T.J. Hammons∗
[1]. Therelative motion of these bodies causes the surface on theoceans to be raised and lowered periodically, as illustratedin Fig. 3. The physics of tidal power is explained inReference [1].Figure 3. Tide-generating forces based on earth–moon in-teractions. Source: O. Siddiqui & R. Bedard [30].In deep water, the wave power spatial flux (in kW/mof wave front crest) is given by significant wave height (Hsin m) and the peak wave period (Tp in s). Based on thesetwo parameters, the incident wave power (J in kW/m ofwave crest length) associated with each sea state record isestimated by the following equation:J = 0.42 × (Hs)2× Tp (kW)It is significant to note that wave power varies withthe square of wave height – that is, a wave whose height isdoubled generates four times as much power.The power of a tidal current is given by the followingequation:Pwater = (1/2) rAV 3(W)where A is the cross-sectional area of flow intercepted bythe turbine device (m2), r is the water density (kg/m3)and V is current velocity speed (m/s). The current ve-locity V varies in a precisely predictable manner as anadditive function of period of the different sinusoidal tidalcomponents.Tidal flow energy studies are in progress at EPRI andthe techno-economic results are not available. Therefore,the focus is on the results of the wave energy feasibilitydefinition study of 2004.4.2 Wave Project Results4.2.1 US Wave Energy ResourcesAn ideal site to deploy, operate and maintain an offshorewave energy power plant must have many attributes. Firstand foremost is a sufficient native energy and energy spec-tra potential.1The US regional wave regimes and the totalannual incident wave energy for each of these regimes areshown in Fig. 4. The total US available incident waveenergy flux is about 2,300 TWh/yr. The DOE EnergyInformation Energy (EIA) estimated in 2003 hydroelectricgeneration in USA to be about 270 TWh which is a lit-tle more than a tenth of the yearly offshore wave energyflux into the US. Therefore, wave energy is a significantresource.Figure 4. US energy resources. Source: O. Siddiqui &R. Bedard [30].4.2.2 Feasibility Definition Study SitesSite attributes characterized by the Project Team includedoffshore bathymetry2and seafloor surface geology, robust-ness of the coastal utility grid, regional maritime infras-tructure for both fabrication and maintenance, conflictswith competing uses of sea space and existence of otherunique characteristics that might minimize project devel-opment costs (e.g. existing ocean outfall easements forrouting power cable and shore crossing).Table 2 identifies the site selected in each of the fivestates that participated in the study, and also provides afew key characteristics of each selected site.4.2.3 Feasibility Study: WEC DevicesTwelve companies responded to EPRI’s request for infor-mation. An initial screening considered two key issues: (1)technology readiness (i.e. readiness of device for demon-stration in the 2006 time period) and (2) survivability inadverse conditions (i.e. sufficiency of technical informationprovided by the device manufacturer to prove the surviv-ability in storm conditions). The eight devices that passedthe initial screening criteria are shown in Table 3.1 Energy as function of wave height and wave period or frequency.2 Bathymetry is the depth of the seafloor below mean waterheight (i.e. the inverse of a topographic map).420Table 2Estimated Performance of Pilot Demonstration PlantsHI OR CA Mass MaineCounty Oahu Douglas SF Cape Cod CumberlandGrid I/C Waimanalo Gardner Wastewater Well OldBeach Plant Fleet OrchardBeach S/SAverage 15.2 21.2 11.2113.8 4.9Annual J(kW/m)Depth (m) 60 60 30 60 60Distance 2 3.5 13 9 9from ShoreCable Makai IPP Outflow Water Dir Drill Dir DrillLanding Pier Pipe Outflow1Sited within the marine sanctuary exclusionary zone.Source: O. Siddiqui & R. Bedard [30].Table 3Estimated Performance of Pilot Demonstration PlantsLength (m) Width (m) Power (kW)1Type RatingOcean 120 4.6 153 Floating 1Power AttenuatorDeliveryEnergetech 25 35 259 OWC – Bottom 2TerminatorWave 150 260 1,369 Floating 2Dragon OvertoppingWave 9.5 9.5 351 Bottom Point 2Swing AbsorberWave Bob 16 15 131 Floating Point 3AbsorberAqua-Energy 6 6 17 Floating Point 3AbsorberOreCON 32 32 532 Floating OWC 3Ind Natural 5.4 5.4 112 Bottom Point 3Resources Inc Absorber1Based on Oregon average annual wave energy resource.Source: O. Siddiqui & R. Bedard [30].These eight devices were then assessed with the ob-jective of determining any critical issues and recommend-ing RD&D needed to achieve technological readiness foran at sea demonstration. As a result of this assessment,the eight devices were grouped into one of three levels ofdevelopment categories:• Level 1 : Development complete and full-scale testingin the ocean underway.• Level 2 : Development near complete. Only deploy-ment, recovery and mooring issues are yet to be val-idated. There are funded plans for full-scale at seatesting.• Level 3 : Most critical RD&D issues are resolved. Ad-ditional laboratory and sub-scale testing, simulationsand systems integration work is needed prior to final-ization of the full-scale design. There are no funded421plans for full-scale at sea testing.At the time of EPRI’s analysis (March 2004), onlyone WEC device manufacturer had attained a Level 1technology readiness status – OPD with its Pelamis device.At the time of this paper (February 2005) there are anadditional four WEC device manufacturers that are close toreaching that status: TeamWorks of the Netherlands withits Wave Swing, Energetechs of Australia with its OWC,Wave Dragon of Denmark with its overtopping device, andOcean Power Technology of the US with a floating buoy.4.2.4 Demonstration-Scale Plant Design: OregonExampleDemonstration-scale (as well as commercial-scale) designswere based on the OPD Pelamis WEC device for the fivesites listed in Table 2. The Pelamis WEC device consistsof four cylindrical steel sections, which are connected bythree hydraulic PCM. Total length of the device is 120 mand device diameter is 4.6 m. Fig. 5 shows the device beingtested off the Scottish coast.Figure 5. OPD Pelamis WEC device. 1 nm = 1 nauticalmile. Source: O. Siddiqui & R. Bedard [30].A second San Francisco, CA design based on theEnergetech OWC WEC device depicted in Fig. 6 was alsotested.Figure 6. Energetech WEC device. Source: O. Siddiqui &R. Bedard [30].The estimated performance of the single unit demon-stration plant at each of the five sites is shown in Table 4.Table 4Estimated Performance of Pelamis Pilot DemonstrationPlantsHI OR CA1Mass MaineDevice Rated 750 750 750 750 750Capacity (kW)Annual 1,989 1,472 1,229 1,268 426Energy Absorbed(MWh/yr)Annual Energy 1,663 1,001 835 964 290Produced(MWh/yr)Average 180 114 95 98 33ElectricalPower (kW)Number of 180 114 95 98 33Homes Poweredby Plant1Energetech site numbers: 1,000 kW, 1,643 MWh/yr, 1,264 MWh/yr,and 144 kW respectively.Source: O. Siddiqui & R. Bedard [30].4.2.5 Commercial-Scale Plant Design: Oregon Exam-pleThe commercial system uses a total of 4 clusters, each onecontaining 45 Pelamis units (i.e. 180 total Pelamis WECdevices), connected to sub-sea cables. Each cluster consistsof 3 rows with 15 devices per row. The other state designsare organized in a similar manner with 4 clusters. Thenumber of devices per cluster varies such that each plantproduces an annual energy output of 300,000 MWh/yr.The electrical interconnection of the devices is accom-plished with flexible jumper cables, connecting the units inmid-water. The introduction of 4 independent sub-sea ca-bles and the interconnection on the surface provides someredundancy in the wave farm arrangement.The estimated performance of the commercial-scaleplant at each of the five sites is shown in Table 5.The device rated capacity has been derated from750 kW in the demonstration plant to 500 kW for the com-mercial plant. The performance assessment of the demon-stration plants shows that the PCMs are overrated andreducing the rated power to 500 kW per device would yielda significant cost reduction and only a relatively small de-crease in annual output (attributed to the fact that the USsites have a lower energy level than UK sites for which thedevice was originally developed).4.2.6 Learning Curves and EconomicsThe costs and cost of electricity shown in the previous sec-tion are for the first commercial-scale wave plant. Learn-ing through production experience reduces costs – a phe-nomenon that follows a logarithmic relationship such that422Table 5Estimated Performance of Pelamis Commercial PlantsHI OR CA Mass MaineDevice Rated 500 500 500 500 500Capacity (kW)Annual Energy 1,989 1,997 1,683 1,738 584Absorbed (MWh/yr)Annual Energy 1,663 1,669 1,407 1,453 488Produced (MWh/yr)Average Electrical 191 191 161 166 56Power at Busbar (kW)Number of OPD 180 180 213 206 615Pelamis UnitsNeeded for300,000 MWh/yrNumber of Homes 34,000 34,000 34,000 34,000 34,000Powered by PlantSource: O. Siddiqui & R. Bedard [30].for every doubling of the cumulative production volume,there is a specific percentage drop in production costs.The specific percentage used in this study was 82%, whichis consistent with documented experience in the wind en-ergy, photovoltaic, shipbuilding, and offshore oil and gasindustries.The industry-documented historical wind energy learn-ing curve is shown as the top line in Fig. 7 [31]. The cost ofelectricity is about 4 cents/kWh in 2004 US dollars basedon 40,000 MW of worldwide installed capacity and a goodwind site. The lower and higher bound cost estimates ofwave energy are also shown in Fig. 7. The 82% learningcurve is applied to the wave power plant installed costbut not to the operation and maintenance part of cost ofelectricity (hence the reason that the three lines are notparallel).Figure 7. Electrical interconnection of demo-plant: Oregonexample. Source: O. Siddiqui & R. Bedard [30].Fig. 7 shows the cost of wave-generated electricity:low band (bottom curve), upper band (middle curve); andwind-generated electricity (top curve) at equal cumulativeproduction volume under all cost estimating assumptionsfor the wave plant. It shows that the cost of wave-generatedelectricity is less than wind-generated electricity at anyequal cumulative production volume under all cost esti-mating assumptions for the wave plant. The lower capitalcost of a wave machine (compared to a wind machine)more than compensates for the higher O&M cost for theremotely located offshore wave machine. A challenge tothe wave energy industry is to drive down O&M costs tooffer even more economic favourability and to delay thecrossover point shown at greater than 40,000 MW.In summary, the techno-economic forecast made by theProject Team is that wave energy will first become commer-cially competitive with the current 40,000 MW installedland-based wind technology at a cumulative productionvolume of 15,000 MW or less in Hawaii and northern Cali-fornia, about 20,000 MW in Oregon and about 40,000 MWin Massachusetts. This forecast was made on the basis of a300,000 MWh/yr (nominal 90 MW at 38% capacity factor)Pelamis WEC commercial plant design and application oftechnology learning curves. Maine was the only state inthe study whose wave climate was such that wave energymay never be able to economically compete with a goodwind energy site.In addition to economics, there are other compellingarguments for investing in offshore wave energy technology.First, with proper sitting, converting ocean wave energy toelectricity is believed to be one of the most environmentallybenign ways to generate electricity. Second, offshore waveenergy offers a way to minimize the “Not In My Backyard”(NIMBY) issues that plague many energy infrastructure423projects, from nuclear to coal and to wind generation.Because these devices have a very low profile and arelocated at a distance from the shore, they are generally notvisible. Third, because wave energy is more predictablethan solar and wind energy, it offers a better possibilitythan either solar or wind of being dispatch able and earninga capacity payment.A characteristic of wave energy that suggests that itmay be one of the lowest cost renewable energy sources isits high power density. Processes in the ocean concentratesolar and wind energy into ocean waves making it easierand cheaper to harvest. Solar and wind energy sources aremuch more diffuse, by comparison.Since a diversity of energy sources is the bedrock ofa robust electricity system, to overlook wave energy isinconsistent with national needs and goals. Wave energyis an energy source that is too important to overlook.4.2.7 RecommendationsThe development of ocean energy technology and the de-ployment of this clean renewable energy technology wouldbe greatly accelerated by adequate support from govern-ments. Appropriate roles for governments in ocean energydevelopment could include:• Providing leadership for the development of an oceanenergy RD&D programme to fill known RD&D gaps,and to accelerate technology development and proto-type system deployment.• Operating national offshore wave test centers to testperformance and reliability of prototype ocean energysystems under real conditions.• Development of design and testing standards for oceanenergy devices.• Joining the International Energy Agency Ocean En-ergy Systems Implementing Agreement to collaborateRD&D activities, and appropriate ocean energy poli-cies with other governments and organizations.• Studying provision of production tax credits, renew-able energy credits, and other incentives to spur privateinvestment in ocean energy technologies and projects,and implementing appropriate incentives to accelerateocean energy deployment.• Ensuring that the public receives a fair return fromthe use of ocean energy resources.• Ensuring that development rights are allocatedthrough a transparent process that takes into accountstate, local, and public concerns.5. Recent Progress in Offshore Renewable EnergyTechnology DevelopmentThe recent progress in offshore renewable energy technol-ogy development is now examined and potential marketsfor tidal power, WEC, and offshore wind are considered.The analysis of market potentials for offshore renewabletechnology is based solely on currently identified projects.There is therefore scope for increased market prospects,particularly around the end of the period in the wave andtidal current stream sectors.5.1 Tidal Current StreamHistorically, tidal projects have been large-scale barragesystems that block estuaries. Within the last few decades,developers have shifted toward technologies that capturethe tidally driven coastal currents or tidal stream. Thechallenge is, “to develop technology and innovate in a waythat will allow this form of low density renewable energyto become practical and economic” [22].Tidal current turbines are basically underwater wind-mills. The tidal currents are used to rotate an underwa-ter turbine. First proposed during the 1970s’ oil crisis,the technology has only recently become a reality withcommercial prospects.Marine Current Turbines (MCT) installed the firstfull-scale prototype turbine (300 kW) off Lynmouth in De-von, UK in 2003. Shortly thereafter, the Norwegian com-pany Hammerfest Støm installed their first grid-connected300 kW prototype device. MCT, arguably the marketleader is now preparing to install its new twin-rotored1 MW device in 2007. The company has plans to install acommercial scale project off the UK coast around the turnof the decade.There are a great number of sites suitable for tidalcurrent turbines. As tidal currents are predictable andreliable, tidal turbines have advantages over offshore windcounterparts. The ideal sites are generally within severalkilometres of the shore in water depths of 20–30 m.5.1.1 Tidal ForecastsDouglas-Westwood Ltd expect 25 MW of tidal currentstream capacity to be brought online in the 2007–2011period (see Fig. 8). The vast majority of this capacitywill be in the UK where 23 MW is forecast. With severalsuccessful large-scale prototypes already tested, the periodto the end of the decade will see further refinement ofdevices and applications for multiple-unit farms in keymarkets. The above forecast shows a sharp growth in 2011from tidal current farms expected from MCT and LunarEnergy.Figure 8. Potential tidal current stream capacity 2007–2011. Source: Douglas-Westwood Ltd [32].4245.1.2 ProjectsShiswa Lake Tidal Power Plant, Korea Korea has aplentiful tidal and tidal current energy resource. Underconstruction is a single stream style generator at AnsanCity’s Shiswa Lake, which will have a capacity of 252 MW,comprised of 12 units of 21 MW generators. Annual powergeneration, when completed in 2008, is projected at 552million kWh. If successful, this project will surpass LaRance (France) as the largest tidal power plant in theworld. Korea is also planning a tidal current power plantin Uldol-muk Strait, a restriction in the strait where maxi-mum water speed exceeds 6.5 m/s. The experimental plantwill utilize helical or “Gorlov” turbines developed by GCKTechnology [26].Yalu River, China By creating a tidal lagoon off-shore, Tidal Electric has taken a novel approach to resolveenvironmental and economic concerns of tidal barrage tech-nology [27]. Due to the highly predictive nature of theocean tides, the company has developed simulation modelswith performance data from available generators to opti-mize design for particular locations. The recent announce-ment of a cooperative agreement with the Chinese govern-ment for ambitious 300 MW offshore tidal power genera-tion facilities off Yalu River, Liaoning Province allows foran engineering feasibility study to be undertaken.Tidal Electric also has plans under consideration forUK-based projects in Swansea Bay (30 MW), Fifoots Point(930 MW), and North Wales (432 MW). These projectshave failed to make progress and will not go ahead in theforeseeable future.5.2 Wave EnergyThe true potential of wave energy will only be realizedin the offshore environment where large developments areconceivable. Nearly 300 concepts for wave energy deviceshave been proposed. The development process for waveenergy can be looked at in three phases. First, small-scale prototype devices, typically with low capacity, will bedeployed. During the second stage, outside funding fromgovernment or private investors is possible for the mostpromising devices. The final stage is the production offull-scale, grid-connected devices that will in some cases bedeployable in farm style configurations.Modular offshore wave energy devices that can bedeployed quickly and cost effectively in a wide range ofconditions will accelerate commercial wave energy. Inthe coming decade, wave energy will become commerciallysuccessful through multiple-unit offshore projects, the firstof which are now being installed. These projects clearlydemonstrate the commercial future for wave energy butvaluable operational experience is necessary before largerprojects are built with a greater number of devices.The growth of shoreline wave energy devices is limitedby the low number of available sites and high installa-tion costs. Deployment costs for shoreline wave energydevices are very high because they are individual site-specific projects and economies of scale are not applicable.Whereas an offshore 50-MW wave farm is conceivable, andwill in time be developed, no shoreline wave energy con-verter can offer such potential for deployment in this way.As such, individual coastal installations are expected to befew and far between. Shoreline wave energy will, however,continue to be relevant, as the average unit capacity isgenerally higher than existing offshore technology. Indi-vidual devices can be very effective, especially for remoteor island communities where, for example, an individualunit of 4 MW could have a big impact.Offshore locations offer greater power potential thanshoreline locations. Shoreline technologies have the benefitof easy access for maintenance purposes, whereas offshoredevices are in most cases more difficult to access. Improve-ments in reliability and accessibility will be critical to thecommercial success of the many devices currently underdevelopment.5.2.1 Wave Energy ForecastDouglas-Westwood Ltd claim there is a potential 46 MWof wave energy projects that could be installed between2007 and 2011. The United Kingdom is expected to bethe dominant player over the next 5 years, with a fore-cast capacity of 28.6 MW, which equates to a 62% marketshare. In comparison with other countries, the UK hasforecast capacity every year to 2008, whereas installationselsewhere are more intermittent. Norway (6 MW) and Por-tugal (4.25 MW) are the next most significant markets andhave several projected installations, but they lag behindthe UK in terms of technology development and projectdeployment. The United Kingdom government has shownreasonable levels of support, which have injected manytechnologies with valuable grants. The result is a num-ber of proven wave technologies with good prospects forcommercial deployment and several more at an advancedprototype stage. Coupled with a world-class natural re-source, the United Kingdom remains the strongest marketinto the next decade.Potential wave energy capacity 2007–2011 is indicatedin Fig. 9.Figure 9. Potential wave energy capacity 2007–2011.Source: Douglas-Westwood Ltd [32].4255.3 Offshore WindThere are 25 operational offshore wind farms in the worldtoday. The 436 installed turbines in these projects providea total of 919 MW.The first offshore wind turbine was installed at Noger-sund off Sweden in 1990. The first offshore wind farmwere installed at Vindeby off the Danish island of Lol-land in 1991. The most recent project is the BeatriceDemonstration Project off Scotland.The first 10 years of the industry saw small projects be-ing built in very shallow water near-shore locations. Thesewind farms in most cases used onshore turbine models withslight adaptations made. These “demonstration” projectshave paved the way for the more recent projects that areof a much larger size.The biggest offshore wind farm yet installed is theNysted development off Denmark which was completed in2003. Just as this project dwarfs those built 10 yearspreviously, within another decade projects will be installedthat are many times greater in size than today’s offshorewind farms.The industry faces problems from increasing costs. Inthe last 5 years, the cost of offshore wind has increasedby up to 65%. This is caused by increased turbine pricesdriven by the extremely strong onshore wind market (par-ticularly in the US), and rising contractor prices basedupon experiences on earlier projects. Cost reductions ofapproximately 25% are essential to help stimulate the in-dustry and help strengthen it.The total global offshore wind capacity forecast forinstallation between 2007 and 2011 stands at 4.2 GW. TheUK is the world’s largest market for the forthcoming 5-yearperiod. A total of 2.2 GW is forecast here, representing 52%of the entire world market. The UK’s “Round 1” projectsare continuing to be installed at the rate of 1–2 per year.The first of the larger “Round 2” projects are expected toenter construction at the turn of the decade, significantlyboosting the UK’s capacity. The UK’s prospects areexpected almost three times those of Germany, the nextlargest market.Germany has so far seen only minor installations,but the first significant activity is expected to begin in2008 with the Borkum West project. Several projectsare forecast for 2009 and 2010. The bulk of projects,however, will not begin construction until the turn of thedecade. Long-term prospects are excellent off Germanybut in the short and mid-term future the industry hasmuch to overcome.The only activity off Denmark in the period will comewith the construction and completion of the Horns Rev IIand Nysted II projects in 2009 and 2010 respectively. Al-though the country showed initial promise for offshore de-velopment, a lack of government commitment has stuntedthe industry here. Long-term prospects are, however,high and a new round of licences is expected shortly fordevelopment in the next decade.Whilst the Netherlands is currently seeing a period ofactivity with the completion of the Egmond aan Zee projectand construction of Q7-WP, it will not be until after thisdecade that the next projects are completed. Whilst notreflected in the above forecast, long-term prospects aregood.North America is yet to install any offshore windprojects. With the onshore market in such good health,the drivers for offshore are not as strong as in Europe wherethe industry is reaching take-off after a period of slow butsteady growth.There are currently three large offshore wind farms inNorth America in advanced stages of planning althoughit is now unlikely that they will be built this decadedue to delays from drawn-out permitting processes andlegal challenges. In addition to this are a number ofmore speculative large projects and several small scaledemonstration projects that could be installed before theend of the decade.The highest profile project is Cape Wind off the coastof Massachusetts. The proposed 420 MW wind farm hascourted controversy since conception. After clearing anumber of regulatory and legal hurdles over a 6-year period,the project faces a ruling from US federal authorities. TheMinerals Management Service (MMS) took over regulationof offshore renewables in the autumn of 2005. The MMSintend to record a decision on the project in the fall of2008.The 144 MW Long Island offshore wind farm is beingdeveloped by FPL Energy. The MMS is due to recorda decision on the project in spring 2008. The projectstarted after The Long Island Power Authority announcedin January 2003 that it was seeking developers to build anoffshore wind farm off Jones Beach.The largest North American project is the 1,750 MWNaiKun wind farm off the coast of British Columbia whichwill be developed in five phases, the first of which isscheduled for completion in 2011.Cumulative installed offshore wind capacity is given inFig. 10. Forecast offshore capacity 2002–2011 is indicatedin Fig. 11.6. ConclusionsFor the entire marine renewables sector, 4.5 GW of installedcapacity is projected between 2007 and 2011. Some 98%of that capacity is in the form of offshore wind farms. TheFigure 10. Cumulative installed offshore wind capacity.Source: Douglas-Westwood Ltd [32].426Figure 11. Forecast offshore wind capacity 2002–2011.Source: Douglas-Westwood Ltd [32].value of the market over the next 5 years is projected at$17 billion.Wave and tidal power will only be a small percentageof the total expenditure on offshore renewables, of theorder of $300 million in total expenditure between them.However, wave and tidal power currently attract higherexpenditures per megawatt. This indicates higher costs ofthe immature developing industries. These costs will fallas time goes by and the industries progresses. The leadingdevices should be comparable with, and in some cases morecompetitive than offshore wind, by early next decade.The more well-established offshore wind sector willlead the offshore renewables industry, and will see stronggrowth throughout the period led by countries such as theUK, the Netherlands, Germany and Denmark. Establishedonshore wind supply chains in Denmark and Germany will,however, see most of the financial benefit of the growthin offshore wind for the short-term. The dominance ofoffshore wind does not mean wave and tidal energy arenot important, they are just less well developed, and theindustry is much younger. From around 2010, wave andtidal should begin to expand commercially. The growth ofwave and tidal power offers significant supply chain growthopportunities for countries that failed to capture the valueof the growth in the wind industry (both onshore andoffshore).Europe is the dominant region, leading in all threesectors. The UK is a particularly important market, drivenby a world-class natural resource, the past 3 years has seennotable successes in wind, wave and tidal energies. Withmore approved offshore wind capacity in the planning stagethan any other country, prospects for the United Kingdomlook bright. The UK is forecast to become world leader inoffshore wind in 2008 and is already the leader in the waveand tidal current stream industries. The UK Energy WhitePaper due May 2007 is expected to increase banding to themain support system for renewables to give greater supportto emerging technologies, particularly offshore renewables.This should provide a strong catalyst for growth.Whilst currently lacking, future growth in other re-gions should not be discounted in the long term. Interestin North America is growing and we will see large projectsprogressing around the end of the decade, particularly inthe offshore wind sector. Greater support and structurewould reap big rewards for the industry here. At presentthough, it lags far behind the established European marketwhich remains the focal point for the marine renewablesindustry. Europe is home to the leading technology de-velopers and superior funding packages are in place in keycountries to stimulate development.AcknowledgementsThe author acknowledges contributions made by PeterO’Donnell (Senior Energy Specialist, Manager GenerationSolar & Renewables Programs, San Francisco EnvironmentOrganization, CA, USA); Omar Siddiqui (Senior Associate,Global Energy Partners LLC, Lafayette, CA, USA); RogerBedard (Offshore Wave Energy Project Manager, EPRI,CA, USA), Andrew Mill (Managing Director EuropeanMarine Energy Centre, UK); Mirko Previsic (Consultant—Offshore Renewables, Sacramento, CA, USA); Anthony TJones (Senior Oceanographer, oceanUS consulting, PalmSprings, CA, USA); and Adam Westwood (RenewableEnergy Manager, Douglas-Westwood Limited, Canterbury,UK, principally for Section 5).References[1] T.J. Hammons, Tidal Power, Proceedings IEEE, 81(3), 1993,419–433. [2] B.V. Davis, A major source of energy from the world’s oceans,IECEC-97 Intersociety Energy Conversion Engineering Con-ference, 1997. [3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Tur-bine for (Canadian) Ministry of Employment and Investment,N.H. Halvorson Consultants Ltd. [4] Renewable Energy: Power for a Sustainable Future; TechnologyUpdate, Tidal Current Power Update & Wave Power Update,Oxford University Press, 2001. [5] P. Fraenkel, Renewables is the tide turning for marine currentturbines? Modern Power System, Marine Current TurbinesLtd, London, UK, June 30, 2001. [6] R. Bedard, Final summary report: offshore wave power feasi-bility demonstration project (E2I EPRI Global WP009 – US,2005). [7] M. Previsic, System level design, performance and costs forSan Francisco Pelamis offshore wave power plant (E2I EPRIGlobal – 006A – SF, 2004). [8] G. Hagerman, Offshore Wave Power in the US: EnvironmentalIssues (E2I Global EPRI – 007 – US, 2004). [10] and [11]. The methodology, guidelines andassumptions for conceptual design of offshore wave en-ergy power plants is given in Reference [12]. System leveldesign, preliminary performance and cost estimates forHawaii, Oregon, Main, Massachusetts, and San FranciscoPelamis offshore wave power plants are given in References[13–17], respectively, and system level design, preliminaryperformance and cost estimate for the San Francisco Ener-getech offshore wave power plant is given in Reference [18].Further, the state of the art for WEC is reviewed in Refer-ence [19], and a technical assessment guide for ocean wavepower is made in Reference [20]. A wave energy resourceassessment for California is given in Reference [21].Most of the EPRI Wave Power (WP) Reports [11,13–18] are available on their website (www.epri.com).4. Feasibility Assessment of Offshore Wave andTidal Current Power Production: A Collabora-tive Public/Private PartnershipCollaborative power production feasibility definition stud-ies on offshore wave energy and tidal current energy onbehalf of a number of public and private entities is beingundertaken at this time (February 2005). The outcome ofthe offshore wave study, which began in 2004 under theEPRI, is a compelling techno-economic case for investingin the RD&D of technology to convert the kinetic energyof ocean waves into electricity. The tidal current studiesbegan in early 2005 and are currently at the site identifica-tion and device assessment stage. Techno-economic resultsfor tidal plant designs at various sites were made in late2005.EPRI Wave Power Reports [11, 13–18] and References[22–29] summarize the activities in this area.4.1 Feasibility of Wave and Tidal Current EnergyThe elements of a wave and tidal current energy feasi-bility study are: (a) identify and characterize potentialsites for assembling and deploying a power plant and forconnecting the plant to the electric grid; (b) identify andassess WEC devices; (c) conduct a conceptual design of ademonstration- and commercial-scale offshore wave powerplant and, based on performance and cost estimates, assessthe techno-economic viability of the wave energy sourceand the energy conversion technology; and (d) identify andassess the environmental and regulatory issues associatedwith implementing the technology.Two characteristics of waves and tides important to thegeneration and dispatch of electricity from WEC devicesare its variability and predictability. While the ocean isnever totally calm, wave power is more continuous thanthe winds that generate it. The average power during thewinter may be six times that obtained during the summer;however, power values may vary by a factor of a hundredwith the random occurrences of storms. Therefore, thepower of waves is highly variable. The predictability ofwave energy is of the order of a few days. The wavesresulting, for example, from storms that occur off the coastof Japan, will take that long to reach the northwest coastof the United States. The power from tidal currents, on theother hand, typically varies according to a diurnal cycle.The major benefit of tidal power is its high predictabilityfor a given site years in advance, provided there is athorough knowledge of the site. A drawback of tidal poweris its low capacity factor, and that its peak availabilitymisses peak demand times because of the 12.5 h cycle ofthe tides.Ocean waves are generated by the winds that resultfrom uneven heating around the globe. Waves are formedby winds blowing over the water surface, which makethe water particles adopt circular motions as depicted inFig. 2. This motion carries kinetic energy, the amountFigure 2. Wave-generating forces based on wind–waterinteraction. Source: M. Previsic [10].419of which is determined by the speed and duration of thewind, the length of sea it blows over, the water depth, seabed conditions and also interactions with the tides. Wavesoccur only in the volume of water closest to the watersurface, whereas in tides, the entire water body moves,from the surface to the seabed.The tides are generated by rotation of the earth withinthe gravitational fields of the moon and sun [1]. Therelative motion of these bodies causes the surface on theoceans to be raised and lowered periodically, as illustratedin Fig. 3. The physics of tidal power is explained inReference [1].Figure 3. Tide-generating forces based on earth–moon in-teractions. Source: O. Siddiqui & R. Bedard [30].In deep water, the wave power spatial flux (in kW/mof wave front crest) is given by significant wave height (Hsin m) and the peak wave period (Tp in s). Based on thesetwo parameters, the incident wave power (J in kW/m ofwave crest length) associated with each sea state record isestimated by the following equation:J = 0.42 × (Hs)2× Tp (kW)It is significant to note that wave power varies withthe square of wave height – that is, a wave whose height isdoubled generates four times as much power.The power of a tidal current is given by the followingequation:Pwater = (1/2) rAV 3(W)where A is the cross-sectional area of flow intercepted bythe turbine device (m2), r is the water density (kg/m3)and V is current velocity speed (m/s). The current ve-locity V varies in a precisely predictable manner as anadditive function of period of the different sinusoidal tidalcomponents.Tidal flow energy studies are in progress at EPRI andthe techno-economic results are not available. Therefore,the focus is on the results of the wave energy feasibilitydefinition study of 2004.4.2 Wave Project Results4.2.1 US Wave Energy ResourcesAn ideal site to deploy, operate and maintain an offshorewave energy power plant must have many attributes. Firstand foremost is a sufficient native energy and energy spec-tra potential.1The US regional wave regimes and the totalannual incident wave energy for each of these regimes areshown in Fig. 4. The total US available incident waveenergy flux is about 2,300 TWh/yr. The DOE EnergyInformation Energy (EIA) estimated in 2003 hydroelectricgeneration in USA to be about 270 TWh which is a lit-tle more than a tenth of the yearly offshore wave energyflux into the US. Therefore, wave energy is a significantresource.Figure 4. US energy resources. Source: O. Siddiqui &R. Bedard [30].4.2.2 Feasibility Definition Study SitesSite attributes characterized by the Project Team includedoffshore bathymetry2and seafloor surface geology, robust-ness of the coastal utility grid, regional maritime infras-tructure for both fabrication and maintenance, conflictswith competing uses of sea space and existence of otherunique characteristics that might minimize project devel-opment costs (e.g. existing ocean outfall easements forrouting power cable and shore crossing).Table 2 identifies the site selected in each of the fivestates that participated in the study, and also provides afew key characteristics of each selected site.4.2.3 Feasibility Study: WEC DevicesTwelve companies responded to EPRI’s request for infor-mation. An initial screening considered two key issues: (1)technology readiness (i.e. readiness of device for demon-stration in the 2006 time period) and (2) survivability inadverse conditions (i.e. sufficiency of technical informationprovided by the device manufacturer to prove the surviv-ability in storm conditions). The eight devices that passedthe initial screening criteria are shown in Table 3.1 Energy as function of wave height and wave period or frequency.2 Bathymetry is the depth of the seafloor below mean waterheight (i.e. the inverse of a topographic map).420Table 2Estimated Performance of Pilot Demonstration PlantsHI OR CA Mass MaineCounty Oahu Douglas SF Cape Cod CumberlandGrid I/C Waimanalo Gardner Wastewater Well OldBeach Plant Fleet OrchardBeach S/SAverage 15.2 21.2 11.2113.8 4.9Annual J(kW/m)Depth (m) 60 60 30 60 60Distance 2 3.5 13 9 9from ShoreCable Makai IPP Outflow Water Dir Drill Dir DrillLanding Pier Pipe Outflow1Sited within the marine sanctuary exclusionary zone.Source: O. Siddiqui & R. Bedard [30].Table 3Estimated Performance of Pilot Demonstration PlantsLength (m) Width (m) Power (kW)1Type RatingOcean 120 4.6 153 Floating 1Power AttenuatorDeliveryEnergetech 25 35 259 OWC – Bottom 2TerminatorWave 150 260 1,369 Floating 2Dragon OvertoppingWave 9.5 9.5 351 Bottom Point 2Swing AbsorberWave Bob 16 15 131 Floating Point 3AbsorberAqua-Energy 6 6 17 Floating Point 3AbsorberOreCON 32 32 532 Floating OWC 3Ind Natural 5.4 5.4 112 Bottom Point 3Resources Inc Absorber1Based on Oregon average annual wave energy resource.Source: O. Siddiqui & R. Bedard [30].These eight devices were then assessed with the ob-jective of determining any critical issues and recommend-ing RD&D needed to achieve technological readiness foran at sea demonstration. As a result of this assessment,the eight devices were grouped into one of three levels ofdevelopment categories:• Level 1 : Development complete and full-scale testingin the ocean underway.• Level 2 : Development near complete. Only deploy-ment, recovery and mooring issues are yet to be val-idated. There are funded plans for full-scale at seatesting.• Level 3 : Most critical RD&D issues are resolved. Ad-ditional laboratory and sub-scale testing, simulationsand systems integration work is needed prior to final-ization of the full-scale design. There are no funded421plans for full-scale at sea testing.At the time of EPRI’s analysis (March 2004), onlyone WEC device manufacturer had attained a Level 1technology readiness status – OPD with its Pelamis device.At the time of this paper (February 2005) there are anadditional four WEC device manufacturers that are close toreaching that status: TeamWorks of the Netherlands withits Wave Swing, Energetechs of Australia with its OWC,Wave Dragon of Denmark with its overtopping device, andOcean Power Technology of the US with a floating buoy.4.2.4 Demonstration-Scale Plant Design: OregonExampleDemonstration-scale (as well as commercial-scale) designswere based on the OPD Pelamis WEC device for the fivesites listed in Table 2. The Pelamis WEC device consistsof four cylindrical steel sections, which are connected bythree hydraulic PCM. Total length of the device is 120 mand device diameter is 4.6 m. Fig. 5 shows the device beingtested off the Scottish coast.Figure 5. OPD Pelamis WEC device. 1 nm = 1 nauticalmile. Source: O. Siddiqui & R. Bedard [30].A second San Francisco, CA design based on theEnergetech OWC WEC device depicted in Fig. 6 was alsotested.Figure 6. Energetech WEC device. Source: O. Siddiqui &R. Bedard [30].The estimated performance of the single unit demon-stration plant at each of the five sites is shown in Table 4.Table 4Estimated Performance of Pelamis Pilot DemonstrationPlantsHI OR CA1Mass MaineDevice Rated 750 750 750 750 750Capacity (kW)Annual 1,989 1,472 1,229 1,268 426Energy Absorbed(MWh/yr)Annual Energy 1,663 1,001 835 964 290Produced(MWh/yr)Average 180 114 95 98 33ElectricalPower (kW)Number of 180 114 95 98 33Homes Poweredby Plant1Energetech site numbers: 1,000 kW, 1,643 MWh/yr, 1,264 MWh/yr,and 144 kW respectively.Source: O. Siddiqui & R. Bedard [30].4.2.5 Commercial-Scale Plant Design: Oregon Exam-pleThe commercial system uses a total of 4 clusters, each onecontaining 45 Pelamis units (i.e. 180 total Pelamis WECdevices), connected to sub-sea cables. Each cluster consistsof 3 rows with 15 devices per row. The other state designsare organized in a similar manner with 4 clusters. Thenumber of devices per cluster varies such that each plantproduces an annual energy output of 300,000 MWh/yr.The electrical interconnection of the devices is accom-plished with flexible jumper cables, connecting the units inmid-water. The introduction of 4 independent sub-sea ca-bles and the interconnection on the surface provides someredundancy in the wave farm arrangement.The estimated performance of the commercial-scaleplant at each of the five sites is shown in Table 5.The device rated capacity has been derated from750 kW in the demonstration plant to 500 kW for the com-mercial plant. The performance assessment of the demon-stration plants shows that the PCMs are overrated andreducing the rated power to 500 kW per device would yielda significant cost reduction and only a relatively small de-crease in annual output (attributed to the fact that the USsites have a lower energy level than UK sites for which thedevice was originally developed).4.2.6 Learning Curves and EconomicsThe costs and cost of electricity shown in the previous sec-tion are for the first commercial-scale wave plant. Learn-ing through production experience reduces costs – a phe-nomenon that follows a logarithmic relationship such that422Table 5Estimated Performance of Pelamis Commercial PlantsHI OR CA Mass MaineDevice Rated 500 500 500 500 500Capacity (kW)Annual Energy 1,989 1,997 1,683 1,738 584Absorbed (MWh/yr)Annual Energy 1,663 1,669 1,407 1,453 488Produced (MWh/yr)Average Electrical 191 191 161 166 56Power at Busbar (kW)Number of OPD 180 180 213 206 615Pelamis UnitsNeeded for300,000 MWh/yrNumber of Homes 34,000 34,000 34,000 34,000 34,000Powered by PlantSource: O. Siddiqui & R. Bedard [30].for every doubling of the cumulative production volume,there is a specific percentage drop in production costs.The specific percentage used in this study was 82%, whichis consistent with documented experience in the wind en-ergy, photovoltaic, shipbuilding, and offshore oil and gasindustries.The industry-documented historical wind energy learn-ing curve is shown as the top line in Fig. 7 [31]. The cost ofelectricity is about 4 cents/kWh in 2004 US dollars basedon 40,000 MW of worldwide installed capacity and a goodwind site. The lower and higher bound cost estimates ofwave energy are also shown in Fig. 7. The 82% learningcurve is applied to the wave power plant installed costbut not to the operation and maintenance part of cost ofelectricity (hence the reason that the three lines are notparallel).Figure 7. Electrical interconnection of demo-plant: Oregonexample. Source: O. Siddiqui & R. Bedard [30].Fig. 7 shows the cost of wave-generated electricity:low band (bottom curve), upper band (middle curve); andwind-generated electricity (top curve) at equal cumulativeproduction volume under all cost estimating assumptionsfor the wave plant. It shows that the cost of wave-generatedelectricity is less than wind-generated electricity at anyequal cumulative production volume under all cost esti-mating assumptions for the wave plant. The lower capitalcost of a wave machine (compared to a wind machine)more than compensates for the higher O&M cost for theremotely located offshore wave machine. A challenge tothe wave energy industry is to drive down O&M costs tooffer even more economic favourability and to delay thecrossover point shown at greater than 40,000 MW.In summary, the techno-economic forecast made by theProject Team is that wave energy will first become commer-cially competitive with the current 40,000 MW installedland-based wind technology at a cumulative productionvolume of 15,000 MW or less in Hawaii and northern Cali-fornia, about 20,000 MW in Oregon and about 40,000 MWin Massachusetts. This forecast was made on the basis of a300,000 MWh/yr (nominal 90 MW at 38% capacity factor)Pelamis WEC commercial plant design and application oftechnology learning curves. Maine was the only state inthe study whose wave climate was such that wave energymay never be able to economically compete with a goodwind energy site.In addition to economics, there are other compellingarguments for investing in offshore wave energy technology.First, with proper sitting, converting ocean wave energy toelectricity is believed to be one of the most environmentallybenign ways to generate electricity. Second, offshore waveenergy offers a way to minimize the “Not In My Backyard”(NIMBY) issues that plague many energy infrastructure423projects, from nuclear to coal and to wind generation.Because these devices have a very low profile and arelocated at a distance from the shore, they are generally notvisible. Third, because wave energy is more predictablethan solar and wind energy, it offers a better possibilitythan either solar or wind of being dispatch able and earninga capacity payment.A characteristic of wave energy that suggests that itmay be one of the lowest cost renewable energy sources isits high power density. Processes in the ocean concentratesolar and wind energy into ocean waves making it easierand cheaper to harvest. Solar and wind energy sources aremuch more diffuse, by comparison.Since a diversity of energy sources is the bedrock ofa robust electricity system, to overlook wave energy isinconsistent with national needs and goals. Wave energyis an energy source that is too important to overlook.4.2.7 RecommendationsThe development of ocean energy technology and the de-ployment of this clean renewable energy technology wouldbe greatly accelerated by adequate support from govern-ments. Appropriate roles for governments in ocean energydevelopment could include:• Providing leadership for the development of an oceanenergy RD&D programme to fill known RD&D gaps,and to accelerate technology development and proto-type system deployment.• Operating national offshore wave test centers to testperformance and reliability of prototype ocean energysystems under real conditions.• Development of design and testing standards for oceanenergy devices.• Joining the International Energy Agency Ocean En-ergy Systems Implementing Agreement to collaborateRD&D activities, and appropriate ocean energy poli-cies with other governments and organizations.• Studying provision of production tax credits, renew-able energy credits, and other incentives to spur privateinvestment in ocean energy technologies and projects,and implementing appropriate incentives to accelerateocean energy deployment.• Ensuring that the public receives a fair return fromthe use of ocean energy resources.• Ensuring that development rights are allocatedthrough a transparent process that takes into accountstate, local, and public concerns.5. Recent Progress in Offshore Renewable EnergyTechnology DevelopmentThe recent progress in offshore renewable energy technol-ogy development is now examined and potential marketsfor tidal power, WEC, and offshore wind are considered.The analysis of market potentials for offshore renewabletechnology is based solely on currently identified projects.There is therefore scope for increased market prospects,particularly around the end of the period in the wave andtidal current stream sectors.5.1 Tidal Current StreamHistorically, tidal projects have been large-scale barragesystems that block estuaries. Within the last few decades,developers have shifted toward technologies that capturethe tidally driven coastal currents or tidal stream. Thechallenge is, “to develop technology and innovate in a waythat will allow this form of low density renewable energyto become practical and economic” [22].Tidal current turbines are basically underwater wind-mills. The tidal currents are used to rotate an underwa-ter turbine. First proposed during the 1970s’ oil crisis,the technology has only recently become a reality withcommercial prospects.Marine Current Turbines (MCT) installed the firstfull-scale prototype turbine (300 kW) off Lynmouth in De-von, UK in 2003. Shortly thereafter, the Norwegian com-pany Hammerfest Støm installed their first grid-connected300 kW prototype device. MCT, arguably the marketleader is now preparing to install its new twin-rotored1 MW device in 2007. The company has plans to install acommercial scale project off the UK coast around the turnof the decade.There are a great number of sites suitable for tidalcurrent turbines. As tidal currents are predictable andreliable, tidal turbines have advantages over offshore windcounterparts. The ideal sites are generally within severalkilometres of the shore in water depths of 20–30 m.5.1.1 Tidal ForecastsDouglas-Westwood Ltd expect 25 MW of tidal currentstream capacity to be brought online in the 2007–2011period (see Fig. 8). The vast majority of this capacitywill be in the UK where 23 MW is forecast. With severalsuccessful large-scale prototypes already tested, the periodto the end of the decade will see further refinement ofdevices and applications for multiple-unit farms in keymarkets. The above forecast shows a sharp growth in 2011from tidal current farms expected from MCT and LunarEnergy.Figure 8. Potential tidal current stream capacity 2007–2011. Source: Douglas-Westwood Ltd [32].4245.1.2 ProjectsShiswa Lake Tidal Power Plant, Korea Korea has aplentiful tidal and tidal current energy resource. Underconstruction is a single stream style generator at AnsanCity’s Shiswa Lake, which will have a capacity of 252 MW,comprised of 12 units of 21 MW generators. Annual powergeneration, when completed in 2008, is projected at 552million kWh. If successful, this project will surpass LaRance (France) as the largest tidal power plant in theworld. Korea is also planning a tidal current power plantin Uldol-muk Strait, a restriction in the strait where maxi-mum water speed exceeds 6.5 m/s. The experimental plantwill utilize helical or “Gorlov” turbines developed by GCKTechnology [26].Yalu River, China By creating a tidal lagoon off-shore, Tidal Electric has taken a novel approach to resolveenvironmental and economic concerns of tidal barrage tech-nology [27]. Due to the highly predictive nature of theocean tides, the company has developed simulation modelswith performance data from available generators to opti-mize design for particular locations. The recent announce-ment of a cooperative agreement with the Chinese govern-ment for ambitious 300 MW offshore tidal power genera-tion facilities off Yalu River, Liaoning Province allows foran engineering feasibility study to be undertaken.Tidal Electric also has plans under consideration forUK-based projects in Swansea Bay (30 MW), Fifoots Point(930 MW), and North Wales (432 MW). These projectshave failed to make progress and will not go ahead in theforeseeable future.5.2 Wave EnergyThe true potential of wave energy will only be realizedin the offshore environment where large developments areconceivable. Nearly 300 concepts for wave energy deviceshave been proposed. The development process for waveenergy can be looked at in three phases. First, small-scale prototype devices, typically with low capacity, will bedeployed. During the second stage, outside funding fromgovernment or private investors is possible for the mostpromising devices. The final stage is the production offull-scale, grid-connected devices that will in some cases bedeployable in farm style configurations.Modular offshore wave energy devices that can bedeployed quickly and cost effectively in a wide range ofconditions will accelerate commercial wave energy. Inthe coming decade, wave energy will become commerciallysuccessful through multiple-unit offshore projects, the firstof which are now being installed. These projects clearlydemonstrate the commercial future for wave energy butvaluable operational experience is necessary before largerprojects are built with a greater number of devices.The growth of shoreline wave energy devices is limitedby the low number of available sites and high installa-tion costs. Deployment costs for shoreline wave energydevices are very high because they are individual site-specific projects and economies of scale are not applicable.Whereas an offshore 50-MW wave farm is conceivable, andwill in time be developed, no shoreline wave energy con-verter can offer such potential for deployment in this way.As such, individual coastal installations are expected to befew and far between. Shoreline wave energy will, however,continue to be relevant, as the average unit capacity isgenerally higher than existing offshore technology. Indi-vidual devices can be very effective, especially for remoteor island communities where, for example, an individualunit of 4 MW could have a big impact.Offshore locations offer greater power potential thanshoreline locations. Shoreline technologies have the benefitof easy access for maintenance purposes, whereas offshoredevices are in most cases more difficult to access. Improve-ments in reliability and accessibility will be critical to thecommercial success of the many devices currently underdevelopment.5.2.1 Wave Energy ForecastDouglas-Westwood Ltd claim there is a potential 46 MWof wave energy projects that could be installed between2007 and 2011. The United Kingdom is expected to bethe dominant player over the next 5 years, with a fore-cast capacity of 28.6 MW, which equates to a 62% marketshare. In comparison with other countries, the UK hasforecast capacity every year to 2008, whereas installationselsewhere are more intermittent. Norway (6 MW) and Por-tugal (4.25 MW) are the next most significant markets andhave several projected installations, but they lag behindthe UK in terms of technology development and projectdeployment. The United Kingdom government has shownreasonable levels of support, which have injected manytechnologies with valuable grants. The result is a num-ber of proven wave technologies with good prospects forcommercial deployment and several more at an advancedprototype stage. Coupled with a world-class natural re-source, the United Kingdom remains the strongest marketinto the next decade.Potential wave energy capacity 2007–2011 is indicatedin Fig. 9.Figure 9. Potential wave energy capacity 2007–2011.Source: Douglas-Westwood Ltd [32].4255.3 Offshore WindThere are 25 operational offshore wind farms in the worldtoday. The 436 installed turbines in these projects providea total of 919 MW.The first offshore wind turbine was installed at Noger-sund off Sweden in 1990. The first offshore wind farmwere installed at Vindeby off the Danish island of Lol-land in 1991. The most recent project is the BeatriceDemonstration Project off Scotland.The first 10 years of the industry saw small projects be-ing built in very shallow water near-shore locations. Thesewind farms in most cases used onshore turbine models withslight adaptations made. These “demonstration” projectshave paved the way for the more recent projects that areof a much larger size.The biggest offshore wind farm yet installed is theNysted development off Denmark which was completed in2003. Just as this project dwarfs those built 10 yearspreviously, within another decade projects will be installedthat are many times greater in size than today’s offshorewind farms.The industry faces problems from increasing costs. Inthe last 5 years, the cost of offshore wind has increasedby up to 65%. This is caused by increased turbine pricesdriven by the extremely strong onshore wind market (par-ticularly in the US), and rising contractor prices basedupon experiences on earlier projects. Cost reductions ofapproximately 25% are essential to help stimulate the in-dustry and help strengthen it.The total global offshore wind capacity forecast forinstallation between 2007 and 2011 stands at 4.2 GW. TheUK is the world’s largest market for the forthcoming 5-yearperiod. A total of 2.2 GW is forecast here, representing 52%of the entire world market. The UK’s “Round 1” projectsare continuing to be installed at the rate of 1–2 per year.The first of the larger “Round 2” projects are expected toenter construction at the turn of the decade, significantlyboosting the UK’s capacity. The UK’s prospects areexpected almost three times those of Germany, the nextlargest market.Germany has so far seen only minor installations,but the first significant activity is expected to begin in2008 with the Borkum West project. Several projectsare forecast for 2009 and 2010. The bulk of projects,however, will not begin construction until the turn of thedecade. Long-term prospects are excellent off Germanybut in the short and mid-term future the industry hasmuch to overcome.The only activity off Denmark in the period will comewith the construction and completion of the Horns Rev IIand Nysted II projects in 2009 and 2010 respectively. Al-though the country showed initial promise for offshore de-velopment, a lack of government commitment has stuntedthe industry here. Long-term prospects are, however,high and a new round of licences is expected shortly fordevelopment in the next decade.Whilst the Netherlands is currently seeing a period ofactivity with the completion of the Egmond aan Zee projectand construction of Q7-WP, it will not be until after thisdecade that the next projects are completed. Whilst notreflected in the above forecast, long-term prospects aregood.North America is yet to install any offshore windprojects. With the onshore market in such good health,the drivers for offshore are not as strong as in Europe wherethe industry is reaching take-off after a period of slow butsteady growth.There are currently three large offshore wind farms inNorth America in advanced stages of planning althoughit is now unlikely that they will be built this decadedue to delays from drawn-out permitting processes andlegal challenges. In addition to this are a number ofmore speculative large projects and several small scaledemonstration projects that could be installed before theend of the decade.The highest profile project is Cape Wind off the coastof Massachusetts. The proposed 420 MW wind farm hascourted controversy since conception. After clearing anumber of regulatory and legal hurdles over a 6-year period,the project faces a ruling from US federal authorities. TheMinerals Management Service (MMS) took over regulationof offshore renewables in the autumn of 2005. The MMSintend to record a decision on the project in the fall of2008.The 144 MW Long Island offshore wind farm is beingdeveloped by FPL Energy. The MMS is due to recorda decision on the project in spring 2008. The projectstarted after The Long Island Power Authority announcedin January 2003 that it was seeking developers to build anoffshore wind farm off Jones Beach.The largest North American project is the 1,750 MWNaiKun wind farm off the coast of British Columbia whichwill be developed in five phases, the first of which isscheduled for completion in 2011.Cumulative installed offshore wind capacity is given inFig. 10. Forecast offshore capacity 2002–2011 is indicatedin Fig. 11.6. ConclusionsFor the entire marine renewables sector, 4.5 GW of installedcapacity is projected between 2007 and 2011. Some 98%of that capacity is in the form of offshore wind farms. TheFigure 10. Cumulative installed offshore wind capacity.Source: Douglas-Westwood Ltd [32].426Figure 11. Forecast offshore wind capacity 2002–2011.Source: Douglas-Westwood Ltd [32].value of the market over the next 5 years is projected at$17 billion.Wave and tidal power will only be a small percentageof the total expenditure on offshore renewables, of theorder of $300 million in total expenditure between them.However, wave and tidal power currently attract higherexpenditures per megawatt. This indicates higher costs ofthe immature developing industries. These costs will fallas time goes by and the industries progresses. The leadingdevices should be comparable with, and in some cases morecompetitive than offshore wind, by early next decade.The more well-established offshore wind sector willlead the offshore renewables industry, and will see stronggrowth throughout the period led by countries such as theUK, the Netherlands, Germany and Denmark. Establishedonshore wind supply chains in Denmark and Germany will,however, see most of the financial benefit of the growthin offshore wind for the short-term. The dominance ofoffshore wind does not mean wave and tidal energy arenot important, they are just less well developed, and theindustry is much younger. From around 2010, wave andtidal should begin to expand commercially. The growth ofwave and tidal power offers significant supply chain growthopportunities for countries that failed to capture the valueof the growth in the wind industry (both onshore andoffshore).Europe is the dominant region, leading in all threesectors. The UK is a particularly important market, drivenby a world-class natural resource, the past 3 years has seennotable successes in wind, wave and tidal energies. Withmore approved offshore wind capacity in the planning stagethan any other country, prospects for the United Kingdomlook bright. The UK is forecast to become world leader inoffshore wind in 2008 and is already the leader in the waveand tidal current stream industries. The UK Energy WhitePaper due May 2007 is expected to increase banding to themain support system for renewables to give greater supportto emerging technologies, particularly offshore renewables.This should provide a strong catalyst for growth.Whilst currently lacking, future growth in other re-gions should not be discounted in the long term. Interestin North America is growing and we will see large projectsprogressing around the end of the decade, particularly inthe offshore wind sector. Greater support and structurewould reap big rewards for the industry here. At presentthough, it lags far behind the established European marketwhich remains the focal point for the marine renewablesindustry. Europe is home to the leading technology de-velopers and superior funding packages are in place in keycountries to stimulate development.AcknowledgementsThe author acknowledges contributions made by PeterO’Donnell (Senior Energy Specialist, Manager GenerationSolar & Renewables Programs, San Francisco EnvironmentOrganization, CA, USA); Omar Siddiqui (Senior Associate,Global Energy Partners LLC, Lafayette, CA, USA); RogerBedard (Offshore Wave Energy Project Manager, EPRI,CA, USA), Andrew Mill (Managing Director EuropeanMarine Energy Centre, UK); Mirko Previsic (Consultant—Offshore Renewables, Sacramento, CA, USA); Anthony TJones (Senior Oceanographer, oceanUS consulting, PalmSprings, CA, USA); and Adam Westwood (RenewableEnergy Manager, Douglas-Westwood Limited, Canterbury,UK, principally for Section 5).References[1] T.J. Hammons, Tidal Power, Proceedings IEEE, 81(3), 1993,419–433.[2] B.V. Davis, A major source of energy from the world’s oceans,IECEC-97 Intersociety Energy Conversion Engineering Con-ference, 1997.[3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Tur-bine for (Canadian) Ministry of Employment and Investment,N.H. Halvorson Consultants Ltd.[4] Renewable Energy: Power for a Sustainable Future; TechnologyUpdate, Tidal Current Power Update & Wave Power Update,Oxford University Press, 2001.[5] P. Fraenkel, Renewables is the tide turning for marine currentturbines? Modern Power System, Marine Current TurbinesLtd, London, UK, June 30, 2001.[6] R. Bedard, Final summary report: offshore wave power feasi-bility demonstration project (E2I EPRI Global WP009 – US,2005).[7] M. Previsic, System level design, performance and costs forSan Francisco Pelamis offshore wave power plant (E2I EPRIGlobal – 006A – SF, 2004).[8] G. Hagerman, Offshore Wave Power in the US: EnvironmentalIssues (E2I Global EPRI – 007 – US, 2004).[9] B. Ram, Wave Power in the US: Permitting and JurisdictionalIssues (E2I Global EPRI DOE NREL – 008 – US).[10] M. Previsic, Wave power technologies, Proc. IEEE PES 05 GM,San Francisco, paper 05GM0542, June 2005, 1–6.[11] E2i/EPRI WP-004-US Rev 1 Assessment of Offshore WaveEnergy Conversion Devices.[12] E2i/EPRI WP-005-US Methodology, Guidelines and Assump-tions for the Conceptual Design of Offshore Wave EnergyPower Plants (Farms). [13] E2i/EPRI WP-006-HI System Level Design, Preliminary Per-formance and Cost Estimate – Hawaii. [14] E2i EPRI WP-006-OR System Level Design, Preliminary Per-formance and Cost Estimate – Oregon. [15] E2i/EPRI WP-006-ME System Level Design, Preliminary Per-formance and Cost Estimate – Maine. [16] E2i/EPRI WP-006-MA System Level Design, Preliminary Per-formance and Cost Estimate – Massachusetts. [18].Further, the state of the art for WEC is reviewed in Refer-ence [19], and a technical assessment guide for ocean wavepower is made in Reference [20]. A wave energy resourceassessment for California is given in Reference [21].Most of the EPRI Wave Power (WP) Reports [11,13–18] are available on their website (www.epri.com).4. Feasibility Assessment of Offshore Wave andTidal Current Power Production: A Collabora-tive Public/Private PartnershipCollaborative power production feasibility definition stud-ies on offshore wave energy and tidal current energy onbehalf of a number of public and private entities is beingundertaken at this time (February 2005). The outcome ofthe offshore wave study, which began in 2004 under theEPRI, is a compelling techno-economic case for investingin the RD&D of technology to convert the kinetic energyof ocean waves into electricity. The tidal current studiesbegan in early 2005 and are currently at the site identifica-tion and device assessment stage. Techno-economic resultsfor tidal plant designs at various sites were made in late2005.EPRI Wave Power Reports [11, 13–18] and References[22–29] summarize the activities in this area.4.1 Feasibility of Wave and Tidal Current EnergyThe elements of a wave and tidal current energy feasi-bility study are: (a) identify and characterize potentialsites for assembling and deploying a power plant and forconnecting the plant to the electric grid; (b) identify andassess WEC devices; (c) conduct a conceptual design of ademonstration- and commercial-scale offshore wave powerplant and, based on performance and cost estimates, assessthe techno-economic viability of the wave energy sourceand the energy conversion technology; and (d) identify andassess the environmental and regulatory issues associatedwith implementing the technology.Two characteristics of waves and tides important to thegeneration and dispatch of electricity from WEC devicesare its variability and predictability. While the ocean isnever totally calm, wave power is more continuous thanthe winds that generate it. The average power during thewinter may be six times that obtained during the summer;however, power values may vary by a factor of a hundredwith the random occurrences of storms. Therefore, thepower of waves is highly variable. The predictability ofwave energy is of the order of a few days. The wavesresulting, for example, from storms that occur off the coastof Japan, will take that long to reach the northwest coastof the United States. The power from tidal currents, on theother hand, typically varies according to a diurnal cycle.The major benefit of tidal power is its high predictabilityfor a given site years in advance, provided there is athorough knowledge of the site. A drawback of tidal poweris its low capacity factor, and that its peak availabilitymisses peak demand times because of the 12.5 h cycle ofthe tides.Ocean waves are generated by the winds that resultfrom uneven heating around the globe. Waves are formedby winds blowing over the water surface, which makethe water particles adopt circular motions as depicted inFig. 2. This motion carries kinetic energy, the amountFigure 2. Wave-generating forces based on wind–waterinteraction. Source: M. Previsic [10].419of which is determined by the speed and duration of thewind, the length of sea it blows over, the water depth, seabed conditions and also interactions with the tides. Wavesoccur only in the volume of water closest to the watersurface, whereas in tides, the entire water body moves,from the surface to the seabed.The tides are generated by rotation of the earth withinthe gravitational fields of the moon and sun [1]. Therelative motion of these bodies causes the surface on theoceans to be raised and lowered periodically, as illustratedin Fig. 3. The physics of tidal power is explained inReference [1].Figure 3. Tide-generating forces based on earth–moon in-teractions. Source: O. Siddiqui & R. Bedard [30].In deep water, the wave power spatial flux (in kW/mof wave front crest) is given by significant wave height (Hsin m) and the peak wave period (Tp in s). Based on thesetwo parameters, the incident wave power (J in kW/m ofwave crest length) associated with each sea state record isestimated by the following equation:J = 0.42 × (Hs)2× Tp (kW)It is significant to note that wave power varies withthe square of wave height – that is, a wave whose height isdoubled generates four times as much power.The power of a tidal current is given by the followingequation:Pwater = (1/2) rAV 3(W)where A is the cross-sectional area of flow intercepted bythe turbine device (m2), r is the water density (kg/m3)and V is current velocity speed (m/s). The current ve-locity V varies in a precisely predictable manner as anadditive function of period of the different sinusoidal tidalcomponents.Tidal flow energy studies are in progress at EPRI andthe techno-economic results are not available. Therefore,the focus is on the results of the wave energy feasibilitydefinition study of 2004.4.2 Wave Project Results4.2.1 US Wave Energy ResourcesAn ideal site to deploy, operate and maintain an offshorewave energy power plant must have many attributes. Firstand foremost is a sufficient native energy and energy spec-tra potential.1The US regional wave regimes and the totalannual incident wave energy for each of these regimes areshown in Fig. 4. The total US available incident waveenergy flux is about 2,300 TWh/yr. The DOE EnergyInformation Energy (EIA) estimated in 2003 hydroelectricgeneration in USA to be about 270 TWh which is a lit-tle more than a tenth of the yearly offshore wave energyflux into the US. Therefore, wave energy is a significantresource.Figure 4. US energy resources. Source: O. Siddiqui &R. Bedard [30].4.2.2 Feasibility Definition Study SitesSite attributes characterized by the Project Team includedoffshore bathymetry2and seafloor surface geology, robust-ness of the coastal utility grid, regional maritime infras-tructure for both fabrication and maintenance, conflictswith competing uses of sea space and existence of otherunique characteristics that might minimize project devel-opment costs (e.g. existing ocean outfall easements forrouting power cable and shore crossing).Table 2 identifies the site selected in each of the fivestates that participated in the study, and also provides afew key characteristics of each selected site.4.2.3 Feasibility Study: WEC DevicesTwelve companies responded to EPRI’s request for infor-mation. An initial screening considered two key issues: (1)technology readiness (i.e. readiness of device for demon-stration in the 2006 time period) and (2) survivability inadverse conditions (i.e. sufficiency of technical informationprovided by the device manufacturer to prove the surviv-ability in storm conditions). The eight devices that passedthe initial screening criteria are shown in Table 3.1 Energy as function of wave height and wave period or frequency.2 Bathymetry is the depth of the seafloor below mean waterheight (i.e. the inverse of a topographic map).420Table 2Estimated Performance of Pilot Demonstration PlantsHI OR CA Mass MaineCounty Oahu Douglas SF Cape Cod CumberlandGrid I/C Waimanalo Gardner Wastewater Well OldBeach Plant Fleet OrchardBeach S/SAverage 15.2 21.2 11.2113.8 4.9Annual J(kW/m)Depth (m) 60 60 30 60 60Distance 2 3.5 13 9 9from ShoreCable Makai IPP Outflow Water Dir Drill Dir DrillLanding Pier Pipe Outflow1Sited within the marine sanctuary exclusionary zone.Source: O. Siddiqui & R. Bedard [30].Table 3Estimated Performance of Pilot Demonstration PlantsLength (m) Width (m) Power (kW)1Type RatingOcean 120 4.6 153 Floating 1Power AttenuatorDeliveryEnergetech 25 35 259 OWC – Bottom 2TerminatorWave 150 260 1,369 Floating 2Dragon OvertoppingWave 9.5 9.5 351 Bottom Point 2Swing AbsorberWave Bob 16 15 131 Floating Point 3AbsorberAqua-Energy 6 6 17 Floating Point 3AbsorberOreCON 32 32 532 Floating OWC 3Ind Natural 5.4 5.4 112 Bottom Point 3Resources Inc Absorber1Based on Oregon average annual wave energy resource.Source: O. Siddiqui & R. Bedard [30].These eight devices were then assessed with the ob-jective of determining any critical issues and recommend-ing RD&D needed to achieve technological readiness foran at sea demonstration. As a result of this assessment,the eight devices were grouped into one of three levels ofdevelopment categories:• Level 1 : Development complete and full-scale testingin the ocean underway.• Level 2 : Development near complete. Only deploy-ment, recovery and mooring issues are yet to be val-idated. There are funded plans for full-scale at seatesting.• Level 3 : Most critical RD&D issues are resolved. Ad-ditional laboratory and sub-scale testing, simulationsand systems integration work is needed prior to final-ization of the full-scale design. There are no funded421plans for full-scale at sea testing.At the time of EPRI’s analysis (March 2004), onlyone WEC device manufacturer had attained a Level 1technology readiness status – OPD with its Pelamis device.At the time of this paper (February 2005) there are anadditional four WEC device manufacturers that are close toreaching that status: TeamWorks of the Netherlands withits Wave Swing, Energetechs of Australia with its OWC,Wave Dragon of Denmark with its overtopping device, andOcean Power Technology of the US with a floating buoy.4.2.4 Demonstration-Scale Plant Design: OregonExampleDemonstration-scale (as well as commercial-scale) designswere based on the OPD Pelamis WEC device for the fivesites listed in Table 2. The Pelamis WEC device consistsof four cylindrical steel sections, which are connected bythree hydraulic PCM. Total length of the device is 120 mand device diameter is 4.6 m. Fig. 5 shows the device beingtested off the Scottish coast.Figure 5. OPD Pelamis WEC device. 1 nm = 1 nauticalmile. Source: O. Siddiqui & R. Bedard [30].A second San Francisco, CA design based on theEnergetech OWC WEC device depicted in Fig. 6 was alsotested.Figure 6. Energetech WEC device. Source: O. Siddiqui &R. Bedard [30].The estimated performance of the single unit demon-stration plant at each of the five sites is shown in Table 4.Table 4Estimated Performance of Pelamis Pilot DemonstrationPlantsHI OR CA1Mass MaineDevice Rated 750 750 750 750 750Capacity (kW)Annual 1,989 1,472 1,229 1,268 426Energy Absorbed(MWh/yr)Annual Energy 1,663 1,001 835 964 290Produced(MWh/yr)Average 180 114 95 98 33ElectricalPower (kW)Number of 180 114 95 98 33Homes Poweredby Plant1Energetech site numbers: 1,000 kW, 1,643 MWh/yr, 1,264 MWh/yr,and 144 kW respectively.Source: O. Siddiqui & R. Bedard [30].4.2.5 Commercial-Scale Plant Design: Oregon Exam-pleThe commercial system uses a total of 4 clusters, each onecontaining 45 Pelamis units (i.e. 180 total Pelamis WECdevices), connected to sub-sea cables. Each cluster consistsof 3 rows with 15 devices per row. The other state designsare organized in a similar manner with 4 clusters. Thenumber of devices per cluster varies such that each plantproduces an annual energy output of 300,000 MWh/yr.The electrical interconnection of the devices is accom-plished with flexible jumper cables, connecting the units inmid-water. The introduction of 4 independent sub-sea ca-bles and the interconnection on the surface provides someredundancy in the wave farm arrangement.The estimated performance of the commercial-scaleplant at each of the five sites is shown in Table 5.The device rated capacity has been derated from750 kW in the demonstration plant to 500 kW for the com-mercial plant. The performance assessment of the demon-stration plants shows that the PCMs are overrated andreducing the rated power to 500 kW per device would yielda significant cost reduction and only a relatively small de-crease in annual output (attributed to the fact that the USsites have a lower energy level than UK sites for which thedevice was originally developed).4.2.6 Learning Curves and EconomicsThe costs and cost of electricity shown in the previous sec-tion are for the first commercial-scale wave plant. Learn-ing through production experience reduces costs – a phe-nomenon that follows a logarithmic relationship such that422Table 5Estimated Performance of Pelamis Commercial PlantsHI OR CA Mass MaineDevice Rated 500 500 500 500 500Capacity (kW)Annual Energy 1,989 1,997 1,683 1,738 584Absorbed (MWh/yr)Annual Energy 1,663 1,669 1,407 1,453 488Produced (MWh/yr)Average Electrical 191 191 161 166 56Power at Busbar (kW)Number of OPD 180 180 213 206 615Pelamis UnitsNeeded for300,000 MWh/yrNumber of Homes 34,000 34,000 34,000 34,000 34,000Powered by PlantSource: O. Siddiqui & R. Bedard [30].for every doubling of the cumulative production volume,there is a specific percentage drop in production costs.The specific percentage used in this study was 82%, whichis consistent with documented experience in the wind en-ergy, photovoltaic, shipbuilding, and offshore oil and gasindustries.The industry-documented historical wind energy learn-ing curve is shown as the top line in Fig. 7 [31]. The cost ofelectricity is about 4 cents/kWh in 2004 US dollars basedon 40,000 MW of worldwide installed capacity and a goodwind site. The lower and higher bound cost estimates ofwave energy are also shown in Fig. 7. The 82% learningcurve is applied to the wave power plant installed costbut not to the operation and maintenance part of cost ofelectricity (hence the reason that the three lines are notparallel).Figure 7. Electrical interconnection of demo-plant: Oregonexample. Source: O. Siddiqui & R. Bedard [30].Fig. 7 shows the cost of wave-generated electricity:low band (bottom curve), upper band (middle curve); andwind-generated electricity (top curve) at equal cumulativeproduction volume under all cost estimating assumptionsfor the wave plant. It shows that the cost of wave-generatedelectricity is less than wind-generated electricity at anyequal cumulative production volume under all cost esti-mating assumptions for the wave plant. The lower capitalcost of a wave machine (compared to a wind machine)more than compensates for the higher O&M cost for theremotely located offshore wave machine. A challenge tothe wave energy industry is to drive down O&M costs tooffer even more economic favourability and to delay thecrossover point shown at greater than 40,000 MW.In summary, the techno-economic forecast made by theProject Team is that wave energy will first become commer-cially competitive with the current 40,000 MW installedland-based wind technology at a cumulative productionvolume of 15,000 MW or less in Hawaii and northern Cali-fornia, about 20,000 MW in Oregon and about 40,000 MWin Massachusetts. This forecast was made on the basis of a300,000 MWh/yr (nominal 90 MW at 38% capacity factor)Pelamis WEC commercial plant design and application oftechnology learning curves. Maine was the only state inthe study whose wave climate was such that wave energymay never be able to economically compete with a goodwind energy site.In addition to economics, there are other compellingarguments for investing in offshore wave energy technology.First, with proper sitting, converting ocean wave energy toelectricity is believed to be one of the most environmentallybenign ways to generate electricity. Second, offshore waveenergy offers a way to minimize the “Not In My Backyard”(NIMBY) issues that plague many energy infrastructure423projects, from nuclear to coal and to wind generation.Because these devices have a very low profile and arelocated at a distance from the shore, they are generally notvisible. Third, because wave energy is more predictablethan solar and wind energy, it offers a better possibilitythan either solar or wind of being dispatch able and earninga capacity payment.A characteristic of wave energy that suggests that itmay be one of the lowest cost renewable energy sources isits high power density. Processes in the ocean concentratesolar and wind energy into ocean waves making it easierand cheaper to harvest. Solar and wind energy sources aremuch more diffuse, by comparison.Since a diversity of energy sources is the bedrock ofa robust electricity system, to overlook wave energy isinconsistent with national needs and goals. Wave energyis an energy source that is too important to overlook.4.2.7 RecommendationsThe development of ocean energy technology and the de-ployment of this clean renewable energy technology wouldbe greatly accelerated by adequate support from govern-ments. Appropriate roles for governments in ocean energydevelopment could include:• Providing leadership for the development of an oceanenergy RD&D programme to fill known RD&D gaps,and to accelerate technology development and proto-type system deployment.• Operating national offshore wave test centers to testperformance and reliability of prototype ocean energysystems under real conditions.• Development of design and testing standards for oceanenergy devices.• Joining the International Energy Agency Ocean En-ergy Systems Implementing Agreement to collaborateRD&D activities, and appropriate ocean energy poli-cies with other governments and organizations.• Studying provision of production tax credits, renew-able energy credits, and other incentives to spur privateinvestment in ocean energy technologies and projects,and implementing appropriate incentives to accelerateocean energy deployment.• Ensuring that the public receives a fair return fromthe use of ocean energy resources.• Ensuring that development rights are allocatedthrough a transparent process that takes into accountstate, local, and public concerns.5. Recent Progress in Offshore Renewable EnergyTechnology DevelopmentThe recent progress in offshore renewable energy technol-ogy development is now examined and potential marketsfor tidal power, WEC, and offshore wind are considered.The analysis of market potentials for offshore renewabletechnology is based solely on currently identified projects.There is therefore scope for increased market prospects,particularly around the end of the period in the wave andtidal current stream sectors.5.1 Tidal Current StreamHistorically, tidal projects have been large-scale barragesystems that block estuaries. Within the last few decades,developers have shifted toward technologies that capturethe tidally driven coastal currents or tidal stream. Thechallenge is, “to develop technology and innovate in a waythat will allow this form of low density renewable energyto become practical and economic” [22].Tidal current turbines are basically underwater wind-mills. The tidal currents are used to rotate an underwa-ter turbine. First proposed during the 1970s’ oil crisis,the technology has only recently become a reality withcommercial prospects.Marine Current Turbines (MCT) installed the firstfull-scale prototype turbine (300 kW) off Lynmouth in De-von, UK in 2003. Shortly thereafter, the Norwegian com-pany Hammerfest Støm installed their first grid-connected300 kW prototype device. MCT, arguably the marketleader is now preparing to install its new twin-rotored1 MW device in 2007. The company has plans to install acommercial scale project off the UK coast around the turnof the decade.There are a great number of sites suitable for tidalcurrent turbines. As tidal currents are predictable andreliable, tidal turbines have advantages over offshore windcounterparts. The ideal sites are generally within severalkilometres of the shore in water depths of 20–30 m.5.1.1 Tidal ForecastsDouglas-Westwood Ltd expect 25 MW of tidal currentstream capacity to be brought online in the 2007–2011period (see Fig. 8). The vast majority of this capacitywill be in the UK where 23 MW is forecast. With severalsuccessful large-scale prototypes already tested, the periodto the end of the decade will see further refinement ofdevices and applications for multiple-unit farms in keymarkets. The above forecast shows a sharp growth in 2011from tidal current farms expected from MCT and LunarEnergy.Figure 8. Potential tidal current stream capacity 2007–2011. Source: Douglas-Westwood Ltd [32].4245.1.2 ProjectsShiswa Lake Tidal Power Plant, Korea Korea has aplentiful tidal and tidal current energy resource. Underconstruction is a single stream style generator at AnsanCity’s Shiswa Lake, which will have a capacity of 252 MW,comprised of 12 units of 21 MW generators. Annual powergeneration, when completed in 2008, is projected at 552million kWh. If successful, this project will surpass LaRance (France) as the largest tidal power plant in theworld. Korea is also planning a tidal current power plantin Uldol-muk Strait, a restriction in the strait where maxi-mum water speed exceeds 6.5 m/s. The experimental plantwill utilize helical or “Gorlov” turbines developed by GCKTechnology [26].Yalu River, China By creating a tidal lagoon off-shore, Tidal Electric has taken a novel approach to resolveenvironmental and economic concerns of tidal barrage tech-nology [27]. Due to the highly predictive nature of theocean tides, the company has developed simulation modelswith performance data from available generators to opti-mize design for particular locations. The recent announce-ment of a cooperative agreement with the Chinese govern-ment for ambitious 300 MW offshore tidal power genera-tion facilities off Yalu River, Liaoning Province allows foran engineering feasibility study to be undertaken.Tidal Electric also has plans under consideration forUK-based projects in Swansea Bay (30 MW), Fifoots Point(930 MW), and North Wales (432 MW). These projectshave failed to make progress and will not go ahead in theforeseeable future.5.2 Wave EnergyThe true potential of wave energy will only be realizedin the offshore environment where large developments areconceivable. Nearly 300 concepts for wave energy deviceshave been proposed. The development process for waveenergy can be looked at in three phases. First, small-scale prototype devices, typically with low capacity, will bedeployed. During the second stage, outside funding fromgovernment or private investors is possible for the mostpromising devices. The final stage is the production offull-scale, grid-connected devices that will in some cases bedeployable in farm style configurations.Modular offshore wave energy devices that can bedeployed quickly and cost effectively in a wide range ofconditions will accelerate commercial wave energy. Inthe coming decade, wave energy will become commerciallysuccessful through multiple-unit offshore projects, the firstof which are now being installed. These projects clearlydemonstrate the commercial future for wave energy butvaluable operational experience is necessary before largerprojects are built with a greater number of devices.The growth of shoreline wave energy devices is limitedby the low number of available sites and high installa-tion costs. Deployment costs for shoreline wave energydevices are very high because they are individual site-specific projects and economies of scale are not applicable.Whereas an offshore 50-MW wave farm is conceivable, andwill in time be developed, no shoreline wave energy con-verter can offer such potential for deployment in this way.As such, individual coastal installations are expected to befew and far between. Shoreline wave energy will, however,continue to be relevant, as the average unit capacity isgenerally higher than existing offshore technology. Indi-vidual devices can be very effective, especially for remoteor island communities where, for example, an individualunit of 4 MW could have a big impact.Offshore locations offer greater power potential thanshoreline locations. Shoreline technologies have the benefitof easy access for maintenance purposes, whereas offshoredevices are in most cases more difficult to access. Improve-ments in reliability and accessibility will be critical to thecommercial success of the many devices currently underdevelopment.5.2.1 Wave Energy ForecastDouglas-Westwood Ltd claim there is a potential 46 MWof wave energy projects that could be installed between2007 and 2011. The United Kingdom is expected to bethe dominant player over the next 5 years, with a fore-cast capacity of 28.6 MW, which equates to a 62% marketshare. In comparison with other countries, the UK hasforecast capacity every year to 2008, whereas installationselsewhere are more intermittent. Norway (6 MW) and Por-tugal (4.25 MW) are the next most significant markets andhave several projected installations, but they lag behindthe UK in terms of technology development and projectdeployment. The United Kingdom government has shownreasonable levels of support, which have injected manytechnologies with valuable grants. The result is a num-ber of proven wave technologies with good prospects forcommercial deployment and several more at an advancedprototype stage. Coupled with a world-class natural re-source, the United Kingdom remains the strongest marketinto the next decade.Potential wave energy capacity 2007–2011 is indicatedin Fig. 9.Figure 9. Potential wave energy capacity 2007–2011.Source: Douglas-Westwood Ltd [32].4255.3 Offshore WindThere are 25 operational offshore wind farms in the worldtoday. The 436 installed turbines in these projects providea total of 919 MW.The first offshore wind turbine was installed at Noger-sund off Sweden in 1990. The first offshore wind farmwere installed at Vindeby off the Danish island of Lol-land in 1991. The most recent project is the BeatriceDemonstration Project off Scotland.The first 10 years of the industry saw small projects be-ing built in very shallow water near-shore locations. Thesewind farms in most cases used onshore turbine models withslight adaptations made. These “demonstration” projectshave paved the way for the more recent projects that areof a much larger size.The biggest offshore wind farm yet installed is theNysted development off Denmark which was completed in2003. Just as this project dwarfs those built 10 yearspreviously, within another decade projects will be installedthat are many times greater in size than today’s offshorewind farms.The industry faces problems from increasing costs. Inthe last 5 years, the cost of offshore wind has increasedby up to 65%. This is caused by increased turbine pricesdriven by the extremely strong onshore wind market (par-ticularly in the US), and rising contractor prices basedupon experiences on earlier projects. Cost reductions ofapproximately 25% are essential to help stimulate the in-dustry and help strengthen it.The total global offshore wind capacity forecast forinstallation between 2007 and 2011 stands at 4.2 GW. TheUK is the world’s largest market for the forthcoming 5-yearperiod. A total of 2.2 GW is forecast here, representing 52%of the entire world market. The UK’s “Round 1” projectsare continuing to be installed at the rate of 1–2 per year.The first of the larger “Round 2” projects are expected toenter construction at the turn of the decade, significantlyboosting the UK’s capacity. The UK’s prospects areexpected almost three times those of Germany, the nextlargest market.Germany has so far seen only minor installations,but the first significant activity is expected to begin in2008 with the Borkum West project. Several projectsare forecast for 2009 and 2010. The bulk of projects,however, will not begin construction until the turn of thedecade. Long-term prospects are excellent off Germanybut in the short and mid-term future the industry hasmuch to overcome.The only activity off Denmark in the period will comewith the construction and completion of the Horns Rev IIand Nysted II projects in 2009 and 2010 respectively. Al-though the country showed initial promise for offshore de-velopment, a lack of government commitment has stuntedthe industry here. Long-term prospects are, however,high and a new round of licences is expected shortly fordevelopment in the next decade.Whilst the Netherlands is currently seeing a period ofactivity with the completion of the Egmond aan Zee projectand construction of Q7-WP, it will not be until after thisdecade that the next projects are completed. Whilst notreflected in the above forecast, long-term prospects aregood.North America is yet to install any offshore windprojects. With the onshore market in such good health,the drivers for offshore are not as strong as in Europe wherethe industry is reaching take-off after a period of slow butsteady growth.There are currently three large offshore wind farms inNorth America in advanced stages of planning althoughit is now unlikely that they will be built this decadedue to delays from drawn-out permitting processes andlegal challenges. In addition to this are a number ofmore speculative large projects and several small scaledemonstration projects that could be installed before theend of the decade.The highest profile project is Cape Wind off the coastof Massachusetts. The proposed 420 MW wind farm hascourted controversy since conception. After clearing anumber of regulatory and legal hurdles over a 6-year period,the project faces a ruling from US federal authorities. TheMinerals Management Service (MMS) took over regulationof offshore renewables in the autumn of 2005. The MMSintend to record a decision on the project in the fall of2008.The 144 MW Long Island offshore wind farm is beingdeveloped by FPL Energy. The MMS is due to recorda decision on the project in spring 2008. The projectstarted after The Long Island Power Authority announcedin January 2003 that it was seeking developers to build anoffshore wind farm off Jones Beach.The largest North American project is the 1,750 MWNaiKun wind farm off the coast of British Columbia whichwill be developed in five phases, the first of which isscheduled for completion in 2011.Cumulative installed offshore wind capacity is given inFig. 10. Forecast offshore capacity 2002–2011 is indicatedin Fig. 11.6. ConclusionsFor the entire marine renewables sector, 4.5 GW of installedcapacity is projected between 2007 and 2011. Some 98%of that capacity is in the form of offshore wind farms. TheFigure 10. Cumulative installed offshore wind capacity.Source: Douglas-Westwood Ltd [32].426Figure 11. Forecast offshore wind capacity 2002–2011.Source: Douglas-Westwood Ltd [32].value of the market over the next 5 years is projected at$17 billion.Wave and tidal power will only be a small percentageof the total expenditure on offshore renewables, of theorder of $300 million in total expenditure between them.However, wave and tidal power currently attract higherexpenditures per megawatt. This indicates higher costs ofthe immature developing industries. These costs will fallas time goes by and the industries progresses. The leadingdevices should be comparable with, and in some cases morecompetitive than offshore wind, by early next decade.The more well-established offshore wind sector willlead the offshore renewables industry, and will see stronggrowth throughout the period led by countries such as theUK, the Netherlands, Germany and Denmark. Establishedonshore wind supply chains in Denmark and Germany will,however, see most of the financial benefit of the growthin offshore wind for the short-term. The dominance ofoffshore wind does not mean wave and tidal energy arenot important, they are just less well developed, and theindustry is much younger. From around 2010, wave andtidal should begin to expand commercially. The growth ofwave and tidal power offers significant supply chain growthopportunities for countries that failed to capture the valueof the growth in the wind industry (both onshore andoffshore).Europe is the dominant region, leading in all threesectors. The UK is a particularly important market, drivenby a world-class natural resource, the past 3 years has seennotable successes in wind, wave and tidal energies. Withmore approved offshore wind capacity in the planning stagethan any other country, prospects for the United Kingdomlook bright. The UK is forecast to become world leader inoffshore wind in 2008 and is already the leader in the waveand tidal current stream industries. The UK Energy WhitePaper due May 2007 is expected to increase banding to themain support system for renewables to give greater supportto emerging technologies, particularly offshore renewables.This should provide a strong catalyst for growth.Whilst currently lacking, future growth in other re-gions should not be discounted in the long term. Interestin North America is growing and we will see large projectsprogressing around the end of the decade, particularly inthe offshore wind sector. Greater support and structurewould reap big rewards for the industry here. At presentthough, it lags far behind the established European marketwhich remains the focal point for the marine renewablesindustry. Europe is home to the leading technology de-velopers and superior funding packages are in place in keycountries to stimulate development.AcknowledgementsThe author acknowledges contributions made by PeterO’Donnell (Senior Energy Specialist, Manager GenerationSolar & Renewables Programs, San Francisco EnvironmentOrganization, CA, USA); Omar Siddiqui (Senior Associate,Global Energy Partners LLC, Lafayette, CA, USA); RogerBedard (Offshore Wave Energy Project Manager, EPRI,CA, USA), Andrew Mill (Managing Director EuropeanMarine Energy Centre, UK); Mirko Previsic (Consultant—Offshore Renewables, Sacramento, CA, USA); Anthony TJones (Senior Oceanographer, oceanUS consulting, PalmSprings, CA, USA); and Adam Westwood (RenewableEnergy Manager, Douglas-Westwood Limited, Canterbury,UK, principally for Section 5).References[1] T.J. Hammons, Tidal Power, Proceedings IEEE, 81(3), 1993,419–433.[2] B.V. Davis, A major source of energy from the world’s oceans,IECEC-97 Intersociety Energy Conversion Engineering Con-ference, 1997.[3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Tur-bine for (Canadian) Ministry of Employment and Investment,N.H. Halvorson Consultants Ltd.[4] Renewable Energy: Power for a Sustainable Future; TechnologyUpdate, Tidal Current Power Update & Wave Power Update,Oxford University Press, 2001.[5] P. Fraenkel, Renewables is the tide turning for marine currentturbines? Modern Power System, Marine Current TurbinesLtd, London, UK, June 30, 2001.[6] R. Bedard, Final summary report: offshore wave power feasi-bility demonstration project (E2I EPRI Global WP009 – US,2005).[7] M. Previsic, System level design, performance and costs forSan Francisco Pelamis offshore wave power plant (E2I EPRIGlobal – 006A – SF, 2004).[8] G. Hagerman, Offshore Wave Power in the US: EnvironmentalIssues (E2I Global EPRI – 007 – US, 2004).[9] B. Ram, Wave Power in the US: Permitting and JurisdictionalIssues (E2I Global EPRI DOE NREL – 008 – US).[10] M. Previsic, Wave power technologies, Proc. IEEE PES 05 GM,San Francisco, paper 05GM0542, June 2005, 1–6.[11] E2i/EPRI WP-004-US Rev 1 Assessment of Offshore WaveEnergy Conversion Devices.[12] E2i/EPRI WP-005-US Methodology, Guidelines and Assump-tions for the Conceptual Design of Offshore Wave EnergyPower Plants (Farms).[13] E2i/EPRI WP-006-HI System Level Design, Preliminary Per-formance and Cost Estimate – Hawaii.[14] E2i EPRI WP-006-OR System Level Design, Preliminary Per-formance and Cost Estimate – Oregon.[15] E2i/EPRI WP-006-ME System Level Design, Preliminary Per-formance and Cost Estimate – Maine.[16] E2i/EPRI WP-006-MA System Level Design, Preliminary Per-formance and Cost Estimate – Massachusetts.[17] E2i/EPRI WP-006-SFa System Level Design, PreliminaryPerformance and Cost Estimate – San Francisco, CaliforniaPelamis Offshore Wave Power Plant.427[18] E2i/EPRI WP-006-SFb System Level Design, PreliminaryPerformance and Cost Estimate – San Francisco EnergetechOffshore Wave Power Plant.[19] Sea Technology Magazine August 2003, Wave Energy Conver-sion – The State of the Art.[20] EPRI – RE Technical Assessment Guide Ocean Wave PowerSection for the years 2001, 2002 and 2003.[21] California Energy Commission – Wave Energy Resource As-sessment for the State of California.[22] A.D. Trapp & M. Watchorn, EB development of tidal streamenergy, Proc. MAREC 2001, 2001, 169–173. [23] A.T. Jones & A. Westwood, Economic forecast for renewableocean energy technologies, presented at EnergyOcean 2004,Palm Beach, Florida, 2004. [24] A.T. Jones & W. Rowley, Global perspective: Economicforecast for renewable ocean energy technologies, MTS Journal,36(4), 2002, 85–90. [26].Yalu River, China By creating a tidal lagoon off-shore, Tidal Electric has taken a novel approach to resolveenvironmental and economic concerns of tidal barrage tech-nology [27]. Due to the highly predictive nature of theocean tides, the company has developed simulation modelswith performance data from available generators to opti-mize design for particular locations. The recent announce-ment of a cooperative agreement with the Chinese govern-ment for ambitious 300 MW offshore tidal power genera-tion facilities off Yalu River, Liaoning Province allows foran engineering feasibility study to be undertaken.Tidal Electric also has plans under consideration forUK-based projects in Swansea Bay (30 MW), Fifoots Point(930 MW), and North Wales (432 MW). These projectshave failed to make progress and will not go ahead in theforeseeable future.5.2 Wave EnergyThe true potential of wave energy will only be realizedin the offshore environment where large developments areconceivable. Nearly 300 concepts for wave energy deviceshave been proposed. The development process for waveenergy can be looked at in three phases. First, small-scale prototype devices, typically with low capacity, will bedeployed. During the second stage, outside funding fromgovernment or private investors is possible for the mostpromising devices. The final stage is the production offull-scale, grid-connected devices that will in some cases bedeployable in farm style configurations.Modular offshore wave energy devices that can bedeployed quickly and cost effectively in a wide range ofconditions will accelerate commercial wave energy. Inthe coming decade, wave energy will become commerciallysuccessful through multiple-unit offshore projects, the firstof which are now being installed. These projects clearlydemonstrate the commercial future for wave energy butvaluable operational experience is necessary before largerprojects are built with a greater number of devices.The growth of shoreline wave energy devices is limitedby the low number of available sites and high installa-tion costs. Deployment costs for shoreline wave energydevices are very high because they are individual site-specific projects and economies of scale are not applicable.Whereas an offshore 50-MW wave farm is conceivable, andwill in time be developed, no shoreline wave energy con-verter can offer such potential for deployment in this way.As such, individual coastal installations are expected to befew and far between. Shoreline wave energy will, however,continue to be relevant, as the average unit capacity isgenerally higher than existing offshore technology. Indi-vidual devices can be very effective, especially for remoteor island communities where, for example, an individualunit of 4 MW could have a big impact.Offshore locations offer greater power potential thanshoreline locations. Shoreline technologies have the benefitof easy access for maintenance purposes, whereas offshoredevices are in most cases more difficult to access. Improve-ments in reliability and accessibility will be critical to thecommercial success of the many devices currently underdevelopment.5.2.1 Wave Energy ForecastDouglas-Westwood Ltd claim there is a potential 46 MWof wave energy projects that could be installed between2007 and 2011. The United Kingdom is expected to bethe dominant player over the next 5 years, with a fore-cast capacity of 28.6 MW, which equates to a 62% marketshare. In comparison with other countries, the UK hasforecast capacity every year to 2008, whereas installationselsewhere are more intermittent. Norway (6 MW) and Por-tugal (4.25 MW) are the next most significant markets andhave several projected installations, but they lag behindthe UK in terms of technology development and projectdeployment. The United Kingdom government has shownreasonable levels of support, which have injected manytechnologies with valuable grants. The result is a num-ber of proven wave technologies with good prospects forcommercial deployment and several more at an advancedprototype stage. Coupled with a world-class natural re-source, the United Kingdom remains the strongest marketinto the next decade.Potential wave energy capacity 2007–2011 is indicatedin Fig. 9.Figure 9. Potential wave energy capacity 2007–2011.Source: Douglas-Westwood Ltd [32].4255.3 Offshore WindThere are 25 operational offshore wind farms in the worldtoday. The 436 installed turbines in these projects providea total of 919 MW.The first offshore wind turbine was installed at Noger-sund off Sweden in 1990. The first offshore wind farmwere installed at Vindeby off the Danish island of Lol-land in 1991. The most recent project is the BeatriceDemonstration Project off Scotland.The first 10 years of the industry saw small projects be-ing built in very shallow water near-shore locations. Thesewind farms in most cases used onshore turbine models withslight adaptations made. These “demonstration” projectshave paved the way for the more recent projects that areof a much larger size.The biggest offshore wind farm yet installed is theNysted development off Denmark which was completed in2003. Just as this project dwarfs those built 10 yearspreviously, within another decade projects will be installedthat are many times greater in size than today’s offshorewind farms.The industry faces problems from increasing costs. Inthe last 5 years, the cost of offshore wind has increasedby up to 65%. This is caused by increased turbine pricesdriven by the extremely strong onshore wind market (par-ticularly in the US), and rising contractor prices basedupon experiences on earlier projects. Cost reductions ofapproximately 25% are essential to help stimulate the in-dustry and help strengthen it.The total global offshore wind capacity forecast forinstallation between 2007 and 2011 stands at 4.2 GW. TheUK is the world’s largest market for the forthcoming 5-yearperiod. A total of 2.2 GW is forecast here, representing 52%of the entire world market. The UK’s “Round 1” projectsare continuing to be installed at the rate of 1–2 per year.The first of the larger “Round 2” projects are expected toenter construction at the turn of the decade, significantlyboosting the UK’s capacity. The UK’s prospects areexpected almost three times those of Germany, the nextlargest market.Germany has so far seen only minor installations,but the first significant activity is expected to begin in2008 with the Borkum West project. Several projectsare forecast for 2009 and 2010. The bulk of projects,however, will not begin construction until the turn of thedecade. Long-term prospects are excellent off Germanybut in the short and mid-term future the industry hasmuch to overcome.The only activity off Denmark in the period will comewith the construction and completion of the Horns Rev IIand Nysted II projects in 2009 and 2010 respectively. Al-though the country showed initial promise for offshore de-velopment, a lack of government commitment has stuntedthe industry here. Long-term prospects are, however,high and a new round of licences is expected shortly fordevelopment in the next decade.Whilst the Netherlands is currently seeing a period ofactivity with the completion of the Egmond aan Zee projectand construction of Q7-WP, it will not be until after thisdecade that the next projects are completed. Whilst notreflected in the above forecast, long-term prospects aregood.North America is yet to install any offshore windprojects. With the onshore market in such good health,the drivers for offshore are not as strong as in Europe wherethe industry is reaching take-off after a period of slow butsteady growth.There are currently three large offshore wind farms inNorth America in advanced stages of planning althoughit is now unlikely that they will be built this decadedue to delays from drawn-out permitting processes andlegal challenges. In addition to this are a number ofmore speculative large projects and several small scaledemonstration projects that could be installed before theend of the decade.The highest profile project is Cape Wind off the coastof Massachusetts. The proposed 420 MW wind farm hascourted controversy since conception. After clearing anumber of regulatory and legal hurdles over a 6-year period,the project faces a ruling from US federal authorities. TheMinerals Management Service (MMS) took over regulationof offshore renewables in the autumn of 2005. The MMSintend to record a decision on the project in the fall of2008.The 144 MW Long Island offshore wind farm is beingdeveloped by FPL Energy. The MMS is due to recorda decision on the project in spring 2008. The projectstarted after The Long Island Power Authority announcedin January 2003 that it was seeking developers to build anoffshore wind farm off Jones Beach.The largest North American project is the 1,750 MWNaiKun wind farm off the coast of British Columbia whichwill be developed in five phases, the first of which isscheduled for completion in 2011.Cumulative installed offshore wind capacity is given inFig. 10. Forecast offshore capacity 2002–2011 is indicatedin Fig. 11.6. ConclusionsFor the entire marine renewables sector, 4.5 GW of installedcapacity is projected between 2007 and 2011. Some 98%of that capacity is in the form of offshore wind farms. TheFigure 10. Cumulative installed offshore wind capacity.Source: Douglas-Westwood Ltd [32].426Figure 11. Forecast offshore wind capacity 2002–2011.Source: Douglas-Westwood Ltd [32].value of the market over the next 5 years is projected at$17 billion.Wave and tidal power will only be a small percentageof the total expenditure on offshore renewables, of theorder of $300 million in total expenditure between them.However, wave and tidal power currently attract higherexpenditures per megawatt. This indicates higher costs ofthe immature developing industries. These costs will fallas time goes by and the industries progresses. The leadingdevices should be comparable with, and in some cases morecompetitive than offshore wind, by early next decade.The more well-established offshore wind sector willlead the offshore renewables industry, and will see stronggrowth throughout the period led by countries such as theUK, the Netherlands, Germany and Denmark. Establishedonshore wind supply chains in Denmark and Germany will,however, see most of the financial benefit of the growthin offshore wind for the short-term. The dominance ofoffshore wind does not mean wave and tidal energy arenot important, they are just less well developed, and theindustry is much younger. From around 2010, wave andtidal should begin to expand commercially. The growth ofwave and tidal power offers significant supply chain growthopportunities for countries that failed to capture the valueof the growth in the wind industry (both onshore andoffshore).Europe is the dominant region, leading in all threesectors. The UK is a particularly important market, drivenby a world-class natural resource, the past 3 years has seennotable successes in wind, wave and tidal energies. Withmore approved offshore wind capacity in the planning stagethan any other country, prospects for the United Kingdomlook bright. The UK is forecast to become world leader inoffshore wind in 2008 and is already the leader in the waveand tidal current stream industries. The UK Energy WhitePaper due May 2007 is expected to increase banding to themain support system for renewables to give greater supportto emerging technologies, particularly offshore renewables.This should provide a strong catalyst for growth.Whilst currently lacking, future growth in other re-gions should not be discounted in the long term. Interestin North America is growing and we will see large projectsprogressing around the end of the decade, particularly inthe offshore wind sector. Greater support and structurewould reap big rewards for the industry here. At presentthough, it lags far behind the established European marketwhich remains the focal point for the marine renewablesindustry. Europe is home to the leading technology de-velopers and superior funding packages are in place in keycountries to stimulate development.AcknowledgementsThe author acknowledges contributions made by PeterO’Donnell (Senior Energy Specialist, Manager GenerationSolar & Renewables Programs, San Francisco EnvironmentOrganization, CA, USA); Omar Siddiqui (Senior Associate,Global Energy Partners LLC, Lafayette, CA, USA); RogerBedard (Offshore Wave Energy Project Manager, EPRI,CA, USA), Andrew Mill (Managing Director EuropeanMarine Energy Centre, UK); Mirko Previsic (Consultant—Offshore Renewables, Sacramento, CA, USA); Anthony TJones (Senior Oceanographer, oceanUS consulting, PalmSprings, CA, USA); and Adam Westwood (RenewableEnergy Manager, Douglas-Westwood Limited, Canterbury,UK, principally for Section 5).References[1] T.J. Hammons, Tidal Power, Proceedings IEEE, 81(3), 1993,419–433.[2] B.V. Davis, A major source of energy from the world’s oceans,IECEC-97 Intersociety Energy Conversion Engineering Con-ference, 1997.[3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Tur-bine for (Canadian) Ministry of Employment and Investment,N.H. Halvorson Consultants Ltd.[4] Renewable Energy: Power for a Sustainable Future; TechnologyUpdate, Tidal Current Power Update & Wave Power Update,Oxford University Press, 2001.[5] P. Fraenkel, Renewables is the tide turning for marine currentturbines? Modern Power System, Marine Current TurbinesLtd, London, UK, June 30, 2001.[6] R. Bedard, Final summary report: offshore wave power feasi-bility demonstration project (E2I EPRI Global WP009 – US,2005).[7] M. Previsic, System level design, performance and costs forSan Francisco Pelamis offshore wave power plant (E2I EPRIGlobal – 006A – SF, 2004).[8] G. Hagerman, Offshore Wave Power in the US: EnvironmentalIssues (E2I Global EPRI – 007 – US, 2004).[9] B. Ram, Wave Power in the US: Permitting and JurisdictionalIssues (E2I Global EPRI DOE NREL – 008 – US).[10] M. Previsic, Wave power technologies, Proc. IEEE PES 05 GM,San Francisco, paper 05GM0542, June 2005, 1–6.[11] E2i/EPRI WP-004-US Rev 1 Assessment of Offshore WaveEnergy Conversion Devices.[12] E2i/EPRI WP-005-US Methodology, Guidelines and Assump-tions for the Conceptual Design of Offshore Wave EnergyPower Plants (Farms).[13] E2i/EPRI WP-006-HI System Level Design, Preliminary Per-formance and Cost Estimate – Hawaii.[14] E2i EPRI WP-006-OR System Level Design, Preliminary Per-formance and Cost Estimate – Oregon.[15] E2i/EPRI WP-006-ME System Level Design, Preliminary Per-formance and Cost Estimate – Maine.[16] E2i/EPRI WP-006-MA System Level Design, Preliminary Per-formance and Cost Estimate – Massachusetts.[17] E2i/EPRI WP-006-SFa System Level Design, PreliminaryPerformance and Cost Estimate – San Francisco, CaliforniaPelamis Offshore Wave Power Plant.427[18] E2i/EPRI WP-006-SFb System Level Design, PreliminaryPerformance and Cost Estimate – San Francisco EnergetechOffshore Wave Power Plant.[19] Sea Technology Magazine August 2003, Wave Energy Conver-sion – The State of the Art.[20] EPRI – RE Technical Assessment Guide Ocean Wave PowerSection for the years 2001, 2002 and 2003.[21] California Energy Commission – Wave Energy Resource As-sessment for the State of California.[22] A.D. Trapp & M. Watchorn, EB development of tidal streamenergy, Proc. MAREC 2001, 2001, 169–173.[23] A.T. Jones & A. Westwood, Economic forecast for renewableocean energy technologies, presented at EnergyOcean 2004,Palm Beach, Florida, 2004.[24] A.T. Jones & W. Rowley, Global perspective: Economicforecast for renewable ocean energy technologies, MTS Journal,36(4), 2002, 85–90.[25] N.J. Baker, M.A. Mueller, M. Watchorn, D. Slee, L. Haydock, &N. Brown, Direct drive power take off for the Stingray tidalcurrent generator, Proc. MAREC 2002, 2002, 1–10.[26] A.M. Gorlov, The helical turbine and its applications for tidaland wave power, Proc. OCEANS 2003, 2003, 1996.[27] P.W. Ullman, Offshore Tidal Power Generation – A newapproach to power conversion of the oceans’ tides, MTSJournal, 36(4), 2002, 16–24. [28] P. Breeze, The Future of Global Offshore Wind Power, ReuterBusiness Insight 2004. [30].In deep water, the wave power spatial flux (in kW/mof wave front crest) is given by significant wave height (Hsin m) and the peak wave period (Tp in s). Based on thesetwo parameters, the incident wave power (J in kW/m ofwave crest length) associated with each sea state record isestimated by the following equation:J = 0.42 × (Hs)2× Tp (kW)It is significant to note that wave power varies withthe square of wave height – that is, a wave whose height isdoubled generates four times as much power.The power of a tidal current is given by the followingequation:Pwater = (1/2) rAV 3(W)where A is the cross-sectional area of flow intercepted bythe turbine device (m2), r is the water density (kg/m3)and V is current velocity speed (m/s). The current ve-locity V varies in a precisely predictable manner as anadditive function of period of the different sinusoidal tidalcomponents.Tidal flow energy studies are in progress at EPRI andthe techno-economic results are not available. Therefore,the focus is on the results of the wave energy feasibilitydefinition study of 2004.4.2 Wave Project Results4.2.1 US Wave Energy ResourcesAn ideal site to deploy, operate and maintain an offshorewave energy power plant must have many attributes. Firstand foremost is a sufficient native energy and energy spec-tra potential.1The US regional wave regimes and the totalannual incident wave energy for each of these regimes areshown in Fig. 4. The total US available incident waveenergy flux is about 2,300 TWh/yr. The DOE EnergyInformation Energy (EIA) estimated in 2003 hydroelectricgeneration in USA to be about 270 TWh which is a lit-tle more than a tenth of the yearly offshore wave energyflux into the US. Therefore, wave energy is a significantresource.Figure 4. US energy resources. Source: O. Siddiqui &R. Bedard [30].4.2.2 Feasibility Definition Study SitesSite attributes characterized by the Project Team includedoffshore bathymetry2and seafloor surface geology, robust-ness of the coastal utility grid, regional maritime infras-tructure for both fabrication and maintenance, conflictswith competing uses of sea space and existence of otherunique characteristics that might minimize project devel-opment costs (e.g. existing ocean outfall easements forrouting power cable and shore crossing).Table 2 identifies the site selected in each of the fivestates that participated in the study, and also provides afew key characteristics of each selected site.4.2.3 Feasibility Study: WEC DevicesTwelve companies responded to EPRI’s request for infor-mation. An initial screening considered two key issues: (1)technology readiness (i.e. readiness of device for demon-stration in the 2006 time period) and (2) survivability inadverse conditions (i.e. sufficiency of technical informationprovided by the device manufacturer to prove the surviv-ability in storm conditions). The eight devices that passedthe initial screening criteria are shown in Table 3.1 Energy as function of wave height and wave period or frequency.2 Bathymetry is the depth of the seafloor below mean waterheight (i.e. the inverse of a topographic map).420Table 2Estimated Performance of Pilot Demonstration PlantsHI OR CA Mass MaineCounty Oahu Douglas SF Cape Cod CumberlandGrid I/C Waimanalo Gardner Wastewater Well OldBeach Plant Fleet OrchardBeach S/SAverage 15.2 21.2 11.2113.8 4.9Annual J(kW/m)Depth (m) 60 60 30 60 60Distance 2 3.5 13 9 9from ShoreCable Makai IPP Outflow Water Dir Drill Dir DrillLanding Pier Pipe Outflow1Sited within the marine sanctuary exclusionary zone.Source: O. Siddiqui & R. Bedard [30].Table 3Estimated Performance of Pilot Demonstration PlantsLength (m) Width (m) Power (kW)1Type RatingOcean 120 4.6 153 Floating 1Power AttenuatorDeliveryEnergetech 25 35 259 OWC – Bottom 2TerminatorWave 150 260 1,369 Floating 2Dragon OvertoppingWave 9.5 9.5 351 Bottom Point 2Swing AbsorberWave Bob 16 15 131 Floating Point 3AbsorberAqua-Energy 6 6 17 Floating Point 3AbsorberOreCON 32 32 532 Floating OWC 3Ind Natural 5.4 5.4 112 Bottom Point 3Resources Inc Absorber1Based on Oregon average annual wave energy resource.Source: O. Siddiqui & R. Bedard [30].These eight devices were then assessed with the ob-jective of determining any critical issues and recommend-ing RD&D needed to achieve technological readiness foran at sea demonstration. As a result of this assessment,the eight devices were grouped into one of three levels ofdevelopment categories:• Level 1 : Development complete and full-scale testingin the ocean underway.• Level 2 : Development near complete. Only deploy-ment, recovery and mooring issues are yet to be val-idated. There are funded plans for full-scale at seatesting.• Level 3 : Most critical RD&D issues are resolved. Ad-ditional laboratory and sub-scale testing, simulationsand systems integration work is needed prior to final-ization of the full-scale design. There are no funded421plans for full-scale at sea testing.At the time of EPRI’s analysis (March 2004), onlyone WEC device manufacturer had attained a Level 1technology readiness status – OPD with its Pelamis device.At the time of this paper (February 2005) there are anadditional four WEC device manufacturers that are close toreaching that status: TeamWorks of the Netherlands withits Wave Swing, Energetechs of Australia with its OWC,Wave Dragon of Denmark with its overtopping device, andOcean Power Technology of the US with a floating buoy.4.2.4 Demonstration-Scale Plant Design: OregonExampleDemonstration-scale (as well as commercial-scale) designswere based on the OPD Pelamis WEC device for the fivesites listed in Table 2. The Pelamis WEC device consistsof four cylindrical steel sections, which are connected bythree hydraulic PCM. Total length of the device is 120 mand device diameter is 4.6 m. Fig. 5 shows the device beingtested off the Scottish coast.Figure 5. OPD Pelamis WEC device. 1 nm = 1 nauticalmile. Source: O. Siddiqui & R. Bedard [30].A second San Francisco, CA design based on theEnergetech OWC WEC device depicted in Fig. 6 was alsotested.Figure 6. Energetech WEC device. Source: O. Siddiqui &R. Bedard [30].The estimated performance of the single unit demon-stration plant at each of the five sites is shown in Table 4.Table 4Estimated Performance of Pelamis Pilot DemonstrationPlantsHI OR CA1Mass MaineDevice Rated 750 750 750 750 750Capacity (kW)Annual 1,989 1,472 1,229 1,268 426Energy Absorbed(MWh/yr)Annual Energy 1,663 1,001 835 964 290Produced(MWh/yr)Average 180 114 95 98 33ElectricalPower (kW)Number of 180 114 95 98 33Homes Poweredby Plant1Energetech site numbers: 1,000 kW, 1,643 MWh/yr, 1,264 MWh/yr,and 144 kW respectively.Source: O. Siddiqui & R. Bedard [30].4.2.5 Commercial-Scale Plant Design: Oregon Exam-pleThe commercial system uses a total of 4 clusters, each onecontaining 45 Pelamis units (i.e. 180 total Pelamis WECdevices), connected to sub-sea cables. Each cluster consistsof 3 rows with 15 devices per row. The other state designsare organized in a similar manner with 4 clusters. Thenumber of devices per cluster varies such that each plantproduces an annual energy output of 300,000 MWh/yr.The electrical interconnection of the devices is accom-plished with flexible jumper cables, connecting the units inmid-water. The introduction of 4 independent sub-sea ca-bles and the interconnection on the surface provides someredundancy in the wave farm arrangement.The estimated performance of the commercial-scaleplant at each of the five sites is shown in Table 5.The device rated capacity has been derated from750 kW in the demonstration plant to 500 kW for the com-mercial plant. The performance assessment of the demon-stration plants shows that the PCMs are overrated andreducing the rated power to 500 kW per device would yielda significant cost reduction and only a relatively small de-crease in annual output (attributed to the fact that the USsites have a lower energy level than UK sites for which thedevice was originally developed).4.2.6 Learning Curves and EconomicsThe costs and cost of electricity shown in the previous sec-tion are for the first commercial-scale wave plant. Learn-ing through production experience reduces costs – a phe-nomenon that follows a logarithmic relationship such that422Table 5Estimated Performance of Pelamis Commercial PlantsHI OR CA Mass MaineDevice Rated 500 500 500 500 500Capacity (kW)Annual Energy 1,989 1,997 1,683 1,738 584Absorbed (MWh/yr)Annual Energy 1,663 1,669 1,407 1,453 488Produced (MWh/yr)Average Electrical 191 191 161 166 56Power at Busbar (kW)Number of OPD 180 180 213 206 615Pelamis UnitsNeeded for300,000 MWh/yrNumber of Homes 34,000 34,000 34,000 34,000 34,000Powered by PlantSource: O. Siddiqui & R. Bedard [30].for every doubling of the cumulative production volume,there is a specific percentage drop in production costs.The specific percentage used in this study was 82%, whichis consistent with documented experience in the wind en-ergy, photovoltaic, shipbuilding, and offshore oil and gasindustries.The industry-documented historical wind energy learn-ing curve is shown as the top line in Fig. 7 [31]. The cost ofelectricity is about 4 cents/kWh in 2004 US dollars basedon 40,000 MW of worldwide installed capacity and a goodwind site. The lower and higher bound cost estimates ofwave energy are also shown in Fig. 7. The 82% learningcurve is applied to the wave power plant installed costbut not to the operation and maintenance part of cost ofelectricity (hence the reason that the three lines are notparallel).Figure 7. Electrical interconnection of demo-plant: Oregonexample. Source: O. Siddiqui & R. Bedard [30].Fig. 7 shows the cost of wave-generated electricity:low band (bottom curve), upper band (middle curve); andwind-generated electricity (top curve) at equal cumulativeproduction volume under all cost estimating assumptionsfor the wave plant. It shows that the cost of wave-generatedelectricity is less than wind-generated electricity at anyequal cumulative production volume under all cost esti-mating assumptions for the wave plant. The lower capitalcost of a wave machine (compared to a wind machine)more than compensates for the higher O&M cost for theremotely located offshore wave machine. A challenge tothe wave energy industry is to drive down O&M costs tooffer even more economic favourability and to delay thecrossover point shown at greater than 40,000 MW.In summary, the techno-economic forecast made by theProject Team is that wave energy will first become commer-cially competitive with the current 40,000 MW installedland-based wind technology at a cumulative productionvolume of 15,000 MW or less in Hawaii and northern Cali-fornia, about 20,000 MW in Oregon and about 40,000 MWin Massachusetts. This forecast was made on the basis of a300,000 MWh/yr (nominal 90 MW at 38% capacity factor)Pelamis WEC commercial plant design and application oftechnology learning curves. Maine was the only state inthe study whose wave climate was such that wave energymay never be able to economically compete with a goodwind energy site.In addition to economics, there are other compellingarguments for investing in offshore wave energy technology.First, with proper sitting, converting ocean wave energy toelectricity is believed to be one of the most environmentallybenign ways to generate electricity. Second, offshore waveenergy offers a way to minimize the “Not In My Backyard”(NIMBY) issues that plague many energy infrastructure423projects, from nuclear to coal and to wind generation.Because these devices have a very low profile and arelocated at a distance from the shore, they are generally notvisible. Third, because wave energy is more predictablethan solar and wind energy, it offers a better possibilitythan either solar or wind of being dispatch able and earninga capacity payment.A characteristic of wave energy that suggests that itmay be one of the lowest cost renewable energy sources isits high power density. Processes in the ocean concentratesolar and wind energy into ocean waves making it easierand cheaper to harvest. Solar and wind energy sources aremuch more diffuse, by comparison.Since a diversity of energy sources is the bedrock ofa robust electricity system, to overlook wave energy isinconsistent with national needs and goals. Wave energyis an energy source that is too important to overlook.4.2.7 RecommendationsThe development of ocean energy technology and the de-ployment of this clean renewable energy technology wouldbe greatly accelerated by adequate support from govern-ments. Appropriate roles for governments in ocean energydevelopment could include:• Providing leadership for the development of an oceanenergy RD&D programme to fill known RD&D gaps,and to accelerate technology development and proto-type system deployment.• Operating national offshore wave test centers to testperformance and reliability of prototype ocean energysystems under real conditions.• Development of design and testing standards for oceanenergy devices.• Joining the International Energy Agency Ocean En-ergy Systems Implementing Agreement to collaborateRD&D activities, and appropriate ocean energy poli-cies with other governments and organizations.• Studying provision of production tax credits, renew-able energy credits, and other incentives to spur privateinvestment in ocean energy technologies and projects,and implementing appropriate incentives to accelerateocean energy deployment.• Ensuring that the public receives a fair return fromthe use of ocean energy resources.• Ensuring that development rights are allocatedthrough a transparent process that takes into accountstate, local, and public concerns.5. Recent Progress in Offshore Renewable EnergyTechnology DevelopmentThe recent progress in offshore renewable energy technol-ogy development is now examined and potential marketsfor tidal power, WEC, and offshore wind are considered.The analysis of market potentials for offshore renewabletechnology is based solely on currently identified projects.There is therefore scope for increased market prospects,particularly around the end of the period in the wave andtidal current stream sectors.5.1 Tidal Current StreamHistorically, tidal projects have been large-scale barragesystems that block estuaries. Within the last few decades,developers have shifted toward technologies that capturethe tidally driven coastal currents or tidal stream. Thechallenge is, “to develop technology and innovate in a waythat will allow this form of low density renewable energyto become practical and economic” [22].Tidal current turbines are basically underwater wind-mills. The tidal currents are used to rotate an underwa-ter turbine. First proposed during the 1970s’ oil crisis,the technology has only recently become a reality withcommercial prospects.Marine Current Turbines (MCT) installed the firstfull-scale prototype turbine (300 kW) off Lynmouth in De-von, UK in 2003. Shortly thereafter, the Norwegian com-pany Hammerfest Støm installed their first grid-connected300 kW prototype device. MCT, arguably the marketleader is now preparing to install its new twin-rotored1 MW device in 2007. The company has plans to install acommercial scale project off the UK coast around the turnof the decade.There are a great number of sites suitable for tidalcurrent turbines. As tidal currents are predictable andreliable, tidal turbines have advantages over offshore windcounterparts. The ideal sites are generally within severalkilometres of the shore in water depths of 20–30 m.5.1.1 Tidal ForecastsDouglas-Westwood Ltd expect 25 MW of tidal currentstream capacity to be brought online in the 2007–2011period (see Fig. 8). The vast majority of this capacitywill be in the UK where 23 MW is forecast. With severalsuccessful large-scale prototypes already tested, the periodto the end of the decade will see further refinement ofdevices and applications for multiple-unit farms in keymarkets. The above forecast shows a sharp growth in 2011from tidal current farms expected from MCT and LunarEnergy.Figure 8. Potential tidal current stream capacity 2007–2011. Source: Douglas-Westwood Ltd [32].4245.1.2 ProjectsShiswa Lake Tidal Power Plant, Korea Korea has aplentiful tidal and tidal current energy resource. Underconstruction is a single stream style generator at AnsanCity’s Shiswa Lake, which will have a capacity of 252 MW,comprised of 12 units of 21 MW generators. Annual powergeneration, when completed in 2008, is projected at 552million kWh. If successful, this project will surpass LaRance (France) as the largest tidal power plant in theworld. Korea is also planning a tidal current power plantin Uldol-muk Strait, a restriction in the strait where maxi-mum water speed exceeds 6.5 m/s. The experimental plantwill utilize helical or “Gorlov” turbines developed by GCKTechnology [26].Yalu River, China By creating a tidal lagoon off-shore, Tidal Electric has taken a novel approach to resolveenvironmental and economic concerns of tidal barrage tech-nology [27]. Due to the highly predictive nature of theocean tides, the company has developed simulation modelswith performance data from available generators to opti-mize design for particular locations. The recent announce-ment of a cooperative agreement with the Chinese govern-ment for ambitious 300 MW offshore tidal power genera-tion facilities off Yalu River, Liaoning Province allows foran engineering feasibility study to be undertaken.Tidal Electric also has plans under consideration forUK-based projects in Swansea Bay (30 MW), Fifoots Point(930 MW), and North Wales (432 MW). These projectshave failed to make progress and will not go ahead in theforeseeable future.5.2 Wave EnergyThe true potential of wave energy will only be realizedin the offshore environment where large developments areconceivable. Nearly 300 concepts for wave energy deviceshave been proposed. The development process for waveenergy can be looked at in three phases. First, small-scale prototype devices, typically with low capacity, will bedeployed. During the second stage, outside funding fromgovernment or private investors is possible for the mostpromising devices. The final stage is the production offull-scale, grid-connected devices that will in some cases bedeployable in farm style configurations.Modular offshore wave energy devices that can bedeployed quickly and cost effectively in a wide range ofconditions will accelerate commercial wave energy. Inthe coming decade, wave energy will become commerciallysuccessful through multiple-unit offshore projects, the firstof which are now being installed. These projects clearlydemonstrate the commercial future for wave energy butvaluable operational experience is necessary before largerprojects are built with a greater number of devices.The growth of shoreline wave energy devices is limitedby the low number of available sites and high installa-tion costs. Deployment costs for shoreline wave energydevices are very high because they are individual site-specific projects and economies of scale are not applicable.Whereas an offshore 50-MW wave farm is conceivable, andwill in time be developed, no shoreline wave energy con-verter can offer such potential for deployment in this way.As such, individual coastal installations are expected to befew and far between. Shoreline wave energy will, however,continue to be relevant, as the average unit capacity isgenerally higher than existing offshore technology. Indi-vidual devices can be very effective, especially for remoteor island communities where, for example, an individualunit of 4 MW could have a big impact.Offshore locations offer greater power potential thanshoreline locations. Shoreline technologies have the benefitof easy access for maintenance purposes, whereas offshoredevices are in most cases more difficult to access. Improve-ments in reliability and accessibility will be critical to thecommercial success of the many devices currently underdevelopment.5.2.1 Wave Energy ForecastDouglas-Westwood Ltd claim there is a potential 46 MWof wave energy projects that could be installed between2007 and 2011. The United Kingdom is expected to bethe dominant player over the next 5 years, with a fore-cast capacity of 28.6 MW, which equates to a 62% marketshare. In comparison with other countries, the UK hasforecast capacity every year to 2008, whereas installationselsewhere are more intermittent. Norway (6 MW) and Por-tugal (4.25 MW) are the next most significant markets andhave several projected installations, but they lag behindthe UK in terms of technology development and projectdeployment. The United Kingdom government has shownreasonable levels of support, which have injected manytechnologies with valuable grants. The result is a num-ber of proven wave technologies with good prospects forcommercial deployment and several more at an advancedprototype stage. Coupled with a world-class natural re-source, the United Kingdom remains the strongest marketinto the next decade.Potential wave energy capacity 2007–2011 is indicatedin Fig. 9.Figure 9. Potential wave energy capacity 2007–2011.Source: Douglas-Westwood Ltd [32].4255.3 Offshore WindThere are 25 operational offshore wind farms in the worldtoday. The 436 installed turbines in these projects providea total of 919 MW.The first offshore wind turbine was installed at Noger-sund off Sweden in 1990. The first offshore wind farmwere installed at Vindeby off the Danish island of Lol-land in 1991. The most recent project is the BeatriceDemonstration Project off Scotland.The first 10 years of the industry saw small projects be-ing built in very shallow water near-shore locations. Thesewind farms in most cases used onshore turbine models withslight adaptations made. These “demonstration” projectshave paved the way for the more recent projects that areof a much larger size.The biggest offshore wind farm yet installed is theNysted development off Denmark which was completed in2003. Just as this project dwarfs those built 10 yearspreviously, within another decade projects will be installedthat are many times greater in size than today’s offshorewind farms.The industry faces problems from increasing costs. Inthe last 5 years, the cost of offshore wind has increasedby up to 65%. This is caused by increased turbine pricesdriven by the extremely strong onshore wind market (par-ticularly in the US), and rising contractor prices basedupon experiences on earlier projects. Cost reductions ofapproximately 25% are essential to help stimulate the in-dustry and help strengthen it.The total global offshore wind capacity forecast forinstallation between 2007 and 2011 stands at 4.2 GW. TheUK is the world’s largest market for the forthcoming 5-yearperiod. A total of 2.2 GW is forecast here, representing 52%of the entire world market. The UK’s “Round 1” projectsare continuing to be installed at the rate of 1–2 per year.The first of the larger “Round 2” projects are expected toenter construction at the turn of the decade, significantlyboosting the UK’s capacity. The UK’s prospects areexpected almost three times those of Germany, the nextlargest market.Germany has so far seen only minor installations,but the first significant activity is expected to begin in2008 with the Borkum West project. Several projectsare forecast for 2009 and 2010. The bulk of projects,however, will not begin construction until the turn of thedecade. Long-term prospects are excellent off Germanybut in the short and mid-term future the industry hasmuch to overcome.The only activity off Denmark in the period will comewith the construction and completion of the Horns Rev IIand Nysted II projects in 2009 and 2010 respectively. Al-though the country showed initial promise for offshore de-velopment, a lack of government commitment has stuntedthe industry here. Long-term prospects are, however,high and a new round of licences is expected shortly fordevelopment in the next decade.Whilst the Netherlands is currently seeing a period ofactivity with the completion of the Egmond aan Zee projectand construction of Q7-WP, it will not be until after thisdecade that the next projects are completed. Whilst notreflected in the above forecast, long-term prospects aregood.North America is yet to install any offshore windprojects. With the onshore market in such good health,the drivers for offshore are not as strong as in Europe wherethe industry is reaching take-off after a period of slow butsteady growth.There are currently three large offshore wind farms inNorth America in advanced stages of planning althoughit is now unlikely that they will be built this decadedue to delays from drawn-out permitting processes andlegal challenges. In addition to this are a number ofmore speculative large projects and several small scaledemonstration projects that could be installed before theend of the decade.The highest profile project is Cape Wind off the coastof Massachusetts. The proposed 420 MW wind farm hascourted controversy since conception. After clearing anumber of regulatory and legal hurdles over a 6-year period,the project faces a ruling from US federal authorities. TheMinerals Management Service (MMS) took over regulationof offshore renewables in the autumn of 2005. The MMSintend to record a decision on the project in the fall of2008.The 144 MW Long Island offshore wind farm is beingdeveloped by FPL Energy. The MMS is due to recorda decision on the project in spring 2008. The projectstarted after The Long Island Power Authority announcedin January 2003 that it was seeking developers to build anoffshore wind farm off Jones Beach.The largest North American project is the 1,750 MWNaiKun wind farm off the coast of British Columbia whichwill be developed in five phases, the first of which isscheduled for completion in 2011.Cumulative installed offshore wind capacity is given inFig. 10. Forecast offshore capacity 2002–2011 is indicatedin Fig. 11.6. ConclusionsFor the entire marine renewables sector, 4.5 GW of installedcapacity is projected between 2007 and 2011. Some 98%of that capacity is in the form of offshore wind farms. TheFigure 10. Cumulative installed offshore wind capacity.Source: Douglas-Westwood Ltd [32].426Figure 11. Forecast offshore wind capacity 2002–2011.Source: Douglas-Westwood Ltd [32].value of the market over the next 5 years is projected at$17 billion.Wave and tidal power will only be a small percentageof the total expenditure on offshore renewables, of theorder of $300 million in total expenditure between them.However, wave and tidal power currently attract higherexpenditures per megawatt. This indicates higher costs ofthe immature developing industries. These costs will fallas time goes by and the industries progresses. The leadingdevices should be comparable with, and in some cases morecompetitive than offshore wind, by early next decade.The more well-established offshore wind sector willlead the offshore renewables industry, and will see stronggrowth throughout the period led by countries such as theUK, the Netherlands, Germany and Denmark. Establishedonshore wind supply chains in Denmark and Germany will,however, see most of the financial benefit of the growthin offshore wind for the short-term. The dominance ofoffshore wind does not mean wave and tidal energy arenot important, they are just less well developed, and theindustry is much younger. From around 2010, wave andtidal should begin to expand commercially. The growth ofwave and tidal power offers significant supply chain growthopportunities for countries that failed to capture the valueof the growth in the wind industry (both onshore andoffshore).Europe is the dominant region, leading in all threesectors. The UK is a particularly important market, drivenby a world-class natural resource, the past 3 years has seennotable successes in wind, wave and tidal energies. Withmore approved offshore wind capacity in the planning stagethan any other country, prospects for the United Kingdomlook bright. The UK is forecast to become world leader inoffshore wind in 2008 and is already the leader in the waveand tidal current stream industries. The UK Energy WhitePaper due May 2007 is expected to increase banding to themain support system for renewables to give greater supportto emerging technologies, particularly offshore renewables.This should provide a strong catalyst for growth.Whilst currently lacking, future growth in other re-gions should not be discounted in the long term. Interestin North America is growing and we will see large projectsprogressing around the end of the decade, particularly inthe offshore wind sector. Greater support and structurewould reap big rewards for the industry here. At presentthough, it lags far behind the established European marketwhich remains the focal point for the marine renewablesindustry. Europe is home to the leading technology de-velopers and superior funding packages are in place in keycountries to stimulate development.AcknowledgementsThe author acknowledges contributions made by PeterO’Donnell (Senior Energy Specialist, Manager GenerationSolar & Renewables Programs, San Francisco EnvironmentOrganization, CA, USA); Omar Siddiqui (Senior Associate,Global Energy Partners LLC, Lafayette, CA, USA); RogerBedard (Offshore Wave Energy Project Manager, EPRI,CA, USA), Andrew Mill (Managing Director EuropeanMarine Energy Centre, UK); Mirko Previsic (Consultant—Offshore Renewables, Sacramento, CA, USA); Anthony TJones (Senior Oceanographer, oceanUS consulting, PalmSprings, CA, USA); and Adam Westwood (RenewableEnergy Manager, Douglas-Westwood Limited, Canterbury,UK, principally for Section 5).References[1] T.J. Hammons, Tidal Power, Proceedings IEEE, 81(3), 1993,419–433.[2] B.V. Davis, A major source of energy from the world’s oceans,IECEC-97 Intersociety Energy Conversion Engineering Con-ference, 1997.[3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Tur-bine for (Canadian) Ministry of Employment and Investment,N.H. Halvorson Consultants Ltd.[4] Renewable Energy: Power for a Sustainable Future; TechnologyUpdate, Tidal Current Power Update & Wave Power Update,Oxford University Press, 2001.[5] P. Fraenkel, Renewables is the tide turning for marine currentturbines? Modern Power System, Marine Current TurbinesLtd, London, UK, June 30, 2001.[6] R. Bedard, Final summary report: offshore wave power feasi-bility demonstration project (E2I EPRI Global WP009 – US,2005).[7] M. Previsic, System level design, performance and costs forSan Francisco Pelamis offshore wave power plant (E2I EPRIGlobal – 006A – SF, 2004).[8] G. Hagerman, Offshore Wave Power in the US: EnvironmentalIssues (E2I Global EPRI – 007 – US, 2004).[9] B. Ram, Wave Power in the US: Permitting and JurisdictionalIssues (E2I Global EPRI DOE NREL – 008 – US).[10] M. Previsic, Wave power technologies, Proc. IEEE PES 05 GM,San Francisco, paper 05GM0542, June 2005, 1–6.[11] E2i/EPRI WP-004-US Rev 1 Assessment of Offshore WaveEnergy Conversion Devices.[12] E2i/EPRI WP-005-US Methodology, Guidelines and Assump-tions for the Conceptual Design of Offshore Wave EnergyPower Plants (Farms).[13] E2i/EPRI WP-006-HI System Level Design, Preliminary Per-formance and Cost Estimate – Hawaii.[14] E2i EPRI WP-006-OR System Level Design, Preliminary Per-formance and Cost Estimate – Oregon.[15] E2i/EPRI WP-006-ME System Level Design, Preliminary Per-formance and Cost Estimate – Maine.[16] E2i/EPRI WP-006-MA System Level Design, Preliminary Per-formance and Cost Estimate – Massachusetts.[17] E2i/EPRI WP-006-SFa System Level Design, PreliminaryPerformance and Cost Estimate – San Francisco, CaliforniaPelamis Offshore Wave Power Plant.427[18] E2i/EPRI WP-006-SFb System Level Design, PreliminaryPerformance and Cost Estimate – San Francisco EnergetechOffshore Wave Power Plant.[19] Sea Technology Magazine August 2003, Wave Energy Conver-sion – The State of the Art.[20] EPRI – RE Technical Assessment Guide Ocean Wave PowerSection for the years 2001, 2002 and 2003.[21] California Energy Commission – Wave Energy Resource As-sessment for the State of California.[22] A.D. Trapp & M. Watchorn, EB development of tidal streamenergy, Proc. MAREC 2001, 2001, 169–173.[23] A.T. Jones & A. Westwood, Economic forecast for renewableocean energy technologies, presented at EnergyOcean 2004,Palm Beach, Florida, 2004.[24] A.T. Jones & W. Rowley, Global perspective: Economicforecast for renewable ocean energy technologies, MTS Journal,36(4), 2002, 85–90.[25] N.J. Baker, M.A. Mueller, M. Watchorn, D. Slee, L. Haydock, &N. Brown, Direct drive power take off for the Stingray tidalcurrent generator, Proc. MAREC 2002, 2002, 1–10.[26] A.M. Gorlov, The helical turbine and its applications for tidaland wave power, Proc. OCEANS 2003, 2003, 1996.[27] P.W. Ullman, Offshore Tidal Power Generation – A newapproach to power conversion of the oceans’ tides, MTSJournal, 36(4), 2002, 16–24.[28] P. Breeze, The Future of Global Offshore Wind Power, ReuterBusiness Insight 2004.[29] L. Coakley, “Long Island Offshore Wind Park – 140 Megawattsof Offshore Wind Energy, presented at EnergyOcean 2004,Palm Beach, Florida, 2004.[30] O. Siddiqui & R. Bedard, Feasibility assessment of offshorewave and tidal current power production, Proc. IEEE PES 05GM, San Francisco, paper 05GM0538, 2005, 1–7.[31] E2i/EPRI WP-08-US-Identification of Permitting Issues.[32] Douglas-Westwood Ltd, The World Offshore Renewable EnergyReport 2007–2011, May 2007.
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