC...... 24 2.6.4 OTEC and the Environment...... 25 2.6.5 economic Considerations and Market Potential...... 27 2.7 Discussion...... 28

3. wave Energy Technology...... 3 0 3.1 introduction and Background...... 30 3.1.1 hydrodynamics...... 34 3.2 Technology Types...... 35 3.2.1 Oscillating Bodies...... 36 3.2.1.1 Pelamis Wave Power...... 36 3.2.1.2 AWS Ocean Energy...... 38 3.2.1.3 Fred Olsen’s FO3...... 39 3.2.1.4 waveBob...... 40 3.2.1.5 Finavera Renewables AquaBuOY...... 40 3.2.1.6 wave Energy Technologies (WET EnGen)...... 42 3.2.1.7 CETO...... 43 3.2.1.8 wave Star Energy...... 44 3.2.1.9 Seabased...... 45 3.2.1.10 bioPower Systems (bioWAVE)...... 46 3.2.1.11 Aquamarine Power (Oyster)...... 47 SOPAC Miscellaneous Report 701 5 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 6 nuku’alofa, Tonga......

Appendix B : Appendix A: bibliography...... 7. 6. 5. 4.

4.4 4.3 4.2 background...... 4.1 3.5 wavePowerPotentialinPacificIslandCountries...... 3.4 3.3 5.3 5.2 5.1 Conclusion andRecommendations...... Salinity GradientTechnology...... Tidal EnergyTechnology...... Discussion...... Case Study:Tide-EnergyProjectneartheMouthofAmazon...... Technology Types...... 4.2.2 4.2.1 Discussion...... Secondary Technologies...... 3.3.1 3.2.3 3.2.2 Discussion...... Pressure RetardedOsmosis(PRO)...... Reversed ElectroDialysis(RD)......

4.2.2.11 wanxiangVerticalTurbines,China...... 4.2.2.10 enermarKoboldTurbine,PonteDiArchimede International 4.2.2.9 gorlovHelicalTurbine,GCKTechnology,US...... 4.2.2.8 4.2.2.7 4.2.2.6 4.2.2.5 4.2.2.4 hammerfestStromAS,Norway...... 4.2.2.3 4.2.2.2 4.2.2.1 Tidal Stream...... 4.2.1.5 environmentImplicationsofTidal Barrage...... 4.2.1.4 4.2.1.3 4.2.1.2 4.2.1.1 Tidal Barrage...... 3.3.1.3 linearGenerator...... 3.3.1.2 hydraulicSystem...... 3.3.1.1 Power Take-OffMethods...... 3.2.3.2 waveDragon...... 3.2.3.1 Overtopping Devices...... 3.2.2.4 3.2.2.3 3.2.2.2 waveGen...... 3.2.2.1 Oscillating WaterColumn...... 3.2.1.14 3.2.1.13 3.2.1.12 Ocean Technologies SessionoftheREM&P EMM 2009,22nd April2009, Economics forOTCinMarshall Islands...... Pulse TidalPS100EnergyConverter,UK...... S.p.A., Italy...... Open-Centre Turbine,OpenHydro,Ireland...... TidEl, SoilMachineDynamicsHydrovision,UK...... Clean Current,Canada...... Underwater ElectricKite,UKSystems,US...... Verdant Power,USA...... SeaFlow andSeaGen,MarineCurrentTechnologies,UK...... Cost EffectivenessofTidalBarrages...... Two-Basin arrage,UNAMEngineeringInstitute,Mexico...... Tidal Delay,WoodshedTechnologiesPtyLtd,Australia...... Offshore TidalLagoons,Electric,UK...... Magnetohydrodynamic Generator...... Seawave Slot-ConeGenerator(SS)...... Orecon...... Offshore WaveEnergy(OWEL)...... Oceanlinx...... SyncWave Systems...... Ocean Navitas...... Trident Energy...... 9 7 3 8 4 8 88 87 78 61 75 73 73 72 72 71 71 70 69 69 68 66 65 65 64 63 63 63 61 60 59 58 57 56 56 55 55 55 53 53 53 52 51 51 50 60 49 48 48 82 80 79 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies List of Figures

Figure 2.1: The open-cycle OTEC at Keahole Point, Hawaii Island...... 12 Figure 2.2: Closed Rankine cycle OTEC flow diagram...... 13 Figure 2.3: T-S diagram of a typical Rankine Cycle operating between pressures of 0.06 bar and 50 bar...... 14 Figure 2.4: evolution of the Rankin cycle to the Uehara Cycle...... 16 Figure 2.5: Diagram of the Uehara Cycle...... 17 Figure 2.6: Open cycle OTEC flow diagram...... 18 Figure 2.7: hybrid OTEC system...... 19 Figure 2.8: Map of suitable sites for OTEC...... 20 Figure 2.9: Artist's impression of an OTEC system...... 29

Figure 3.1: wave generation...... 30 Figure 3.2: Approximate global distribution of wave power levels...... 31 Figure 3.3: illustration of the wave nomenclature shown on Table 3.1...... 32 Figure 3.4: illustration of how wave period and amplitude affect the wave power density...... 32 Figure 3.5: Power per meter of wave front...... 33 Figure 3.6: Types of wave energy converters...... 35 Figure 3.7: Pelamis attenuator...... 37 Figure 3.8: Archimedes Wave-swing energy system by AWS Ocean Energy...... 38 Figure 3.9: Fred Olsen’s FO3...... 39 Figure 3.10: The WaveBob...... 40 Figure 3.11: Diagram of the AquaBuOY’s operation...... 41 Figure 3.12: Diagram of the WET EnGen...... 42 Figure 3.13: WET EnGen prototype at Sandy Cove, Nova Scotia...... 42 Figure 3.14: The CETO I prototype in Fremantle, Australia...... 43 Figure 3.15: CETO II wave energy converter...... 44 Figure 3.16: Wave Star prototype at Nissum Bredning, Denmark...... 45 Figure 3.17: Diagram of the direct drive linear generator...... 45 Figure 3.18: bioWAVE model being tested in a wave tank...... 46 Figure 3.19: Full-scale Oyster...... 47 Figure 3.20: Oyster wave energy conversion system...... 47 Figure 3.21: DECM wave tank trials...... 48 Figure 3.22: Trident’s 20 kW prototype...... 48 Figure 3.23: Aegir Dynamos’ operational diagram and full-scale device...... 49 Figure 3.24: SyncWave Power Resonator prototype “Charlotte”...... 49 Figure 3.25: Diagram of the LIMPET...... 51 Figure 3.26: Oceanlinx’s OWC...... 52 Figure 3.27: Grampus model in wave tank tests...... 53 Figure 3.28: Wave Dragon diagram and prototype...... 54 Figure 3.29: Ramp used in the Wave Dragon...... 54 Figure 3.30: Artist's Impression of the Seawave Slot-Cone generator...... 55 Figure 3.31: TFPM machine with flux concentration and stationary magnets...... 57 Figure 3.32: 100 KW laboratory prototype MWEC system during testing at SARA in March 2007...... 58

Figure 4.1: barrage in La Rance at high tide...... 63 Figure 4.2: barrage in La Rance at low tide...... 64 Figure 4.3: The SeaGen rotors can be raised above the surface for maintenance...... 66 Figure 4.4: SeaGen’s predecessor, the 300 kW ‘SeaFlow’ turbine off the north coast of Devon...... 67 Figure 4.5: Verdant Power Free Flow Turbines at RITE Project, New York City...... 68 Figure 4.6: hammerfest Strom’s prototype being deployed...... 69 Figure 4.7: Underwater Electric Kite prototype...... 69 SOPAC Miscellaneous Report 701 7 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 8 List of Figure 4.14: Figure 4.15: Figure 4.16: Figure 4.17: Figure 4.18: Figure 4.19: Figure 4.20: Figure 5.1: Figure 5.2: Table 3.2: wavenomenclatureforcalculatingwavepower...... Table 3.1: Figure 4.11: Table 3.4: eMINETEconomicAnalysis...... Table 3.3: Figure 4.13: Figure 4.12: Gorlov Helicalturbine...... Table 3.5: Table 3.6: Figure 4.8: Table 2.1: Figure 4.9: Table 2.2: Figure 4.10: Pulse Tidal’s100kWHumberprototypesystem...... Comparison betweenusinghydrofoilsversusturbines...... Rural artisansassembled,installed,andoperatethis6-bladeGorlovhelicalturbine...... Managing tidalflowwithtwojetties,aduct,andgate...... Automotive alternator...... Pulley, 1.08mindiameterandbelt...... 6-blade Gorlovhelicalturbine...... Diagram ofReverseElectrodialysis...... Diagram ofthePROprocess...... Development statusofoscillatingbodies...... Open Hydroturbineatthetestsite...... Pelamis feasibilitystudy,NewCaledonia...... Kobold turbine...... Development statusofOWCtechnology...... Comparison ofbuoyandGEOSATMeanSignificantWaveHeight...... Clean Current’sprototypedeployment...... Comparison ofrequiredseawaterforOTECplant...... Diagram ofCleanCurrent'sprototype...... The netbenefits...... TidEl prototype...... Tables ...... 73 74 74 75 76 77 77 77 79 81 28 71 31 37 36 72 71 38 50 59 70 17 70 A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies Ocean Based Renewable Energy Technologies

Executive Summary

At the 2009 Pacific Energy Ministers' Meeting (PEMM) held in Tonga, Pacific Island Leaders recognised that energy security is an imperative for economic growth and human development. Pacific island economies are the most vulnerable in the world to rising oil prices and therefore there is an urgent need to reduce this vulnerability through the use of renewable sources of energy. The Pacific Ocean, the largest ocean in the world could be one of the renewable energy sources for Pacific Island Countries.

Energy from the oceans can be divided into three main categories, ocean thermal, wave energy and tidal current energy. Apart from the above there is another category called salinity gradient which uses the known property of mixing freshwater with seawater to release energy. The challenge is to utilise this energy, since the energy released from the mixing only gives a very small increase in the local temperature of the water. Two concepts for converting this energy into electricity instead of heat have been identified, Reversed Electro Dialysis (RED) and Pressure Retarded Osmosis (PRO).

Ocean Thermal Energy Conversion or OTEC for short is a technology that utilises the heat energy stored in the ocean’s natural temperature gradient. In principle, OTEC utilises the difference in temperature between the warm, surface seawater and the cold, deep seawater to drive a turbine that is connected to a generator which in turn produces electricity. Ideally for practical operation, it is desirable that the temperature difference between the warm surface water and the cold deep water be at least 20˚C. OTEC has potential in a limited number of Pacific Island Countries.

Harnessing energy from tides using tidal barrages has by far the longest history of successful generation of electricity from ocean resources. It represents an older and mature technology with a potential for negative environmental impacts. In La Rance, France, a 240 MW tidal barrage has been in operation for over 40 years. Tidal stream energy represents a different approach to extracting energy from tides or other marine currents. Rather than using a dam structure, the devices are placed directly “in-stream” and generate energy from the flow of water. SeaGen is the world’s first large scale commercial tidal stream generator and generates 1.2 MW between 18-20 hours a day. New Zealand is currently working towards the development of a project on the Kaipara Harbour on the West Coast north of Auckland.

A variety of technologies have been proposed to capture the energy from waves. Some of the more promising designs such as the Pelamis and the Archimedes wave swing are undergoing demonstration testing at commercial scales. While all wave energy technologies are intended to be installed at or near the water’s surface, they differ in their orientation to the waves with which they are interacting and in the manner in which they convert the energy of the waves into other energy forms.

This report traces the development of the above ocean energy conversion methods, along with their impact on the environment, economic viability, sustainability and applicability to the Pacific region. SOPAC Miscellaneous Report 701 9 SOPAC Miscellaneous Report 701 Ocean BasedRenewableEnergyTechnologies 10 1. Introduction the moon and the sun and the interaction of their gravitational forces. A number of factors relating to Salinity Gradient: technology Temperature Gradient: the time.increase constrainedchannels where areas coastal in apparent more are conditions Tide water being While The trials of various concepts and reported successes of several deployments in the ocean the in renewabledeployments several of successes reported and concepts various of trials The broadly Marine Current: Marine Ocean in Harnessing by electrolysis. Ocean Tides: (e) SalinityGradient. pre-commercial deployment. few very infancyof with experiencinganythe kind stage in mostly are resources energy ocean sources, currents combined with phenomena a create multitudeglobal wind currents. of atmospheric These wind with technology mature and older an represents It resources. ocean from electricity of generation been complex through transferred is that energy solar concentrated of form a wavesis ocean in energy The water, andthistemperature difference energy. createsthermal largest solar collectors. The sun’s heat warms the surface water a lot more than the deep ocean The been seawater earth’s water world’s a elusive. in through explored the Waves: potential operation categorized are wind-wave such flow gravitational resource energy have elevation energy responsible oceans

Oceans desalination,

and as Kinetic for for At gained for salinity increase energy sector, from interactions. hold negative into: potential and over cover

and for significant conversion (OTEC) processes. using modularsystems. deep-water Thermal energy due to temperature gradient between sea surface and pressure-retarded energy associated with the salinity gradient using a can be harnessed technologies. types oftechnologies. Energy associated with ocean waves can be harnessed using modular estuary. barrages building by harnessed be can tides with associated energy Potential

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Ocean Based Renewable Energy Technologies Ocean Based Renewable Energy Technologies

2. Ocean Thermal Energy Conversion Technology

2.1 Introduction

Ocean Thermal Energy Conversion or OTEC for short is a method for generating electricity that utilises the heat energy stored in the ocean’s natural temperature gradient. In principle, OTEC utilises the difference in temperature between the warm, surface seawater and the cold, deep seawater to drive a turbine that is connected to a generator which in turn produces electricity. Ideally, for practical operation, it is always desirable that the temperature difference between the warm surface water and the cold deep water be at least 20°C. The temperature difference that exists between the surface and deep sea water throughout the tropical regions of the world is usually constant all year round.

OTEC operates on a reverse principle to refrigerators and air conditioners where an OTEC fluid with a low boiling point (e.g. ammonia) is used and turned into vapour by heating it up with warm sea water. The pressure of the expanding vapour turns a turbine and produces electricity. Cold sea water is then used to reliquefy the fluid. One important by product of these techniques is fresh water. This is also an indirect method of utilising solar energy. A large amount of solar energy is collected and stored in tropical oceans. The surface of the water acts as the collector for solar heat, while the upper layer of the sea constitutes infinite heat storage reservoir. Thus the heat contained in the ocean could be converted to electricity by utilising the temperature difference between the warm surface waters and the colder waters in the depths of about 20 – 750 m. 2.2 Background and History of OTEC [1]

In 1881, Jacques Arsene d’Arsonval, a French physicist, proposed tapping the thermal energy of the ocean. It was d’Arsonval’s student, Georges Claude who actually built the first OTEC plant at Matanzas Bay, Cuba, in 1930. The system generated 22 kW of electricity using a low- pressure turbine. In 1935, Claude constructed another plant aboard a 10,000 tonnes cargo vessel moored off the coast of Brazil. Weather and waves destroyed both plants before they could become net power generators.

Then in 1956, French researchers designed a 3 MW plant for Abidjan, Côte d’Ivoire. The plant was never completed due to the large amounts of cheap oil that became available in the 1950s and competition from inexpensive hydroelectric power. In 1962, J. Hilbert Anderson and James H. Anderson, Jr. started designing a cycle to accomplish what Claude had not. They focused on developing new, more efficient component designs. After working through some of the problems in Claude’s design they patented their new “closed cycle” design in 1967. SOPAC Miscellaneous Report 701 11 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 12 the plantwasdestroyedbyacyclonein1984. engineering expectations by surpassed producing 30 plant kW The of net used. power during was continuous operating exchanger tests. Unfortunately heat shell-and-tube titanium fluid, working a the and was Freon meters. 580 of depth a to bed sea the on laid pipe cold-water employed plant This grid. power real a to sent was power the where system OTEC an from to power a school and several other places in used was electricity remaining the and itself plant the power to used was kW 90 electricity; of kW 120 about produced 1981, October, of 14th the on operational became which plant, The of island the on plant OTEC cycle closed kW 120 a deployed and built successfully Tokyo The countries. other to export for primarily technology, the of Although Japan has no potential OTEC sites it has been a major contributor to the development power andanetof15kW. Navy barge moored approximately 2 km off Keahole Point. The plant produced 52 kW of gross at up went plant USA. the in costs electricity highest because and water cold deep to access excellent water, surface warm the to technology. OTEC for Kona coast of C research in 1974, when the when 1974, Natural in research OTEC in involved became (USA) America of States United The Figure 2.1:Theopen-cycleOTE C atKeaholePoint,Hawai'iIsland(Source: [1]). Energy Hawaii. The laboratory has now become one of the world’s leading test facilities Laboratory of C,” the plant was mounted on a converted U.S. converted a on mounted was plant the “Mini-OTEC,” as Known NELHA. C, due OTEC, for USA the in location best the be to said often is Hawai'i Hawai'i Authority (NELHA) was established at Keahole Point on the C demonstration OTEC cycle closed kW 50 first the 1979, In Nauru. This set a world record for power output lectric Power Company Power Electric awai'i has the has Hawai'i Nauru. A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

India piloted a 1 MW floating OTEC plant 30 km off shore from Tuticorin, South East of India. This was a result of collaborative work done between Saga University of Japan and the National Institute of Ocean Technology (NIOT) in India. NIOT has also set up an island-based low temperature thermal desalination plant at Kavaratti, India, in 2005; and demonstrated an experimental barge-mounted desalination plant off the Chennai Coast, India, in 2007. 2.3 Technology Types

OTEC obtains the thermal energy associated with the temperature difference between the warm seawater in surface layer and the cold seawater at greater depth. When there is any thermal head, the heat should transfer from the higher temperature side to the lower temperature side naturally. It is the differential in temperature of the fluid that is used to create an increase in pressure in another. This increase in pressure is utilised to generate mechanical work which in turn generates electricity. The open-cycle, closed Rankine cycle, Kalina cycle and the Uehara cycle are some considerations for OTEC operation.

OTEC systems rely on the basic relationship between pressure, temperature and volume of a fluid, which is governed by the following equation known as the Ideal Gas Law:-

PV = nRT where (P) is the absolute pressure of the gas, (V) is the volume of the gas, (n) PV/T = nR is the amount of the gas usually represented in moles, (R) is the gas constant PV/T = constant (which is 8.314472 JK-1mol-1 in SI units) and T is the absolute temperature.

2.3.1 Closed-Cycle OTEC (CC-OTEC) The operation of a CC-OTEC plant mainly uses anhydrous ammonia as the working fluid. Figure 2.2 shows a simplified flow diagram of the CC-OTEC cycle.

Turbine Generator Warm Surface Seawater

Warm Seawater Pump Evaporator Condenser

Working Fluid

Pump Cold Seawater Pump

Cold Seawater

Figure 2.2: Closed rankine Cycle OTEC flow diagram (Source: [5]). SOPAC Miscellaneous Report 701 13 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 14 of choiceduetoitslowboilingpoint. the white billowy clouds, seen leaving cooling towers. invisible until it comes in contact with cool, saturated air, at which point it condenses and forms work. useful to converted be not could that heat waste the represents and cycle) power Rankine closed-loop the from (not systems cooling the by generated is stations power from billowing seen often vapour water The constantly. re-used is and loop closed a follows cycle Rankine a in fluid working The plants. generation power in found commonly are that engines heat steam by used is which cycle Rankine the following by operates CC-OTEC evaporator. turbine into liquid. The ammonia liquid ammonia vapour The liquid. into ammonia turbine the converts condenser the through passing water sea Cold an expander where it passes through and rotates a turbine which is connected to a generator. liquid and (evaporator exchanger heat condenser). and turbine pump, a components: three has which loop, closed a around pumped ammonia, as such fluid, working a uses system closed-cycle The pump, Variables: 50 bar(Source:[3]) and bar 0.06 of pressures between operating cycle Rankine typical a of diagram T-S 2.3: Figure Box 1: therm W m Q into high-pressure ammonia vapour at vapour ammonia high-pressure into 4 . . . turb ProcessesoftheRankinecycle[2] In Figure 2.2 warm seawater passing through the evaporator converts the ammonia processes, dimensionless (turbine) expansion and pump) (feed compression the of efficiency Isentropic dimensionless) input, heat per output power (net process the of efficiency Thermodynamic time) unit per (energy system the to provided or by consumed power Mechanical Mass flowrate(massperunittime) Heat flowratetoorfromthesystem(energyperunittime) from the condenser is then pumped again into the into again pumped then is condenser the from 3 . The high-pressure vapour high-pressure The 5. In CC-OTEC, ammonia is usually the fluid ote that steam is steam that Note is then fed into fed then is 1 rm the from 2

A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

h1,h2,h3,h4 The “specific enthalpies” at indicated points on the T-S diagram

h4s The final “specific enthalpy” of the fluid if the turbine was isentropic

p1, p2, The pressures before and after the compression process There are four processes in the Rankine cycle, each changing the state of the working fluid. These states are identified by number in Figure 2.3. Process 1-2: The working fluid is pumped from low to high pressure, as the fluid is a liquid at this stage, the pump requires little input energy. Process 2-3: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapour. Process 3-4: The dry saturated vapour expands through a turbine, generating power. This decreases the temperature and pressure of the vapour, and some condensation may occur. Process 4-1: The wet vapour then enters a condenser where it is condensed at a constant pressure and temperature to become a saturated liquid. The pressure and temperature of the condenser is fixed by the temperature of the cooling coils as the fluid is undergoing a phase-change. Based on a unit mass flow rate of ammonia vapour (kg per second), the CC–OTEC standard

2.3.1.1 Kalina and Uehara Cycles [3] Looking back on the history of thermal cycle technology, every approach has been tried with the Rankine cycle, of which the theory was established by Rankine in 1851, but invented by Watt in 1769. The Rankine cycle is based on using a singly composed thermal medium as the working fluid.

In 1985, Dr Kalina put forward a new cycle employing quite a different concept with an ammonia/water mixture as the heat medium. The new cycle was called the ‘Kalina cycle’ and attained significant improvement of cycle efficiency, which was a large jump up on previous known cycles; however, the efficiency varied depending upon conditions. For example under the condition of 28˚C warm water and 4˚C cold water, the expected thermal cycle efficiency of the conventional Rankine cycle is 3%, while 5% efficiency is expected by applying the Kalina cycle. SOPAC Miscellaneous Report 701 15 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 16 with respecttoeachcycle. Uehara cycle, where additional components as depicted by the different colours are added on extraction of vapor from the turbine [3]. Figure 2.4 shows the evolution of of the Rankin means cycle by to condenser the the for load the lessening by cycle Kalina the than efficiency higher theoretically assures cycle Uehara The 1994. in invented, was mixture ammonia/water using cycle thermal new a load, condenser relieving of purpose the For condenser. the exchangers particularly heat the on load in increase considerable a in results which cycle thermal the in mixture a of composed medium heat a employing for consequence a however is There improve itsefficiencymuchmore[4]. efficiency. The Uehara cycle further adds a second turbine, a heater, and an after-condenser to cycle the improve to absorber an and regenerator, a separator, a added had cycle Kalina The 2.5. Figure in shown cycle Uehara the as known 1994, in system new a developed colleague required. were condenser of area surface the and seawater cold deep of amount large a value, in lower considerably fluid. pure a using conventional cycle the of Rankine that than smaller was cycle Kalina the in condenser and evaporator of the ammonia-water mixture as the working fluid of the Kalina cycle for OTEC, the performance used they If 4˚C. was temperature seawater cold inlet the and 28˚C was temperature seawater the Kalina cycle and found that efficiency of the Kalina cycle became 5% when the inlet warm and Uehara 1993, In Figure 2.4:EvolutionoftheRankinCycletoUehara(Source [3]). Seawater Warm Pump Kalina Cycle Rankin Cycle Uehara Cycle Circulation Pump Evaporator

C using OTEC of analysis performance parametric the conducted Ikegami

Circulation Pump n order to correct the defect of the Kalina cycle, Uehara and his and Uehara cycle, Kalina the of defect the correct to order In pcal, h promne f h cnesr became condenser the of performance the Especially, Separator

Regenerator

Condenser After Heater Turbine 1

Cold Seawater

Pump Turbine 2 Absorber Condenser

A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Separator Turbine 1 Evaporator

Heater Turbine 2 Regenerator Warm Seawater Tank 2 Pump

Absorber

Circulation Pump

Diffuser Condenser Tank 1

Circulation Pump

After Cold Seawater Condenser Pump

Figure 2.5: Diagram of the Uehara Cycle (Source [3]).

Table 2.1: Comparison of required seawater for OTEC plant [4] Condition: Gross output 100MW Surface water temp. 28˚C Depth water temp. 4˚C Conventional Rankine Advanced Uehara Warm surface seawater 200 m3/s 110 m3/s Cold Depth seawater 200 m3/s 120 m3/s

2.3.2 Open-Cycle OTEC (OC-OTEC) The open-cycle system is generally similar to the closed-cycle system and uses the same basic components. In principle OC-OTEC consists of the following main steps: 1. Flash evaporation of a fraction of the warm seawater by reduction of pressure below the saturation value corresponding to its temperature. 2. expansion of the vapour through a turbine to generate power. 3. heat transfer to the cold seawater thermal sink resulting in condensation of the working fluid. 4. Compression of the non-condensable gases (air released from the seawater streams at the low operating pressure) to pressures required to discharge them from the system. In the case of a surface condenser the condensate (desalinated water) must be compressed to pressures required to discharge it from the power generating system. SOPAC Miscellaneous Report 701 17 SOPACSOPAC MiscellaneousMiscellaneous ReportReport 701701 A SOPACDesktopStudyofOcean-based-RenewableenergyTechnologies A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 18 18

seawater passing through the evaporator the through passing seawater fluid. working the as seawater warm the uses system open-cycle The Figure 2.6:Open-cycleOTeCflowdiagramSOURC Description oftheflashevaporationprocessexcerptedfrom[5]: After turbine/generator. desalinated waterispurefreshwaterwhichcanbeusedfordomesticandcommercialuse. the drives which steam), to leaving the turbine converted is evaporator the entering seawater passing through the evaporator the through passing seawater fluid. working the as seawater warm the uses system open-cycle The Figure 2.6:Open-cycleOTECflowdiagram(Source[6]). Description oftheflashevaporationprocessexcerptedfrom[5]: After turbine/generator. desalinated waterispurefreshwaterwhichcanbeusedfordomesticandcommercialuse. the drives which steam), to leaving the turbine converted is evaporator the entering Pump Seawater Warm is closedandparallelstheRankine cycle.” cycle the environment, its and engine heat OC-OTeC the both includes that system a For it usually is perceived as the means to reduce pressure in the system below atmospheric. a compressor. Although the primary role of the compressor is to discharge exhaust gases, come out of solution, and air that may have leaked have into that gases the dissolved vapour, system, water residual must any include be which gases, pressurised condensable with the elevation of the condenser is suitably high, it can be compressed hydrostatically. if or, pump a of means by discharge of point the at conditions ambient to pressurized be effluent from the low-pressure condenser must be returned to the environment. working fluid. the become to vaporized is that mass of fraction small the to seawater warm the of bulk the from energy thermal of transfer a as seen be can evaporation flash above, mentioned as Thus, boiling. of cessation the and temperature liquid the phase of lowering liquid a in the results and from comes energy This vaporization. of heat its it with away carries it generated, is steam As steam. pure relatively is produced vapour the plants, desalination undergoes device. throttling seawater other thermal in or As boil. to begins spray the in water environment, low-pressure this to exposed valve warm throttling a when through passing occurs by pressure which in reduction a processes transfer mass and heat “Flash evaporation is a distinguishing feature of the OC-OTeC where by it involves complex is closedandparallelstheRankine cycle.” cycle the environment, its and engine heat OC-OT EC the both includes that system a For it usually is perceived as the means to reduce pressure in the system below atmospheric. a compressor. Although the primary role of the compressor is to discharge exhaust gases, come out of solution, and air that may have leaked have into that gases the dissolved vapour, system, water residual must any include be which gases, pressurised condensable with the elevation of the condenser is suitably high, it can be compressed hydrostatically. if or, pump a of means by discharge of point the at conditions ambient to pressurized be Effluent from the low-pressure condenser must be returned to the environment. working fluid. the become to vaporized is that mass of fraction small the to seawater warm the of bulk the from energy thermal of transfer a as seen be can evaporation flash above, mentioned as Thus, boiling. of cessation the and temperature liquid the phase of lowering liquid a in the results and from comes energy This vaporization. of heat its it with away carries it generated, is steam As steam. pure relatively is produced vapour the plants, desalination undergoes device. throttling seawater other thermal in or As boil. to begins spray the in water environment, low-pressure this to Exposed valve warm throttling a when through passing occurs by pressure which in reduction a processes transfer mass and heat “Flash evaporation is a distinguishing feature of the OC-OTEC where by it involves complex D Throttling

Seawater evice Warm Warm Pump Evap

Seawater Surface Warm

orator 3, the steam is cooled by the cold seawater to form desalinated water. The 3, the steam is cooled by the cold seawater to form desalinated water. The Diffuser

Circulation Pump Evaporator Flash Desalinated 1

Circulation Pump Water is converted to steam to converted is 1 is converted to steam to converted is 1 Separator

Regenerator

Condenser 2

Turbine

3 Tank 2

Condenser After

Heater Tank 1 (0.5% of warm seawater warm of (0.5% 2

(0.5% of warm seawater warm of (0.5% 2

Pump Seawater Cold n Figure 2.6 the warm the 2.6 Figure In n Figure 2.6 the warm the 2.6 Figure in Turbine 1

Cold Condensable Cold Seawater Seawater

Generator Turbine 2 gases Non Liquid can liquid can Pump -

Condenser 4

Non- non-

Absorber

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2.3.3 Hybrid OTEC System

Turbine Warm Surface Generator Seawater

Non- Condensable Warm Flash Condenser gases Seawater Evaporator Pump

Vacuum Pump Throttling Working Device Fluid Pump Cold Seawater Desalinated Pump Water Cold Seawater

Figure 2.7: Hybrid OTEC system (Source [6]).

The hybrid cycle shown in Figure 2.7 is an attempt to combine the best features of both the closed-cycle and open-cycle systems. In a hybrid OTEC system, warm seawater enters a vacuum chamber where it is flash evaporated into steam, similar to the open-cycle evaporation process. The steam vaporises the ammonia working fluid of a closed-cycle loop on the other side of an ammonia vaporiser. The vaporised fluid then drives a turbine to produce electricity. The steam condenses within the heat exchanger and provides desalinated water.

Although components to test the technology are widely available, no commercial-scale plants or even pilot plants connected to a grid exist. The most ambitious prototype to date was an Indian research vessel that carried a 1 MW OTEC plant in 2002. That effort, a collaboration with the Japanese company Xenesys Inc. and Saga University in Japan, was unsuccessful due to a failure of the deep sea cold water pipe [6].

Alternatively hybrid OTEC could also be described as either closed-cycle or open-cycle OTEC, incorporated with other renewable energy technologies such as wind power, solar power, wave power or tidal power. 2.4 Plant Design and Location

The location of a commercial OTEC plant has to be in an environment that is stable enough for an efficient system operation. The temperature differential at the site has to be at least 20°C. Generally the natural ocean thermal gradient necessary for OTEC operation is found between latitudes 20°N and 20°S. SOPAC Miscellaneous Report 701 19 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 20 OTEC plants,upto 100MW,couldbeconsidered. feasible largest the of several countries industrialised and populous of case the in whereas islands, Pacific small most in suffice generally would plants MW 10 to 1 magnitude. in of orders consumption local match should outputs plant water desalinated and electricity the and plant, the operate to personnel adequate with size plant OTEC the with compatible be should base population the Moreover, systems. communication and including roads project, good of airports, type harbours, this for desirable infrastructure the lack to likely is it development, phases. installation and construction plant the during problems logistical serious by accompanied often are advantages such Paradoxically, development. economic isolated and remote provide to means communities with some degree of the energy independence, and to as offer them a potential for seen safe be may it where its character in renewable lies OTEC of favour in argument One factors. political from and socioeconomic sites, to OTEC logistics potential evaluating when considered be to points other many are There 2. 1. [5]: world the throughout resource thermal ocean the of availability the summarises following The Figure 2.8:MapofsuitablesitesforOTEC(Source:[7]) based OTECphase. the through plants. scale large OTEC a development of on an ambitious floating recovered floating-plant program, be following the with initial only experimental land- could extent OTEC of considerable benefits potential a The to relaxed OTEC be land-based would of implementation technologies, practical the for of profile, constraint severe bathymetric The favourable locations. a island of consist sites OTEC land-based, possible. best, is The enhancement temperature seawater warm some unless continents, major of shoreline the along sites desirable of number the restrict greatly and bathymetry, seafloor resource thermal i.e., selection, site OTEC affecting factors physical The Peninsula. enhancement for the temperature significant require would phenomena upwelling seasonal moreover, Africa; 20˚N and 20˚S, are adequate, except for the West Coasts of South America and of Southern Tropical waters, defined as extending from the equatorial region boundary to, respectively, water temperatureiswarmerbyabout2˚CalongtheEastCoastofAfrica. the on required be would ponds) solar with (e.g., enhancement temperature seasonal significant America; South of Coast West the for except adequate are 10˚S and 10˚N between lying as defined waters, Equatorial West Coast of Northern Africa, the est Coast of Southern Africa; moreover, deep moreover, Africa; Southern of Coast West

Horn of Africa, and off the Arabian f an island is under is island an If A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

2.5 Other Uses of OTEC Technology Section 2.5 and its following sub-sections are excerpted from Wikipedia [1]ction 2.5 and its following sub-sections are excerpted from Wikipedia [1]. 2.5.1 Air Conditioning The cold (5°C) seawater made available by an OTEC system creates an opportunity to provide large amounts of cooling to operations that are related to or close to the plant. The cold seawater delivered to an OTEC plant can be used in chilled-water coils to provide air- conditioning for buildings. It is estimated that a pipe 0.3 meters in diameter can deliver 0.08 cubic meters of water per second (4700 gallons per minute); If 6°C water is received through such a pipe, it could provide more than enough air-conditioning for a large building. If this system operates 8,000 hours per year and local electricity sells for 5¢-10¢ per kilowatt-hour, it would save $200,000-$400,000 in energy bills annually.

The InterContinental Resort and Thalasso-Spa on the island of Bora Bora uses an OTEC system to air-condition its buildings. The system accomplishes this by passing cold seawater through a heat exchanger where it cools freshwater in a closed loop system. This cool freshwater is then pumped to buildings and is used for cooling directly with no conversion to electricity taking place.

2.5.2 Chilled-soil Agriculture OTEC technology also supports chilled-soil agriculture. When cold seawater flows through underground pipes, it chills the surrounding soil. The temperature difference between plant roots in the cool soil and plant leaves in the warm air allows many plants that evolved in temperate climates to be grown in the subtropics. The Common Heritage Corporation, a former tenant at the Natural Energy Laboratory in Hawai'i and the holder of the patent on this process, maintained a demonstration garden with more than 100 different fruits and vegetables, many of which would not normally survive in Hawai'i. No chilled-soil agriculture is presently being undertaken at the NELHA.

2.5.3 Aquaculture Aquaculture is the most well known by-product of OTEC. It is widely considered to be one of the most important ways to reduce the financial and energy costs of pumping large volumes of water from the deep ocean. Deep ocean water contains high concentrations of essential nutrients that are depleted in surface waters due to biological consumption. This "artificial upwelling" mimics the natural upwelling that is responsible for fertilising and supporting the world's largest marine ecosystems, and the largest densities of life on the planet.

Cold-water delicacies, such as salmon and lobster, thrive in the nutrient-rich, deep, seawater from the OTEC process. Microalgae such as Spirulina, a health food supplement, also can be cultivated in the nutrient-rich water. Given the OTEC process uses cold, deep-ocean water and warm ocean water from the surface, it can be combined in various ratios to deliver seawater of a specific temperature conducive to maintaining an optimal environment for aquaculture. For example, Maine lobster could be grown in a tropical island environment in a temperature controlled mixture of cold and warm seawater. Seafood not indigenous to tropical waters can also be raised in pools created by OTEC-pumped water, such as Salmon, lobster, abalone, trout, oysters and clams. This extends the variety of fresh seafood products available for nearby markets. Likewise, the low-cost refrigeration provided by the cold seawater can be used to upgrade or maintain the quality of indigenous fish, which tend to deteriorate quickly in warm tropical regions. SOPAC Miscellaneous Report 701 21 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 22 change inarelativelysmallamountoftime. to subject be could distribution and production hydrogen large-scale for costs markets, world on products petroleum of price increasing the Considering fuels. and sources energy other oil. crude of barrel per to relative distribution, and transportation, production, of cost the liquid include challenges main The US$250 of to equivalent cost be production would the harbour the Unfortunately, to hydrogen. delivered liquid hydrogen of hour per kg 1,300 yield to compounds added to improve the overall efficiency. A 100 MW-net plantship can be configured electrolyte with electrolysis for medium pure relatively a as used be can generated steam The process. OTEC the by generated electricity using electrolysis via produced be can Hydrogen HydrogenProduction 2.5.5 water eachday. desalinated of meters cubic 4,300 about produce could plant MW 2 a that indicates analysis communities where supplies of natural freshwater local for agriculture to or dispensed drinking are and limited. collected System be can and impurities of free relatively is condensate This a surface condenser, the spent steam is condensed by indirect contact with the cold seawater. Desalinated water can be produced in open or hybrid-cycle plants using surface condensers. Desalination 2.5.4 losses, isnegligible forthedesignspresented herein. frictional to due rise, temperature seawater The column. water surrounding the and pipe the gravitational energy due to the differences in density between the heavier (colder) water inside i.e., head, density the for seawater, cold the of case the in and losses frictional pipe-fluid the for accounting determined is seawater pump to required power The pumps. of operation the in generator turbine the by generated power the of 30% to 20 of consumption the in resulting arises from the large quantities of warm and cold seawater required for heat transfer processes, concepts of thermodynamics used for conventional steam power plants. The elementary major difference same the with assessed is cycles generating power OTEC of performance The Technical Challenges 2.6.1 The Limitationsof OTEC 2.6 ocean employ that processes extraction energy. mineral of viability the improving were sciences) wave-energy technology. They found developments in other technologies (especially materials with seawater in dissolved uranium of extraction the combining of began concept the recently investigating Japanese The process. extraction the of cost the is problem remaining the be can and concentrations, extracted easily, such high as magnesium; in however, with occur OTEC plants supplying that the pumped minerals water, to limited is method this Generally seawater. from minerals the separate to expensive very often is it significantly, More needed. water of volume would large the pump to solution required is energy much in because part in unprofitable, be dissolved elements trace for ocean the mining that solution. concluded in analyses dissolved and forms other elements and 57 salts its in for water contained ocean mine to potential the is opportunity undeveloped Another Mineral Extraction 2.5.6 2.6.1 –2.6.4areexcerptedfrom[5]. following sub-sections 2.6.1 – 2.6.4 are excerpted from Technologies [5] te at ms economic most past, the In he following sub-sections In A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

The ideal energy conversion for 26°C and 4°C warm and cold seawaters is 8%. An actual OTEC plant will transfer heat irreversibly and produce entropy at various points in the cycle yielding an energy conversion of 3 to 4%. These values are small compared to efficiencies obtained for conventional power plants; however, OTEC uses a resource that is constantly renewed by the sun. Considering practical sizes for the cold water pipe OTEC is presently limited to sizes of no more than about 100 MW. In the case of the open-cycle, due to the low- pressure steam, the turbine is presently limited to sizes of no more than 2.5 MW. The thermal performance of CC-OTEC and OC-OTEC is comparable. Floating vessels approaching the dimensions of supertankers, housing factories operated with OTEC-generated electricity, or transmitting the electricity to shore via submarine power cables have been conceptualised. Large diameter pipes suspended from these plantships extending to depths of 1,000 m are required to transport the deep ocean water to the heat exchangers onboard. The design and operation of these cold water pipes are major issues that have been resolved by researchers and engineers in the USA.

It has been determined that approximately 4 cubic meters per second of warm seawater and 2 cubic meters per second of cold seawater (ratio of 2:1), with a nominal temperature difference of 20°C, are required per MW of exportable or net electricity (net = gross – in-house usage). To keep the water pumping losses at about 20 to 30% of the gross power, an average speed of less than 2 meters per second is considered for the seawater flowing through the pipes transporting the seawater resource to the OTEC power block. Therefore, a 100 MW plant would use 400 cubic meters per second of 26°C water flowing through a 16 m inside diameter pipe extending to a depth of 20 m; and 200 cubic meters per second of 4°C water flowing through an 11 m diameter pipe extending to depths of 1,000 m. Using similar arguments, a 20 m diameter pipe is required for the mixed water return. To minimise the environmental impact due to the return of the processed water to the ocean (mostly changes in temperature), a discharge depth of 60 m is sufficient for most sites considered feasible, resulting in a pipe extending to depths of 60 m.

The amount of total world power that could be provided by OTEC must be balanced with the impact to the marine environment that might be caused by the relatively massive amounts of seawater required to operate OTEC plants. The discharge water from a 100 MW plant would be equivalent to the nominal flow of the Colorado River into the Pacific Ocean (1/10 the Danube, or 1/30 the Mississippi, or 1/5 the Nile into the Atlantic). The discharge flow from 60,000 MW of OTEC plants would be equivalent to the combined discharge from all rivers flowing into the Atlantic and Pacific Oceans (361,000 cubic meters per second). Although river runoff composition is considerably different from the OTEC discharge, providing a significant amount of power to the world with OTEC might have an impact on the environment below the oceanic mixed layer and, therefore, could have long-term significance in the marine environment; however, numerous countries throughout the world could use OTEC as a component of their energy equation with relatively minimal environmental impact. Tropical and subtropical island sites could be made independent of conventional fuels for the production of electricity and desalinated water by using plants of appropriate size. The larger question of OTEC as a significant provider of power for the world cannot be assessed, beyond the experimental plant stage, until some operational and environmental impact data is made available through the construction and operation of the pre-commercial plant. SOPAC Miscellaneous Report 701 23 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 24 normal operations. through failure fatigue-induced in result might kind in second the while failure; result strength ultimate might that period, return long relatively a with phenomena, environmental extreme on based is kind first The loads. fatigue-induced as well as loads survivability consideration into take must cable power submarine the and systems mooring CWPs, OTEC of design The submarine the for riser power cable. the install and design to required backgrounds technological and momentum the engineering the provide provides also industry offshore also The vessel. surface water the position to necessary return mixed the and intake water warm position The for keeping. used be can industry or offshore the m, by 1,000 developed than thrusters more positioning dynamic of depths water for designed systems, floating ocean-mooring the Deep to plant. cable the power submarine are the challenges of attachment engineering the and present system that position-keeping plants floating OTEC for components Other the and practical designs. verified be must periods extended in used be can over pipes soft before established water constraints repair and maintenance of inspection, m 1,000 to m 800 in pumps of intake, water seem to offer the cold most innovative alternative the to conventional concepts; at however, the operability located pumps with pipes), soft (e.g., fabrics elastomeric reinforced of made pipes Pressurised applicable. are FRP or concrete steel, of made pipes segmented than 1.6 m. 1.6 than less diameter of pipes polyethylene high-density for design validated a land- is there plants For based plants. OTEC floating for recommended is pipe of type This plants. OTEC floating from suspended pipes for developed technology design the validate to used was obtained data The barge. a to attached pipe construction long, sandwich (FRP) m plastic 120 reinforced fibreglass diameter, m 2.4 instrumented an of sea at test and deployment transportation, fabrication, design, the been has achieved outcome greatest The tests. at-sea and laboratory with integrated studies analytical computer-aided on relying programme a with USA the by addressed was challenge This experience. evolutionary of lack a by complicated magnitude significant of challenge engineering an presented CWP) pipe, water cold (i.e., surface the to water cold of quantities large transport to pipe cost-effective a of installation and design The Challenges Engineering 2.6.2 and maintenance. fringes (i.e., fish, reef, etc). The arrangement also requires coastal additional expense on in the impact construction dwelling up any avoid to water the discharging before depth appropriate an reach to as so offshore meters hundred several out carried be to need may This seawater. warm and cold the of discharging the be would plant land-based a of disadvantage Another of coldwaterresultinginthe3kmlongpipeline beingatleast8mindiameter. with other present energy alternatives. A 50 MW plant will require 150 cubic meters per second economically compete cannot MW 50 than smaller plants OTEC that show Studies designs. 1,000 about m. of The depth cost a from associated required with seawater deep the of cold volumes water large the pipe transport represents to 75% pipe water of the costs of current plant cold long km 3 a for need the is plants OTEC land-based of disadvantages main the of One Disadvantages ofOTEC 2.6.3 n the case of larger diameter pipes offshore techniques used to deploy large deploy to used techniques offshore pipes diameter larger of case the In

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To minimise construction costs of the cold water and discharge pipes, a floating OTEC plant could be an option; however, the costs associated with the maintenance and mooring facility of such a structure is significant. Further to the structural needs of the OTEC plant there is also energy required for pumping the seawater from depths of about 1,000 m.

2.6.4 OTEC and the Environment OTEC offers one of the most benign power production technologies, since the handling of hazardous substances is limited to the working fluid (e.g., ammonia), and no noxious by-products are generated. OTEC requires drawing seawater from the mixed layer and the deep ocean and returning it to the mixed layer, close to the thermocline, which could be accomplished with minimal environmental impact. The carbon dioxide out-gassing from the seawater used for the operation of an OC-OTEC plant is less than 1% of the approximately 700 grams per kWh amount released by fuel oil plants. The value is even lower in the case of a CC-OTEC plant.

A sustained flow of cold, nutrient-rich, bacteria-free deep ocean water could cause sea surface temperature anomalies and bio-stimulation if resident times in the mixed layer and the euphotic zone, respectively, are long enough (i.e., upwelling). The euphotic zone is the upper layer of the ocean in which there is sufficient light for photosynthesis. This has been taken to mean the 1% light penetration depth (e.g., 120 m in Hawai'ian waters). This is unduly conservative, because most biological activity requires radiation levels of at least 10% of the sea surface value. Since light intensity decreases exponentially with depth, the critical 10% light penetration depth corresponds to, for example, 60 m in Hawai'ian waters. The analyses of specific OTEC designs indicate that mixed seawater returned at depths of 60 m results in a dilution coefficient of 4 (i.e., 1 part OTEC effluent is mixed with 3 parts of the ambient seawater) and equilibrium (neutral buoyancy) depths below the mixed layer throughout the year. This water return depth also provides the vertical separation, from the warm water intake at about 20 m, required to avoid recirculation into the plant. This value will vary as a function of ocean current conditions. It follows that the marine food web should be minimally affected and that persistent sea surface temperature anomalies should not be induced.

To have effective heat transfer it is necessary to protect the heat exchangers from bio-fouling. It has been determined that bio-fouling only occurs in OTEC heat exchangers exposed to surface seawater. Therefore, it is only necessary to protect the CC-OTEC evaporators. Chlorine has been proposed along with several mechanical means. Depending upon the type of evaporator, both chemical and mechanical means could be used. To protect marine life, the Environmental Protection Agency (EPA) in the USA allows a maximum chlorine discharge of 0.5 mg a litre and an average of 0.1 mg a litre. CC-OTEC plants need to use chlorine at levels of less than 10% of the EPA limits. The power plant components will release small quantities of working fluid during operations. Marine discharges will depend on the working fluid, the biocides, the depth of intake and the discharge configuration chosen.

Other potentially significant concerns are related to the construction phase. These are similar to those associated with the construction of any power plant, shipbuilding and the construction of offshore platforms. What is unique to OTEC is the movement of seawater streams with flow rates comparable to those of rivers and the effect of passing such streams through the OTEC components before returning them to the ocean. The use of biocides and ammonia are similar to other human activities. If occupational health and safety regulations like those in effect in the USA are followed, working fluid and biocide (most probably anhydrous ammonia SOPAC Miscellaneous Report 701 25 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 26 shock. plant. the intakes. the protecting screens Impingement is the fatal to on the organism. caught An are entrained organism is plant drawn into OTEC and passes an through by impinged Organisms not recommended. is chlorine of quantities large of storage therefore situ; in generated be can Chlorine plants. refrigeration systems. Chlorine is used in municipal water treatment plants and in steam power rink skating ice in and fertiliser a as used is Ammonia chemicals. these involving applications industrial other for those to similar are risks the system, either with occur accident an Should and chlorine can damage the eyes, skin, and mucous membranes, and can inhibit respiration. hazardous to the populace in surrounding areas, depending on their proximity. A sites. plant the major release of working fluid or biocide would be hazardous to plant workers, and potentially outside detect to low too be should plant a from emissions chlorine) and of OTECplantsontheenvironment canbeavoidedormitigatedbyproperdesign. power generation. The consensus among researchers is that the potentially detrimental effects conventional to alternative safe and benign environmentally an is OTEC that assure to design essential that all potentially significant concerns be examined and assessed for each site and hazard to operating personnel and the local population than conventional fossil-fuel plants. CC-OTEC power plant operates as a hazards. low-temperature, maintenance low-pressure Rankine and cycle, shop it poses and less equipment, material-handling heavy gases, compressed of use machinery, rotating hazards, electrical plants: generation power electric Other risks associated with the OT EC power system are the safety issues associated with steam be may site enhanced. OTEC an near assets recreational community, local planning the with adequate coordination Through and effects. two these between achieved balance the on depend will life aquatic on operation OTEC of effect net The populations. fish reduce may biocides of and larvae, as well as juvenile fish, due to impingement and entrainment and to the discharge due to redistribution of nutrients may improve fishing; however, the losses of inshore fish eggs area. the in fishing increasing potentially plant, the to attracted be will Fish fishing. recreational and commercial affect may operation and construction plant OTEC have long-term significanceforsomeorganisms. could sources natural from redistributed or plant the from released constituents trace of aggregate the that suggests system circulation plant OTEC an of size sheer the however, plant; the through passing water of volumes great with diluted quickly be will plants OTEC by released metals trace Furthermore, species. subtropical and tropical of conducted been have affect local biota. Trace elements differ in their toxicity and resistance to corrosion. Few studies effluent. the to elements trace add will seawater by eroded or corroded piping) metallic impellers, pump exchangers, heat (e.g., elements structural Metallic contrary. the to exists evidence further unless assumed be should capture upon mortality 100% and capture 100% assessment, of purpose the for that of the phytoplankton crops from the surface may be killed by entrainment. Prudence suggests zooplankton entrained by the warm-water intake may be less than 100%, in fact only a fraction and phytoplankton for rates mortality that suggest experiments be Although may killed. waters or damaged intake the by entrained or impinged organisms all, not if Many, plant. the of vicinity immediate the in zones recirculation or turbulence in result not does withdrawal that so hydrodynamically tailored be to need inlets The impingement. and entrainment minimise grease). or oil and metals (trace tand raim my lo e xoe t wrig li ad rc constituents trace and fluid working to exposed be also may organisms Entrained ntrained organisms may be exposed to biocides, and temperature and pressure and temperature and biocides, to exposed be may organisms Entrained t is difficult to predict whether metals released from a plant will plant a from released metals whether predict to difficult is It ntakes should be designed to limit the inlet flow velocity to velocity flow inlet the limit to designed be should Intakes nhanced productivity Enhanced Both ammonia iven the Given It is A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

2.6.5 Economic Considerations and Market Potential OTEC is capital intensive and the very first plants will most probably be small requiring substantial capital investment. Given the relatively high cost of crude oil and of fossil fuel in general, the development of OTEC technologies is likely to be promoted by both government agencies and the private industry.

A scenario most applicable to the Pacific Island Countries can be installing a 10 MW land- based OC-OTEC plants which could be capable of producing cost competitive electricity and desalinated water. The following analysis is focused on Fiji with the hope of subsequent application across the Pacific as the Pacific Island Countries have similar characteristics1. (also refer to Appendix A)

Assumptions for the Analysis 1. The economic lifetime of the OTEC system was estimated at 20 years. 2. The operations and maintenance cost is estimated at 1% of the initial capital cost. 3. The analysis is done in Fijian dollars. 4. The variables used in the analysis were: • the value of carbon emission saved; • the value of desalinated water produced; • fuel cost savings; and • operations and maintenance cost. 5. That out of the total value of desalinated water produced, the cost incurred in supplying these to the household is about 50%. This includes pipelines, labour cost and water treatment. Thus only 50% remains as the net gain. 6. The volume of water produced can be used to support the needs of a 100,000 population in developing communities. 7. Fuel price is based on the Fiji Electricity Authority (FEA) charges for domestic purposes. The per kWh cost has remained quite constant over the years. The FEA charges its customers 21 cents per kWh of electricity used. Since the electricity charges haven’t varied much over the 5 years, the electricity revenue will be quite stable. 8. Fuel price increases by 1% every year as the expectations are that fuel prices will keep on increasing in the future. (http://www.highbeam.com/doc/1P2-16647301.html) 9. The water rates in Fiji have remained at 15 cents for water consumed below 50 cubic meters over the past decade; however, in the revised legislation in 1985, the rate was 9.2 cents per cubic meter. Therefore, a price of 15 cents per cubic meter is used to value the water produced so that the value is in current terms. 10. Minimal maintenance needs for the first five years, with maintenance and operation increasing at 2% thereafter. 11. The desalinated water will be further treated to meet the local standards and further infrastructure will be needed to integrate the water produced in Fiji’s existing drinking water network. This will involve costs of about 40% in the first year and in the following years, it would fall to 10% as the infrastructure will exist and the only cost will be to treat the water and other maintenance.

1 Some of the characteristics involve small size, small population, limited access to capital, and reliance on remittances. SOPAC Miscellaneous Report 701 27 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 28 n h nt o dsat future. distant too not the project in sustainable a of development the ensure could acceptable and consistent are that assessment impact environmental including study feasibility a and parameters development right The point. this at available technologies energy and renewable other carefully, with along weighed considered be should region Pacific the into OTEC adopt to consideration The not. or region the in plant another build to whether on consensus a form to which on basis a provide results research current and 1981) October from months 10 for operated (which plant Table 2.2:Thenetbenefits 14. 13. 12. hydro power,biomass andwind. cheaper than the currently available renewable energy technologies such as solar photovoltaic, energy generation needs. Another consideration would be whether OTEC eventually works out under itsbelt,toldtheApril2009 PEMMmeetingthatitwasnotCfromitsfuture ruling outOT answered. fully be might appropriateness and concerns the to that look at options to build a pilot/demonstration plant at these sites; so that the issues relating studies feasibility from provided recommendations the carefully consider should researchers plants, OTEC for potential the having as identified region Pacific the in countries few a With islanders relyuponasasourceoffood,incomeandrecreation. Pacific many which environment marine the to hazards potential the against weighed be to have benefits the but purposes cooling suitability, for water cold and agriculture of for water nutrient-rich question will the people many technology, what is energy Pacific” perhaps agree to, given its benefits of not the only producing electricity but also desalinated water, new for “OTEC other arises. sustainability any and appropriateness of introduction the Like Discussion 2.7 constrained willnotbeabletoaffordanOTECplant. Pacific Pacific, the in OTEC stage, for exists potential current huge though the at Thus, Pacific. the in countries by unaffordable simply cost and high capital quite initial is the Otherwise, crisis. financial global current the considering difficult very be probably would which technology; this fund can countries donor some if possible be only analysis shows that it can be feasible to implement the plant in the Pacific. This however, would financial analysis, implementing OTEC in the Pacific Pacific would the not be in viable; however, situation gross margin current the US$99.65/bbl in 2008 in nominal terms; however, large capital costs of OTEC and considering years. 5 past the over rising been has price oil the as prices oil in increase future any against hedge a as act can OTEC Gross MarginAnalysis Financial Analysis Analysis Type Economic Analysis 10 MWofOTECpowerwillreplacefossilfuelpower. from carbon whichwasthenconvertedtoFijiandollarsusingthecurrentexchangerate. adopted was carbon of Price That thedemandforwaterandelectricityisstable. n 2002, the crude oil price was US$22.81/bbl and increased to increased and US$22.81/bbl was price oil crude the 2002, In 'xeine aog PICs among 'experience' OTEC national only the with Nauru, Net Profit/Loss(FJ$) (223,946,382) Net Present 17,849,595 (243,100,405) i nt utbe O te ai of basis the On suitable. not is OTEC Countries, Island http://www.pointcarbon.com/productsandservices/ Value sland countries being financially being countries Island essons learnt from the from learnt Lessons Nauru A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

The Pacific region can always sit back and wait for the right opportunity; however, while doing so, the region should be aware of the developments in the technology and what the resource-rich nations are doing with respect to renewables. The region should also consider improving its institutional structures for managing renewable energy technologies as deciding factors in the introduction of a technology is economic viability; whether the technologies are environmentally sound; and whether it would be sustainable in the region.

The Pacific small island states on their own will definitely not be able to adopt and sustain the sophisticated technologies of the type that OTEC is. The region would need assistance and guidance from its neighbouring developed nations when considering the introduction of OTEC technology.

Figure 2.9: Artist's impression of an OTEC system (Source: www.energyisland.com) SOPAC Miscellaneous Report 701 29 SOPAC Miscellaneous Report 701 Ocean BasedRenewableEnergyTechnologies A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 30 3. described asunitsofpowerpermeterwavecrestlength[8] over distance the and blowing is wind which the wind excites the the waves, also known that as “fetch”. The power potential time for waves can be of amount the speed, wind the upon kinetic energy (movement of water molecules). The amount of energy transferred and is dependent level) sea above wave in water of (mass energy potential of form the in is water to wind the pressure differences are a product of differential solar heating. the The energy transferred from in differences pressure by created are that winds by produced are energy. solar of form concentrated a be to considered generally are waves Oceanic IntroductionandBackground 3.1 formations. seabed adequate with shorelines approach they as concentrated be to can waves and due easier decreases generally output power their frictional losses to the seabed; however, the management of power-generating units shorelines, would be approach waves oceanic As Figure 3.1:Wavegeneration(Source:[9])

Technology Wave Energy arth’s atmosphere, Earth’s Waves

A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies OceanA SOPAC Based Desktop Renewable Study of E nergyOcean- TechnologiesBased-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

3. Wave Energy With the correct seabed formation close to shore, powerful wave “hotspots” can occur, which are ideal locations for near-shore applications. That said, even near-shore hotspots are only about one-third as powerful as the average deep-water locations which consist of depths Technology greater than 40 m. Seasonal variation is also a factor when determining where the greatest wave power potential is situated.

It is known that wave power is more energy dense than wind power and produces power for a larger percentage of the year. Typical annual average values for good offshore locations can range between 20 and 70 kW per meter which occur mostly in moderate to high latitudes. Seasonal variations are in general considerably larger in the Northern Hemisphere than in the Southern Hemisphere, which makes the southern coasts of South America, Africa and Australia particularly attractive for wave energy [10]. 3.0 WAVE ENERGY CALCULATIONS

“The utilization factor for wave power – the ratio of yearly energy production to the installed power of the equipment – is typically 2 times higher than that of wind power. That is whereas for example a wind power plant only delivers energy corresponding to full power during 25% of the time (i.e. 2,190 h out of the 8,760 h per year) a wave power plant is expected to deliver 50% (4,380 h/year).” [14]

While we know that wave power is more energy dense than wind power and produces power for a larger percentage of the year, we still do not know how to calculate the power available from a wave. This is important for the design process of a wave energy converter. First, the power and forces acting on the device should be assessed, then the device may be sized for the desired energy output. The next sections explain how to calculate the wave energy and power and how to size point absorbers and oscillating water columns for a given power level. More information on these wave energy converters can be found in section 5.

3.1 WAVE ENERGY AND POWER The following analysis describes a wave’s energy and power characteristics. Table 1 complements Fig. 2’s depiction of the variables used in Section 3’s wave energy analysis with units. Figure 3.2: Approximate global distribution of wave power levels. (Source: T.W. Thorpe, “An Overview of Wave Energy Technologies: Status, Performance and Costs.”) Table 1. Wave Nomenclature as used in Fig. 2 and Section 3

Table 3.1: Wave nomenclature for calculating waveVariables power (Source [11]).

SWL mean seawater level (surface) 2 Edensity wave energy density [J/m ]

Ewavefront energy per meter wave front [J/m] 2 Pdensity wave power density [W/m ]

Pwavefront power per meter wave front [W/m] h depth below SWL [m] ω wave frequency [rad/sec] λ (or L) wavelength [m] = gT2/(2π) 3 ρwater seawater density [1000 kg/m ] g gravitational constant [9.81 m/s2] A wave amplitude [m] J. Vining. University of Wisconsin Madison. Dec. 2005. Ocean Wave Energy Conversion. 4 H wave height [m] T wave period [s]

C celerity (wave front velocity) [m/s] SOPAC Miscellaneous Report 701

31

Fig. 2 Wave Nomenclature [19]

3.1.1 Energy and Power Density The energy density of a wave, shown in equation 1, is the mean energy flux crossing a vertical plane parallel to a wave’s crest. The energy per wave period is the wave’s power density. Equation 2 shows how this can be found by dividing the energy density by the wave period [18, 19]. Fig. 3 illustrates how wave period and amplitude affect the power density.

2 2 Edensity = ρwatergH /8 = ρwatergA /2 (1) 2 2 Pdensity = Edensity/T = ρwatergH /(8T) = ρwatergA /(2T) (2)

J. Vining. University of Wisconsin Madison. Dec. 2005. Ocean Wave Energy Conversion. 5 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies J. Vining. University of Wisconsin Madison. Dec. 2005. Ocean Wave EnergyConversion.5 P E 19]. Fig. 3illustrates density. how power amplitudeaffect waveperiodand the Equation 2showshowthiscanbefoundbydividing theenergydensitybywaveperiod[18, plane paralleltoawave’screst.Theenergype The energy density of a wave, shown in equation 1, is the mean energy flux crossing a vertical 3.1.1 EnergyandPowerDensity 32 period. power wave’s the is density. period wave per energy The crest. wave’s a to parallel plane vertical a crossing flux energy mean the is below, (1) equation in shown wave, a of density energy The Figure 3.3:IllustrationofthewavenomenclatureshownonTable3.1 (Source:[11]) Figure 3.4:Illustrationofhowwaveperiod and amplitudeaffectthepower density(Source[11]). density density Equation (2) shows how this can be found by dividing the energy density by the wave = E = = ρ = g C T H A water density gH /T = ρ = /T z Fig. 2WaveNomenclature[19] 2 /8 = = /8 y gravitational constant [9.81 m/s[9.81 constant gravitational wave period [s] wave height [m] wave amplitude [m] celerity (wave front velocity) [m/s] x water ρ water gH gA 2 /(8T) = = /(8T) 2 /2 r waveperiodisthewave’spowerdensity. h z = ρ L water -h C gA H 2 /(2T) A 2 ] SWL (1) (2) A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies Fig. 3 Wave PowerA SOPAC Density Desktop Study of Ocean-Based-Renewable Energy Technologies

3.1.2 Power Per Meter of Wave Front A wave resource is typically described in terms of power per meter of wave front (or wave crest). This can be calculated by multiplying the energy density by the wave celerity (wave front A wave resource is typically described in terms of power per meter of wave front (or wave velocity) ascrest). equation This can3 demonstrat be calculatedes [19]. by multiplying Fig. 4 characterizes the energy density an increase by the in wave the amplitudecelerity (wave and period of a frontwave velocity) increases as equation the pow (3)er demonstrates.per meter of waveFigure front.3.5 characterises that an increase in the amplitude and period of a wave increases the power per meter of wave front.

2 2 2 2 Pwavefront = C*Edensity = ρwaterg H /(16ω) = ρwaterg A /(4ω) (3)

J. Vining. University of Wisconsin Madison. Dec. 2005. Ocean Wave Energy Conversion. 6

Fig. 4 Power Per Meter of Wave Front

3.1.3 Energy at Varying Depths

To properlyFigure size an3.5: underwaterPower per meter wave of wave energy front (Sourceconverter, [11]). the wave power at the operating depth must be known. In general, the wave power below sea level decays exponentially by -2πd/λ To properly size an underwater wave energy converter, the wave power at the operating depth where d is themust depth be known. below In sea general, level. the This wave pr opertypower belowis valid sea for level waves decays in waterexponentially with depths by -2πd/ λ greater thanwhere λ/2. Equationd is the depth 4 gives below the sea relationship level. This betweenproperty isdepth valid andfor waves surface in energywater with [1]. depths greater than λ/2. Equation (4) gives the relationship between depth and surface energy.

E(d) = E(d=SWL) * e-2πd/λ (4)

3.2 ENERGY CONVERSION IN POINT ABSORBER The equations governing the float and tube type point absorber presented below are different yet work on the same principle. As previously mentioned, more information on these wave energy converters is presented in section 5. SOPAC Miscellaneous Report 701 33 J. Vining. University of Wisconsin Madison. Dec. 2005. Ocean Wave Energy Conversion. 7 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 34 in Trondheim,Norway,andantes,France. in case, the was This facilities. laboratory large very of use the converter energy wave the of requires testing large-scale for need the stage, construction prototype the towards progresses development the As geometry established. final well the already when is basin plant wave the a of in out carried are 1:10) to 1:80 (scales tests model reasons, these For applied). currently are corrections empirical less or more where structures, off-shore in and engineering naval in occur also (they important be to known are effects Such water oscillations(non-linearwaves). amplitude large accurately, model to capable being not and turbulence) eddy (large effects fluid (viscous) real to due water in losses for account to unable being its in lie limitations main in awavysea.Numericalmodellingistobeappliedthefirststagesofplantdesign.The ships of hydrodynamics the in those from different very not are applied be to techniques The studied be theoretically numerically, or by may testing a physical absorption model in a energy wave basin or the wave flume. converter, energy wave a of design and development the In difficult theoreticalandpracticalproblemthatisfarfromhavingbeensatisfactorilysolved. to order a in is waves random real PTO in control) latching (including the control Phase near-resonance. achieve controlling adequately by increased significantly be can energy wave absorbed of amount The conditions. near-resonance at operate should it i.e. waves, incoming the of frequency the match should oscillation of frequency own its absorber, efficient an be to is device the if that, revealed converters OWC and oscillating-body on studies theoretical early The absorption. energy wave of process hydrodynamic the is relevant Particularly procedures. control involves and introduces, it constraints the as well as efficiency its by characterised is The utilisation of wave energy involves a chain of energy conversion processes, each of which multiple-scattering method,theplane-wavemethodandpoint-absorberapproximation. the as such practice, in devised be to have methods approximate and complex extremely is array in significant devices a between interaction provide hydrodynamic The to grids. electrical is large energy to contribution wave if required are arrays in devices of numbers Large it however waves; requires muchmorecomputingtimeascomparedwiththefrequency-domainanalysis. irregular in converters of studies active-control for tool appropriate the is a time-domain theory had to be developed. The time-domain model produces time-series and analysis. Since, frequency-domain in practice, of most use converters are the equipped with and strongly non-linear equations mechanisms, governing the of linearisation the allowed This motions. and waves amplitude small was theory the of assumption additional An PTO. linear a with waves regular from extraction energy the addressed developments theoretical first The extracted energyhoweverareadditionalissues. the maximising for requirements the and (PTO) mechanism take-off power a of presence The mid-1970s. the preceding decades the in place took which seas, wavy in ships of dynamics in liquid of pressure and energy motion. forces, the of study mathematical the is Hydrodynamics .. Hydrodynamics[10] 3.1.1 ave energy converters could benefit from previous studies on the, largely similar, largely the, on studies previous from benefit could converters energy Wave urope, of the large wave tanks wave large the of Europe, A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

3.2 Technology Types

Unlike wind energy, there are numerous ways in which energy can be absorbed from waves. Recent reviews identified about 100 projects at various stages of development. The number does not seem to be decreasing as new concepts and new technologies replace or outnumber those that are being abandoned.

Several methods have been proposed to classify wave energy systems, according to location, to working principle and to size; however, the classification in Table 3.2 is based mostly on working principle. The examples shown are not an exhaustive list and were chosen from the projects that have reached the prototype stage or at least were the object of extensive development effort.

Isolated: Pico, LIMPET Fixed structure Oscillating water column In breakwater: Sakata, Mutriku (Air turbine) Floating: Oceanlinx

Essentially translation (heave): AquaBuoy, FO3, Wavebob, PowerBuoy Floating Oscillating bodies Essentially rotation: Pelamis (Hydraulic motor, hydraulic turbine, linear electrical generator) Essentially translation (heave): AWS, CETO Submerged Rotation (bottom-hinged): WaveRoller, Oyster

Shoreline (with concentration): Tapchan Fixed structure Overtopping In breakwater (without concentration): SSG (Low-head hydraulic turbine) Floating structure (with concentration): Wave Dragon

Figure 3.6: Types of wave energy converters (Source: [10])

A variety of technologies have been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales. While all wave energy technologies are intended to be installed at or near the water's surface, they differ in their orientation to the waves with which they are interacting and in the manner in which they convert the energy of the waves into other energy forms, usually electricity. SOPAC Miscellaneous Report 701 35 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 36 full-scale demonstrationstage[10]. development, and only in the last few years have some systems reached, or come close to, the mooring, with Challenges access for process. maintenance and the consequently need for development long underwater electrical cables, the has and hindered their in systems overcome to first-generation obstacles with more have compared complex more general in are regimes available in deep water at depths greater than 40 m. Offshore wave wave energy converters powerful more the exploit They offshore submerged. fully basically rarely more or are floating either devices devices, generation third as classified sometimes bodies Oscillating OscillatingBodies 3.2.1 500 homes. approximately of demand electricity annual the meet to power sufficient provide to able be to average produce 25-40% of the full rated output over the course of a year. upon the conditions of the installation site. Depending on the wave resource, machines will on machine. per modules conversion power 4 with diameter in m 3.5 are which segments 5 of up made According to Pelamis single seabedcable. a through shore to linked and together connected be can devices Several bed. sea the on to produce electricity. Power from all the joints is fed down a single umbilical cable to a junction hydraulic motors via wave-induced smoothing accumulators. The hydraulic motors drive electrical generators The 3.7. Figure through fluid high-pressure pump in which rams, hydraulic by shown resisted is joints these as of motion joints hinged by linked sections cylindrical of Pelamis The Pelamis 3.2.1.1 Table 3.2:Developmentstatusofoscillatingbodies[12] Company SyncWave Energy Ocean Navitas Trident Energy C-Wave Ocean WaveMaster Aquamarine Power(Oyster) BioPower Systems Seabased Wave StarEnergy Renewable EnergyHoldings(CTO) Wave EnergyTechnologies Finavera Renewables(AquaBuoy) WaveBob Fred Olsen(FO3) AWS OceanEnergy Pelamis WavePower . The energy produced by Pelamis is dependent is Pelamis by produced energy The kW. 750 at rated is machine Each Wave nergy Converter is a semi-submerged, articulated structure composed structure articulated semi-submerged, a is Converter Energy Wave Power, current production machines are approximately 180 m long, Wave Power Country Canada UK UK UK UK UK Australia Sweden Denmark Australia Canada Canada Ireland Norway UK UK Year 2004 2006 2003 2002 2002 2007 2006 2003 2000 1999 2004 2006 1999 2004 (1848) 2004 1998 Each machine is said Stage Prototype Prototype Prototype Prototype Prototype Prototype Pre-Pilot Pilot Pilot Pilot Pilot Pre-Commercial Pre-Commercial Pre-Commercial Pre-Commercial Commercial A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Sea trials of a full-sized prototype measuring 120 m long, 3.5 m in diameter and rated at 750 kW took place in 2004. In September of 2008, a set of three Pelamis devices costing around US$11.5 million was deployed at Agucadoura (off the Portuguese northern coast), making it the first grid-connected wave farm in the world. The combined power generation of the three devices stood at 2.25 MW, which is said to be powering 1,500 homes. In mid November, all three devices were disconnected from the grid and towed back to shore due to the global financial crisis affecting investors [13].

Figure 3.7: Pelamis attenuator (Source: www.pelamiswave.com)

The Pelamis technology was evaluated using the EMINENT tool against a reference technology being an Enercon E53 wind turbine. The EMINENT tool assess the performance and market potential of early stage technologies (EST) in a pre-defined energy chain, under national conditions, in terms of financial, energy and environmental criteria [14]. The Orkney Islands in Scotland were chosen as the test site from the EMINENT database to perform the simulations.

Table 3.3: EMINET economic analysis [15] Parameter Pelamis Wind Turbine Total investment for single end user (Euro) 2,125.00 8,410.00 Total depreciation for single end user (Euro/yr) 141.70 560.00 Total maintenance for single end use (Euro/yr) 21.25 126.10 Total costs for single end user (Euro/yr) 162.90 696.00 Specific cost (Euro/MWh delivered) 36.50 156.00 Number of households served by one unit 477.00 164.00 Operational costs of EST (Euro/yr) 21.25 135.40 Number of consumers in Orkney Islands 8,982.00 8,982.00 Total number of EST that can be sold in this sector 18.00 54.00

At the 2009 Regional Energy Officials' Meeting (REM) that was held in Tonga, a New Caledonian based company called the Société de Recherche du Pacifique (SRP) presented a feasibility study which was conducted in 2007 on the Pelamis in New Caledonia and is summarised in Table 3.4. SOPAC Miscellaneous Report 701 37 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 38 demonstrator isnowunderway[16]. installed off the coast of Portugal. Detailed engineering for a 250 kW optimised pre-commercial was that plant pilot a via 2004 in full-scale at proven been has concept power-absorption The is convertedtoelectricitybymeansofahydraulicsystemandmotor-generatorset. and the cylinder expands. The relative movement between the floater and the lower part or silo within the cylinder to balance the pressures. The reverse happens as the wave trough passes water the approaches, crest pressure on wave the top a of the cylinder As increases and the electricity. upper part or into 'floater' compresses converted the gas movement down with and cylinder, up lower-fixed a against casing upper air-filled an move waves Passing seabed. Archimedes The AWS OceanEnergy 3.2.1.2 (Source: http://www.membrana.ru/articles/technic/2007/06/22/180100.html) Figure 3.8:ArchimedesWave-SwingenergysystembyASOcean Energy Table 3.4:Pelamisfeasibilitystudy,NewCaledonia.

Policy forwaveenergy Offer fromtheutilityENERCAL Break-even sellingprice Annual potentialproduction Average output Number ofmachines Location French andNCgrant Current productionsource S) energy system is a cylinder shaped buoy, moored to the to moored buoy, shaped cylinder a is system energy (AWS) Wave-Swing Pelamis Feasibility StudyNew Caledonia(NC)

but renewablepoliciestobeimplemented So farnegotiationdirectwithUtility € 0.20/kWhstillunderreview 1.4 GWhduetotheNCgrid) Up to70%ofthetotalcost 100% Dieselgeneration 1.7 GWh(constraintat (avoided costbasis) 1 Pelamis750kW East ofMaré € 0.24/kWh 190 kW A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Advantages • Survivability – The AWS is submerged at least 6 m below the sea surface and therefore avoids the high storm loadings to which other devices are subjected. This reduces mooring costs and the risk of damage. • Simplicity – The AWS has one main moving part and limited auxiliaries which greatly reduces failure risk and maintenance requirements. • Maintainability – all maintainable parts are accessible by remotely operated underwater vehicles, enabling maintenance in most sea conditions. This minimises down time in the event of a fault and can have the AWS working within a day improving the efficiency of power production.

Challenges and Limitations The major development challenge with the AWS was the development of the large linear generator which had never been constructed at such sizes before. It had to be custom built which made it more expensive than a standard generator coupled with a gearbox. The construction of the linear generator involved many commercial parties.

Another challenge was the large force acting on the AWS with the occurrence of strong and high waves. These waves had the potential to destroy the AWS with forces reaching up to 5 mega Newton. Building a larger structure to cope with these waves was not a feasible option, so the AWS was equipped with a water-driven braking system to act as a safety device. Excessive movements of the floater in high waves are damped by the water brakes that are capable of reducing the floaters’ movements. The damping is provided by the water enclosed in the water brakes. In case of excessively rough sea states, the system automatically enters the safety mode, which brings down the floater by releasing the air pressure and locking it in the lower position [17].

Environmental Implications Observations on environmental issues were irregular due to the brief interval of the test period; however the structure was extremely well accepted by shellfish and small fish at the test site in Portugal. Dolphins were also observed in the direct vicinity of the plant during the tests. Despite the scarceness of data, the observations indicate that the AWS could be placed in restricted fishing areas where it could also act as habitat protection. The absence of noisy high-speed rotational equipment and the submergence of the AWS provide negligible environmental impact.

3.2.1.3 Fred Olsen’s FO3 The FO3 shown in Figure 3.9 looks like a traditional rig, but one striking difference is the floating, egg-shaped cylinders hanging underneath it. Energy is absorbed from the waves as they move the cylinders up and down. This linear, vertical motion is then converted to rotational motion by means of a hydraulic system – a hydraulic motor drives a generator to produce electricity. Another important difference is that the rig structure is built using lightweight composite material instead of steel. Figure 3.9: Fred Olsen’s FO3 (Source: www.fredolsen-renewables.com) SOPAC Miscellaneous Report 701 39 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 40

estimated 3–4millionEurostobuild[18]. ob is an is WaveBob WaveBob 3.2.1.4 2.8 of cost a at power produce to is goal The turbine. wind one of productivity the to equivalent approximately is and households, 600 produce will model full-scale the 2.52 MW from estimates, 6 meter high waves with a period of 9 seconds. This production is power enough to supply power Olsen’s Fred to According These fourelementsconstitute thePowerTakeOffsystem(PTO). pump. hose and piston; tube; acceleration buoy; elements: four of consists Aqua BuOY The electrical an driving turbine a of generator. Thepoweristransmittedtoshorebymeans ofanunderseatransmissionline[21]. consisting system conversion a into directed is seawater the kinetic energy into pressurised seawater by means of two-stroke hose pumps. Pressurised electricity. into the waves oncoming of of energy motion vertical kinetic the converts that structure buoy floating a is AquaBuOY Finavera The Finavera Renewables AquaBuOY 3.2.1.5 Figures 3.10:TheWaveBob(Source:www.wavebob.com) [20]. and frequency by adding or power subtracting buoyancy wave to height, smooth out wave the variable predicted load to of the respond ocean can that system damping a by controlled is The environment. marine harsh the in survive to robust be and conditions of variety a absorb to able be must structures These storms. raging to swells mild from variability with A major part of the innovation relies on the control mechanism where the challenge is to cope the electricitygridon-shore. prevailing wave climate and so maximise the amount of useful power that may be delivered to The main advantage of the and pullingmotionbythewavesonshaftscreateelectricity[19]. pushing The weight. submerged a to shafts by connected buoy a of consists which ‘device' a rish company established by physicist by established company Irish WaveBob is its ability to automatically adjust its response to suit the uro per kWh. per Euro nergy transfer takes place by converting by place takes transfer Energy illiam Dick in 1999. The 1999. in Dick William ach full-scale platform will cost an cost will platform full-scale Each

ob is WaveBob WaveBob

A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

The acceleration tube is a vertical, hollow cylinder rigidly mounted under the body of the buoy. The tube is open at both ends to allow unimpeded entry and exit of seawater in either direction. Positioned at the midpoint of the acceleration tube is the piston, a broad, neutrally buoyant disk. When the buoy is at rest, the piston is held at the midpoint by the balanced tension of two hose pumps that are attached to opposite sides of the piston and extend to the top and bottom of the acceleration tube, respectively [21].

The hose-pump is a steel reinforced rubber hose whose internal volume is reduced when the hose is stretched, thereby acting as a pump. The pressurised seawater is subsequently expelled into a high-pressure accumulator, and in turn fed to a turbine which drives a generator. Generated electricity is brought to shore via a standard submarine cable.

Figure 3.11: Diagram of the AquaBuOY’s operation (Source: http://www.greencarcongress.com/2007/12/pge-and-finaver.html)

AquaBuOY prototype 2.0 which was situated off the United States west coast sank to the bottom in about 50 m of water (27th October, 2008). The failure of a bilge pump was said to be the cause, just a day before the AquaBuOY was scheduled to be removed. The collection of operational data was fortunately successful. The salvage crew managed to remove the anchor, mooring lines, tackle and other related paraphernalia, but had to leave the US$2 million piece of equipment resting on the ocean floor until favourable weather conditions permitted its retrieval [22]. SOPAC Miscellaneous Report 701 41 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 42 in depth. According to According depth. in Cove, Sandy at tested being is prototype kW 20 A seas. rough and storms withstand to able be to said also is design The meters. of hundreds many to meters 50 from ranging in depths energy water wave strongest the capture to itself adjusts automatically that motion and design Johns, St. and Ottawa in facilities tank wave indoor Canadian the at conducted tests many in as well as trials sea the allows which contact device of to be fully point compliant on single all three a axes. This at has been successfully moored demonstrated in is both spar The degrees. 45 of incline an h mi faue f the of feature main The Wave Energy 3.2.1.6 CAD$0.09/kWh [23]. ova Scotia, which is approximately 5 meters x 5 meters on top and about 4.5 meters 4.5 about and top on meters 5 x meters 5 approximately is which Scotia, Nova

iue 3.13: Figure (Source: www.waveenergytech.com) Figure 3.12:DiagramoftheWETEnGen (Source: www.waveenergytech.com) Spar T, the cost of electricity from a 1 MW 1 a from electricity of cost the WET, Float WET WET n s t Sat la wih rvl aog rgd pr at spar rigid a along travels which Float Smart its is EnGen n rttp a Sny Cove, Sandy at prototype EnGen Technologies (WET EnGen) scheme underdevelopment Intertial ReactionPointMooring ewfoundland. The device has a unique a has device The Newfoundland. Mechanism Conversion Power ational Research Council’s Research National v Scotia Nova WET en farm would be would farm EnGen

A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

3.2.1.7 CETO The original idea behind CETO was to harvest the high density of energy from waves with a low- cost mass-produced device, while also simplifying the associated infrastructure by pumping pressurised sea water ashore, rather than electricity. This has the additional benefit of allowing onshore based desalination depending on the deployment area.

CETO I (Figure 3.14) was designed to utilise water pressure from waves travelling overhead to move a large diaphragm in an immersed chamber. The diaphragm in turn drives a lever pivoted between 2 pumps, giving a pressure stroke in one of the pumps with the diaphragm either rising or falling. The pumps take seawater from outside the submerged chamber and it is fed ashore through a piped system [24].

Figure 3.14: The CETO I prototype in Fremantle, Australia (Source: [25])

As with CETO I, CETO II (Figure 3.15) is a seabed mounted device. The size and mass, however, have been reduced considerably to save on manufacturing costs. Rather than using water column pressure CETO II uses a submerged buoyant spherical actuator which moves with the subsurface water in a cyclical and elliptical manner. This motion is used to pull the pump in one direction on the pressure stroke and allows the suction stroke to occur under gravity. Each actuator operates a single pump. Similar to CETO I, high pressure water is collected from an array of pumps and fed ashore via a pipe work system for extraction of energy or desalination of water [24].

Throughout 2008, the performance of the pilot scale CETO II unit based at Fremantle, Western Australia, was tested in a range of sea and swell conditions. The results confirmed excellent correlation between predicted and measured performance. Additionally, excellent results were achieved in predicting pump output based on incident wave heights and periods. Carnegie Corporation Limited, which owns the CETO technology has secured funding of AUD$12.5 million from the Australian state government’s Low Emissions Energy Development (LEED) fund. The commercial demonstration project which will be called CETO III is planned to be a 50 MW peak installed wave energy plant that has the potential to save 240,000 tonnes of carbon dioxide emissions a year [26]. SOPAC Miscellaneous Report 701 43 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 44 wave machine produces energy around 90% of the time, and that it will run on maximum [28]. on time run the of will 30% it power that and time, the of 90% around energy produces machine wave the that show tests and Calculations electricity. produce to waves high cm 10 needing only The has and m 2 of withstood 12stormstodate[28]. depth a scale at pilot standing The experience generator. operational kW of hours 5.5 16,000 a has powering machine m 1 of diameter a with each floats, shaped at tested being machine scale pilot The is automaticallyactivated.Thefloatscanalsobesetin the safepositionviaInternet. seabed the on sensor ahead of the machine which measures the a waves and ensures that the storm security using system position safe a to lifted are floats the storm a of event the In The bar. 200 to pressure drivesahydraulicmotor,whichinturngeneratorproducingelectricity[27]. up of pressure a with system transmission common machine’s the into oil the base of at their own hydraulic cylinder. positioned each are floats The water. the in submerged partially are which floats shaped The Wave StarEnergy 3.2.1.8 rm h Danish the from 500 kWversionofthemachine. Wave Star as shown in Figure 3.16 is a multi-point absorber equipped with 20 hemisphere- Wave Star is able to generate electricity from very small waves, with the pilot scale machine

(Source: www.ceto.com.au) Figure 3.15:CETOIIwaveenergyconverter D) o osrc a construct to (EUDP) Programme Demonstration & Development Energy n July of 2008, of July In When a float is raised, a piston in the cylinder presses Nissum ave Star received USD$4.25 million in support in million USD$4.25 received Star Wave enn, emr, a 4 hemisphere- 40 has Denmark, Bredning,

A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Figure 3.16: Wave Star prototype at Nissum Bredning, Denmark (Source: www.wavestarenergy.com)

3.2.1.9 Seabased Seabased's wave power technology utilises a unique directly driven permanent magnet linear generator. The generator is specially designed to take advantage of the slow movement of the waves that is transferred to it by a buoy on the ocean surface. The buoy action is transferred directly to the generator with no intermediate mechanical gearing since the generator is optimised to output high power even at slow speeds. The movement of the waves causes the translator (corresponding to the turning rotor of a conventional generator) to move up and down within the stator, thus converting the kinetic energy of the wave to electric energy. Powerful neodymium-iron-boron magnets are mounted on the translator to create an alternating magnetic field which penetrates the stator windings. The stroke length of the Figure 3.17: Diagram of the direct drive linear translator is limited by end stops at top and generator (Source: www.seabased.com) bottom. The encapsulated generators are to be anchored to the seabed using a concrete foundation [29], refer to Figure 3.17. SOPAC Miscellaneous Report 701 45 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 46 2009 [31]. to the islands' power distribution grid. The pilot projects are scheduled to be operational during unit at King Tasmania. islands, Flinders and King for with collaborating is Systems developed BioPower being are projects pilot kW 250 Two seabed the against flat [31]. lying position safe a assumes and operating ceases automatically sea. As they sway in the tide, electricity is generated. the of motion the to oscillating constantly are which blades buoyant three of consists system The bed. ocean the on found plants sea of motion swaying the mimics system bioWAVE The 3.2.1.10 BioPower Systems(bioWAVE) 50/60 perfect amplitude. and frequency in both individual varies the plants power from current electric generated The components. electrical the on demands new create but end, mechanical the at complexity of level low a have systems driven Directly received. Marine Substation (LVMS) which rectifies, inverts and transforms the variable alternating current for thenext2-3years[30]. operation in be to expected is and 2009 April in deployed was system power wave The grid. kV 22 the to generators kW 40 the connecting cable sub-sea a and switchgear under-water climate of Runde wave rough the in endurance and performance for tested being currently is technology The physical damage[29]. from them protects seabed the on placement their and foundations concrete with fitted are substations marine The grid. electrical onshore the to distances long over transmitted be can electricity the that so voltage the transforms further substation This (MVMS). Substation Marine

Figure 3.18:bioWAVEmodelbeingtestedinawave tank(Source:www.biopowersystems.com) n larger wave energy parks, groups of groups parks, energy wave larger In Island and a 20 m unit at Flinders z alternating current, the generating plants are connected to a to connected are plants generating the current, alternating Hz Island, Norway. The installation consists of two Seabased wave power devices, ydro Tasmania to deploy and test a 25 m bioWAVE m 25 a test and deploy to Tasmania Hydro Island. VMS are connected to a Medium Voltage Medium a to connected are LVMS In extreme wave conditions the bioWAVE Both units are expected to be connected n order to convert the electricity to a to electricity the convert to order In ow Voltage Low A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

3.2.1.11 Aquamarine Power (Oyster) The Oyster consists of an oscillator fitted with pistons and fixed to the near shore seabed at depths of 10-12 m. Each passing wave activates the oscillator, pumping high- pressure water through a sub-sea pipeline to the shore where it is converted to electricity using conventional hydro-electric generators [32].

Aquamarine was able to validate the Oyster’s power generation predictions with their commercial demonstrator at the New and Renewable Energy Centre (NaREC) near Newcastle, England. The output from a single pumping cylinder delivered more than 170 kW of electricity proving that a full-scale device, with two pumping cylinders, will deliver well in excess of the modelled output of 350 kW. The testing period spanned 2 months (March-April 2009), enabling the company to optimise the system settings, test different components with respect to performance and fatigue and obtain Figure 3.19: Full-scale Oyster operational experience while producing the (Source: www.aquamarinepower.com) predicted quantities of electricity [33]. More tests are scheduled for 2009.

Figure 3.20: Oyster wave energy conversion system (Source: www.aquamarinepower.com) SOPAC Miscellaneous Report 701 47 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 48

equipment oraircompressionisrequired[34]. Trident by designed generators linear patented the through electricity only one principal moving part. The system works by using floats, placed in the sea, to generate Trident Trident Energy 3.2.1.12 magnet alternatorthatiscommonly usedinwindturbines[36]. permanent standard a to transferred then is energy rotational This 96.5%. of efficiency an at upward the motion both of converts the Dynamo waves Aegir and The the it. downward to motion shaft of a gravity via into waves singular of direction motion rotational the energy transfers float buoyancy a while position stationary relatively a in remains which column central sealed Ocean 3.2.1.13 Ocean Navitas at leastsixmonths.Thisdeploymentisexpectedtotake placelaterin2009[35]. of coast east the off km 8 3.22) (Figure Trident of design the validate to data necessary the of all provided tests the from obtained results in April The 2007 which ended in July of 2007. The University. company Southampton commenced an offshore test project John of Professor Chaplin by verified independently were results The 2005. in development and research of months 15 after solution viable Trident [34]. mode and operating the machinery in reverse motor is into generators the This switching by done chamber. protective a into float the retracts automatically mechanism self-protect repair. float occasional and rollers guide tube the of purely servicing the to confined is and combination girder float\ the is part moving only the as minimal be to said is Maintenance directions. wave and wavelengths heights, wave of spectrum full the use to able be to said is DECM The Figure 3.21:DECMwavetanktrials(Source:www.tridentenergy.co.uk) Energy has developed the Direct avitas’ technology is called the Aegir Dynamo shown in Figure 3.23. Figure in shown Dynamo Aegir the called is technology Navitas’ device kW 20 a deploy to planning is Trident Currently, platform. test offshore Energy’s M s a as DECM the confirmed Energy n storm conditions, a conditions, storm In

ngland where it is expected to generate electricity for electricity generate to expected is it where England Energy Conversion Method (DECM) which consists of

Figure 3.22:Trident’s20kWprototype(Source:[35])

Energy. t is housed in a in housed is It o hydraulic No A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Figure 3.23: Aegir Dynamos’ operational diagram and full-scale device (Source: [37])

The technology has been designed for deployment in two formats, one for off-grid shore-based applications to service isolated coastal communities, and one for offshore buoy formats to generate commercial levels of electrical energy in farms. Tests have confirmed the company's prediction that it converts 96.5% of captured wave energy into electricity, and with a conversion module weighing only 1.5 tonnes, generates over 30 kWh of electricity from waves of only 1.2 meters in height [37].

As of December 2008, Ocean Nativas is seeking investment to facilitate the construction of sea trial devices for both a 45 kW shore-based design for isolated coastal communities and a 200 kW Buoy for commercial power generation [37].

3.2.1.14 SyncWave Systems The SyncWave Power Resonator (SPR) is a surface penetrating, slack-moored, self-reacting, and tuneable phase-lag point absorber. It is comprised of two floats and a controller deployed in deep waters offshore. Under the regular stimulation of ocean swell the floats naturally heave out of phase due to differences in their physical properties.

Figure 3.24: SyncWave Power Resonator prototype "Charlotte" (Source: http://www.marinuspower.com/pages/proj_SyncWave.html) SOPAC Miscellaneous Report 701 49 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 50 The SPR is scheduled to be demonstrated in 2011 off the off 2011 in demonstrated be to scheduled is SPR The productive [38]. maximally system the keep to corrections applies constantly and time, over frequency wave to electricity and sent to shorebyanundersea cable. SWEL tracks changes in seastateand antenna an tunes like to a radio spectrum signal. This delivers wave consistent energy the to the power of take-off, which is frequency converted dominant the with resonate to SyncWave as a propagating energy field-like a radio wave. SyncWave Systems designed SWEL to force resource wave the of view company's the is technologies competing with difference key The seas. extreme in modes operating safe to SyncWave limits and conditions, wave of range full contribution fromCianbroCorporation[39]. awarded earlier in 2009 from the of Province the from grant million US$1.6 recent a including project demonstration its complete to required funds total the of 60% approximately raised now has Systems SyncWave Canada. The SyncWave built breakwateratMutrikuPort,innorthernSpain[10]. newly the in also and Portugal) (northern River Douro the of mouth the in breakwater new a of “breakwater OWC” was adopted in the 750 kW OWC plant planned to be installed in the head the of option The generation. power for equipment electrical and mechanical the as well as OWC the accommodate to of shape special one a had where breakwater 1990), the up (in making foundations Japan the Sakata, of harbour the in time first been the has for This successfully easier. done much become plant energy wave the of operations the the are and costs shared integrating construction The however, advantages. several expensive; has breakwater quite a into structure is plant OWC size significant of plants OWC Constructing within ayearofcommissioning[40]. to robust year storms’. The first extremely device, built in the 1980s on the southern be coast of to need chambers and withstand not only daily operational zone stresses but these also exceptional circumstances, such surf as ‘100- however, the waves; over built incoming chambers entrapping concrete enclosed on based were devices Early was designedforthistypeofapplicationandisusedinmostOWCdevicestoday[11]. during a wave trough and will flow out of the housing during a wave crest. The housing the into flow will Air rotate. to continues turbine the configuration, turbine correct the passing air turns a turbine. As the wave recedes, air is sucked back into the chamber and, with waves rise and fall. wave induced air pressurisation. The device entraps air in a fixed-volume chamber, into which The Oscillating Oscillating 3.2.2 Table 3.5:DevelopmentstatusofOWCtechnology[12] *

Orecon Offshore WaveEnergy(OWEL) Oceanlinx WaveGen Company ritish Columbia's British having a symmetricalairfoil. blades the to due is this OWC; an in stream air the of direction changing the of spite in rotation of sense its keep The ells Turbine was developed by Prof. Alan Prof. by developed was Turbine Wells Energy Water Column (OWC) operates much like a wind turbine using the principle of With each rising wave, air is expelled through a port in the chamber and the Fund in April 2009. April in Fund ICE Latching System (SWELS) controller optimises their relative motion in the Government of Canada, and a US$1 million pledge of in-kind Water Column Country Australia ells of Queen's University Queen's of Wells U.K U.K U.K t has also received US$2.2 million in a grant a in million US$2.2 received also has It est Coast of Vancouver of Coast West Year 2002 2001 1997 1990 elfast in the late 1980s. late the in Belfast Norway, was destroyed Commercial Commercial Wells Turbine* Prototype Prototype Stage t is able to able is It Island, A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

3.2.2.1 WaveGen WaveGen is a Scottish company, which has developed an oscillating water column device that is built into the face of a cliff on the island of Islay, off western Scotland. The device, called LIMPET, was the world's first grid-connected commercial-scale wave energy plant. The plant was commissioned in November 2000 and comprises a large concrete structure, which traps the water rising in a breaking wave. The oscillating water column that is created within the chamber causes the air above it to be alternately blown out and sucked back, driving A Wells Turbine. A Wells Turbine has the unusual property of rotating in the same direction, regardless of the air current direction. The turbine drives a 500 kW generator, which contributes to the island’s electricity supply.

One of the major problems with shoreline-based OWCs is their construction, which must necessarily take place on rocky shores exposed to wind and waves. To protect the LIMPET from the extreme forces of nature, the unit was built back from the coastline with the removal of an embankment [41].

The Wells Turbine rotates in the same direction regardless of the direction of the air Reinforced concrete capture flow, thus generating irrespective of upward or set into chamber rock face. downward movement of the water column.

Air is compressed and decompressed by the Oscillating Water Column (OWC). This causes air to be forced out and then sucked back through the Wells Turbine.

Figure 3.25: Diagram of the LIMPET (Source: www.wavegen.co.uk)

3.2.2.2 Oceanlinx Oceanlinx has produced a new type of oscillating water column. The system uses a parabolic wall, which focuses wave energy into the column. Initial testing has been facilitated through a grant of AUD$750,000 from the Australian Greenhouse Office's Renewable Energy Commercialisation Program, for the construction of a 300 kW wave power generator on the breakwater at Port Kembla, Australia. The ocean trial of the device began on 26th October, 2005. A proportion of the power generated was used to produce desalinated water on-board the device. The power measurements indicated that the device performed better than previously predicted from wave tank, wind tunnel, and computational fluid dynamic (CFD) testing. In 2 m waves with periods of seven seconds, the results from the trial indicated the device produced 321 kW, compared with previous predictions of 268 kW. In October 2008, Oceanlinx received AUD$16 million from an investor syndicate comprising the New Energy Fund, Espírito Santo

Ventures and Emerald Technology Ventures to further develop their technology and to progress SOPAC Miscellaneous Report 701 key projects [25]. 51 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 52

point intime[42]. algorithm based upon the particular conditions and energy content of the site at any particular parameters in real time, such as the blade angle and turbine speed. These are calibrated in the The signal from the transducer is sent to a programmable logic controller which adjusts various activating it. duration and shape of each wave. The system is calibrated to prevent small-scale “noise” from The transducer sends a voltage signal proportional to the pressure which identifies the height, exerted on the ocean floor by each wave as it approaches or as it enters the capture pressure chamber. the measures which transducer pressure a with system sensor a uses turbine The for muchmaintenance. need the reducing reliability, and efficiency improves This turbine. the from torque higher and Oceanlinx turbine; however, uses variable pitch blades which results in slower rotational speed attempts to address this have mostly resulted in turbines with varying degrees of efficiency. The considered by wave energy experts as a significant barrier to commercialising OWC. Previous is and performance, economic device’s the in element key a is OWC an in used turbine The construction and oceantesting[44]. prototype includes which development, of stage next the advance to as so obtained be can shareholders. from the by investigating funded South Kingdom’s United the being is and research The configurations requirements. mooring and geometric loadings structural internal Grampus’ studying includes research The OWEL has now embarked on a new development phase to optimise the yet simpleconstructiontechnique[43]. full-scale a 2-year Initial Development Programme sponsored a by the Carbon by Trust. The initial followed study predicted that Award Smart DTI a through financed study feasibility a completed has the called OWC floating a developing is Kingdom, United the in based OWEL Offshore 3.2.2.3 Figure 3.26:Oceanlinx’sOWC(Source:www.oceanlinx.com) rampus would produce commercially viable quantities of power from its robust its from power of quantities viable commercially produce would Grampus t is hoped that a more detailed understanding on performance and costs and performance on understanding detailed more a that hoped is It Wave Energy(OWEL) RDA) and contributions and (SWRDA) Agency Development Regional West Grampus’ performance. rampus and Grampus A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Figure 3.27: Grampus model in wave tank tests (Source: www.owel.co.uk)

3.2.2.4 Orecon Orecon has developed a buoy-type wave energy converter with Multi Resonant Chambers which employs the simplicity of an OWC, but is said to be more efficient. The company’s mooring system has been designed with an artificial reef, which is expected to boost the marine population around the WEC [45].

Orecon was established in 2002 by Nicola Harper and Fraser Johnson who formed the company as a result of their postgraduate project at the University of Plymouth, UK. Until early 2008, Orecon’s founders were struggling through lack of investment. Now with US$24 million in venture capital from Advent Ventures, Venrock, Wellington Partners and Northzone Ventures, it is moving ahead rapidly to manufacture a full-scale 1.5 MW prototype [46].

3.2.3 Overtopping Devices The overtopping wave energy converter works in much the same way a hydroelectric dam works. Reservoirs are filled by incoming waves to levels above the average surrounding ocean. The water is then released, and gravity causes it to fall back toward the ocean surface. The energy of the falling water is used to turn hydro turbines. The turbines are coupled to generators which produce electricity. The overtopping WEC can be placed on the shoreline or near shore but are more commonly placed at a near shore location. As with the OWC, the overtopping WEC may be slack moored or fixedly moored to the ocean bottom, and the issues associated with these mooring options are the same as with the OWC. It should be noted that overtopping wave energy converters are not as common as OWC [11].

3.2.3.1 Wave Dragon The Wave Dragon is essentially an overtopping device where oncoming waves surge up a ramp and overtop into the reservoir. Energy is extracted as this water passes through a series of low-head hydro turbines back down to the sea. There are additionally two wings, hinged to the platform, which reflect the waves towards the ramp to improve the performance.

The Wave Dragon is of very simple construction and has only the turbines as the moving parts, which is useful for operating offshore under extreme forces and fouling. The Wave Dragon is moored in relatively deep water to take advantage of the ocean waves before they lose energy as they reach the coastal area. The device is designed to stay as stationary as possible. The first prototype was deployed in Nissum Bredning, Denmark. The 237 tonne prototype was towed to the test site in March 2003 and was tested continuously until January 2005 [47]. SOPAC Miscellaneous Report 701 53 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 54 • • • • • Some oftheresultsobtainedfromprototypetestingincludefollowing: produce to depth meters 30 to 20 than between 4to11MW,dependingonwaveactivity[25]. more at offshore sited be to designed is Dragon The significantly. increases overtopping that shown has testing model and effect, this wave A beach. a reaching when approaching a beach faces changes its geometry. wave The special elliptical every shape of the that ramp optimises loss energy the minimise to steep The Figure 3.28:WaveDragondiagramandprototype(Source:www.wavedragon.net) •

Figure 3.29:Ramp usedintheWaveDragon(Source: www.wavedragon.net) prtn ad aneac eprec fo rnig h trie i a offshore an in turbines the running from experience maintenance and Operating improved. Almost all subsystems (remote control, frequency converters etc.) have subsequently been Control systemalgorithmshavebeenoptimisedbasedontherealseaexperiences. of de-attachmentsthewavereflectorsduringstormsthesejointshavebeenmodified. The redesign of the joint between the main platform and wave reflector: Due to a number also been has performance system verified. converter generator/frequency turbine/PM The performance. verified has which operation of hours 20,000 environment hasledtoanumberofmodificationsontheturbines.

Wave Dragon's ramp can be compared to a beach; however, it is very short and relatively

v Dao' wv eeg absorption energy wave Dragon's Wave Wave A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

3.2.3.2 Seawave Slot-Cone Generator (SSG) WAVEenergy was established in April 2004 to develop the Seawave Slot-Cone Generator (SSG) concept. The SSG concept is based on the wave overtopping principle utilising multiple reservoirs placed on top of each other. The potential energy of the incoming wave will be stored in the reservoirs before running through turbines and generating electricity. The patented multi-reservoir concept ensures that all the different height of waves are utilised for energy production, resulting in a high degree of efficiency [48].

Currently WAVEenergy is trying to develop a multi-stage water turbine (MST) which can utilise different heights of water head on a common turbine wheel. The multi-stage technology will minimise the number of start/stop sequence on the turbine even if only one reservoir is supplying water to the turbine, resulting in a high degree of utilisation. The MST project commenced in January 2005 and is in co-operation with the Norwegian University of Science and Technology (NTNU). The Project is supported by the Renergi programme of the Norwegian Research Council [49].

Figure 3.30: Artist's impression of the Seawave Slot-Cone Generator (Source: www.waveenergy.no) 3.3 Secondary Technologies [11] 3.3.1 Power Take-Off Methods Designers face the task of selecting a power take-off method to convert the linear motion of a point absorber to electrical energy. The conversion method must take into account that the linear forces transferred to the point absorber can exceed 1 Mega Newton with velocities of 2.2 m/s [10]. Typically, this conversion process involves some intermediary to convert linear motion to the rotary motion needed to run a conventional electric generator. The most popular and widely used intermediary is a hydraulic system. Conversely, linear generators or magnetohydrodynamic generators can directly convert the point absorber’s linear motion to electrical energy. There is no consensus on which method is best, and each has its pros and cons based on the designer’s criteria. SOPAC Miscellaneous Report 701 55 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 56 ytm hv a rvn rc rcr ad ot nier ae el esd n hi ue as and buildthandirectdrives. use their in versed well are engineers design to expensive less usually are systems hydraulic Furthermore, drives. direct to opposed most and record track proven a have systems Some companies prefer hydraulics over direct drive systems. A central reason is that hydraulic lower thanthoseexperiencedbyaWECwhicharetypicallyontheorderof2m/s. speeds at work to designed are systems hydraulic Also, oil. leak could valve or seal broken a point absorbers use oil as the hydraulic fluid (some use seawater), it should be well noted that possible since access for maintenance will be difficult. Although not all of the hydraulics-based at mas oe aneac ise ad the and issues maintenance more means parts moving More system. hydraulic a of parts moving many the is problem Another inverter. and generator the in present losses the to addition in motor hydraulic the of turning and pumping indirect. is process conversion the because inefficient mechanically is method take-off power hydraulic The disadvantages. and advantages have systems Hydraulic the hydraulicmotortoagenerator,conversionprocessiscomplete. This motor creates motor. the rotary motion hydraulic needed to drive the a standard electric feeds generator, and by then coupling pump The pump. hydraulic the through fluid hydraulic motor. The linear wave motion acts to move the piston up and down which pumps pressurised The hydraulic system in a point absorber consists of a piston, a hydraulic pump, and a hydraulic Hydraulic System 3.3.1.1 comparative criteriainclude cost,efficiency,anddurability. Other force. necessary the providing while minimised be should which size, its to coupled is machine a of force reciprocating The needed. is machine large physically a design, of virtue in drives direct by experienced speeds low at forces high the offset to provide can machine the that stress shear of amount the is criteria important more the of One other. a For • • • • • corresponding application.Thedifferenttypesoflinear generators arelistedbelow: its for generator linear suited best the identifying been has difficulty for main The years. few generators past linear surrounding activity of lot a been has There mass production. option. expensive more a generators linear using makes This system. hydraulics-based a like off-the-shelf bought be can that something a of specifications the fit to tailored specially be must it that is generator linear a using to drawback The system. hydraulic a than efficient more is and parts moving electricity rather than relying on gearboxes and hydraulics as intermediaries. Thus, it has fewer generator’s rotor. The benefit of the linear generator is that it directly converts wave motion into traditional a of motion rotational the to opposed as down and up moves it application this In to electrical energy; however, the rotor in a linear generator is usually referred to as a ‘translator’. Linear generators are like conventional rotary generators in that they convert mechanical energy LinearGenerator 3.3.1.2 Transverse fluxPM(TFPM). Longitudinal fluxPM(FPM);and Switched reluctance; Induction; Permanent magnet(PM)synchronous; C application, there are several criteria that differentiate these machines from each from machines these differentiate that criteria several are there application, WEC vrhls, ot cn e iiie through minimised be can costs Nevertheless, sol b a mitnnefe as maintenance-free as be should WEC apiain i the in applications WEC osses occur during occur Losses C and so is not is so and WEC Cs, and by and WECs, A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Out of all the machines listed, the TFPM pictured in Figure 3.31 is considered the most suitable for the direct drive of a point absorber [10]. It has the best efficiency and is also the smallest because of its high shear stress density. The PM synchronous machine may also be considered as an alternative to the TFPM, but the TFPM is considerably more efficient. While a TFPM is costly, it is still slightly cheaper than the PM synchronous.

translator core

stator PM n S stator flux concentrator n S n

stator coil

Figure 3.31: TFPM machine with flux concentration and stationary magnets (Source: [4])

Despite the advantages of using TFPMs in point absorbers, they have a few setbacks that will need further research consideration. As mentioned, the TFPM supplies more shear stress than the other machines listed, with levels ranging from 20 to 40 kN/m2, and so can provide 1 MN of reactionary force. The problem with providing so much shear stress by means of neodymium-iron-boron permanent magnets is the substantial attractive forces between the stator and translator. The bearings suffer dangerous loads as a result and thus become a maintenance concern. To balance the attractive forces between the stator and translator, a double-sided stator may be used as opposed to a single-sided stator where the windings are placed on one side [10]. Despite better balance with a double-sided stator, deviations in the air gap still occur with the consequence of severe bearing loads.

3.3.1.3 Magnetohydrodynamic Generator The magnetohydrodynamic (MHD) generator is also a direct drive mechanical/electrical converter. The MHD generator works on the principle that flowing seawater can conduct electric current in the presence of a strong magnetic field. Over passing waves induce seawater to flow through a hollow tube with flared inlet and outlet sections which boost water velocity by means of the Bernoulli principle. Electromagnets or other mechanisms such as super conductors generate a magnetic field perpendicular to the flow of water. The strong magnetic field stimulates an electric current in the passing seawater which is collected by electrodes placed in the tube. This conversion method is highly desirable due to the lack of moving parts.

Scientific Applications & Research Associates (SARA) has developed a 100 kW prototype MHD generator which it claims will cut the costs of wave energy conversion (WEC) systems by a factor of three [50]. SOPAC Miscellaneous Report 701 57 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 58 represents the undisturbedwaveclimate. buoy thus and point fixed a than rather the site measurement the around area ocean the from derived from height wave significant the mean with measurements long-term can waters the undisturbed comparing in by offshore present quantified energy be wave the to exposure of degree The accuracy ofglobalnumerical wavemodeldatafortheregion. undisturbed offshore in locations three at made were used for interpretative purposes. Further, short-term directional wave measurements were around also and islands the from data wind long-term and data wind Satellite winds. and waves ocean of variability temporal and spatial the describe to region, the across with precision combined satellite altimeter wave height and wind speed measurements, were which were available specific, site as considered be must which measurements, wave The power extractioninmindandtheexposureofsiteto oceanwaves. of combination a via with factors including chosen local energy requirements and were infrastructure with the locations possibility of future wave The Kiribati. except groups, island of each these of shores the to close locations chosen carefully six at made were measurements 1994. to 1989 from region the of resource energy wave the map to initiated Samoa, Fiji, Tuvalu, Vanuatu, South the of climate wave the of study comprehensive first The wave energypotentialoftheregionwasmissing. the of evaluation technical the for needed data sufficient that realised was it studies, feasibility renewable this utilising to respect with energy source as an alternative to expensive imported fossil fuels. Subsequent region to a number of Pacific South in the energy in generated wave was of interest harnessing for technology the in in developments than more much year, the through continuous and non-seasonal are to compared powerful less are Pacific the in resources Wave Wave Power Potential inPacific 3.4 Island Countries [51] Island Countries

during testingatSARAinMarch2007(Source:[50]) system MWEC prototype laboratory KW 100 3.32: Figure ST liee ma sgiiat ae egt te atr being latter the height, wave significant mean altimeter GEOSAT sen iiai Tna n te Cook the and Tonga Kiribati, Western ocations as ground truth for assessing the assessing for truth ground as Iocations Northern est Pacific, encompassing Pacific, West lns ws therefore was Islands, urope; however they however Europe; rp, considerable Europe, rp. Following Europe. ong-term wave Long-term ew Zealand New A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Table 3.6: Comparison of buoy and GEOSAT Mean Significant Wave Height [51] Mean Height above Sea Mean Height above Sea Location Level (Buoy) Level (GEOSAT) Tongatapu, Tonga 1.8 m 2.4 m Samoa 1.8 m 2.3 m Funafuti, Tuvalu 1.8 m 2.0 m Efate, Vanuatu 1.8 m 2.2 m Rarotonga, Cook Islands 2.2 m 2.6 m Kandavu, Fiji 2.1 m 2.3 m

The study concluded according to the data in Table 3.6 that these areas have a rich wave energy climate and exhibit relatively small inter-seasonal changes which hold great potential for wave power applications. Nearer the coasts, wave energy is still reasonably high, but seasonality is somewhat stronger due to island sheltering and seasonal changes in the dominant wind direction. 3.5 Discussion

Unlike the case of wind energy, the present situation shows a wide variety of wave energy systems, at several stages of development, competing against each other, without it being clear which types will be the final winners.

In general, the development, from concept to commercial stage, has been found to be a difficult, slow and expensive process. Although substantial progress has been achieved in the theoretical and numerical modelling of wave energy converters and of their energy conversion chain, model testing is a time-consuming and considerably expensive task but is still essential. In almost every system, optimal wave energy absorption involves some kind of resonance, which implies that the geometry and size of the structure are linked to wavelength. For these reasons, if pilot plants are to be tested in the open ocean, they must be full-sized structures. It is difficult for wave energy technology to follow what was done in the wind turbine industry where relatively small machines where developed first, and were subsequently scaled up to larger sizes and capacity as the market developed. The high costs of constructing, deploying, maintaining and testing large prototypes, under sometimes very harsh environmental conditions, has hindered the development of wave energy systems; in most cases, such operations were possible only with substantial financial support.

Unit costs of produced electrical energy claimed by technology development teams are frequently unreliable. At the present stage of technological development and for the systems that are closer to commercial stage, it is widely acknowledged that the costs are about three times larger than those of energy generated from the onshore wind. It is not surprising that the deployment of full-sized prototypes under open-ocean conditions has been taking (or is planned to take) place in coastal areas of countries where specially generous feed-in tariffs are in force, and/or where government supported infrastructures (especially cable connections) are available for testing.

It also should be mentioned that factors affecting Pacific Island Countries will differ from those countries that are involved with the development of wave energy conversion. The Pacific being prone to cyclonic activity as well as being made up of small grids pose a real challenge for designing wave energy systems. SOPAC Miscellaneous Report 701 59 SOPAC Miscellaneous Report 701 Ocean BasedRenewableEnergyTechnologies A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 60 4. Tidal energy is generated by the relative motion of the Background 4.1 during its rotation around the around rotation its during the Sun due to it being much closer to the earth. As a result, the tide closely follows the moon via gravitational forces. The Moon exerts more than twice the gravitational force on the tides as many other sites around the world, such as the shore. near meters 17 and 16 between For coastline. a along the in tides the instance, estuaries river and bays narrow into water of masses huge bringing shelves, continental reaches it when dramatically increase can tide the however, kilometers; ocean open the in small very of hundreds over distributed wave the of is centre the in centimeters several measures wave it where tide the of height or amplitude The surface. ocean noticeable overmillionsofyears [52]. the system, increasing the rate of slowdown this is negligible because the effect would only be energy. rotational its of 17% lost has Earth period of rotation has increased from 21.9 hours to the 24 hours we see now; in this period the of the rotation the caused has energy of loss This turbulence. in and seabed viscous the at to dissipation due and coastlines, around restrictions natural the through water of pumping to Tidal movement causes a continual loss of mechanical energy in the the in tides region of2to3m/sormore. spring during velocities peak have occur. typically can currents tidal velocities rapid particle relatively water These high very islands, between straits as such topography, to-and-fro-motion. simple a involve normally not do and path elliptical an follow to tend but predictable, thus being oscillations, energy of the water particles in a tide. Tidal currents have the same periodicities as the vertical kinetic the energy, current tidal and tide, a of energy potential the energy, range tidal between currents. tidal termed motions water horizontal roughly by accompanied are tides the of fall and rise the with associated movements water vertical The generating forcesofthesunandmoonareactingatrightanglestoeachother. m. 17 to up of ranges estuaries, tidal particularly creating coastlines, effect this Some accentuate tide. solar the to on superimposed is tide lunar the directions. same the in acting are Moon the and Sun the of forces generating tide the when occur tides Spring month. lunar each during changes tides of magnitude The of Australia,andtheOkhotskSeaRussia. 3 2 ebbcycles-themovement ofthetideouttosea Diurnal tide-high andlowtidesthatoccuronlyonce adayatintervalsof 24hours arth to slow in the 4.5 billion years since formation. During the last 620 million years the years million 620 last the During formation. since years billion 4.5 the in slow to Earth

Technology Tidal Energy ay of Fundy in Canada are the greatest in the world, with amplitude with world, the in greatest the are Canada in Fundy of Bay arth, creating diurnal creating Earth, here tidal currents are channelled through constraining through channelled are currents tidal Where igh tides close to these figures can be observed at observed be can figures these to close tides High hile tidal power may take additional energy from energy additional take may power tidal While Bristol Channel in 2 tide and ebb and tide Earth, Sun and the Moon, which interact t has therefore to be distinguished be to therefore has It eap tides occur when the tide the when occur tides Neap England, the Kimberly coast 3 cycles at any particular any at cycles Earth–Moon system due n this situation, this In A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies OceanA SOPAC Based Desktop Renewable Study of E nergyOcean- TechnologiesBased-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

4. Tidal Energy 4.2 Technology Types

Tidal power can be classified into two main types: Technology 1) Tidal stream systems make use of the kinetic energy of moving water to power turbines, in a similar way to windmills that use moving air. This method is gaining in popularity because of the lower cost and lower ecological impact compared to barrages. 2) barrages make use of the potential energy in the difference in height (or head) between high and low tides. Barrages are essentially dams across the full width of a tidal estuary, and suffer from very high civil infrastructure costs, a worldwide shortage of viable sites, and environmental issues. • Tidal lagoons, are similar to barrages, but can be constructed as self-contained structures, not fully across an estuary, and are claimed to incur much lower cost and impact overall. Furthermore they can be configured to generate electricity continuously which is not the case with barrages.

Modern advances in turbine technology may eventually see large amounts of power generated from the ocean, especially tidal currents using the tidal stream designs but also from the major thermal current systems such as the Gulf Stream, which is covered by the more general term marine current power. Tidal stream turbines may be arrayed in high-velocity areas where natural tidal current flows are concentrated such as the west and east coasts of Canada, the Strait of Gibraltar, the Bosporus, and numerous sites in Southeast Asia and Australia. Such flows occur almost anywhere where there are entrances to bays and rivers, or between land masses where water currents are concentrated.

4.2.1 Tidal Barrage A barrage consists of a number of large concrete caissons built from one side of the water to the other, together with some form of embankment where the barrage is connected to land. The barrage contains turbines (usually in the deepest water), sluice gates and ship locks to facilitate the transfer of ships. A barrage will maximise its energy in locations with a large basin area and maximal difference between high and low tide. The power generated is proportionate to the square of the tidal range and also to the area of the reservoir. A tidal range of at least 7 m is required for economical operation and for sufficient head of water for the turbines.

Ebb generation: The basin is filled through the sluices until high tide. Then the sluice gates are closed. (At this stage there may be "Pumping" to raise the level further). The turbine gates are kept closed until the sea level falls to create sufficient head across the barrage, and then are opened so that the turbines generate until the head is again low. Then the sluices are opened, turbines disconnected and the basin is filled again. The cycle repeats itself. Ebb generation (also known as outflow generation) takes its name from the fact that generation occurs as the tide changes tidal direction.

Flood generation: The basin is filled through the turbines, which generate at tide flood. This is generally much less efficient than ebb generation, because the volume contained in the upper half of the basin (which is where ebb generation operates) is greater than the volume of the lower half (filled first during flood generation). Therefore the available level difference between the basin side and the sea side of the barrage reduces more quickly than it would in ebb generation. Rivers flowing into the basin may further reduce the energy potential, instead of enhancing it as in ebb generation. SOPAC Miscellaneous Report 701 61 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 62 mechanical breakdown, on the northern coast of coast northern the on breakdown, mechanical A 240 MW tidal barrage has been successfully operated at square ofthetidalheightvariation[52]. the correlation between the potential energy is not a linear relationship, rather, is related by the ft 12 by raised been (3.71 m) at low tide. The cost of a 2 ft rise have is returned by the benefits of a 12 ft rise. This is since will this m), (3.05 ft 10 of tide high a on pumping by cm) (0.61 head. ft 2 the to related strongly is output power because generation, during the water level in the basin at high tide (for ebb generation). This energy is more than returned Pumping: Turbines are able to be powered in reverse by excess energy in the grid to increase averages 11 which turbines bulb five using currently plant Jiangxia MW 3.2 over the being of largest capacity The combined MW. 5 total a have which plants tidal seven are there where China, In output butareonlydesignedforoneway(ebb)generation. similar a for turbine bulb the than compact more are turbines Stratflo The diameter. in m 7.6 Canada’s in operated has which plant, tidal Royal Annapolis the is scale real any of barrage operational other The per kWh[53]. 0.02 below now is production electricity of cost the and recovered, been since long has tidal range averages 8 m and reaches up to 13.5 m. The initial capital cost of 620 million Francs 600 around of output annual an to accounting MW 68 of average an generates station power The at 10 MW, have a diameter of 5.3 m and are capable of operating on both ebb and flood tides. rated each turbines, bulb 24 are There dams. coffer using construction of years six after 1966 consideration. TheSihwaTidal barrageplantisexpectedtostartoperationin2009 [54]. under are Korea in barrages tidal for sites Further day. per twice power generate to it allowing generation, tide ebb one-way, a on based is plant The future. near the in completed is it once (passing barrage tidal largest the barrage Sihwa the make will which in whose large amount of inflow/discharge is expected to substantially improve the water quality the sea. The new plan for the site calls for the creation of a tidal barrage type generation plant, pollution. substantial in resulted recharge freshwater of amount low the with combined lake new the of use industrial with the goal of reclaiming an area of the sea for agriculture and a freshwater reservoir; however, In 1994, the Korean the planthasaratedcapacityofonly0.4MW[54]. to electronics power through put then is m), (2.3 site the at present range tidal small the to due Unfortunately, grid). the to it synchronise output whose speeds variable at run generator turbine/generator that uses an “asynchronous synchronous generator” (possibly a synchronous into position, where it was sunk to close off the channel. The plant contained a reversible bulb Ura between channel wide Kislaya In Haishan, providingupto640kWand150,respectively. of generators for the tidal barrage, tidal the for generators of MW 254 on underway now is Construction Sihwa. Lake GWh. The uba, Russia, a tidal barrage was built in 1968 to take advantage of a natural 50 m 50 natural a of advantage take to 1968 in built was barrage tidal a Russia, Guba, GWh per year. Additional tidal barrage plants were constructed in La Rance barrage has six sluice gates and a lifting road bridge over a lock. The Government built a 12.7 km barrage across an estuary near Ansan, Korea, Stratflo turbine of turbine Stratflo MW 18 single a uses and 1984 since Fundy of Bay n 2001, holes were added to the barrage to reconnect the lake with lake the reconnect to barrage the to added were holes 2001, In ay and the sea. A floating power plant was built and then towed then and built was plant power floating A sea. the and Bay rittany, France. Brittany, La Rance without major incident or t was first commissioned in commissioned first was It a Rance) in the world the in Rance) La wtr s raised is water If Baishakou and Euro

A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

4.2.1.1 Offshore Tidal Lagoons, Tidal Electric, UK Representing a new approach to tidal barrages, Tidal Electric has developed a system based on an artificial offshore lagoon. The lagoon would be located in shallow water in an area with a suitably large tidal range. A lagoon system would be created there by an encircling wall made of concrete or rock fill, and would consist of either one large lagoon or multiple smaller ones. Several reversible, low-head turbines would be used to allow generation on both flood and ebb tides, and in the case of the multiple lagoon system, keeping each reservoir at different heights during the tidal cycle could allow for continuous power generation. The Tidal Electric system does not require an estuary to be closed off, which should minimise the impact on the environment and other ocean users. The company has developed a proposal for a tidal lagoon at Swansea Bay, UK.

4.2.1.2 Tidal Delay, Woodshed Technologies Pty Ltd, Australia The Tidal Delay technology is designed for areas where an isthmus or bay has created a natural partially-closed tidal barrage. In such areas, the change in the level of water in the constrained area can lag the level of the sea, leading to a head difference between the two locations. The tidal delay system uses a pipe either passing over the isthmus (using the siphon effect) or an underground pipe running between the ocean and the constrained area. In both cases, the water would be run through a bi-directional turbine to generate power. Although the technology required is already well understood, the amount of power that can be generated and the feasibility of the system depends on both the length of pipe necessary and the tidal range available at the site [54].

4.2.1.3 Two-Basin Barrage, UNAM Engineering Institute, Mexico Several sites in the Mar de Corts region (between the Baja Peninsula and mainland Mexico) have been identified as possible sites for tidal barrages due to their substantial tidal range. Over 3.4 GW (28.5 TWh/year) of possible barrage power has been identified in this region. Seeking to improve the power delivery characteristics, engineers at UNAM have developed a concept for a two-basin system requiring only a small barrage. The system would take advantage of the two naturally existing basins at Puerto Peasco that drain through a narrow inlet, and could provide up to 86 MW of power [54].

Figure 4.1: Barrage in La Rance at high tide (Source: http://phares.ac-rennes.fr/trotteurs2/article.php?sid=455) SOPAC Miscellaneous Report 701 63 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 64 • The Environment Implicationsof 4.2.1.4 • • pre-barrage conditionshavebeenrecorded. tidal barrages due to it being in operation for more than 40 years. The following changes from Shorebirds. of feedstock fortheouterestuaryratherthenviceversa. source a become therefore has basin The seaward. invertebrates of dispersal ready not was productive to the it same degree, and previously the ease of whereas water exchange past nursery the barrage ensures a become has basin the that observed now is It deteriorated. respects some in has barrage the of seaward however conditions; barrage adjacent intertidalzones. the barrage, the barrage has increased the time available per tide cycle for feeding on the reasons a time difference between the occurrences of high and low tides on each side of operational for necessarily is there because that fact the that noted also is it and this, for basin. The enhanced-with-barrage availability of feedstock is regarded as a primary reason increased along the northern coast of France, greater increases have been recorded in the Sediments. Invertebrate seems tobepubliclyacceptable. dredging of the navigation channel towards the head of the estuary, the prevailing regime maintenance some for now need the from Apart it. along openings the of use and layout the to due barrage the near circulation water in changes such with together area, that in coastline towards the seaward end of the basin may be the result of reduced wave action pre-barrage. The occurrence of some fine sediment deposition in the shallow waters of the the Rance a Rance La

(Source: http://www.flickr.com/photos/londonlooks/252191517) Figure 4.2:BarrageinLaRanceatlowtide arrage, in France, is a good example for studying the environmental effects of effects environmental the studying for example good a is France, in Barrage, Estuary, presumably because the currents in that location are now weaker than Although the numbers and variety of shorebirds and waders have generally have waders and shorebirds of variety and numbers the Although Fine sediments have accumulated in the deeper channel toward the head of Fauna. This resource in the basin in now more prolific and varied than in pre- Tidal Barrages [55] A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

• Fisheries. The fish fauna has developed to be much more abundant and diverse than in pre-barrage conditions, again reflecting the enhanced productivity of the modified substrates of the basin area. The species present include some which are known to pass through the barrage regularly and others which migrate annually. No separate provision exists for fish passage. Mortality is reported to be very low, as is recorded elsewhere for turbines of a similar type, size and speed located in river barrages. The species present at Rance include cuttlefish, a species which is very delicate and easily damaged. Salmon have not been present for the perceived reasons that the waters of its feeder rivers are too warm and lack the gravel-based substrates which support spawning. • Macro-algae. Production in the basin area is said to be similar to that recorded along the nearby open coast, where it is not a problem.

4.2.1.5 Cost Effectiveness of Tidal Barrages The major factors in determining the cost effectiveness of a tidal power site are the size (length and height) of the barrage required, and the difference in height between high and low tide. These factors can be expressed in what is called a site's "Gibrat" ratio. The Gibrat ratio is the ratio of the length of the barrage in meters to the annual energy production in kilowatt hours. The smaller the Gibrat site ratio, the more desirable the site. Some examples of Gibrat ratios for tidal barrages are La Rance (France) at 0.36, Severn (England) at 0.87 and Passamaquoddy in the Bay of Fundy (Canada) at 0.92 [56].

4.2.2 Tidal Stream Tidal stream energy represents a different approach to extracting energy from tides (or other marine currents). Rather than using a dam structure, the devices are placed directly “in-stream” and generate energy from the flow of water. There are a number of different technologies for extracting energy from marine currents, including horizontal and vertical-axis turbines, as well as others such as venturis and oscillating foils. Additionally, there is a variety of methods for fixing tidal current devices in place, including seabed anchoring via a gravity base or driven piles, as well as floating or semi-floating platforms fixed in place via mooring lines.

The energy available at a site is proportional to the cube of the current velocity at the site and to the cross-sectional area. This means that, in general, the power that can be generated by a turbine is roughly proportional to its area, and that achieving high power outputs is dependent on having high flow velocities. For this reason, tidal current systems are best suited to areas where narrow channels or other features generate high velocity (2 to 3 m/s or more) flows. The velocity of a tidal current, and thus its power, varies throughout the day in a pattern similar to the height of the tide.

Horizontal-axis turbines are perhaps the most common means of extracting power from marine currents and are somewhat similar in design to those used for wind power. Although there are a variety of approaches, including ducts, variable pitch blades and rim generators, all of these devices consist of a turbine with a horizontal-axis of rotation, aligned parallel to the current flow. These axial-flow turbines generally use a power take off mechanism involving a generator coupled to the turbine’s shaft, either directly or via a gearbox, to produce electricity. SOPAC Miscellaneous Report 701 65 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 66 with horizontalaxisturbines. to their shape, can have a larger cross-sectional turbine area in shallow water than is possible due and direction, any from flows fluid with well work turbines vertical-axis advantages; same or controlled the of some possess them of All flows. fluid restrict or direct to ducts shaped or moving) freely (either blades pitch variable incorporating some with use, in several designs are different There them. for designs developing nevertheless are companies power ocean Vertical-axis capture. power effective the increase and device the through flows fluid accelerate and steer help can The horizontal-axis devices are further split into two categories: Ducted and non-ducted, ducts be connectedtothepowergrid. to order in conversion frequency require which designs, many in used are generators speed can seabed, the variable- that means flows tidal of speed varying The problematic. on gearbox a of use the make fixed those especially maintenance, for devices accessing of difficulty the attractive, gearbox a of use the make can turbines the of rotation of speed low the While otfry in Portaferry Strangford generator. stream tidal commercial large-scale first world's the is 4.3 Figure Following the success of SeaFlow, MCT designed and built the SeaGen. SeaGen as shown in the reach to targeted peakpowerlevelsof300kW[54]. able was it however grid-connected, not was device initial The seafloor. the to maintenance. The assembly was attached to a single ‘monopile’ base that was then anchored turbine was mounted on a movable assembly, which allowed UK it to be raised out of the water for 2-bladed, a 11 m of diameter consisted variable-pitch rotor 4.4 connected Figure through a in gearbox shown to an device induction The generator. The kW. 300 of power rated a with UK, The SeaFlow Project involved a full-scale demonstration device installed in the SeaFlowCurrent andSeaGen,Marine 4.2.2.1 environment. to scientists monitor the interaction of the of system with the team independent an for procedure. installation the hinder could which weather bad from sheltered fairly is time same the at and current, tidal fast very a has it because generator tidal commercial first world's the Strangford Narrows [57]. Strangford of out and in forced are tides the while day and a hours 18 20 between for MW 1.2 generates It 2008. July in grid the to connected was and Narrows between Strangford and Lough was chosen as the site for i as a ovnet place convenient a also is It Northern ae aln u o ue n h wn pwr nuty hwvr several however, industry; power wind the in use of out fallen have turbines ead n pi 2008 April in Ireland ough through the through Lough

the surfaceformaintenance.(Source: [57]) Figure 4.3:TheSeaGenrotorscanberaisedabove Technologies, t was installed in installed was It Bristol Channel,

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The SeaGen generator weights 300 tonnes and consists of twin axial-flow rotors of 16 m in diameter, each driving a generator through a gearbox like a hydro electric or wind turbine. These turbines have a patented feature by which the rotor blades can be pitched through 180 degrees allowing them to operate in both ebb and flood tides. The power units of each system are mounted on arm-like extensions either side of a tubular steel monopole some 3 m in diameter and the arms with the power units can be raised above the surface for safe and easy maintenance access.

SeaGen has been licensed to operate over a period of 5 years, during which there will be a comprehensive environmental monitoring programme to determine the precise impact on the marine environment.

During the commissioning of the system, a software error caused the blades of one of the turbines to be damaged. This resulted in the turbine operating at half power until November 2008 when a new blade was fitted. Due to the difficulty in sourcing replacements, SeaGen was only fully commissioned in November 2008.

Figure 4.4: SeaGen's predecessor, the 300 kW 'SeaFlow' turbine off the north coast of Devon (Source: [57]) SOPAC Miscellaneous Report 701 67 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 68 edn Pwr a be tsig t hrzna-xs re lw ubns n the in turbines Flow New Free horizontal-axis its testing been has Power Verdant Verdant Power, USA 4.2.2.2 (Source: www.verdantpower.com) Figure 4.5:VerdantPowerFreeFlowTurbinesatRITEProject, New York City of Department U.S. the at regimen testing a to subjected was and strength structural enhanced for optimised was hub) and (blades assembly rotor new company's The Motorgate parkingstructureonRooseveltIslandinNewYorkCity[58]. turbines are now delivering clean renewable energy to a the in units the re-installed successfully and rotors In late September of 2008, Verdant Power retrofitted two of its tidal turbines with 5th-generation [54]. System Flow Free the demonstrating successfully Project, RITE the at array in turbines scale the into kW 35 at rated turbine System Flow Free full-scale first company’s the of installation the with 2006 in began which Demonstration, 2 Phase Project’s RITE the completing successfully by milestone major huh l ohr ytm opnns prtd eod xettos wt water-to-wire with expectations, beyond operated components efficiencies of30to40%andthedeliveryover45MWhelectricity[58]. system other all though failures, structural experienced turbines these on installed rotors 4th-Generation the 2007, In successfully withoutincident. tests the passed assembly rotor entire The development. and research efficiency energy and Renewable hydrofoil to align the turbine to the tidal flows. The seabed anchored turbines are 5 m in diameter, three-bladed and fixed-pitch, and use a small can bescaledforplacementdirectlywithinapopulationcenter. System Flow Free the how of example prime a is Project RITE The (tidal). System Hydropower Kinetic Flow Free Power’s Verdant from electricity commercial deliver and demonstrate test,

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4.2.2.3 Hammerfest Strom AS, Norway The Hammerfest tidal turbine is a 3-bladed, seabed-anchored device that turns (like a wind generator) to face varying tidal flows. A 300 KW prototype was installed in Kvalsund in Northern Norway in 2003 and is able to generate power on both the flood and ebb tides. During a 4 year period the tidal system provided valuable operational data and electricity to the nearby town of Hammerfest. The prototype has since been removed from service for major inspection, and is expected to be reinstalled in 2009 for ongoing research [54].

Figure 4.6: Hammerfest Strom’s prototype being deployed (Source: http://www.islayenergytrust.wordpress.com)

4.2.2.4 Underwater Electric Kite, UEK Systems, US The Underwater Electric Kite consists of a pair of contra-rotating, ducted turbines, and uses buoyancy control to operate at varying heights within the stream. This design avoids the need to fix the device to the seabed, and allows it to move freely to the highest flow areas in the current. The UEK is designed for rivers as well as tidal streams, with the current prototype employing a pair of 3 m diameter turbines for a maximum output of 90 kW in 2.5 m/s currents. The first prototype was deployed near a hydro plant in St. Catherine, Ontario, and more tests/ developments are being explored near a hydro plant in Manitoba. The company also has plans to deploy the UEK in Zambia, Columbia, and at other sites worldwide [54].

Figure 4.7: Underwater Electric Kite prototype SOPAC Miscellaneous Report 701 (Source: http://peswiki.com/index.php/Directory:Underwater_Electric_ Kite_Corporation) 69 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 70 redesigned andreplacedbeforetheprototypewasre-deployedinJuneof2008[54]. initial water lubricated bearing system on the prototype didn’t perform to expectations and was the off-grid location. at generation diesel replacing for used were system storage battery a and of power, kW solar 7 turbine, the incorporating system energy renewable combined Rocks, a Race where at Columbia, facility research the at installed was device prototype first The stator. the forms cowling surrounding the and rotor the form blade turbine each of ends the where generator, magnet permanent rim-type a is generator The kW. 65 at rated generator magnet permanent variable-speed a with configuration, ducted a uses turbine tidal Current Clean The CleanCurrent,Canada 4.2.2.5 Figure 4.8:CleanCurrent’sprototypedeployment(Source:www.cleancurrent.com)

(Source: www.cleancurrent.com) Figure 4.9:DiagramofCleanCurrent'sprototype Guide Vane Augmenter Duct In May 2007, the prototype was extracted for inspection and modification. The

Generator Housing Blade Rotor Hole British A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

4.2.2.6 TidEl, Soil Machine Dynamics Hydrovision, UK The TidEl device uses a pair of fixed-pitch turbines mounted on a central boom. It is partially buoyant and anchored to the seafloor via mooring lines, allowing it to float at any depth and rotate to face any direction. The arbitrary positioning of the device allow it to be placed in the middle of a channel, avoiding problems with cavitations that can occur near the surface while also removing the need for extensive mountings to be built on the seafloor. This design also allows the device to be placed in the highest flow areas of a channel, and to be floated to the surface for performing maintenance. The full-size device will use a pair of three-bladed, 15 m diameter turbines to generate up to 1 MW of power, and will use a rectifier-inverter for providing stable output. Thus far, a 1:10 scale device has been built Figure 4.10: TidEl prototype (Source: http:// and tested, and development of a full-size prototype www.reuk.co.uk/TidEl-Tidal-Turbines.htm) is underway [54].

4.2.2.7 Open-Centre Turbine, OpenHydro, Ireland The OpenHydro tidal turbine is an open-centre, rim-generator style tidal turbine, similar to the Clean Current Turbine, at least from the perspective of machine design. The 6 m diameter turbine uses high solidity blades and is mounted on a twin pile structure that can raise and lower the turbine into/out of the water for testing and maintenance. Commercial devices would be permanently anchored to the seafloor. The company conducted 18 months of rigorous testing at the European Marine Energy Centre (EMEC) off the coast of Scotland at Orkney, and its 250 kW turbine prototype was successfully connected to the UK power grid in 2008. OpenHydro has purchased Florida Hydro, a company that was developing a similar open- centre turbine and which had conducted tests of a 5.6 kW prototype. OpenHydro has secured funding for a second turbine in the same location, and has plans to install a turbine in Bay of Fundy, Nova Scotia, Canada, as well [54].

Figure 4.11: OpenHydro turbine at the test site (Source: www.openhydro.com) SOPAC Miscellaneous Report 701 71 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 72 to applyPacificIslandcountriesthathavelargerivers. in used to provide power for a remote community [54]. The one the and grid-connected, is and kW 5 to up generates Maine in turbine The Ocean R&D Ocean Korean the tests, successful the Following Strait. Uldomok in deployed was turbines of pair a 2002 in where Korea, South in occurred also has Testing m/s. 1.5 of currents in kW 0.8 to up performed in 2004 in partnership with Verdant Power. During the it. test, a small through turbine generated flowing water the of energy Extensive the prototype tests have of occurred, including a 35% test in Amesbury, to Massachusetts, that was up capture to turbine the allows and turbines vertical in occur otherwise can that vibrations of amount the reduces shape helical The turbines. axis vertical other by employed typically blades straight the than rather shape, The GorlovHelical 4.2.2.8 projects toprovidepower islandnationssuchIndonesia,MalaysiaandPhilippines [54]. and device, improved an towards occurring is development Further system. control automatic fully a with enhanced been have system power and turbine overall the and output, electrical 2005 has been supplying power to the local grid. A rectifier-inverter is used to provide a stable S.p.A., International Italy since and 2001, since operating been has turbine The m/s. 2.0 of currents from kW 25 to up installed in the Strait of Messina, prototype, The buoy. floating a from suspended turbine axis vertical a is Turbine Kobold The Kobold Enermar 4.2.2.9 generators. orlov turbine is a vertical axis turbine, which uses blades that are twisted into a helix a into twisted are that blades uses which turbine, axis vertical a is turbine Gorlov GCK Technology has also deployed small turbines in Maine, plant based on a larger turbine and a pair of pair a and turbine larger a on based plant MW 1 a on work began Institute

dcp1EngTurbine.jpg) (Source: http://www.etfoundation.org/assets/images/ Figure 4.12:GorlovHelicalturbine Italy, uses three blades with a 6 m diameter turbine, generating Turbine, GCK Turbine, Ponte DiArchimede Technology, US Brazil experience is a good example New York, and razil is Brazil Brazil. A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Figure 4.13: Kobold turbine (Source: www.pontediarchimede.com)

4.2.2.10 Wanxiang Vertical Turbines, China Two significant tidal turbine prototypes have been created in China. The Wanxiang-1, with a 70 kW capacity, consisted of two vertical axis turbines mounted on a small floating barge. Operational for several years, the barge produced between 5 and 20 kW of power in 2-2.5 m/s currents. The Wanxiang-2 uses gravity-based anchoring to sit on the seabed, with the generators and electronics mounted above the waterline. It employs two vertical-axis turbines, and has a rated capacity of 40 kW. No performance data is available for the second device [54].

4.2.2.11 Pulse Tidal PS100 Energy Converter, UK [59] The Pulse Tidal technology is based on twin hydrofoils positioned across the tidal flow. Moving water pushes the foils either up or down according to the angle of the foil in the water. The vertical forces act in the same way that air moving over a wing provides lift. A conventional generator above the water surface is driven by the foils moving below the surface.

The PS100 was commissioned in August of 2009 and is the culmination of 10 years of development by inventor Marc Paish who is Pulse’s chief technology officer. The 100 kW Humber prototype system uses tidal streams to oscillate horizontal blades rather than extracting energy in the same way as a wind turbine through rotary blades. This mode of operation is the key to the device’s unique access to shallow water and has so far shown that it can harness enough energy to power 70 homes.

The device is connected to the UK’s national grid through nearby industrial plant Millennium Inorganic Chemicals and is also by Ethernet through neighbouring resin manufacturing company Cray Valley. The wireless Ethernet link means that the device can be operated and monitored remotely via the Internet, ensuring that as much information as possible can be gathered from this prototype and fed into the design of the next generation of devices. SOPAC Miscellaneous Report 701 73 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 74

(Source: http://www.pulsegeneration.co.uk) Figure 4.15:Comparisonbetween usinghydrofoilsversusturbines Figure 4.14:PulseTidal’s100kWHumberprototypesystem(Source: [59]) A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

4.3 Case Study: Tide-Energy Project near the Mouth of the Amazon [60]

The project goal: use tidal energy to generate electricity This project has developed technology to generate electricity on a small scale using tidal energy. It will enable rural residents near the mouth of the Amazon to meet energy needs in a way that is environmentally sound, decentralised, and economical.

Tidal energy: clean, renewable, and proven The advantages of the tide as a non-polluting and sustainable energy resource are clear. But it may be difficult to capture that energy at sea or on a coast. Conditions near the mouth of the Amazon do, however, offer that possibility. This is proven by the use of tidal energy to power more than 30 sugar cane mills in the region in the past. In fact, this project began by studying their traditional technology. As it will be shown, with modern technology there is no doubt that it is practical and efficient to capture tidal energy under the same natural conditions.

A requirement: decentralised technology More than 100,000 rural residents live dispersed in the area where the tide-powered mills were located. They have no possibility of receiving centrally generated electricity, because power lines are uneconomical to reach them. Only decentralised technology can meet their demand. Currently, the options available to them are solar panels and diesel generators. Tide energy offers them an economical option, one that can be installed at less than half the cost of solar panels and operates much more cheaply than diesel generators.

Figure 4.16: Rural artisans assembled, installed, and operate this 6-blade Gorlov helical turbine (Source: [60]) SOPAC Miscellaneous Report 701 75 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 76 for theturbinetooperateeffectively, thegateisopened. of the stream and hasten the development of a low head of water. can be closed with a gate. This is done at low and high tide to briefly delay the flow into or out Gate mounted initfromdebris. turbine helical the protect duct the of ends both at screens and Posts streambed. the on built duct a through falling, and rising both tidewater, of flow the force and stream the of banks the Jetties and yearround. season and of the moon year. the of phase the on depending m, 3.5 to 1.5 from is tide the of range The day. a Site and tide: The station sits near the mouth of a closed tidal basin that fills and empties twice region. from boat by half-hour one about community rural a in located University, whoisaconsultanttotheproject. Implementation: Alexander Professor by tested and developed been has design innovative This 70%. nearly of efficiency an attain may duct, a in operating when and, versions blade straight conventional, than flow free in efficient more 50% about is turbine This turbine. The technology uses jetties to force the flow of tidewater through a duct and run a helical-blade breakthrough:An important thehelicalturbine Location: and and Figure 4.17:Managingtidalflowwithtwojetties,aduct,andgate(Source: [60])

head: The field station was built on Combu on built was station field The duct: The man in Figure 4.17 is standing on one of the two jetties that extend from In addition to managing tidal flow by forcing it through the duct, the duct itself Given of the immense discharge of the Amazon, the tidewater there is fresh thefieldstation sland near the mouth of the Amazon. the of mouth the near Island elém, the largest city in the in city largest the Belém, When the head is sufficient ro of Gorlov Northeastern t is It A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Environmental impact: The environmental impact of this technology is minimal. Although the tidal flow is managed, the stream still fills at high tide and empties completely at low tide, as it would under natural conditions. Shrimp and small fish pass unharmed through the screens and turbine, and larger fish can move through passages built in the jetties, so natural conditions are also maintained for aquatic life.

Generating equipment: the helical turbine, transmission, and generator Configuration: A helical turbine (bottom) rotates on a shaft that joins it to a pulley (middle). The pulley turns an alternator (right) by means of a belt. The alternator charges batteries to store the energy captured, as is usual with other intermittent sources such as solar and wind when used off the grid. All of the equipment in this system was manufactured or purchased locally, except for the helical turbine blades themselves.

Figure 4.18: Automotive alternator (Source: [60])

Figure 4.19: Pulley, 1.08 m in diameter and belt (Source: [60])

Operation: This shows a 6-blade Gorlov Helical Turbine, mounted in a duct opened for viewing. The turbine is 1.12 m in diameter and 0.83 m in height. Normally, it operates while completely submerged. The helical turbine is self-starting and smooth running. Also, it rotates in the same direction regardless of the direction of the flow of water, so it can capture energy from both rising and falling tides.

Figure 4.20: 6-blade Gorlov helical turbine (Source: [60]) The result: accessible, affordable technology This technology was developed in close collaboration with local technicians, workshops and rural artisans. As a result, it is accessible to rural residents. About 90% of a tide-powered generating station can be built using locally available labour, material and equipment. The technically refined helical turbine blades are the only outside components. SOPAC Miscellaneous Report 701 77 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 78 available toallBrazilians. to help meet their deadlines under deadlines their meet help to this do would Concessionaires concessionaires. electric private from assistance financial and Moreover, the construction of tide-powered generating stations may be hastened by technical for themselvesandofferbatterychargingservicetotheirneighbors. energy the use would who residents, rural of hundreds by operated and owned, built, be can stations these small-scale, inherently and affordable, accessible, is technology the Because elsewhere automotive batteriesforcommunityandhouseholduse,assomealreadydointowns. and Amazon the inexpensive of charge would residents rural stations, mouth those At coast. Atlantic the adjacent the along near built be will stations generating powered tide- small, of hundreds that expected is it phase, pilot the in viable proves technology this If Expected outcome: powered boat,whichthousandsofpeopleintheregionalreadyown. and structures diesel the small a of of that roughly is cost station generating tide-powered The individual an for affordable. equipment is technology this residents local for Moreover, reductions. in theUSA,requirements forenergysecurityandfulfillinginternationallynegotiated carbon many in tariffs feed-in of prevalence the countries, many in legislation change climate and energy new to related mostly are initiatives These technology. tidal of out roll the and development the assisting in role major a play to likely are that drivers many however, are, There finance. of availability the importantly most and infrastructure grid of the of reliability operational on devices, their maintenance term and operating costs, permitting long and consent for the projects, availability in depend, will technology the of viability The for designandmanufacture,transporttositeappropriate installationvessels. addition, technology developers and stakeholders will need to establish a robust supply chain technology. the of viability the gives in it governments and as utilities power paramount investors, is to confidence experience This sea. the in urgent experience an operational now have is to There need environment. operating the within itself prove to is technology the for issue important most The wind. of that than faster much be should progress the regimes, emerging the of that with comparable is wind energy development in the 1980s; however, given the availability of favourable regulatory technology the of status current the people Some that infancy. believe their in still are industry associated the and technology energy Tidal Discussion 4.4 their owners. for income create and them service and build to labour skilled and will businesses small stations foster generating tide-powered of operation and construction the indigenous, largely is technology this because Moreover, imported. are which panels, solar to and environment, energy resource. Tide energy technology will have broad, positive impact in the region. In sum: theregionalimpact It offers a viable, economical alternative to diesel generation, which harms the many stations, many owners, many jobs aw 10438, which requires them to make electric power electric make to them requires which 10438, Law U countries, the change in policy in change the countries, EU It uses a clean, renewable In A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of OceanOcean- Based-Renewableased Renewable Energy Technologies

5. Salinity Gradient Technology

It has been known for centuries that the mixing of freshwater and seawater releases energy. The challenge is to utilise this energy, since the energy released from the occurring mixing only gives a very small increase in the local temperature of the water. During the last few decades at least two concepts for converting this energy into electricity instead of heat have been identified. These are Reversed Electro Dialysis (RED) and Pressure Retarded Osmosis (PRO). With the use of one or both these technologies one might be able to utilise the enormous potential of a new, renewable energy source. On a global basis, this potential represents the production of more than 1,600 TWh of electricity per year. 5.1 Reversed Electro Dialysis (RED)

RED is a concept using the difference in chemical potential between both solutions as the driving force of the process. The chemical potential difference generates a voltage that uses membranes for electro dialysis to produce an electrical current. This concept is under development in the Netherlands and there are preparations for the first prototype to be built.

Figure 5.1: Diagram of Reverse Electro Dialysis (Source: [61]) SOPAC Miscellaneous Report 701 79 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 80 in energy generator in reverse electrodialysis mode. The principle was first described by R. Plattle the as principle plant based on electrodialysis, where an external voltage is applied, could also be used same as an the on based desalination a that means This dynamo. are a and engine electrical an of dialysis action complementary reverse and dialysis of processes The brackish water. blood. the of out ions drives system this across difference voltage a Applying water. is membranes the of side other the On ions. negative or positive to permeable selectively each membranes, the of types two from between blood derived is it because battery” passing by achieved is This haemodialysis. by “dialytic blood desalinate to used currently technology a called also is cell electrochemical This electrode properties. temperature and the ratio of the concentrations of the solutions, the internal resistance and the energy. The voltage obtained depends on the number of membranes in the stack, the absolute This charge separation produces a potential difference that can be utilised directly as electrical ions. negative and ions positive both lose will membranes such two between separated freshwater from Seawater 5.1. Figure see ions, negative for permeable selectively is that one and ions positive for permeable selectively is that one namely membranes, of types two requires It second offreshwater.Thefreshwater feedoperatesatambientpressure[63]. per meter cubic 1 of rate flow a from MW 1 of generation the enabling plant, hydropower a in m 100–145 of head water a to equivalent bars, 11–15 of range the in are pressures operating energy is recycled in the pressure exchanger to add pressure to the feed of salty water. Optimal While 1/3 of the brackish water is fed though the turbine to generate power, 2/3 is returned and The diluted and now brackish water (dark blue) from the membrane module is split in two flows. twice thatofthefreshwater. about is water salty of feed volumetric The membrane. the of side salty less the from received properties. retention salt excellent and flux water high key energy transfer in the power production process. This requires membranes with particularly the is and water pressure high of flow volumetric the increases process osmotic The (bluish). water salty pressurised the into membrane the across osmosis by transferred is gradient salt contain spiral wound or hollow fibre membranes. could modules Such modules. membrane the entering before filtered and (grayish) plant the In the Pressure Retarded Osmosis (PRO) process, water with no or low salt gradient is fed into PressureRetardedOsmosis 5.2 disadvantage oftheunpredictableintermittentcharactermostformsgreenenergy[62]. Blue ocean. the of colour blue the with it associate to and generation, hydropower of water the for coal” “white and generation, power lignite-fired for coal” “brown generation, power coal-fired for and “Energy category the in 2004 for Award innovation Dutch the won KEMA method. Modification” “Electrical the using membranes cheap of production the on focusing KEMA in the tr 1954. Nature Blue nergy is a part of the general class of renewable energy or “green energy” without the without energy” “green or energy renewable of class general the of part a is Energy MA in order to differentiate it from “black” from it differentiate to order in K EMA by chosen was “Blue” name The Energy. Netherlands revived the investigation in 2002 under the brand name “Blue prmna rsls ee band n mrc and America in obtained were results Experimental lectrodialysis is also used to produce freshwater from freshwater produce to used also is Electrodialysis In the module, 80–90% of the water with low n the module it is diluted by the water the by diluted is it module the In re i te seventies. the in Israel Environment” Energy”, A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Statkraft, a North European power producer and a company with a strong hydropower tradition, has engaged in the research and development of osmotic power and enabling technologies since 1997. Today, Statkraft, with its international membrane research and development partners, is the main active technology developer globally and hence an osmotic power knowledge hub. It has made achievements in terms of new and more energy efficient membrane technology during the last few years. Commercially available reverse osmosis membranes only produce modest efficiencies of less than 0.1 watt per square meter when utilised in the PRO process. Statkraft therefore developed a special PRO membrane which has an improved membrane performance of about 4 watt per square meter.

Statkraft has also assessed the environmental optimisation and pre-environmental impact of an osmotic power plant located at a river outlet and has not found any serious obstacles. A combination of river flow regulatory compliance and careful engineering of the intake and outlet of brackish water would reduce the impact on the river environment to a minimum. The operation and maintenance of an osmotic power plant would be similar to that of a regular water treatment plant, for which the impact on the local environment is well documented. Statkraft has gone a step further and developed a way to backwash the PRO membranes which is considered to be more environmentally friendly compared to the use of cleaning chemicals currently being used in water treatment today [63].

Figure 5.2: Diagram of the PRO process (Source: www.statkraft.com) SOPAC Miscellaneous Report 701 81 SOPAC Miscellaneous Report A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 82 • • retarded osmosisandreverseelectrodialysis,differinthefactorsdescribedbelow: pressure- gradients, salinity on based production energy for processes membrane two The Discussion 5.3 • • • • More development funds are spent on PRO membranes, resulting in low-priced membranes, membranes theyshouldbetreatedaschemicalwaste. chemicals by treated be accumulated in the ion exchange membranes of be RED. At the end of the life of the RED to has can seawater in present fouling ions heavy however, environment; the by to friendly less potentially membranes the of deterioration PRO, In mass, thesaltcontentofseawater,hastopasstwomembranes. membrane. the pass to has seawater of mass the of 99% PRO, In seawater andfreshwater. of mixture a for better performs RED study, evaluation recent a of basis the On RED. than brines as such streams salt concentrated highly for appropriate more be to seems PRO the applicationofgenerators.ForRED,electrodessupplyanelectricaloutputdirectly. In PRO, pressure or high, mechanical energy, should be converted into electrical energy by the in design membrane stackofRED. spacing the on placed be should emphasis more losses, energy pump mechanical some reducing For RED. in detrimental requires less are leakages although also membranes, the of strength This ignored. be cannot stack the in membranes the severe put hand, in freshwater RED the pumping action of the water streams through the tiny channels between and seawater for bar requirements 20-25 on the differences, mechanical strength and pressure leakage of the the membrane stack. PRO, On the other In accelerate thisdevelopmentprocess. development to has breakthrough longer technical some or expected be a to is membranes low-priced of time RED, For application. the for benefit short-term of be can which D only 1% of the of 1% only RED In A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies Ocean Based Renewable Energy Technologies

6. Conclusion and Recommendations

From the three main ocean energy conversion systems it can be seen that wave power holds the most potential for Pacific Island Countries. This is also reflected in the research and technology development being done with a majority of companies focusing on wave power. Like the introduction of any other new energy technology, the question of suitability, appropriateness and sustainability arises. “OTEC for the Pacific” is what many people will perhaps agreed to, given its benefits of not only producing electricity but also desalinated water, nutrient-rich water for agriculture and cold water for cooling purposes but the benefits have to be weighed against the potential hazards to the marine environment which many Pacific islanders rely upon as a source of food, income and recreation.

Lessons learnt from the Nauru plant (which operated for 10 months from October 1981) and current research results provide a basis on which to form a consensus on whether to build another plant in the region or not. The consideration to adopt OTEC into the Pacific region may at this point lack the right development parameters and a feasibility study including environmental impact assessment that are consistent and acceptable that could lead to the development of a sustainable project in the not too distant future. OTEC should be considered alongside the currently available renewable energy technologies such as solar photovoltaic, hydro power, biomass and wind, although the same potential for all these technologies may not be readily available or accessible in all countries.

Unlike the case of wind energy, the present state of research shows a wide variety of wave energy systems, at several stages of development. In general, the development, from concept to commercial stage, has been found to be a difficult, slow and expensive process. Although substantial progress has been achieved in wave energy technology; it is however difficult to simulate what was done in the wind turbine industry where relatively small machines were developed first, and were subsequently scaled up to larger sizes and capacity as the market developed. The high cost of constructing, deploying, maintaining and testing large prototypes, under sometimes very harsh environmental conditions, has hindered the development of wave energy systems; in most cases, such operations were possible only with substantial financial support.

Wave resource studies conducted in six Pacific Island Countries showed potential for wave power generation; however the capacity and expertise to adopt and sustain the wave energy conversion technologies is presently limited. The region needs assistance and guidance from its neighbouring developed nations to help initiate and provide technical support with these technologies. Tidal energy technology is still emerging rather like wind energy development in the 1980s; however, given the availability of favourable regulatory regimes, the progress should be much faster than that of wind. The most important issue for tidal technology is to prove itself within the operating environment, hence the urgency to have operational experience at sea.

The Pacific region can always sit back and wait for the right opportunity, however, while doing so, the region should be aware of the ongoing developments in ocean energy conversion technology. The region should also encourage more collaboration with countries involved with the development of ocean energy conversion technologies to facilitate more rapid technology transfer into the region and to help improve and build technical capacity within the region for operating renewable ocean-based technologies. SOPAC Miscellaneous Report 701 83 SOPAC Miscellaneous Report 701 Ocean BasedRenewableEnergyTechnologies Ocean BasedRenewableEnergyTechnologies 84 7. ioletti, R. and Potter, and R. bioletti, [8] [7] [6] [5] [4] [3] wikipediawebsite(2009):http://en.wikipedia.org/wiki/Rankine_cycle [2] wikipediawebsite(2009):http://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion [1] [9] [11] [10] blum, P; “Portugal’s [13] englander,D.andBradford,T;“ForecastingtheFutureofOceanPower”; Executive Summary. [12] [14] [15] [16] thermal-energy-conversion/2s9w7n3adoa4y/5# “Ocean Thermal hydro/A-new-wave-Ocean-power_176_p4.html. Magazine, Power power”; Ocean wave: new “A S; Patel. Vol. 6,No.4,Winter2002/2003,pp.25-35. Vega, “Uehara Cycle”;www.opotec.jp/english/uehara_cycle.html Aspects ofThermalEnergyConversionTechnologies”. Kobayashi. “Hydroelectric Alberta ResearchCouncilEdmonton,Alberta,T6N14,Canada. iig J “Ocean J; Vining, Systems. Report, Annual 2008 FERC TechnicalConference. 2005. Computer and Electrical euao R, eer, . Ppo A, Alves, A., Pipio, S., Pereira, R., Segurado, and-wind-energy-projects-dwindling/ from: Retrieved 2009; 15, er, . Kee, . Bltv I “ Nw mrig ehooy Plms eosrto o the of Demonstration Pelamis – Technology the Emerging by New Assessment “A I; Bulatov, J., Kleme�, S., Perry, version=1&_urlVersion=0&_userid=10&md5=8cab9b9c28f55768bf011ac600e2bfb9. 4VPCVF91&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_ technology assessment tools”; http://www.sciencedirect.com/science?_ob=ArticleURL&_udi= B6VFX- “Archimedes Waveswing”;http://www.awsocean.com/archimedes_waveswing.aspx?Site=1 2009. Bibliography .A. (2003), “Ocean Thermal “Ocean (2003), L.A. H, Jitsuhara. S, Dr. Uehara. nrto fo Ocean from Generation Energy Conversion”; Wave Wave and To” h Uiest o Manchester, of University The Tool” EMINENT ; “Offshore Alternative “Offshore I; International ngineering Department University of University Department Engineering eg Conversion”; Energy http://mendocoastcurrent.wordpress.com/2009/03/16/portugals-wave- Wind nergy Conversion Primer”, Marine Technology Society Journal, Society Technology Marine Primer”, Conversion Energy eg Agency Energy Energy Projects Dwindling”; http://knol.google.com/k/arun-kumar-reddy-kothapally/ocean- H, Dr; “The Present Status and Features of OTEC and Recent vs Tds Cret ad rm reFoig Rivers”; Free-Flowing from and Currents & Tides Waves, “oprsn between “Comparison L; Energy 9: Advanced 699: EC peetn Areet n Ocean on Agreement Implementing eneration”; Carbon & Carbon Generation”; http://www.powermag.com/renewables/ International isconsin – Madison, December Madison, – Wisconsin ad te energy other and EMINENT so, otgl 23 March 2-3 Portugal, Lisbon, dpnet td Report, Study Independent Herald Tribune, March nergy Management Energy Energy Ocean Based Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

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[19] waveBob website (2009): http://www.wavebob.com/about_us/

[20] wikipedia website (2009): http://en.wikipedia.org/wiki/Wavebob

[21] “The AquaBuOY”; http://www.finavera.com/en/wavetech/advantages

[22] “Sunken buoy rescue under way”; http://www.newportnewstimes.com/articles/2008/07/25/news/ news01.txt

[23] Muhawi, D; “Wave Energy Technologies”; http://www.ecoworld.com/blog/editor/muhawi/2008/02/20/ wave-energy-technologies/

[24] Mckay, T., Lomax, C., Denny, M., Cook, D; “Technical Appraisal of the CETO Wave Power Generation Devices”.

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[26] “CETO Technology”; http://www.ceto.com.au/ceto-technology/what-is-ceto.php

[27] “How Wave Star works”; http://www.wavestarenergy.com

[28] “Wave Star Energy gets DKK 20m in development support”; http://www.investindk.com/visNyhed. asp?artikelID=20020

[29] Seabased website (2009); www.seabased.com

[30] “Deployment of wave energy converters in Norway”; http://www.rundecentre.no/english/wave- energy-deployment.htm

[31] “bioWAVE”; http://www.biopowersystems.com/technologies.php

[32] Aquamarine website (2009); www.aquamarinepower.com

[33] “Oyster Wave Energy System Produces Electricity”; http://www.renewableenergyworld.com/rea/ news/article/2009/04/aquamarines-oyster-system-delivers-commercial-electricity

[34] Trident Energy website (2009): http://www.tridentenergy.co.uk/technology

[35] “Trident Energy prepares to deploy wave power machine in Suffolk”; http://www.newenergyfocus. com/do/ecco.py/view_item?listid=1&listcatid=119&listitemid=2570

[36] Ocean Navitas website (2009); http://www.oceannavitas.com/technology.html

[37] “Ocean Navitas confirms conversion”; http://social.waveenergytoday.com/content/ocean-navitas- confirms-conversion

[38] “SyncWave launches $15 m project demonstrating low cost of wave energy”; http://www.bymnews. com/new/index2.php?option=com_content&do_pdf=1&id=37893

[39] “SyncWave Receives CAN $2M Grant from BC“; http://www.renewableenergyworld.com/rea/news/ article/2009/04/syncwave-receives-can-2m-grant-from-british-columbia

[40] “Marine Energy: Summary of Current Developments and Outlook for New Zealand”; Power Projects Limited, 18 May 2005.

[41] “Feasibility of Developing Wave Power as a Renewable Energy Resource for Hawai'i”; Department of Business, Economic Development, and Tourism, January 2002. SOPAC Miscellaneous Report 701 85

A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

[42] “The Denniss-Auld Turbine”; http://www.oceanlinx.com/works.asp

[43] OWEL website (2009); http://owel.co.uk

[44] “U.K Company refines wave energy converter”; HRW magazine, March 2009, page 48.

[45] Orecon website (2009); www.orecon.com/en/the-technology

[46] “ORECon raises $24m”; The Engineer Online; http://www.theengineer.co.uk/Articles/305041/ ORECon+raises+24m.htm

[47] “Prototype testing in Denmark”; http://www.wavedragon.net/index.php?option=com_content&task=v iew&id=12&Itemid=14

[48] “The Seawave Slot-Cone Generator (SSG) concept”; http://www.waveenergy.no/WorkingPrinciple. htm

[49] “MST Project”; http://www.waveenergy.no/MSTProject.htm

[50] “MHD Wave Energy Conversion (MWEC)”; http://www.sara.com/RAE/ocean_wave.html

[51] barstow, S. F. and Haug, O; “The Wave Climate of the South West Pacific”; Sopac Technical Report 206.

[52] wikipedia website (2009): http://en.wikipedia.org/wiki/Tidal_power

[53] “La Rance Tidal Power Plant”; http://www.reuk.co.uk/La-Rance-Tidal-Power-Plant.htm

[54] Khan, J and Bhuyan, G.S; “Ocean Energy: Global Technology Development Status”; IEA-OES Document No.: T0104.

[55] Shaw ,T.L; “La Rance Tidal Power Barrage Ecological Observations relevant to a Severn Barrage Project”; Shawater Limited

[56] “Tidal Energy”; http://www.oceanenergycouncil.com/index.php/Tidal-Energy/Tidal-Energy.html

[57] wikipedia website (2009): http://en.wikipedia.org/wiki/SeaGen

[58] “Verdant Power turbines retrofitted with new rotors to delivering energy from NYC's East River”; http:// www.oceanenergycouncil.com/index.php/Tidal-Energy-News/Verdant-Power-turbines-retrofitted- with-new-rotors-to-delivering-energy-from-NYC-s-East-River.html

[59] “Power Produced by the Pulse Stream 100 Tidal Energy Converter”; Press Release August 2009, IT Power.

[60] Anderson, S; “The Tide-Energy Project near the Mouth of the Amazon: Applying helical turbine technology at a small scale for rural communities”; May 2006.

[61] Ferreira, F; “Reverse Electrodialysis”; http://www.leonardo-energy.org/23-reverse-electrodialysis.

[62] Van den Ende, E & Groeman, F; “Blue Energy Briefing Paper”; KEMA Consulting October 2007.

[63] Skilhagen, S. E, Dugstad, J. E, Aaberg, R.J; “Osmotic power - power production based on the osmotic pressure difference between waters with varying salt gradients”; Statkraft Development AS, Lilleakerveien 6, No-0216 Oslo, Norway.

[64] Vega, L.A. “OTEC Economics”, Presentation at Energy Ocean Conference, August 2007, Turtle Bay Resort, Oahu, Hawai'i.

[65] “Proceedings of the Pacific Energy Ministers' Meeting and Regional Energy Officials' Meeting, 20-24 April, 2009". A CROP Energy Working Group Report. SOPAC Joint Contribution Report 200. SOPAC Miscellaneous Report 701 86

A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies Ocean Based Renewable Energy Technologies Appendix A Economics for OTEC in Marshall Islands [64]

Vega (2007) did an analysis of the unit cost of electricity produced by OTEC plants in Marshall Islands. The formula provided in Box A1 was used to determine the unit cost of producing electricity

Box A1: Cost of Electricity Production

COE ($/kWh) = CC + OMR & R + Fuel (for OTEC is zero) {+ Profit – Environment Credit}

CC = Capital Cost Amortization (N.B. much higher for OTEC) OMR & R = Operations + Maintenance + Repair + Replacement

Cost of Electricity (May’ 05-June’ 06) 10 MW capacity (diesel gensets)

COE ($/kWh): [0.16 + 0.05] = 0.21 [Fuel + OMR&R]

According to Vega, the U.S Navy was willing to issue a Power-Purchase-Agreement if only the cost of electricity was reduced by at least 10% (0.9 x 0.21 = 0.19 $/kWh); however, considering the situation at that time and the cost associated in producing electricity, the 10% reduction was not feasible with a 10 MW OTEC plant.

On the other hand, in Hawai'i a 100 MW OTEC Plant which is stationed 10 km offshore delivers: • 800 million kWh/year to the electrical grid; and • 32 million-gallons-per-day (MGD) of water.

Using the same formula (Box A1), he found out that an OTEC 50 MW was cost competitive in Hawai'i. Vega admitted that providing an updated assessment for a 100 MW plant would be encouraging but it would be very difficult to obtain financing for such a large plant. SOPAC Miscellaneous Report 701 87 SOPAC Miscellaneous Report 701 Ocean BasedRenewableEnergyTechnologies A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologiesOceanasedRenewable 88 REM &PEMM2009[65] Ocean Technologies Session ofthe Appendix B follows: energy have been renewable commercialised or are near commercialisation. The presenters were introduced as Ocean-based biomass. that well-established technologies the of and some on focus would session and the and area hydro new a are technologies proven solar, the wind, of as understanding such good technologies a have (PICs) Countries Island Pacific that highlighting presenters four the and session the introduced (USP) Kumar Ajal Dr South Pacific. the of University the of Kumar Ajal Dr facilitator, the introduced and presenters the particularly presented the working and procedure order for to the session session. the called (SOPAC) Mario Rupeni Mr Session, Ocean the of Chair The Introduction The presentationsbytheabove resourcepeopleareattachedtothissummaryrecord. Andrea Athanas Luke Gowing Garry Barbara Anthony Derrick Venus and Vlaeminck Kaipara projectbutlookingatothers. the from off starting generation energy marine on working started years 5 last the in and geothermal and hydro in development; energy of history Agro projects. resource and environmental Environmental and Biodiversity,theWorldConservationUnion(IUCN). Senior Programme Officer, Argo of Directors sustainable development. a at aiming technologies new of project and services delivering of aim with and engineers mostly staff permanent six with 1982 in established Pacific the energy. in wave of studies terms in preliminary some done has and 2005 in up set Director of SRP. SRP is a limited private company based in the inceptionphasehewasProgrammeManagerforREP-5Project. an “Energy asaToolforSustainableDevelopmentSmallIslandStates”.At on consultancy a doing was he when Pacific the in of Director Managing mtd s an is Limited Environmental T Power based in UK has had experience working experience had has UK in based Power IT He also welcomed participants to the session t was a privately-funded company initially and initially company privately-funded a was It Energy, vrnetl oslat ouig on focusing consultant Environmental Ecosystems and Limited, nvironmental has a 20-year a has Environmental w eln. h Argo The Zealand. New Livelihoods New Caledonia paper EU-UN Business A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies OceanA SOPAC Based Desktop Renewable Study of E Ocean-nergy TechnologiesBased-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

PLENARY DISCUSSION

Questions 1 – Do Pacific Island Countries have relevant temperature gradient or enough tidal power to generate energy from the ocean?

IT Power reported that there are some temperature differentials in the ocean as well as tidal current around the Pacific but still not as great as in other areas of the world. The question always comes down to the economics and whether an appropriate technology is available at the present time. The technology is not yet there but potentially in the future the technologies are economical given the recent renewed interest to invest in OTEC. There is potential for wave and tidal power but several years away. Let the UK and EU countries spend their money now to get the costs down through their installations and then have a fix on the economics and looks at its relevance to the Pacific situations.

The Northern Hemisphere focus such as UK is predominantly focused on high yield areas with massive tidal current for 15 MW tidal generations. But it is worth considering the PICs for local situations such as soft lagoon with reasonable current, not massive high current where there is a possibility of deploying small-scale generation project such as the system used in river situations so it is basically local solution to a local problem. There may be a possibility of putting together a combination that looks at generating relatively low level of electricity which could be disproportionately available at local scale.

Wave resources in the Pacific are less powerful compared to the Northern Europe, but at least the Pacific region have non-seasonal waves that is regular that does match quite well with the energy consumption. Promoting the advantages of wave energy such as reducing the use of land maybe useful.

Republic of Marshall Islands raised a concern on the human resource issues. There are a lot of things that the Pacific need to use which are proven technology and the concern was diversion [of scarce] resources. The Pacific could lose or spend the money to prove things therefore it may be prudent to maintain watching briefs on the technologies while the larger countries who could, do spend the money to prove things before the smaller PICs get involved. The other issue is to get technologies that are small and economic. The impacts of the new technologies on human resources and capacity building within utilities would be similar to the wind turbine into grids technology; implying that similar issues would be associated with marine turbines therefore translating into diversion of resources.

World Bank highlighted the large number of feasibility studies and the efforts that have gone into them; i.e. the hydrology and bathymetry studies for a marine energy feasibility study, which comparable to efforts that go into a hydro feasibility study.

SRP highlighted that full feasibility studies on wave technologies (seabed nature and bathymetry) can cost as much as a million Euro for a complete feasibility study. Generally data collection can be done by countries and become available for project developers. Wave resources measurements can cost up to 107,000 Euro.

IT Power confirmed the similarity in the levels of required effort for hydro feasibility and marine energy feasibility studies. SOPAC Miscellaneous Report 701 89 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 90 Pacific; of cyclones? be interestedinthechallenge oflendingNauruahandtore-assessand pursuethisoption. welcomed discussions. They also welcomed presenters and developmental partners that may OTEC. with experience supply, their electricity after even for option alternative an as technology OTEC the about forgotten not has established. was it time the at grid the into feeding only was system The disaster. a to Agro regulatory measuresshouldbeconsideredbeforehand. value, so if some these machines away are going took to be beauty considered for scenic the of Pacific; it place was advised a that some in instruments/machines wave big of placement the in shown As aspects. tourism the impact way any in so maybe a way forward is to put in place regulatory measures that these technologies do not tourism is countries island the for revenue of sources major the of one that out pointed IUCN last OTEC in Nauru commented that they had not forgotten about the alternative OTEC technology since the vicinity of12msothemachinecantheoreticallysurvive aworseevent. been designed for a 29 m wave height. So far the most extreme wave experienced was in the has machine the therefore and calculated was height wave m 21 potential a Caledonia, New in example For cyclone. the like event, weather extreme the during wave the of climatology damaging. be could wave the but water; above is machine the of part small a only as impact an of much too have not does wind The cyclone. the by created be would that wave the (2) and wind; the (1) risks: two SRP are devices the underwater andwerethereforetosomeextentshieldedfromextremewaves. of some that is consideration One designable. are things these but waves sometimes, there are devices that suffered dramatically from under-estimating the power of the IT Power answered that in the United Kingdom and Scotland offshore climate are often extreme Question energy andhewascertainlygoingtodohisbitalongthoselinesinVanuatu. brought they because beautiful were installations energy that arguing about convincing more between burning diesel fuel and looking at wind turbines and he suggested that officials needed to be was choice The beautiful. were turbines wind like installations energy that people far. so meeting the during discussed UNELCO made a general point that the promotion of renewable energy had been thoroughly ensure thatenergyinstallationsarecompatiblewithinandinfactbenefitlocalcommunities. fisheries and local communities should be involved in the process. Robust process. Those who would potentially be impacted by the development, e.g. tourism industries, IUCN offeredthattherewastheroleofstakeholders’engagementinEIAandconsultation expectations were. the what on clear very be would developers potential so place in procedures process. the in impacts environmental all addressing and reported with respect to the Pelamis machines they were familiar with, that there were there that with, familiar were they machines Pelamis the to respect with reported New

have completely agreed and that this was the whole key to proper planning proper to key whole the was this that and agreed completely Zealand Nauru (31 kW capacity). The 2 – these With hat is done when doing the complete study is to also look at the at look also to is study complete the doing when done is What same the ocean-based technologies e thought that officials needed to convince certain key certain convince to needed officials that thought He C and OTEC in interest continued their stressed Nauru Nauru installation unfortunately did not last long due technologies been ew Zealand presentation where the where presentation Zealand New ws motn ta tee were there that important was It through heading EIA practices can help the experience into Nauru the A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

SRP used the opportunity to rephrase a question posed during their presentation. Would one of the development partners capable in the sense of rules and criteria to elect some funds? Would partners be attracted to funding the feasibility studies that need to be undertaken and/or at what stage should developers contact potential donors and how should developers move forward on how studies could be funded?

Question 3 – Given Nauru’s OTEC experience and the mechanical systems presented, which is the more appropriate for the PICs and why?

IT Power offered that it would take different applications for different countries; and it is still unclear on which technology would enjoy success in each area. IT Power recommended that officials keep up to date with the technologies by looking at international energy agencies and social energy groups’ quarterly newsletter on ocean energy to get a feel for what other technologies might be coming on board.

The OTEC for example, has a fantastic long term potential when looking from the resource perspective. OTEC works but to date the economics are not proven so the question is when would a commercial product be available that would be reliable? It is difficult to say what would be the best option in the long term and therefore repeated the recommendation that countries maintain a watching brief on those technologies through organisations like the International Energy Agency; and he noted that there was conference on ocean energy coming up soon in New Zealand as well – while at the same time feasibility studies would help to identify which particular technologies are most appropriate.

Al Binger from CCCCC earlier presented along with colleagues from SPREP some very detailed numbers on the costing of OTEC systems. For those really interested in OTEC, there is a 30-kW working plant at Kyushu at Saga University situated in Imari [Japan] which has been operational now for more than 5 years; so there is enough data available to basically make the projections as to what the cost is.

The big unknown in OTEC is the bathymetry; and estimates have that 40% of the cost is in the pipeline; so you have the option of whether you base the plant offshore in which case you look at an oil rigging type of structures or you basically bring the three water pipes onshore. His view was that the idea of OTEC being somewhere in the future is really not so accurate anymore. OTEC is not a new technology; and when new renewable energy technology is discussed OTEC is there like in this instance, like doing a OTEC a big favour. The first paper on OTEC was written in 1881 but the problem with OTEC and the nature of the resource is that it is basically confined to tropical oceans and where the bathymetry is very fast so that there are no long pipelines. So for groups of countries who are interested in OTEC he thought that the countries needed to make it happen for themselves; and he suggested a small consortium of island states that have a vested interest to actually push the donors to help. With what is about to happen with climate change, OTEC is a wonderful adaptation technology because if the loss of aquifers and freshwater supply occurs due to sea-level rise this could be one way one could actually change the economics. SOPAC Miscellaneous Report 701 91 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 92 ehoois ht ok n h Pcfc countries. Pacific the in work that technologies was probablythebestoption. technology off-the-shelf commercial Proven principle. guiding good a was this technologies; other any consider not would they and setting similar a in or PICs the in years five least at for National that the Pacific could not wait for the for wait not could Pacific the that is difficulty The applications. generation in-river small-scale from apart around, already are that here applications local applicable for was technology that was there possible that quite was It is. industry the where of terms in scale the of end other the on right are presenters and years actually happening. According to the speaker, the presentations heard were rather conservative in terms of what was technologies, makethemsuitablefortheregionandlookatinfuture. or loan financing. demand side. These activities also need funding and funding is limited whether through grant Apart working. and side supply these the in both have efficiency energy of to terms in potential great challenging see they RETs, and from difficult quite be to it found They countries. these in ground the on work actually they that and energy; renewable in technologies proven The regions. other and Pacific the in work their on viewpoint donor’s a provided Commission European part oftherenewableenergymenu. work together to advance the knowledge and disseminate the information so that it became a energies. development technology; and in that context makes OTEC very different from the other ocean sustainable a as rather but technology energy an as it view don’t OTEC understand do that energy alone the but to look at what it contributes to on the sustainable development of an island state. economics Most the base to not technology the at looking when that advised He –the exhaust water comes out at about 12 to 14 degrees Celsius which is ideal for mariculture. by OTEC as a by-product, it is notably orders of magnitude cheaper. A look at the end products Looking at the cost to desalinate a litre of salt water in terms of energy versus having it produced and interestin maintainingthesystem. maintenance of lack the was problem major the and technologies the sustain to project the in interest no was there – gasifier charcoal the e.g. countries, into brought technologies were country. a into technology any introducing before consideration prime Papua the of ahead were game inthemorepracticalsense. technology the receiving those and developers the implementation for a line in were technology be the when that so assessments site of time the at step first reasonable considerations environmental that work preparatory the during that counselled IUCN proven technologyandforget about OTEC? renewable technologyorshouldthePICsconcentrate onwhatever todevelopQuestion 4–Isittooearly aroadmapfor thisocean the from view the with concurred UNDP gap andaneedtofocusonthelower-yieldtechnologies. a was there hence Pacific; the of typical not are that environment yields higher at looking are New nergy Policy has concluded that it would focus on technologies that have worked have that technologies on focus would it that concluded has Policy Energy e emphasised that maybe the issue for small island states was how to collectively to how was states island small for issue the maybe that emphasised He commented that the maintenance of the technology was also to be a be to also was technology the of maintenance the that commented Guinea rpa Cmiso ws rig t bs t esr te dseiae only disseminated they ensure to best its trying was Commission European What can be best for the region is to let the western countries develop these He had attended various conferences in Scotland that were held every two uropean countries turbine developers to finish as they as finish to developers turbine countries European EU. avsd fcs n eibe n proven and reliable on focus a advised He ifre te etn ta te Tokelau the that meeting the informed He n the late 1970s, there 1970s, late the In A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies

Nauru responded to earlier suggestions for pursuing technologies that are proven now. In the unique case of Nauru they needed to explore every option applicable and did not wish to be limited; so that they fully explored the opportunity to achieve their renewable energy targets.

Tuvalu suggested that given the difficulties with introducing new technologies into the PICs that training be undertaken within PICs to develop the ability to do their own feasibility studies rather than spending millions; so that when developers came into countries, data required was available and probably by that time the technology would be viable.

World Bank noted what other donor colleagues have mentioned in general about aiming to use commercial technologies because as sometimes these new technologies may add up to the complexity of the current technologies. The type of technology applicable in the north was not going to work in the South and if PICs were to wait for appropriate and proven technologies, this might take fifteen years of waiting.

The proposal from Al Binger that SIDs should get together and build a lobby group demanding that there is a need for development of ocean technology that was appropriate and worked in the small island environment. World Bank was not committing but was certain there would be sources of financing that could be interested to take this on if there was a strong enough lobby for it. So the idea of getting together and making the case for work to start on appropriate technology that was feasible for this part of the world was better than just waiting for something to happen.

SRP offered that identifying the devices and undertaking the resource assessment studies could be done in parallel.

IT Power pointed out that the EC was supporting technology development indirectly in Europe; however most of the money was going into larger units. Many technologies under development are modular, so 1-2 MW (small) tidal current units for shallow water have also been developed and are being developed, although to a lesser extent than the larger units.

Argo New Zealand observed that the environmental lead up time in terms of getting resources information and other environmental stakeholders’ views also takes time so that the technology evaluation and adaptation should also run in parallel in general with environmental considerations.

IUCN recommended establishing the kind of ownership and regulatory frameworks to provide a mechanism for incentive for maintenance of the equipment. Also, the regulatory framework should ensure that the seabed ownership issues are addressed and put in place.

Republic of the Marshall Islands commented that when the countries should club together and that perhaps resources and finance should be brought forward so that may be needed in the coming future.

Al Binger advised about some new technology developed by Google that can scan lots of bathymetry. He had started looking at the bathymetry collected by this technology; at close to 1000 meters would mean a lot of the information that would be needed would be available. He said it was a lot cheaper to fly around and use sonar to map the bathymetry. He prompted that maybe SOPAC or SPC or one of the agencies in the Pacific who has resource assessment in their portfolio to look at providing good information. Fiji, he said, had developed some OTEC sites so there seemed to be some information already available to work with. SOPAC Miscellaneous Report 701 93 SOPAC Miscellaneous Report 701 A SOPACDesktopStudyofOcean-Based-RenewableEnergyTechnologies 94 doing asimilarproject? been developed.Also,Kyosujustlostinterestintheproject. that it was not sensible to try to re-habilitate it using the open cycle as other efficient cycles have efficient system so when the cold water pipe broke it was its second failure; most the and not it was was which decided cycle, open the on based was and Japan southern in Utility Electric Question you canavoidenvironmentalimpacts. the marine environment so that it was possible to overlay the information and determine where IUCN and sothisinformationisavailable. collected been has bathymetry shallow-water Pacific of portion good A Programme. Islands SOPAC informed the meeting that SOPAC does do these assessments through its Ocean and The sessionclosedwithacocktailhostedbyITPower assessment, whichdatacanbeaccessedbeginningat theSOPACwebsite. proposal. Finally that some work has already been undertaken by SOPAC in terms of resource collective a do and technologies suitable identify to collaborate to need also SIDS resources. that overcome. be challenges to need are installations small-sized of costs and isolation, geographic economies, countries' island small for however Canada; in operational is be system OTEC would 7-MW it A placed. where on depends technology the of appropriateness The implement. to able their human resources so that when the technology is introduced the manpower is ready and It seems clear that OTEC is still being refined and while it is being refined PICs need to develop (Ajal Kumar ofUSP) SUMMING UPBY Al being worthdoing. IT Power pointed out that this fell under the need for feasibility studies and resource assessments and resource needs assessment after the accident that stopped operations informed the meeting that the original project in project original the that meeting the informed Binger why mentioned that was 6 – the OTEC Google also has the conservation priority areas indicated, particularly for n terms of resource assessment, the Pacific will need time to assess to time need will Pacific the assessment, resource of terms In installation has been not THE FACILITATOR experienced rehabilitated? auru was developed by Kyosu by developed was Nauru in What Nauru will but be the the fate island of A SOPAC Desktop Study of Ocean-Based-Renewable Energy Technologies SOPAC Miscellaneous Report 95 96