ENERGY POTENTIAL OF THE OCEANS IN EUROPE AND NORTH AMERICA: TIDAL, WAVE, CURRENTS, OTEC AND OFFSHORE WIND

T.J. Hammons∗

References

  1. [1]. The relative motion of these bodies causes the surface on the oceans to be raised and lowered periodically, as illustrated in Fig. 3. The physics of tidal power is explained in Reference [1]. Figure 3. Tide-generating forces based on earth–moon interactions. Source: O. Siddiqui & R. Bedard [30]. In deep water, the wave power spatial flux (in kW/m of wave front crest) is given by significant wave height (Hs in m) and the peak wave period (Tp in s). Based on these two parameters, the incident wave power (J in kW/m of wave crest length) associated with each sea state record is estimated by the following equation: J = 0.42 × (Hs)2 × Tp (kW) It is significant to note that wave power varies with the square of wave height – that is, a wave whose height is doubled generates four times as much power. The power of a tidal current is given by the following equation: Pwater = (1/2) rAV 3 (W) where A is the cross-sectional area of flow intercepted by the turbine device (m2 ), r is the water density (kg/m3 ) and V is current velocity speed (m/s). The current velocity V varies in a precisely predictable manner as an additive function of period of the different sinusoidal tidal components. Tidal flow energy studies are in progress at EPRI and the techno-economic results are not available. Therefore, the focus is on the results of the wave energy feasibility definition study of 2004. 4.2 Wave Project Results 4.2.1 US Wave Energy Resources An ideal site to deploy, operate and maintain an offshore wave energy power plant must have many attributes. First and foremost is a sufficient native energy and energy spectra potential.1 The US regional wave regimes and the total annual incident wave energy for each of these regimes are shown in Fig. 4. The total US available incident wave energy flux is about 2,300 TWh/yr. The DOE Energy Information Energy (EIA) estimated in 2003 hydroelectric generation in USA to be about 270 TWh which is a little more than a tenth of the yearly offshore wave energy flux into the US. Therefore, wave energy is a significant resource. Figure 4. US energy resources. Source: O. Siddiqui & R. Bedard [30]. 4.2.2 Feasibility Definition Study Sites Site attributes characterized by the Project Team included offshore bathymetry2 and seafloor surface geology, robustness of the coastal utility grid, regional maritime infrastructure for both fabrication and maintenance, conflicts with competing uses of sea space and existence of other unique characteristics that might minimize project development costs (e.g. existing ocean outfall easements for routing power cable and shore crossing). Table 2 identifies the site selected in each of the five states that participated in the study, and also provides a few key characteristics of each selected site. 4.2.3 Feasibility Study: WEC Devices Twelve companies responded to EPRI’s request for information. An initial screening considered two key issues: (1) technology readiness (i.e. readiness of device for demonstration in the 2006 time period) and (2) survivability in adverse conditions (i.e. sufficiency of technical information provided by the device manufacturer to prove the survivability in storm conditions). The eight devices that passed the 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 water height (i.e. the inverse of a topographic map). 420 Table 2 Estimated Performance of Pilot Demonstration Plants HI OR CA Mass Maine County Oahu Douglas SF Cape Cod Cumberland Grid I/C Waimanalo Gardner Wastewater Well Old Beach Plant Fleet Orchard Beach S/S Average 15.2 21.2 11.21 13.8 4.9 Annual J (kW/m) Depth (m) 60 60 30 60 60 Distance 2 3.5 13 9 9 from Shore Cable Makai IPP Outflow Water Dir Drill Dir Drill Landing Pier Pipe Outflow 1Sited within the marine sanctuary exclusionary zone. Source: O. Siddiqui & R. Bedard [30]. Table 3 Estimated Performance of Pilot Demonstration Plants Length (m) Width (m) Power (kW)1 Type Rating Ocean 120 4.6 153 Floating 1 Power Attenuator Delivery Energetech 25 35 259 OWC – Bottom 2 Terminator Wave 150 260 1,369 Floating 2 Dragon Overtopping Wave 9.5 9.5 351 Bottom Point 2 Swing Absorber Wave Bob 16 15 131 Floating Point 3 Absorber Aqua-Energy 6 6 17 Floating Point 3 Absorber OreCON 32 32 532 Floating OWC 3 Ind Natural 5.4 5.4 112 Bottom Point 3 Resources Inc Absorber 1Based on Oregon average annual wave energy resource. Source: O. Siddiqui & R. Bedard [30]. These eight devices were then assessed with the objective of determining any critical issues and recommending RD&D needed to achieve technological readiness for an at sea demonstration. As a result of this assessment, the eight devices were grouped into one of three levels of development categories: • Level 1 : Development complete and full-scale testing in the ocean underway. • Level 2 : Development near complete. Only deployment, recovery and mooring issues are yet to be validated. There are funded plans for full-scale at sea testing. • Level 3 : Most critical RD&D issues are resolved. Additional laboratory and sub-scale testing, simulations and systems integration work is needed prior to finalization of the full-scale design. There are no funded 421 plans for full-scale at sea testing. At the time of EPRI’s analysis (March 2004), only one WEC device manufacturer had attained a Level 1 technology readiness status – OPD with its Pelamis device. At the time of this paper (February 2005) there are an additional four WEC device manufacturers that are close to reaching that status: TeamWorks of the Netherlands with its Wave Swing, Energetechs of Australia with its OWC, Wave Dragon of Denmark with its overtopping device, and Ocean Power Technology of the US with a floating buoy. 4.2.4 Demonstration-Scale Plant Design: Oregon Example Demonstration-scale (as well as commercial-scale) designs were based on the OPD Pelamis WEC device for the five sites listed in Table 2. The Pelamis WEC device consists of four cylindrical steel sections, which are connected by three hydraulic PCM. Total length of the device is 120 m and device diameter is 4.6 m. Fig. 5 shows the device being tested off the Scottish coast. Figure 5. OPD Pelamis WEC device. 1 nm = 1 nautical mile. Source: O. Siddiqui & R. Bedard [30]. A second San Francisco, CA design based on the Energetech OWC WEC device depicted in Fig. 6 was also tested. Figure 6. Energetech WEC device. Source: O. Siddiqui & R. Bedard [30]. The estimated performance of the single unit demonstration plant at each of the five sites is shown in Table 4. Table 4 Estimated Performance of Pelamis Pilot Demonstration Plants HI OR CA1 Mass Maine Device Rated 750 750 750 750 750 Capacity (kW) Annual 1,989 1,472 1,229 1,268 426 Energy Absorbed (MWh/yr) Annual Energy 1,663 1,001 835 964 290 Produced (MWh/yr) Average 180 114 95 98 33 Electrical Power (kW) Number of 180 114 95 98 33 Homes Powered by Plant 1Energetech 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 Example The commercial system uses a total of 4 clusters, each one containing 45 Pelamis units (i.e. 180 total Pelamis WEC devices), connected to sub-sea cables. Each cluster consists of 3 rows with 15 devices per row. The other state designs are organized in a similar manner with 4 clusters. The number of devices per cluster varies such that each plant produces an annual energy output of 300,000 MWh/yr. The electrical interconnection of the devices is accomplished with flexible jumper cables, connecting the units in mid-water. The introduction of 4 independent sub-sea cables and the interconnection on the surface provides some redundancy in the wave farm arrangement. The estimated performance of the commercial-scale plant at each of the five sites is shown in Table 5. The device rated capacity has been derated from 750 kW in the demonstration plant to 500 kW for the commercial plant. The performance assessment of the demonstration plants shows that the PCMs are overrated and reducing the rated power to 500 kW per device would yield a significant cost reduction and only a relatively small decrease in annual output (attributed to the fact that the US sites have a lower energy level than UK sites for which the device was originally developed). 4.2.6 Learning Curves and Economics The costs and cost of electricity shown in the previous section are for the first commercial-scale wave plant. Learning through production experience reduces costs – a phenomenon that follows a logarithmic relationship such that 422 Table 5 Estimated Performance of Pelamis Commercial Plants HI OR CA Mass Maine Device Rated 500 500 500 500 500 Capacity (kW) Annual Energy 1,989 1,997 1,683 1,738 584 Absorbed (MWh/yr) Annual Energy 1,663 1,669 1,407 1,453 488 Produced (MWh/yr) Average Electrical 191 191 161 166 56 Power at Busbar (kW) Number of OPD 180 180 213 206 615 Pelamis Units Needed for 300,000 MWh/yr Number of Homes 34,000 34,000 34,000 34,000 34,000 Powered by Plant Source: 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%, which is consistent with documented experience in the wind energy, photovoltaic, shipbuilding, and offshore oil and gas industries. The industry-documented historical wind energy learning curve is shown as the top line in Fig. 7 [31]. The cost of electricity is about 4 cents/kWh in 2004 US dollars based on 40,000 MW of worldwide installed capacity and a good wind site. The lower and higher bound cost estimates of wave energy are also shown in Fig. 7. The 82% learning curve is applied to the wave power plant installed cost but not to the operation and maintenance part of cost of electricity (hence the reason that the three lines are not parallel). Figure 7. Electrical interconnection of demo-plant: Oregon example. Source: O. Siddiqui & R. Bedard [30]. Fig. 7 shows the cost of wave-generated electricity: low band (bottom curve), upper band (middle curve); and wind-generated electricity (top curve) at equal cumulative production volume under all cost estimating assumptions for the wave plant. It shows that the cost of wave-generated electricity is less than wind-generated electricity at any equal cumulative production volume under all cost estimating assumptions for the wave plant. The lower capital cost of a wave machine (compared to a wind machine) more than compensates for the higher O&M cost for the remotely located offshore wave machine. A challenge to the wave energy industry is to drive down O&M costs to offer even more economic favourability and to delay the crossover point shown at greater than 40,000 MW. In summary, the techno-economic forecast made by the Project Team is that wave energy will first become commercially competitive with the current 40,000 MW installed land-based wind technology at a cumulative production volume of 15,000 MW or less in Hawaii and northern California, about 20,000 MW in Oregon and about 40,000 MW in Massachusetts. This forecast was made on the basis of a 300,000 MWh/yr (nominal 90 MW at 38% capacity factor) Pelamis WEC commercial plant design and application of technology learning curves. Maine was the only state in the study whose wave climate was such that wave energy may never be able to economically compete with a good wind energy site. In addition to economics, there are other compelling arguments for investing in offshore wave energy technology. First, with proper sitting, converting ocean wave energy to electricity is believed to be one of the most environmentally benign ways to generate electricity. Second, offshore wave energy offers a way to minimize the “Not In My Backyard” (NIMBY) issues that plague many energy infrastructure 423 projects, from nuclear to coal and to wind generation. Because these devices have a very low profile and are located at a distance from the shore, they are generally not visible. Third, because wave energy is more predictable than solar and wind energy, it offers a better possibility than either solar or wind of being dispatch able and earning a capacity payment. A characteristic of wave energy that suggests that it may be one of the lowest cost renewable energy sources is its high power density. Processes in the ocean concentrate solar and wind energy into ocean waves making it easier and cheaper to harvest. Solar and wind energy sources are much more diffuse, by comparison. Since a diversity of energy sources is the bedrock of a robust electricity system, to overlook wave energy is inconsistent with national needs and goals. Wave energy is an energy source that is too important to overlook. 4.2.7 Recommendations The development of ocean energy technology and the deployment of this clean renewable energy technology would be greatly accelerated by adequate support from governments. Appropriate roles for governments in ocean energy development could include: • Providing leadership for the development of an ocean energy RD&D programme to fill known RD&D gaps, and to accelerate technology development and prototype system deployment. • Operating national offshore wave test centers to test performance and reliability of prototype ocean energy systems under real conditions. • Development of design and testing standards for ocean energy devices. • Joining the International Energy Agency Ocean Energy Systems Implementing Agreement to collaborate RD&D activities, and appropriate ocean energy policies with other governments and organizations. • Studying provision of production tax credits, renewable energy credits, and other incentives to spur private investment in ocean energy technologies and projects, and implementing appropriate incentives to accelerate ocean energy deployment. • Ensuring that the public receives a fair return from the use of ocean energy resources. • Ensuring that development rights are allocated through a transparent process that takes into account state, local, and public concerns. 5. Recent Progress in Offshore Renewable Energy Technology Development The recent progress in offshore renewable energy technology development is now examined and potential markets for tidal power, WEC, and offshore wind are considered. The analysis of market potentials for offshore renewable technology 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 and tidal current stream sectors. 5.1 Tidal Current Stream Historically, tidal projects have been large-scale barrage systems that block estuaries. Within the last few decades, developers have shifted toward technologies that capture the tidally driven coastal currents or tidal stream. The challenge is, “to develop technology and innovate in a way that will allow this form of low density renewable energy to become practical and economic” [22]. Tidal current turbines are basically underwater windmills. The tidal currents are used to rotate an underwater turbine. First proposed during the 1970s’ oil crisis, the technology has only recently become a reality with commercial prospects. Marine Current Turbines (MCT) installed the first full-scale prototype turbine (300 kW) off Lynmouth in Devon, UK in 2003. Shortly thereafter, the Norwegian company Hammerfest Støm installed their first grid-connected 300 kW prototype device. MCT, arguably the market leader is now preparing to install its new twin-rotored 1 MW device in 2007. The company has plans to install a commercial scale project off the UK coast around the turn of the decade. There are a great number of sites suitable for tidal current turbines. As tidal currents are predictable and reliable, tidal turbines have advantages over offshore wind counterparts. The ideal sites are generally within several kilometres of the shore in water depths of 20–30 m. 5.1.1 Tidal Forecasts Douglas-Westwood Ltd expect 25 MW of tidal current stream capacity to be brought online in the 2007–2011 period (see Fig. 8). The vast majority of this capacity will be in the UK where 23 MW is forecast. With several successful large-scale prototypes already tested, the period to the end of the decade will see further refinement of devices and applications for multiple-unit farms in key markets. The above forecast shows a sharp growth in 2011 from tidal current farms expected from MCT and Lunar Energy. Figure 8. Potential tidal current stream capacity 2007– 2011. Source: Douglas-Westwood Ltd [32]. 424 5.1.2 Projects Shiswa Lake Tidal Power Plant, Korea Korea has a plentiful tidal and tidal current energy resource. Under construction is a single stream style generator at Ansan City’s Shiswa Lake, which will have a capacity of 252 MW, comprised of 12 units of 21 MW generators. Annual power generation, when completed in 2008, is projected at 552 million kWh. If successful, this project will surpass La Rance (France) as the largest tidal power plant in the world. Korea is also planning a tidal current power plant in Uldol-muk Strait, a restriction in the strait where maximum water speed exceeds 6.5 m/s. The experimental plant will utilize helical or “Gorlov” turbines developed by GCK Technology [26]. Yalu River, China By creating a tidal lagoon offshore, Tidal Electric has taken a novel approach to resolve environmental and economic concerns of tidal barrage technology [27]. Due to the highly predictive nature of the ocean tides, the company has developed simulation models with performance data from available generators to optimize design for particular locations. The recent announcement of a cooperative agreement with the Chinese government for ambitious 300 MW offshore tidal power generation facilities off Yalu River, Liaoning Province allows for an engineering feasibility study to be undertaken. Tidal Electric also has plans under consideration for UK-based projects in Swansea Bay (30 MW), Fifoots Point (930 MW), and North Wales (432 MW). These projects have failed to make progress and will not go ahead in the foreseeable future. 5.2 Wave Energy The true potential of wave energy will only be realized in the offshore environment where large developments are conceivable. Nearly 300 concepts for wave energy devices have been proposed. The development process for wave energy can be looked at in three phases. First, smallscale prototype devices, typically with low capacity, will be deployed. During the second stage, outside funding from government or private investors is possible for the most promising devices. The final stage is the production of full-scale, grid-connected devices that will in some cases be deployable in farm style configurations. Modular offshore wave energy devices that can be deployed quickly and cost effectively in a wide range of conditions will accelerate commercial wave energy. In the coming decade, wave energy will become commercially successful through multiple-unit offshore projects, the first of which are now being installed. These projects clearly demonstrate the commercial future for wave energy but valuable operational experience is necessary before larger projects are built with a greater number of devices. The growth of shoreline wave energy devices is limited by the low number of available sites and high installation costs. Deployment costs for shoreline wave energy devices are very high because they are individual sitespecific projects and economies of scale are not applicable. Whereas an offshore 50-MW wave farm is conceivable, and will in time be developed, no shoreline wave energy converter can offer such potential for deployment in this way. As such, individual coastal installations are expected to be few and far between. Shoreline wave energy will, however, continue to be relevant, as the average unit capacity is generally higher than existing offshore technology. Individual devices can be very effective, especially for remote or island communities where, for example, an individual unit of 4 MW could have a big impact. Offshore locations offer greater power potential than shoreline locations. Shoreline technologies have the benefit of easy access for maintenance purposes, whereas offshore devices are in most cases more difficult to access. Improvements in reliability and accessibility will be critical to the commercial success of the many devices currently under development. 5.2.1 Wave Energy Forecast Douglas-Westwood Ltd claim there is a potential 46 MW of wave energy projects that could be installed between 2007 and 2011. The United Kingdom is expected to be the dominant player over the next 5 years, with a forecast capacity of 28.6 MW, which equates to a 62% market share. In comparison with other countries, the UK has forecast capacity every year to 2008, whereas installations elsewhere are more intermittent. Norway (6 MW) and Portugal (4.25 MW) are the next most significant markets and have several projected installations, but they lag behind the UK in terms of technology development and project deployment. The United Kingdom government has shown reasonable levels of support, which have injected many technologies with valuable grants. The result is a number of proven wave technologies with good prospects for commercial deployment and several more at an advanced prototype stage. Coupled with a world-class natural resource, the United Kingdom remains the strongest market into the next decade. Potential wave energy capacity 2007–2011 is indicated in Fig. 9. Figure 9. Potential wave energy capacity 2007–2011. Source: Douglas-Westwood Ltd [32]. 425 5.3 Offshore Wind There are 25 operational offshore wind farms in the world today. The 436 installed turbines in these projects provide a total of 919 MW. The first offshore wind turbine was installed at Nogersund off Sweden in 1990. The first offshore wind farm were installed at Vindeby off the Danish island of Lolland in 1991. The most recent project is the Beatrice Demonstration Project off Scotland. The first 10 years of the industry saw small projects being built in very shallow water near-shore locations. These wind farms in most cases used onshore turbine models with slight adaptations made. These “demonstration” projects have paved the way for the more recent projects that are of a much larger size. The biggest offshore wind farm yet installed is the Nysted development off Denmark which was completed in 2003. Just as this project dwarfs those built 10 years previously, within another decade projects will be installed that are many times greater in size than today’s offshore wind farms. The industry faces problems from increasing costs. In the last 5 years, the cost of offshore wind has increased by up to 65%. This is caused by increased turbine prices driven by the extremely strong onshore wind market (particularly in the US), and rising contractor prices based upon experiences on earlier projects. Cost reductions of approximately 25% are essential to help stimulate the industry and help strengthen it. The total global offshore wind capacity forecast for installation between 2007 and 2011 stands at 4.2 GW. The UK is the world’s largest market for the forthcoming 5-year period. A total of 2.2 GW is forecast here, representing 52% of the entire world market. The UK’s “Round 1” projects are continuing to be installed at the rate of 1–2 per year. The first of the larger “Round 2” projects are expected to enter construction at the turn of the decade, significantly boosting the UK’s capacity. The UK’s prospects are expected almost three times those of Germany, the next largest market. Germany has so far seen only minor installations, but the first significant activity is expected to begin in 2008 with the Borkum West project. Several projects are forecast for 2009 and 2010. The bulk of projects, however, will not begin construction until the turn of the decade. Long-term prospects are excellent off Germany but in the short and mid-term future the industry has much to overcome. The only activity off Denmark in the period will come with the construction and completion of the Horns Rev II and Nysted II projects in 2009 and 2010 respectively. Although the country showed initial promise for offshore development, a lack of government commitment has stunted the industry here. Long-term prospects are, however, high and a new round of licences is expected shortly for development in the next decade. Whilst the Netherlands is currently seeing a period of activity with the completion of the Egmond aan Zee project and construction of Q7-WP, it will not be until after this decade that the next projects are completed. Whilst not reflected in the above forecast, long-term prospects are good. North America is yet to install any offshore wind projects. With the onshore market in such good health, the drivers for offshore are not as strong as in Europe where the industry is reaching take-off after a period of slow but steady growth. There are currently three large offshore wind farms in North America in advanced stages of planning although it is now unlikely that they will be built this decade due to delays from drawn-out permitting processes and legal challenges. In addition to this are a number of more speculative large projects and several small scale demonstration projects that could be installed before the end of the decade. The highest profile project is Cape Wind off the coast of Massachusetts. The proposed 420 MW wind farm has courted controversy since conception. After clearing a number of regulatory and legal hurdles over a 6-year period, the project faces a ruling from US federal authorities. The Minerals Management Service (MMS) took over regulation of offshore renewables in the autumn of 2005. The MMS intend to record a decision on the project in the fall of 2008. The 144 MW Long Island offshore wind farm is being developed by FPL Energy. The MMS is due to record a decision on the project in spring 2008. The project started after The Long Island Power Authority announced in January 2003 that it was seeking developers to build an offshore wind farm off Jones Beach. The largest North American project is the 1,750 MW NaiKun wind farm off the coast of British Columbia which will be developed in five phases, the first of which is scheduled for completion in 2011. Cumulative installed offshore wind capacity is given in Fig. 10. Forecast offshore capacity 2002–2011 is indicated in Fig. 11. 6. Conclusions For the entire marine renewables sector, 4.5 GW of installed capacity is projected between 2007 and 2011. Some 98% of that capacity is in the form of offshore wind farms. The Figure 10. Cumulative installed offshore wind capacity. Source: Douglas-Westwood Ltd [32]. 426 Figure 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 percentage of the total expenditure on offshore renewables, of the order of $300 million in total expenditure between them. However, wave and tidal power currently attract higher expenditures per megawatt. This indicates higher costs of the immature developing industries. These costs will fall as time goes by and the industries progresses. The leading devices should be comparable with, and in some cases more competitive than offshore wind, by early next decade. The more well-established offshore wind sector will lead the offshore renewables industry, and will see strong growth throughout the period led by countries such as the UK, the Netherlands, Germany and Denmark. Established onshore wind supply chains in Denmark and Germany will, however, see most of the financial benefit of the growth in offshore wind for the short-term. The dominance of offshore wind does not mean wave and tidal energy are not important, they are just less well developed, and the industry is much younger. From around 2010, wave and tidal should begin to expand commercially. The growth of wave and tidal power offers significant supply chain growth opportunities for countries that failed to capture the value of the growth in the wind industry (both onshore and offshore). Europe is the dominant region, leading in all three sectors. The UK is a particularly important market, driven by a world-class natural resource, the past 3 years has seen notable successes in wind, wave and tidal energies. With more approved offshore wind capacity in the planning stage than any other country, prospects for the United Kingdom look bright. The UK is forecast to become world leader in offshore wind in 2008 and is already the leader in the wave and tidal current stream industries. The UK Energy White Paper due May 2007 is expected to increase banding to the main support system for renewables to give greater support to emerging technologies, particularly offshore renewables. This should provide a strong catalyst for growth. Whilst currently lacking, future growth in other regions should not be discounted in the long term. Interest in North America is growing and we will see large projects progressing around the end of the decade, particularly in the offshore wind sector. Greater support and structure would reap big rewards for the industry here. At present though, it lags far behind the established European market which remains the focal point for the marine renewables industry. Europe is home to the leading technology developers and superior funding packages are in place in key countries to stimulate development. Acknowledgements The author acknowledges contributions made by Peter O’Donnell (Senior Energy Specialist, Manager Generation Solar & Renewables Programs, San Francisco Environment Organization, CA, USA); Omar Siddiqui (Senior Associate, Global Energy Partners LLC, Lafayette, CA, USA); Roger Bedard (Offshore Wave Energy Project Manager, EPRI, CA, USA), Andrew Mill (Managing Director European Marine Energy Centre, UK); Mirko Previsic (Consultant— Offshore Renewables, Sacramento, CA, USA); Anthony T Jones (Senior Oceanographer, oceanUS consulting, Palm Springs, CA, USA); and Adam Westwood (Renewable Energy Manager, Douglas-Westwood Limited, Canterbury, UK, principally for Section 5). References [1] T.J. Hammons, Tidal Power, Proceedings IEEE, 81(3), 1993, 419–433.
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  9. [10] and
  10. [11]. The methodology, guidelines and assumptions for conceptual design of offshore wave energy power plants is given in Reference
  11. [12]. System level design, preliminary performance and cost estimates for Hawaii, Oregon, Main, Massachusetts, and San Francisco Pelamis offshore wave power plants are given in References [13–17], respectively, and system level design, preliminary performance and cost estimate for the San Francisco Energetech offshore wave power plant is given in Reference [18]. Further, the state of the art for WEC is reviewed in Reference [19], and a technical assessment guide for ocean wave power is made in Reference [20]. A wave energy resource assessment 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 and Tidal Current Power Production: A Collaborative Public/Private Partnership Collaborative power production feasibility definition studies on offshore wave energy and tidal current energy on behalf of a number of public and private entities is being undertaken at this time (February 2005). The outcome of the offshore wave study, which began in 2004 under the EPRI, is a compelling techno-economic case for investing in the RD&D of technology to convert the kinetic energy of ocean waves into electricity. The tidal current studies began in early 2005 and are currently at the site identification and device assessment stage. Techno-economic results for tidal plant designs at various sites were made in late 2005. 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 Energy The elements of a wave and tidal current energy feasibility study are: (a) identify and characterize potential sites for assembling and deploying a power plant and for connecting the plant to the electric grid; (b) identify and assess WEC devices; (c) conduct a conceptual design of a demonstrationand commercial-scale offshore wave power plant and, based on performance and cost estimates, assess the techno-economic viability of the wave energy source and the energy conversion technology; and (d) identify and assess the environmental and regulatory issues associated with implementing the technology. Two characteristics of waves and tides important to the generation and dispatch of electricity from WEC devices are its variability and predictability. While the ocean is never totally calm, wave power is more continuous than the winds that generate it. The average power during the winter may be six times that obtained during the summer; however, power values may vary by a factor of a hundred with the random occurrences of storms. Therefore, the power of waves is highly variable. The predictability of wave energy is of the order of a few days. The waves resulting, for example, from storms that occur off the coast of Japan, will take that long to reach the northwest coast of the United States. The power from tidal currents, on the other hand, typically varies according to a diurnal cycle. The major benefit of tidal power is its high predictability for a given site years in advance, provided there is a thorough knowledge of the site. A drawback of tidal power is its low capacity factor, and that its peak availability misses peak demand times because of the 12.5 h cycle of the tides. Ocean waves are generated by the winds that result from uneven heating around the globe. Waves are formed by winds blowing over the water surface, which make the water particles adopt circular motions as depicted in Fig. 2. This motion carries kinetic energy, the amount Figure 2. Wave-generating forces based on wind–water interaction. Source: M. Previsic [10]. 419 of which is determined by the speed and duration of the wind, the length of sea it blows over, the water depth, sea bed conditions and also interactions with the tides. Waves occur only in the volume of water closest to the water surface, whereas in tides, the entire water body moves, from the surface to the seabed. The tides are generated by rotation of the earth within the gravitational fields of the moon and sun [1]. The relative motion of these bodies causes the surface on the oceans to be raised and lowered periodically, as illustrated in Fig. 3. The physics of tidal power is explained in Reference [1]. Figure 3. Tide-generating forces based on earth–moon interactions. Source: O. Siddiqui & R. Bedard [30]. In deep water, the wave power spatial flux (in kW/m of wave front crest) is given by significant wave height (Hs in m) and the peak wave period (Tp in s). Based on these two parameters, the incident wave power (J in kW/m of wave crest length) associated with each sea state record is estimated by the following equation: J = 0.42 × (Hs)2 × Tp (kW) It is significant to note that wave power varies with the square of wave height – that is, a wave whose height is doubled generates four times as much power. The power of a tidal current is given by the following equation: Pwater = (1/2) rAV 3 (W) where A is the cross-sectional area of flow intercepted by the turbine device (m2 ), r is the water density (kg/m3 ) and V is current velocity speed (m/s). The current velocity V varies in a precisely predictable manner as an additive function of period of the different sinusoidal tidal components. Tidal flow energy studies are in progress at EPRI and the techno-economic results are not available. Therefore, the focus is on the results of the wave energy feasibility definition study of 2004. 4.2 Wave Project Results 4.2.1 US Wave Energy Resources An ideal site to deploy, operate and maintain an offshore wave energy power plant must have many attributes. First and foremost is a sufficient native energy and energy spectra potential.1 The US regional wave regimes and the total annual incident wave energy for each of these regimes are shown in Fig. 4. The total US available incident wave energy flux is about 2,300 TWh/yr. The DOE Energy Information Energy (EIA) estimated in 2003 hydroelectric generation in USA to be about 270 TWh which is a little more than a tenth of the yearly offshore wave energy flux into the US. Therefore, wave energy is a significant resource. Figure 4. US energy resources. Source: O. Siddiqui & R. Bedard [30]. 4.2.2 Feasibility Definition Study Sites Site attributes characterized by the Project Team included offshore bathymetry2 and seafloor surface geology, robustness of the coastal utility grid, regional maritime infrastructure for both fabrication and maintenance, conflicts with competing uses of sea space and existence of other unique characteristics that might minimize project development costs (e.g. existing ocean outfall easements for routing power cable and shore crossing). Table 2 identifies the site selected in each of the five states that participated in the study, and also provides a few key characteristics of each selected site. 4.2.3 Feasibility Study: WEC Devices Twelve companies responded to EPRI’s request for information. An initial screening considered two key issues: (1) technology readiness (i.e. readiness of device for demonstration in the 2006 time period) and (2) survivability in adverse conditions (i.e. sufficiency of technical information provided by the device manufacturer to prove the survivability in storm conditions). The eight devices that passed the 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 water height (i.e. the inverse of a topographic map). 420 Table 2 Estimated Performance of Pilot Demonstration Plants HI OR CA Mass Maine County Oahu Douglas SF Cape Cod Cumberland Grid I/C Waimanalo Gardner Wastewater Well Old Beach Plant Fleet Orchard Beach S/S Average 15.2 21.2 11.21 13.8 4.9 Annual J (kW/m) Depth (m) 60 60 30 60 60 Distance 2 3.5 13 9 9 from Shore Cable Makai IPP Outflow Water Dir Drill Dir Drill Landing Pier Pipe Outflow 1Sited within the marine sanctuary exclusionary zone. Source: O. Siddiqui & R. Bedard [30]. Table 3 Estimated Performance of Pilot Demonstration Plants Length (m) Width (m) Power (kW)1 Type Rating Ocean 120 4.6 153 Floating 1 Power Attenuator Delivery Energetech 25 35 259 OWC – Bottom 2 Terminator Wave 150 260 1,369 Floating 2 Dragon Overtopping Wave 9.5 9.5 351 Bottom Point 2 Swing Absorber Wave Bob 16 15 131 Floating Point 3 Absorber Aqua-Energy 6 6 17 Floating Point 3 Absorber OreCON 32 32 532 Floating OWC 3 Ind Natural 5.4 5.4 112 Bottom Point 3 Resources Inc Absorber 1Based on Oregon average annual wave energy resource. Source: O. Siddiqui & R. Bedard [30]. These eight devices were then assessed with the objective of determining any critical issues and recommending RD&D needed to achieve technological readiness for an at sea demonstration. As a result of this assessment, the eight devices were grouped into one of three levels of development categories: • Level 1 : Development complete and full-scale testing in the ocean underway. • Level 2 : Development near complete. Only deployment, recovery and mooring issues are yet to be validated. There are funded plans for full-scale at sea testing. • Level 3 : Most critical RD&D issues are resolved. Additional laboratory and sub-scale testing, simulations and systems integration work is needed prior to finalization of the full-scale design. There are no funded 421 plans for full-scale at sea testing. At the time of EPRI’s analysis (March 2004), only one WEC device manufacturer had attained a Level 1 technology readiness status – OPD with its Pelamis device. At the time of this paper (February 2005) there are an additional four WEC device manufacturers that are close to reaching that status: TeamWorks of the Netherlands with its Wave Swing, Energetechs of Australia with its OWC, Wave Dragon of Denmark with its overtopping device, and Ocean Power Technology of the US with a floating buoy. 4.2.4 Demonstration-Scale Plant Design: Oregon Example Demonstration-scale (as well as commercial-scale) designs were based on the OPD Pelamis WEC device for the five sites listed in Table 2. The Pelamis WEC device consists of four cylindrical steel sections, which are connected by three hydraulic PCM. Total length of the device is 120 m and device diameter is 4.6 m. Fig. 5 shows the device being tested off the Scottish coast. Figure 5. OPD Pelamis WEC device. 1 nm = 1 nautical mile. Source: O. Siddiqui & R. Bedard [30]. A second San Francisco, CA design based on the Energetech OWC WEC device depicted in Fig. 6 was also tested. Figure 6. Energetech WEC device. Source: O. Siddiqui & R. Bedard [30]. The estimated performance of the single unit demonstration plant at each of the five sites is shown in Table 4. Table 4 Estimated Performance of Pelamis Pilot Demonstration Plants HI OR CA1 Mass Maine Device Rated 750 750 750 750 750 Capacity (kW) Annual 1,989 1,472 1,229 1,268 426 Energy Absorbed (MWh/yr) Annual Energy 1,663 1,001 835 964 290 Produced (MWh/yr) Average 180 114 95 98 33 Electrical Power (kW) Number of 180 114 95 98 33 Homes Powered by Plant 1Energetech 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 Example The commercial system uses a total of 4 clusters, each one containing 45 Pelamis units (i.e. 180 total Pelamis WEC devices), connected to sub-sea cables. Each cluster consists of 3 rows with 15 devices per row. The other state designs are organized in a similar manner with 4 clusters. The number of devices per cluster varies such that each plant produces an annual energy output of 300,000 MWh/yr. The electrical interconnection of the devices is accomplished with flexible jumper cables, connecting the units in mid-water. The introduction of 4 independent sub-sea cables and the interconnection on the surface provides some redundancy in the wave farm arrangement. The estimated performance of the commercial-scale plant at each of the five sites is shown in Table 5. The device rated capacity has been derated from 750 kW in the demonstration plant to 500 kW for the commercial plant. The performance assessment of the demonstration plants shows that the PCMs are overrated and reducing the rated power to 500 kW per device would yield a significant cost reduction and only a relatively small decrease in annual output (attributed to the fact that the US sites have a lower energy level than UK sites for which the device was originally developed). 4.2.6 Learning Curves and Economics The costs and cost of electricity shown in the previous section are for the first commercial-scale wave plant. Learning through production experience reduces costs – a phenomenon that follows a logarithmic relationship such that 422 Table 5 Estimated Performance of Pelamis Commercial Plants HI OR CA Mass Maine Device Rated 500 500 500 500 500 Capacity (kW) Annual Energy 1,989 1,997 1,683 1,738 584 Absorbed (MWh/yr) Annual Energy 1,663 1,669 1,407 1,453 488 Produced (MWh/yr) Average Electrical 191 191 161 166 56 Power at Busbar (kW) Number of OPD 180 180 213 206 615 Pelamis Units Needed for 300,000 MWh/yr Number of Homes 34,000 34,000 34,000 34,000 34,000 Powered by Plant Source: 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%, which is consistent with documented experience in the wind energy, photovoltaic, shipbuilding, and offshore oil and gas industries. The industry-documented historical wind energy learning curve is shown as the top line in Fig. 7 [31]. The cost of electricity is about 4 cents/kWh in 2004 US dollars based on 40,000 MW of worldwide installed capacity and a good wind site. The lower and higher bound cost estimates of wave energy are also shown in Fig. 7. The 82% learning curve is applied to the wave power plant installed cost but not to the operation and maintenance part of cost of electricity (hence the reason that the three lines are not parallel). Figure 7. Electrical interconnection of demo-plant: Oregon example. Source: O. Siddiqui & R. Bedard [30]. Fig. 7 shows the cost of wave-generated electricity: low band (bottom curve), upper band (middle curve); and wind-generated electricity (top curve) at equal cumulative production volume under all cost estimating assumptions for the wave plant. It shows that the cost of wave-generated electricity is less than wind-generated electricity at any equal cumulative production volume under all cost estimating assumptions for the wave plant. The lower capital cost of a wave machine (compared to a wind machine) more than compensates for the higher O&M cost for the remotely located offshore wave machine. A challenge to the wave energy industry is to drive down O&M costs to offer even more economic favourability and to delay the crossover point shown at greater than 40,000 MW. In summary, the techno-economic forecast made by the Project Team is that wave energy will first become commercially competitive with the current 40,000 MW installed land-based wind technology at a cumulative production volume of 15,000 MW or less in Hawaii and northern California, about 20,000 MW in Oregon and about 40,000 MW in Massachusetts. This forecast was made on the basis of a 300,000 MWh/yr (nominal 90 MW at 38% capacity factor) Pelamis WEC commercial plant design and application of technology learning curves. Maine was the only state in the study whose wave climate was such that wave energy may never be able to economically compete with a good wind energy site. In addition to economics, there are other compelling arguments for investing in offshore wave energy technology. First, with proper sitting, converting ocean wave energy to electricity is believed to be one of the most environmentally benign ways to generate electricity. Second, offshore wave energy offers a way to minimize the “Not In My Backyard” (NIMBY) issues that plague many energy infrastructure 423 projects, from nuclear to coal and to wind generation. Because these devices have a very low profile and are located at a distance from the shore, they are generally not visible. Third, because wave energy is more predictable than solar and wind energy, it offers a better possibility than either solar or wind of being dispatch able and earning a capacity payment. A characteristic of wave energy that suggests that it may be one of the lowest cost renewable energy sources is its high power density. Processes in the ocean concentrate solar and wind energy into ocean waves making it easier and cheaper to harvest. Solar and wind energy sources are much more diffuse, by comparison. Since a diversity of energy sources is the bedrock of a robust electricity system, to overlook wave energy is inconsistent with national needs and goals. Wave energy is an energy source that is too important to overlook. 4.2.7 Recommendations The development of ocean energy technology and the deployment of this clean renewable energy technology would be greatly accelerated by adequate support from governments. Appropriate roles for governments in ocean energy development could include: • Providing leadership for the development of an ocean energy RD&D programme to fill known RD&D gaps, and to accelerate technology development and prototype system deployment. • Operating national offshore wave test centers to test performance and reliability of prototype ocean energy systems under real conditions. • Development of design and testing standards for ocean energy devices. • Joining the International Energy Agency Ocean Energy Systems Implementing Agreement to collaborate RD&D activities, and appropriate ocean energy policies with other governments and organizations. • Studying provision of production tax credits, renewable energy credits, and other incentives to spur private investment in ocean energy technologies and projects, and implementing appropriate incentives to accelerate ocean energy deployment. • Ensuring that the public receives a fair return from the use of ocean energy resources. • Ensuring that development rights are allocated through a transparent process that takes into account state, local, and public concerns. 5. Recent Progress in Offshore Renewable Energy Technology Development The recent progress in offshore renewable energy technology development is now examined and potential markets for tidal power, WEC, and offshore wind are considered. The analysis of market potentials for offshore renewable technology 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 and tidal current stream sectors. 5.1 Tidal Current Stream Historically, tidal projects have been large-scale barrage systems that block estuaries. Within the last few decades, developers have shifted toward technologies that capture the tidally driven coastal currents or tidal stream. The challenge is, “to develop technology and innovate in a way that will allow this form of low density renewable energy to become practical and economic” [22]. Tidal current turbines are basically underwater windmills. The tidal currents are used to rotate an underwater turbine. First proposed during the 1970s’ oil crisis, the technology has only recently become a reality with commercial prospects. Marine Current Turbines (MCT) installed the first full-scale prototype turbine (300 kW) off Lynmouth in Devon, UK in 2003. Shortly thereafter, the Norwegian company Hammerfest Støm installed their first grid-connected 300 kW prototype device. MCT, arguably the market leader is now preparing to install its new twin-rotored 1 MW device in 2007. The company has plans to install a commercial scale project off the UK coast around the turn of the decade. There are a great number of sites suitable for tidal current turbines. As tidal currents are predictable and reliable, tidal turbines have advantages over offshore wind counterparts. The ideal sites are generally within several kilometres of the shore in water depths of 20–30 m. 5.1.1 Tidal Forecasts Douglas-Westwood Ltd expect 25 MW of tidal current stream capacity to be brought online in the 2007–2011 period (see Fig. 8). The vast majority of this capacity will be in the UK where 23 MW is forecast. With several successful large-scale prototypes already tested, the period to the end of the decade will see further refinement of devices and applications for multiple-unit farms in key markets. The above forecast shows a sharp growth in 2011 from tidal current farms expected from MCT and Lunar Energy. Figure 8. Potential tidal current stream capacity 2007– 2011. Source: Douglas-Westwood Ltd [32]. 424 5.1.2 Projects Shiswa Lake Tidal Power Plant, Korea Korea has a plentiful tidal and tidal current energy resource. Under construction is a single stream style generator at Ansan City’s Shiswa Lake, which will have a capacity of 252 MW, comprised of 12 units of 21 MW generators. Annual power generation, when completed in 2008, is projected at 552 million kWh. If successful, this project will surpass La Rance (France) as the largest tidal power plant in the world. Korea is also planning a tidal current power plant in Uldol-muk Strait, a restriction in the strait where maximum water speed exceeds 6.5 m/s. The experimental plant will utilize helical or “Gorlov” turbines developed by GCK Technology [26]. Yalu River, China By creating a tidal lagoon offshore, Tidal Electric has taken a novel approach to resolve environmental and economic concerns of tidal barrage technology [27]. Due to the highly predictive nature of the ocean tides, the company has developed simulation models with performance data from available generators to optimize design for particular locations. The recent announcement of a cooperative agreement with the Chinese government for ambitious 300 MW offshore tidal power generation facilities off Yalu River, Liaoning Province allows for an engineering feasibility study to be undertaken. Tidal Electric also has plans under consideration for UK-based projects in Swansea Bay (30 MW), Fifoots Point (930 MW), and North Wales (432 MW). These projects have failed to make progress and will not go ahead in the foreseeable future. 5.2 Wave Energy The true potential of wave energy will only be realized in the offshore environment where large developments are conceivable. Nearly 300 concepts for wave energy devices have been proposed. The development process for wave energy can be looked at in three phases. First, smallscale prototype devices, typically with low capacity, will be deployed. During the second stage, outside funding from government or private investors is possible for the most promising devices. The final stage is the production of full-scale, grid-connected devices that will in some cases be deployable in farm style configurations. Modular offshore wave energy devices that can be deployed quickly and cost effectively in a wide range of conditions will accelerate commercial wave energy. In the coming decade, wave energy will become commercially successful through multiple-unit offshore projects, the first of which are now being installed. These projects clearly demonstrate the commercial future for wave energy but valuable operational experience is necessary before larger projects are built with a greater number of devices. The growth of shoreline wave energy devices is limited by the low number of available sites and high installation costs. Deployment costs for shoreline wave energy devices are very high because they are individual sitespecific projects and economies of scale are not applicable. Whereas an offshore 50-MW wave farm is conceivable, and will in time be developed, no shoreline wave energy converter can offer such potential for deployment in this way. As such, individual coastal installations are expected to be few and far between. Shoreline wave energy will, however, continue to be relevant, as the average unit capacity is generally higher than existing offshore technology. Individual devices can be very effective, especially for remote or island communities where, for example, an individual unit of 4 MW could have a big impact. Offshore locations offer greater power potential than shoreline locations. Shoreline technologies have the benefit of easy access for maintenance purposes, whereas offshore devices are in most cases more difficult to access. Improvements in reliability and accessibility will be critical to the commercial success of the many devices currently under development. 5.2.1 Wave Energy Forecast Douglas-Westwood Ltd claim there is a potential 46 MW of wave energy projects that could be installed between 2007 and 2011. The United Kingdom is expected to be the dominant player over the next 5 years, with a forecast capacity of 28.6 MW, which equates to a 62% market share. In comparison with other countries, the UK has forecast capacity every year to 2008, whereas installations elsewhere are more intermittent. Norway (6 MW) and Portugal (4.25 MW) are the next most significant markets and have several projected installations, but they lag behind the UK in terms of technology development and project deployment. The United Kingdom government has shown reasonable levels of support, which have injected many technologies with valuable grants. The result is a number of proven wave technologies with good prospects for commercial deployment and several more at an advanced prototype stage. Coupled with a world-class natural resource, the United Kingdom remains the strongest market into the next decade. Potential wave energy capacity 2007–2011 is indicated in Fig. 9. Figure 9. Potential wave energy capacity 2007–2011. Source: Douglas-Westwood Ltd [32]. 425 5.3 Offshore Wind There are 25 operational offshore wind farms in the world today. The 436 installed turbines in these projects provide a total of 919 MW. The first offshore wind turbine was installed at Nogersund off Sweden in 1990. The first offshore wind farm were installed at Vindeby off the Danish island of Lolland in 1991. The most recent project is the Beatrice Demonstration Project off Scotland. The first 10 years of the industry saw small projects being built in very shallow water near-shore locations. These wind farms in most cases used onshore turbine models with slight adaptations made. These “demonstration” projects have paved the way for the more recent projects that are of a much larger size. The biggest offshore wind farm yet installed is the Nysted development off Denmark which was completed in 2003. Just as this project dwarfs those built 10 years previously, within another decade projects will be installed that are many times greater in size than today’s offshore wind farms. The industry faces problems from increasing costs. In the last 5 years, the cost of offshore wind has increased by up to 65%. This is caused by increased turbine prices driven by the extremely strong onshore wind market (particularly in the US), and rising contractor prices based upon experiences on earlier projects. Cost reductions of approximately 25% are essential to help stimulate the industry and help strengthen it. The total global offshore wind capacity forecast for installation between 2007 and 2011 stands at 4.2 GW. The UK is the world’s largest market for the forthcoming 5-year period. A total of 2.2 GW is forecast here, representing 52% of the entire world market. The UK’s “Round 1” projects are continuing to be installed at the rate of 1–2 per year. The first of the larger “Round 2” projects are expected to enter construction at the turn of the decade, significantly boosting the UK’s capacity. The UK’s prospects are expected almost three times those of Germany, the next largest market. Germany has so far seen only minor installations, but the first significant activity is expected to begin in 2008 with the Borkum West project. Several projects are forecast for 2009 and 2010. The bulk of projects, however, will not begin construction until the turn of the decade. Long-term prospects are excellent off Germany but in the short and mid-term future the industry has much to overcome. The only activity off Denmark in the period will come with the construction and completion of the Horns Rev II and Nysted II projects in 2009 and 2010 respectively. Although the country showed initial promise for offshore development, a lack of government commitment has stunted the industry here. Long-term prospects are, however, high and a new round of licences is expected shortly for development in the next decade. Whilst the Netherlands is currently seeing a period of activity with the completion of the Egmond aan Zee project and construction of Q7-WP, it will not be until after this decade that the next projects are completed. Whilst not reflected in the above forecast, long-term prospects are good. North America is yet to install any offshore wind projects. With the onshore market in such good health, the drivers for offshore are not as strong as in Europe where the industry is reaching take-off after a period of slow but steady growth. There are currently three large offshore wind farms in North America in advanced stages of planning although it is now unlikely that they will be built this decade due to delays from drawn-out permitting processes and legal challenges. In addition to this are a number of more speculative large projects and several small scale demonstration projects that could be installed before the end of the decade. The highest profile project is Cape Wind off the coast of Massachusetts. The proposed 420 MW wind farm has courted controversy since conception. After clearing a number of regulatory and legal hurdles over a 6-year period, the project faces a ruling from US federal authorities. The Minerals Management Service (MMS) took over regulation of offshore renewables in the autumn of 2005. The MMS intend to record a decision on the project in the fall of 2008. The 144 MW Long Island offshore wind farm is being developed by FPL Energy. The MMS is due to record a decision on the project in spring 2008. The project started after The Long Island Power Authority announced in January 2003 that it was seeking developers to build an offshore wind farm off Jones Beach. The largest North American project is the 1,750 MW NaiKun wind farm off the coast of British Columbia which will be developed in five phases, the first of which is scheduled for completion in 2011. Cumulative installed offshore wind capacity is given in Fig. 10. Forecast offshore capacity 2002–2011 is indicated in Fig. 11. 6. Conclusions For the entire marine renewables sector, 4.5 GW of installed capacity is projected between 2007 and 2011. Some 98% of that capacity is in the form of offshore wind farms. The Figure 10. Cumulative installed offshore wind capacity. Source: Douglas-Westwood Ltd [32]. 426 Figure 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 percentage of the total expenditure on offshore renewables, of the order of $300 million in total expenditure between them. However, wave and tidal power currently attract higher expenditures per megawatt. This indicates higher costs of the immature developing industries. These costs will fall as time goes by and the industries progresses. The leading devices should be comparable with, and in some cases more competitive than offshore wind, by early next decade. The more well-established offshore wind sector will lead the offshore renewables industry, and will see strong growth throughout the period led by countries such as the UK, the Netherlands, Germany and Denmark. Established onshore wind supply chains in Denmark and Germany will, however, see most of the financial benefit of the growth in offshore wind for the short-term. The dominance of offshore wind does not mean wave and tidal energy are not important, they are just less well developed, and the industry is much younger. From around 2010, wave and tidal should begin to expand commercially. The growth of wave and tidal power offers significant supply chain growth opportunities for countries that failed to capture the value of the growth in the wind industry (both onshore and offshore). Europe is the dominant region, leading in all three sectors. The UK is a particularly important market, driven by a world-class natural resource, the past 3 years has seen notable successes in wind, wave and tidal energies. With more approved offshore wind capacity in the planning stage than any other country, prospects for the United Kingdom look bright. The UK is forecast to become world leader in offshore wind in 2008 and is already the leader in the wave and tidal current stream industries. The UK Energy White Paper due May 2007 is expected to increase banding to the main support system for renewables to give greater support to emerging technologies, particularly offshore renewables. This should provide a strong catalyst for growth. Whilst currently lacking, future growth in other regions should not be discounted in the long term. Interest in North America is growing and we will see large projects progressing around the end of the decade, particularly in the offshore wind sector. Greater support and structure would reap big rewards for the industry here. At present though, it lags far behind the established European market which remains the focal point for the marine renewables industry. Europe is home to the leading technology developers and superior funding packages are in place in key countries to stimulate development. Acknowledgements The author acknowledges contributions made by Peter O’Donnell (Senior Energy Specialist, Manager Generation Solar & Renewables Programs, San Francisco Environment Organization, CA, USA); Omar Siddiqui (Senior Associate, Global Energy Partners LLC, Lafayette, CA, USA); Roger Bedard (Offshore Wave Energy Project Manager, EPRI, CA, USA), Andrew Mill (Managing Director European Marine Energy Centre, UK); Mirko Previsic (Consultant— Offshore Renewables, Sacramento, CA, USA); Anthony T Jones (Senior Oceanographer, oceanUS consulting, Palm Springs, CA, USA); and Adam Westwood (Renewable Energy 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 Conference, 1997. [3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Turbine for (Canadian) Ministry of Employment and Investment, N.H. Halvorson Consultants Ltd. [4] Renewable Energy: Power for a Sustainable Future; Technology Update, Tidal Current Power Update & Wave Power Update, Oxford University Press, 2001. [5] P. Fraenkel, Renewables is the tide turning for marine current turbines? Modern Power System, Marine Current Turbines Ltd, London, UK, June 30, 2001. [6] R. Bedard, Final summary report: offshore wave power feasibility demonstration project (E2I EPRI Global WP009 – US, 2005). [7] M. Previsic, System level design, performance and costs for San Francisco Pelamis offshore wave power plant (E2I EPRI Global – 006A – SF, 2004). [8] G. Hagerman, Offshore Wave Power in the US: Environmental Issues (E2I Global EPRI – 007 – US, 2004). [9] B. Ram, Wave Power in the US: Permitting and Jurisdictional Issues (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 Wave Energy Conversion Devices. [12] E2i/EPRI WP-005-US Methodology, Guidelines and Assumptions for the Conceptual Design of Offshore Wave Energy Power Plants (Farms).
  12. [13] E2i/EPRI WP-006-HI System Level Design, Preliminary Performance and Cost Estimate – Hawaii.
  13. [14] E2i EPRI WP-006-OR System Level Design, Preliminary Performance and Cost Estimate – Oregon.
  14. [15] E2i/EPRI WP-006-ME System Level Design, Preliminary Performance and Cost Estimate – Maine.
  15. [16] E2i/EPRI WP-006-MA System Level Design, Preliminary Performance and Cost Estimate – Massachusetts.
  16. [18]. Further, the state of the art for WEC is reviewed in Reference
  17. [19], and a technical assessment guide for ocean wave power is made in Reference
  18. [20]. A wave energy resource assessment for California is given in Reference
  19. [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 and Tidal Current Power Production: A Collaborative Public/Private Partnership Collaborative power production feasibility definition studies on offshore wave energy and tidal current energy on behalf of a number of public and private entities is being undertaken at this time (February 2005). The outcome of the offshore wave study, which began in 2004 under the EPRI, is a compelling techno-economic case for investing in the RD&D of technology to convert the kinetic energy of ocean waves into electricity. The tidal current studies began in early 2005 and are currently at the site identification and device assessment stage. Techno-economic results for tidal plant designs at various sites were made in late 2005. 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 Energy The elements of a wave and tidal current energy feasibility study are: (a) identify and characterize potential sites for assembling and deploying a power plant and for connecting the plant to the electric grid; (b) identify and assess WEC devices; (c) conduct a conceptual design of a demonstrationand commercial-scale offshore wave power plant and, based on performance and cost estimates, assess the techno-economic viability of the wave energy source and the energy conversion technology; and (d) identify and assess the environmental and regulatory issues associated with implementing the technology. Two characteristics of waves and tides important to the generation and dispatch of electricity from WEC devices are its variability and predictability. While the ocean is never totally calm, wave power is more continuous than the winds that generate it. The average power during the winter may be six times that obtained during the summer; however, power values may vary by a factor of a hundred with the random occurrences of storms. Therefore, the power of waves is highly variable. The predictability of wave energy is of the order of a few days. The waves resulting, for example, from storms that occur off the coast of Japan, will take that long to reach the northwest coast of the United States. The power from tidal currents, on the other hand, typically varies according to a diurnal cycle. The major benefit of tidal power is its high predictability for a given site years in advance, provided there is a thorough knowledge of the site. A drawback of tidal power is its low capacity factor, and that its peak availability misses peak demand times because of the 12.5 h cycle of the tides. Ocean waves are generated by the winds that result from uneven heating around the globe. Waves are formed by winds blowing over the water surface, which make the water particles adopt circular motions as depicted in Fig. 2. This motion carries kinetic energy, the amount Figure 2. Wave-generating forces based on wind–water interaction. Source: M. Previsic [10]. 419 of which is determined by the speed and duration of the wind, the length of sea it blows over, the water depth, sea bed conditions and also interactions with the tides. Waves occur only in the volume of water closest to the water surface, whereas in tides, the entire water body moves, from the surface to the seabed. The tides are generated by rotation of the earth within the gravitational fields of the moon and sun [1]. The relative motion of these bodies causes the surface on the oceans to be raised and lowered periodically, as illustrated in Fig. 3. The physics of tidal power is explained in Reference [1]. Figure 3. Tide-generating forces based on earth–moon interactions. Source: O. Siddiqui & R. Bedard [30]. In deep water, the wave power spatial flux (in kW/m of wave front crest) is given by significant wave height (Hs in m) and the peak wave period (Tp in s). Based on these two parameters, the incident wave power (J in kW/m of wave crest length) associated with each sea state record is estimated by the following equation: J = 0.42 × (Hs)2 × Tp (kW) It is significant to note that wave power varies with the square of wave height – that is, a wave whose height is doubled generates four times as much power. The power of a tidal current is given by the following equation: Pwater = (1/2) rAV 3 (W) where A is the cross-sectional area of flow intercepted by the turbine device (m2 ), r is the water density (kg/m3 ) and V is current velocity speed (m/s). The current velocity V varies in a precisely predictable manner as an additive function of period of the different sinusoidal tidal components. Tidal flow energy studies are in progress at EPRI and the techno-economic results are not available. Therefore, the focus is on the results of the wave energy feasibility definition study of 2004. 4.2 Wave Project Results 4.2.1 US Wave Energy Resources An ideal site to deploy, operate and maintain an offshore wave energy power plant must have many attributes. First and foremost is a sufficient native energy and energy spectra potential.1 The US regional wave regimes and the total annual incident wave energy for each of these regimes are shown in Fig. 4. The total US available incident wave energy flux is about 2,300 TWh/yr. The DOE Energy Information Energy (EIA) estimated in 2003 hydroelectric generation in USA to be about 270 TWh which is a little more than a tenth of the yearly offshore wave energy flux into the US. Therefore, wave energy is a significant resource. Figure 4. US energy resources. Source: O. Siddiqui & R. Bedard [30]. 4.2.2 Feasibility Definition Study Sites Site attributes characterized by the Project Team included offshore bathymetry2 and seafloor surface geology, robustness of the coastal utility grid, regional maritime infrastructure for both fabrication and maintenance, conflicts with competing uses of sea space and existence of other unique characteristics that might minimize project development costs (e.g. existing ocean outfall easements for routing power cable and shore crossing). Table 2 identifies the site selected in each of the five states that participated in the study, and also provides a few key characteristics of each selected site. 4.2.3 Feasibility Study: WEC Devices Twelve companies responded to EPRI’s request for information. An initial screening considered two key issues: (1) technology readiness (i.e. readiness of device for demonstration in the 2006 time period) and (2) survivability in adverse conditions (i.e. sufficiency of technical information provided by the device manufacturer to prove the survivability in storm conditions). The eight devices that passed the 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 water height (i.e. the inverse of a topographic map). 420 Table 2 Estimated Performance of Pilot Demonstration Plants HI OR CA Mass Maine County Oahu Douglas SF Cape Cod Cumberland Grid I/C Waimanalo Gardner Wastewater Well Old Beach Plant Fleet Orchard Beach S/S Average 15.2 21.2 11.21 13.8 4.9 Annual J (kW/m) Depth (m) 60 60 30 60 60 Distance 2 3.5 13 9 9 from Shore Cable Makai IPP Outflow Water Dir Drill Dir Drill Landing Pier Pipe Outflow 1Sited within the marine sanctuary exclusionary zone. Source: O. Siddiqui & R. Bedard [30]. Table 3 Estimated Performance of Pilot Demonstration Plants Length (m) Width (m) Power (kW)1 Type Rating Ocean 120 4.6 153 Floating 1 Power Attenuator Delivery Energetech 25 35 259 OWC – Bottom 2 Terminator Wave 150 260 1,369 Floating 2 Dragon Overtopping Wave 9.5 9.5 351 Bottom Point 2 Swing Absorber Wave Bob 16 15 131 Floating Point 3 Absorber Aqua-Energy 6 6 17 Floating Point 3 Absorber OreCON 32 32 532 Floating OWC 3 Ind Natural 5.4 5.4 112 Bottom Point 3 Resources Inc Absorber 1Based on Oregon average annual wave energy resource. Source: O. Siddiqui & R. Bedard [30]. These eight devices were then assessed with the objective of determining any critical issues and recommending RD&D needed to achieve technological readiness for an at sea demonstration. As a result of this assessment, the eight devices were grouped into one of three levels of development categories: • Level 1 : Development complete and full-scale testing in the ocean underway. • Level 2 : Development near complete. Only deployment, recovery and mooring issues are yet to be validated. There are funded plans for full-scale at sea testing. • Level 3 : Most critical RD&D issues are resolved. Additional laboratory and sub-scale testing, simulations and systems integration work is needed prior to finalization of the full-scale design. There are no funded 421 plans for full-scale at sea testing. At the time of EPRI’s analysis (March 2004), only one WEC device manufacturer had attained a Level 1 technology readiness status – OPD with its Pelamis device. At the time of this paper (February 2005) there are an additional four WEC device manufacturers that are close to reaching that status: TeamWorks of the Netherlands with its Wave Swing, Energetechs of Australia with its OWC, Wave Dragon of Denmark with its overtopping device, and Ocean Power Technology of the US with a floating buoy. 4.2.4 Demonstration-Scale Plant Design: Oregon Example Demonstration-scale (as well as commercial-scale) designs were based on the OPD Pelamis WEC device for the five sites listed in Table 2. The Pelamis WEC device consists of four cylindrical steel sections, which are connected by three hydraulic PCM. Total length of the device is 120 m and device diameter is 4.6 m. Fig. 5 shows the device being tested off the Scottish coast. Figure 5. OPD Pelamis WEC device. 1 nm = 1 nautical mile. Source: O. Siddiqui & R. Bedard [30]. A second San Francisco, CA design based on the Energetech OWC WEC device depicted in Fig. 6 was also tested. Figure 6. Energetech WEC device. Source: O. Siddiqui & R. Bedard [30]. The estimated performance of the single unit demonstration plant at each of the five sites is shown in Table 4. Table 4 Estimated Performance of Pelamis Pilot Demonstration Plants HI OR CA1 Mass Maine Device Rated 750 750 750 750 750 Capacity (kW) Annual 1,989 1,472 1,229 1,268 426 Energy Absorbed (MWh/yr) Annual Energy 1,663 1,001 835 964 290 Produced (MWh/yr) Average 180 114 95 98 33 Electrical Power (kW) Number of 180 114 95 98 33 Homes Powered by Plant 1Energetech 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 Example The commercial system uses a total of 4 clusters, each one containing 45 Pelamis units (i.e. 180 total Pelamis WEC devices), connected to sub-sea cables. Each cluster consists of 3 rows with 15 devices per row. The other state designs are organized in a similar manner with 4 clusters. The number of devices per cluster varies such that each plant produces an annual energy output of 300,000 MWh/yr. The electrical interconnection of the devices is accomplished with flexible jumper cables, connecting the units in mid-water. The introduction of 4 independent sub-sea cables and the interconnection on the surface provides some redundancy in the wave farm arrangement. The estimated performance of the commercial-scale plant at each of the five sites is shown in Table 5. The device rated capacity has been derated from 750 kW in the demonstration plant to 500 kW for the commercial plant. The performance assessment of the demonstration plants shows that the PCMs are overrated and reducing the rated power to 500 kW per device would yield a significant cost reduction and only a relatively small decrease in annual output (attributed to the fact that the US sites have a lower energy level than UK sites for which the device was originally developed). 4.2.6 Learning Curves and Economics The costs and cost of electricity shown in the previous section are for the first commercial-scale wave plant. Learning through production experience reduces costs – a phenomenon that follows a logarithmic relationship such that 422 Table 5 Estimated Performance of Pelamis Commercial Plants HI OR CA Mass Maine Device Rated 500 500 500 500 500 Capacity (kW) Annual Energy 1,989 1,997 1,683 1,738 584 Absorbed (MWh/yr) Annual Energy 1,663 1,669 1,407 1,453 488 Produced (MWh/yr) Average Electrical 191 191 161 166 56 Power at Busbar (kW) Number of OPD 180 180 213 206 615 Pelamis Units Needed for 300,000 MWh/yr Number of Homes 34,000 34,000 34,000 34,000 34,000 Powered by Plant Source: 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%, which is consistent with documented experience in the wind energy, photovoltaic, shipbuilding, and offshore oil and gas industries. The industry-documented historical wind energy learning curve is shown as the top line in Fig. 7 [31]. The cost of electricity is about 4 cents/kWh in 2004 US dollars based on 40,000 MW of worldwide installed capacity and a good wind site. The lower and higher bound cost estimates of wave energy are also shown in Fig. 7. The 82% learning curve is applied to the wave power plant installed cost but not to the operation and maintenance part of cost of electricity (hence the reason that the three lines are not parallel). Figure 7. Electrical interconnection of demo-plant: Oregon example. Source: O. Siddiqui & R. Bedard [30]. Fig. 7 shows the cost of wave-generated electricity: low band (bottom curve), upper band (middle curve); and wind-generated electricity (top curve) at equal cumulative production volume under all cost estimating assumptions for the wave plant. It shows that the cost of wave-generated electricity is less than wind-generated electricity at any equal cumulative production volume under all cost estimating assumptions for the wave plant. The lower capital cost of a wave machine (compared to a wind machine) more than compensates for the higher O&M cost for the remotely located offshore wave machine. A challenge to the wave energy industry is to drive down O&M costs to offer even more economic favourability and to delay the crossover point shown at greater than 40,000 MW. In summary, the techno-economic forecast made by the Project Team is that wave energy will first become commercially competitive with the current 40,000 MW installed land-based wind technology at a cumulative production volume of 15,000 MW or less in Hawaii and northern California, about 20,000 MW in Oregon and about 40,000 MW in Massachusetts. This forecast was made on the basis of a 300,000 MWh/yr (nominal 90 MW at 38% capacity factor) Pelamis WEC commercial plant design and application of technology learning curves. Maine was the only state in the study whose wave climate was such that wave energy may never be able to economically compete with a good wind energy site. In addition to economics, there are other compelling arguments for investing in offshore wave energy technology. First, with proper sitting, converting ocean wave energy to electricity is believed to be one of the most environmentally benign ways to generate electricity. Second, offshore wave energy offers a way to minimize the “Not In My Backyard” (NIMBY) issues that plague many energy infrastructure 423 projects, from nuclear to coal and to wind generation. Because these devices have a very low profile and are located at a distance from the shore, they are generally not visible. Third, because wave energy is more predictable than solar and wind energy, it offers a better possibility than either solar or wind of being dispatch able and earning a capacity payment. A characteristic of wave energy that suggests that it may be one of the lowest cost renewable energy sources is its high power density. Processes in the ocean concentrate solar and wind energy into ocean waves making it easier and cheaper to harvest. Solar and wind energy sources are much more diffuse, by comparison. Since a diversity of energy sources is the bedrock of a robust electricity system, to overlook wave energy is inconsistent with national needs and goals. Wave energy is an energy source that is too important to overlook. 4.2.7 Recommendations The development of ocean energy technology and the deployment of this clean renewable energy technology would be greatly accelerated by adequate support from governments. Appropriate roles for governments in ocean energy development could include: • Providing leadership for the development of an ocean energy RD&D programme to fill known RD&D gaps, and to accelerate technology development and prototype system deployment. • Operating national offshore wave test centers to test performance and reliability of prototype ocean energy systems under real conditions. • Development of design and testing standards for ocean energy devices. • Joining the International Energy Agency Ocean Energy Systems Implementing Agreement to collaborate RD&D activities, and appropriate ocean energy policies with other governments and organizations. • Studying provision of production tax credits, renewable energy credits, and other incentives to spur private investment in ocean energy technologies and projects, and implementing appropriate incentives to accelerate ocean energy deployment. • Ensuring that the public receives a fair return from the use of ocean energy resources. • Ensuring that development rights are allocated through a transparent process that takes into account state, local, and public concerns. 5. Recent Progress in Offshore Renewable Energy Technology Development The recent progress in offshore renewable energy technology development is now examined and potential markets for tidal power, WEC, and offshore wind are considered. The analysis of market potentials for offshore renewable technology 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 and tidal current stream sectors. 5.1 Tidal Current Stream Historically, tidal projects have been large-scale barrage systems that block estuaries. Within the last few decades, developers have shifted toward technologies that capture the tidally driven coastal currents or tidal stream. The challenge is, “to develop technology and innovate in a way that will allow this form of low density renewable energy to become practical and economic”
  20. [22]. Tidal current turbines are basically underwater windmills. The tidal currents are used to rotate an underwater turbine. First proposed during the 1970s’ oil crisis, the technology has only recently become a reality with commercial prospects. Marine Current Turbines (MCT) installed the first full-scale prototype turbine (300 kW) off Lynmouth in Devon, UK in 2003. Shortly thereafter, the Norwegian company Hammerfest Støm installed their first grid-connected 300 kW prototype device. MCT, arguably the market leader is now preparing to install its new twin-rotored 1 MW device in 2007. The company has plans to install a commercial scale project off the UK coast around the turn of the decade. There are a great number of sites suitable for tidal current turbines. As tidal currents are predictable and reliable, tidal turbines have advantages over offshore wind counterparts. The ideal sites are generally within several kilometres of the shore in water depths of 20–30 m. 5.1.1 Tidal Forecasts Douglas-Westwood Ltd expect 25 MW of tidal current stream capacity to be brought online in the 2007–2011 period (see Fig. 8). The vast majority of this capacity will be in the UK where 23 MW is forecast. With several successful large-scale prototypes already tested, the period to the end of the decade will see further refinement of devices and applications for multiple-unit farms in key markets. The above forecast shows a sharp growth in 2011 from tidal current farms expected from MCT and Lunar Energy. Figure 8. Potential tidal current stream capacity 2007– 2011. Source: Douglas-Westwood Ltd [32]. 424 5.1.2 Projects Shiswa Lake Tidal Power Plant, Korea Korea has a plentiful tidal and tidal current energy resource. Under construction is a single stream style generator at Ansan City’s Shiswa Lake, which will have a capacity of 252 MW, comprised of 12 units of 21 MW generators. Annual power generation, when completed in 2008, is projected at 552 million kWh. If successful, this project will surpass La Rance (France) as the largest tidal power plant in the world. Korea is also planning a tidal current power plant in Uldol-muk Strait, a restriction in the strait where maximum water speed exceeds 6.5 m/s. The experimental plant will utilize helical or “Gorlov” turbines developed by GCK Technology [26]. Yalu River, China By creating a tidal lagoon offshore, Tidal Electric has taken a novel approach to resolve environmental and economic concerns of tidal barrage technology [27]. Due to the highly predictive nature of the ocean tides, the company has developed simulation models with performance data from available generators to optimize design for particular locations. The recent announcement of a cooperative agreement with the Chinese government for ambitious 300 MW offshore tidal power generation facilities off Yalu River, Liaoning Province allows for an engineering feasibility study to be undertaken. Tidal Electric also has plans under consideration for UK-based projects in Swansea Bay (30 MW), Fifoots Point (930 MW), and North Wales (432 MW). These projects have failed to make progress and will not go ahead in the foreseeable future. 5.2 Wave Energy The true potential of wave energy will only be realized in the offshore environment where large developments are conceivable. Nearly 300 concepts for wave energy devices have been proposed. The development process for wave energy can be looked at in three phases. First, smallscale prototype devices, typically with low capacity, will be deployed. During the second stage, outside funding from government or private investors is possible for the most promising devices. The final stage is the production of full-scale, grid-connected devices that will in some cases be deployable in farm style configurations. Modular offshore wave energy devices that can be deployed quickly and cost effectively in a wide range of conditions will accelerate commercial wave energy. In the coming decade, wave energy will become commercially successful through multiple-unit offshore projects, the first of which are now being installed. These projects clearly demonstrate the commercial future for wave energy but valuable operational experience is necessary before larger projects are built with a greater number of devices. The growth of shoreline wave energy devices is limited by the low number of available sites and high installation costs. Deployment costs for shoreline wave energy devices are very high because they are individual sitespecific projects and economies of scale are not applicable. Whereas an offshore 50-MW wave farm is conceivable, and will in time be developed, no shoreline wave energy converter can offer such potential for deployment in this way. As such, individual coastal installations are expected to be few and far between. Shoreline wave energy will, however, continue to be relevant, as the average unit capacity is generally higher than existing offshore technology. Individual devices can be very effective, especially for remote or island communities where, for example, an individual unit of 4 MW could have a big impact. Offshore locations offer greater power potential than shoreline locations. Shoreline technologies have the benefit of easy access for maintenance purposes, whereas offshore devices are in most cases more difficult to access. Improvements in reliability and accessibility will be critical to the commercial success of the many devices currently under development. 5.2.1 Wave Energy Forecast Douglas-Westwood Ltd claim there is a potential 46 MW of wave energy projects that could be installed between 2007 and 2011. The United Kingdom is expected to be the dominant player over the next 5 years, with a forecast capacity of 28.6 MW, which equates to a 62% market share. In comparison with other countries, the UK has forecast capacity every year to 2008, whereas installations elsewhere are more intermittent. Norway (6 MW) and Portugal (4.25 MW) are the next most significant markets and have several projected installations, but they lag behind the UK in terms of technology development and project deployment. The United Kingdom government has shown reasonable levels of support, which have injected many technologies with valuable grants. The result is a number of proven wave technologies with good prospects for commercial deployment and several more at an advanced prototype stage. Coupled with a world-class natural resource, the United Kingdom remains the strongest market into the next decade. Potential wave energy capacity 2007–2011 is indicated in Fig. 9. Figure 9. Potential wave energy capacity 2007–2011. Source: Douglas-Westwood Ltd [32]. 425 5.3 Offshore Wind There are 25 operational offshore wind farms in the world today. The 436 installed turbines in these projects provide a total of 919 MW. The first offshore wind turbine was installed at Nogersund off Sweden in 1990. The first offshore wind farm were installed at Vindeby off the Danish island of Lolland in 1991. The most recent project is the Beatrice Demonstration Project off Scotland. The first 10 years of the industry saw small projects being built in very shallow water near-shore locations. These wind farms in most cases used onshore turbine models with slight adaptations made. These “demonstration” projects have paved the way for the more recent projects that are of a much larger size. The biggest offshore wind farm yet installed is the Nysted development off Denmark which was completed in 2003. Just as this project dwarfs those built 10 years previously, within another decade projects will be installed that are many times greater in size than today’s offshore wind farms. The industry faces problems from increasing costs. In the last 5 years, the cost of offshore wind has increased by up to 65%. This is caused by increased turbine prices driven by the extremely strong onshore wind market (particularly in the US), and rising contractor prices based upon experiences on earlier projects. Cost reductions of approximately 25% are essential to help stimulate the industry and help strengthen it. The total global offshore wind capacity forecast for installation between 2007 and 2011 stands at 4.2 GW. The UK is the world’s largest market for the forthcoming 5-year period. A total of 2.2 GW is forecast here, representing 52% of the entire world market. The UK’s “Round 1” projects are continuing to be installed at the rate of 1–2 per year. The first of the larger “Round 2” projects are expected to enter construction at the turn of the decade, significantly boosting the UK’s capacity. The UK’s prospects are expected almost three times those of Germany, the next largest market. Germany has so far seen only minor installations, but the first significant activity is expected to begin in 2008 with the Borkum West project. Several projects are forecast for 2009 and 2010. The bulk of projects, however, will not begin construction until the turn of the decade. Long-term prospects are excellent off Germany but in the short and mid-term future the industry has much to overcome. The only activity off Denmark in the period will come with the construction and completion of the Horns Rev II and Nysted II projects in 2009 and 2010 respectively. Although the country showed initial promise for offshore development, a lack of government commitment has stunted the industry here. Long-term prospects are, however, high and a new round of licences is expected shortly for development in the next decade. Whilst the Netherlands is currently seeing a period of activity with the completion of the Egmond aan Zee project and construction of Q7-WP, it will not be until after this decade that the next projects are completed. Whilst not reflected in the above forecast, long-term prospects are good. North America is yet to install any offshore wind projects. With the onshore market in such good health, the drivers for offshore are not as strong as in Europe where the industry is reaching take-off after a period of slow but steady growth. There are currently three large offshore wind farms in North America in advanced stages of planning although it is now unlikely that they will be built this decade due to delays from drawn-out permitting processes and legal challenges. In addition to this are a number of more speculative large projects and several small scale demonstration projects that could be installed before the end of the decade. The highest profile project is Cape Wind off the coast of Massachusetts. The proposed 420 MW wind farm has courted controversy since conception. After clearing a number of regulatory and legal hurdles over a 6-year period, the project faces a ruling from US federal authorities. The Minerals Management Service (MMS) took over regulation of offshore renewables in the autumn of 2005. The MMS intend to record a decision on the project in the fall of 2008. The 144 MW Long Island offshore wind farm is being developed by FPL Energy. The MMS is due to record a decision on the project in spring 2008. The project started after The Long Island Power Authority announced in January 2003 that it was seeking developers to build an offshore wind farm off Jones Beach. The largest North American project is the 1,750 MW NaiKun wind farm off the coast of British Columbia which will be developed in five phases, the first of which is scheduled for completion in 2011. Cumulative installed offshore wind capacity is given in Fig. 10. Forecast offshore capacity 2002–2011 is indicated in Fig. 11. 6. Conclusions For the entire marine renewables sector, 4.5 GW of installed capacity is projected between 2007 and 2011. Some 98% of that capacity is in the form of offshore wind farms. The Figure 10. Cumulative installed offshore wind capacity. Source: Douglas-Westwood Ltd [32]. 426 Figure 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 percentage of the total expenditure on offshore renewables, of the order of $300 million in total expenditure between them. However, wave and tidal power currently attract higher expenditures per megawatt. This indicates higher costs of the immature developing industries. These costs will fall as time goes by and the industries progresses. The leading devices should be comparable with, and in some cases more competitive than offshore wind, by early next decade. The more well-established offshore wind sector will lead the offshore renewables industry, and will see strong growth throughout the period led by countries such as the UK, the Netherlands, Germany and Denmark. Established onshore wind supply chains in Denmark and Germany will, however, see most of the financial benefit of the growth in offshore wind for the short-term. The dominance of offshore wind does not mean wave and tidal energy are not important, they are just less well developed, and the industry is much younger. From around 2010, wave and tidal should begin to expand commercially. The growth of wave and tidal power offers significant supply chain growth opportunities for countries that failed to capture the value of the growth in the wind industry (both onshore and offshore). Europe is the dominant region, leading in all three sectors. The UK is a particularly important market, driven by a world-class natural resource, the past 3 years has seen notable successes in wind, wave and tidal energies. With more approved offshore wind capacity in the planning stage than any other country, prospects for the United Kingdom look bright. The UK is forecast to become world leader in offshore wind in 2008 and is already the leader in the wave and tidal current stream industries. The UK Energy White Paper due May 2007 is expected to increase banding to the main support system for renewables to give greater support to emerging technologies, particularly offshore renewables. This should provide a strong catalyst for growth. Whilst currently lacking, future growth in other regions should not be discounted in the long term. Interest in North America is growing and we will see large projects progressing around the end of the decade, particularly in the offshore wind sector. Greater support and structure would reap big rewards for the industry here. At present though, it lags far behind the established European market which remains the focal point for the marine renewables industry. Europe is home to the leading technology developers and superior funding packages are in place in key countries to stimulate development. Acknowledgements The author acknowledges contributions made by Peter O’Donnell (Senior Energy Specialist, Manager Generation Solar & Renewables Programs, San Francisco Environment Organization, CA, USA); Omar Siddiqui (Senior Associate, Global Energy Partners LLC, Lafayette, CA, USA); Roger Bedard (Offshore Wave Energy Project Manager, EPRI, CA, USA), Andrew Mill (Managing Director European Marine Energy Centre, UK); Mirko Previsic (Consultant— Offshore Renewables, Sacramento, CA, USA); Anthony T Jones (Senior Oceanographer, oceanUS consulting, Palm Springs, CA, USA); and Adam Westwood (Renewable Energy 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 Conference, 1997. [3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Turbine for (Canadian) Ministry of Employment and Investment, N.H. Halvorson Consultants Ltd. [4] Renewable Energy: Power for a Sustainable Future; Technology Update, Tidal Current Power Update & Wave Power Update, Oxford University Press, 2001. [5] P. Fraenkel, Renewables is the tide turning for marine current turbines? Modern Power System, Marine Current Turbines Ltd, London, UK, June 30, 2001. [6] R. Bedard, Final summary report: offshore wave power feasibility demonstration project (E2I EPRI Global WP009 – US, 2005). [7] M. Previsic, System level design, performance and costs for San Francisco Pelamis offshore wave power plant (E2I EPRI Global – 006A – SF, 2004). [8] G. Hagerman, Offshore Wave Power in the US: Environmental Issues (E2I Global EPRI – 007 – US, 2004). [9] B. Ram, Wave Power in the US: Permitting and Jurisdictional Issues (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 Wave Energy Conversion Devices. [12] E2i/EPRI WP-005-US Methodology, Guidelines and Assumptions for the Conceptual Design of Offshore Wave Energy Power Plants (Farms). [13] E2i/EPRI WP-006-HI System Level Design, Preliminary Performance and Cost Estimate – Hawaii. [14] E2i EPRI WP-006-OR System Level Design, Preliminary Performance and Cost Estimate – Oregon. [15] E2i/EPRI WP-006-ME System Level Design, Preliminary Performance and Cost Estimate – Maine. [16] E2i/EPRI WP-006-MA System Level Design, Preliminary Performance and Cost Estimate – Massachusetts. [17] E2i/EPRI WP-006-SFa System Level Design, Preliminary Performance and Cost Estimate – San Francisco, California Pelamis Offshore Wave Power Plant. 427 [18] E2i/EPRI WP-006-SFb System Level Design, Preliminary Performance and Cost Estimate – San Francisco Energetech Offshore Wave Power Plant. [19] Sea Technology Magazine August 2003, Wave Energy Conversion – The State of the Art. [20] EPRI – RE Technical Assessment Guide Ocean Wave Power Section for the years 2001, 2002 and 2003. [21] California Energy Commission – Wave Energy Resource Assessment for the State of California. [22] A.D. Trapp & M. Watchorn, EB development of tidal stream energy, Proc. MAREC 2001, 2001, 169–173.
  21. [23] A.T. Jones & A. Westwood, Economic forecast for renewable ocean energy technologies, presented at EnergyOcean 2004, Palm Beach, Florida, 2004.
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  23. [26]. Yalu River, China By creating a tidal lagoon offshore, Tidal Electric has taken a novel approach to resolve environmental and economic concerns of tidal barrage technology
  24. [27]. Due to the highly predictive nature of the ocean tides, the company has developed simulation models with performance data from available generators to optimize design for particular locations. The recent announcement of a cooperative agreement with the Chinese government for ambitious 300 MW offshore tidal power generation facilities off Yalu River, Liaoning Province allows for an engineering feasibility study to be undertaken. Tidal Electric also has plans under consideration for UK-based projects in Swansea Bay (30 MW), Fifoots Point (930 MW), and North Wales (432 MW). These projects have failed to make progress and will not go ahead in the foreseeable future. 5.2 Wave Energy The true potential of wave energy will only be realized in the offshore environment where large developments are conceivable. Nearly 300 concepts for wave energy devices have been proposed. The development process for wave energy can be looked at in three phases. First, smallscale prototype devices, typically with low capacity, will be deployed. During the second stage, outside funding from government or private investors is possible for the most promising devices. The final stage is the production of full-scale, grid-connected devices that will in some cases be deployable in farm style configurations. Modular offshore wave energy devices that can be deployed quickly and cost effectively in a wide range of conditions will accelerate commercial wave energy. In the coming decade, wave energy will become commercially successful through multiple-unit offshore projects, the first of which are now being installed. These projects clearly demonstrate the commercial future for wave energy but valuable operational experience is necessary before larger projects are built with a greater number of devices. The growth of shoreline wave energy devices is limited by the low number of available sites and high installation costs. Deployment costs for shoreline wave energy devices are very high because they are individual sitespecific projects and economies of scale are not applicable. Whereas an offshore 50-MW wave farm is conceivable, and will in time be developed, no shoreline wave energy converter can offer such potential for deployment in this way. As such, individual coastal installations are expected to be few and far between. Shoreline wave energy will, however, continue to be relevant, as the average unit capacity is generally higher than existing offshore technology. Individual devices can be very effective, especially for remote or island communities where, for example, an individual unit of 4 MW could have a big impact. Offshore locations offer greater power potential than shoreline locations. Shoreline technologies have the benefit of easy access for maintenance purposes, whereas offshore devices are in most cases more difficult to access. Improvements in reliability and accessibility will be critical to the commercial success of the many devices currently under development. 5.2.1 Wave Energy Forecast Douglas-Westwood Ltd claim there is a potential 46 MW of wave energy projects that could be installed between 2007 and 2011. The United Kingdom is expected to be the dominant player over the next 5 years, with a forecast capacity of 28.6 MW, which equates to a 62% market share. In comparison with other countries, the UK has forecast capacity every year to 2008, whereas installations elsewhere are more intermittent. Norway (6 MW) and Portugal (4.25 MW) are the next most significant markets and have several projected installations, but they lag behind the UK in terms of technology development and project deployment. The United Kingdom government has shown reasonable levels of support, which have injected many technologies with valuable grants. The result is a number of proven wave technologies with good prospects for commercial deployment and several more at an advanced prototype stage. Coupled with a world-class natural resource, the United Kingdom remains the strongest market into the next decade. Potential wave energy capacity 2007–2011 is indicated in Fig. 9. Figure 9. Potential wave energy capacity 2007–2011. Source: Douglas-Westwood Ltd [32]. 425 5.3 Offshore Wind There are 25 operational offshore wind farms in the world today. The 436 installed turbines in these projects provide a total of 919 MW. The first offshore wind turbine was installed at Nogersund off Sweden in 1990. The first offshore wind farm were installed at Vindeby off the Danish island of Lolland in 1991. The most recent project is the Beatrice Demonstration Project off Scotland. The first 10 years of the industry saw small projects being built in very shallow water near-shore locations. These wind farms in most cases used onshore turbine models with slight adaptations made. These “demonstration” projects have paved the way for the more recent projects that are of a much larger size. The biggest offshore wind farm yet installed is the Nysted development off Denmark which was completed in 2003. Just as this project dwarfs those built 10 years previously, within another decade projects will be installed that are many times greater in size than today’s offshore wind farms. The industry faces problems from increasing costs. In the last 5 years, the cost of offshore wind has increased by up to 65%. This is caused by increased turbine prices driven by the extremely strong onshore wind market (particularly in the US), and rising contractor prices based upon experiences on earlier projects. Cost reductions of approximately 25% are essential to help stimulate the industry and help strengthen it. The total global offshore wind capacity forecast for installation between 2007 and 2011 stands at 4.2 GW. The UK is the world’s largest market for the forthcoming 5-year period. A total of 2.2 GW is forecast here, representing 52% of the entire world market. The UK’s “Round 1” projects are continuing to be installed at the rate of 1–2 per year. The first of the larger “Round 2” projects are expected to enter construction at the turn of the decade, significantly boosting the UK’s capacity. The UK’s prospects are expected almost three times those of Germany, the next largest market. Germany has so far seen only minor installations, but the first significant activity is expected to begin in 2008 with the Borkum West project. Several projects are forecast for 2009 and 2010. The bulk of projects, however, will not begin construction until the turn of the decade. Long-term prospects are excellent off Germany but in the short and mid-term future the industry has much to overcome. The only activity off Denmark in the period will come with the construction and completion of the Horns Rev II and Nysted II projects in 2009 and 2010 respectively. Although the country showed initial promise for offshore development, a lack of government commitment has stunted the industry here. Long-term prospects are, however, high and a new round of licences is expected shortly for development in the next decade. Whilst the Netherlands is currently seeing a period of activity with the completion of the Egmond aan Zee project and construction of Q7-WP, it will not be until after this decade that the next projects are completed. Whilst not reflected in the above forecast, long-term prospects are good. North America is yet to install any offshore wind projects. With the onshore market in such good health, the drivers for offshore are not as strong as in Europe where the industry is reaching take-off after a period of slow but steady growth. There are currently three large offshore wind farms in North America in advanced stages of planning although it is now unlikely that they will be built this decade due to delays from drawn-out permitting processes and legal challenges. In addition to this are a number of more speculative large projects and several small scale demonstration projects that could be installed before the end of the decade. The highest profile project is Cape Wind off the coast of Massachusetts. The proposed 420 MW wind farm has courted controversy since conception. After clearing a number of regulatory and legal hurdles over a 6-year period, the project faces a ruling from US federal authorities. The Minerals Management Service (MMS) took over regulation of offshore renewables in the autumn of 2005. The MMS intend to record a decision on the project in the fall of 2008. The 144 MW Long Island offshore wind farm is being developed by FPL Energy. The MMS is due to record a decision on the project in spring 2008. The project started after The Long Island Power Authority announced in January 2003 that it was seeking developers to build an offshore wind farm off Jones Beach. The largest North American project is the 1,750 MW NaiKun wind farm off the coast of British Columbia which will be developed in five phases, the first of which is scheduled for completion in 2011. Cumulative installed offshore wind capacity is given in Fig. 10. Forecast offshore capacity 2002–2011 is indicated in Fig. 11. 6. Conclusions For the entire marine renewables sector, 4.5 GW of installed capacity is projected between 2007 and 2011. Some 98% of that capacity is in the form of offshore wind farms. The Figure 10. Cumulative installed offshore wind capacity. Source: Douglas-Westwood Ltd [32]. 426 Figure 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 percentage of the total expenditure on offshore renewables, of the order of $300 million in total expenditure between them. However, wave and tidal power currently attract higher expenditures per megawatt. This indicates higher costs of the immature developing industries. These costs will fall as time goes by and the industries progresses. The leading devices should be comparable with, and in some cases more competitive than offshore wind, by early next decade. The more well-established offshore wind sector will lead the offshore renewables industry, and will see strong growth throughout the period led by countries such as the UK, the Netherlands, Germany and Denmark. Established onshore wind supply chains in Denmark and Germany will, however, see most of the financial benefit of the growth in offshore wind for the short-term. The dominance of offshore wind does not mean wave and tidal energy are not important, they are just less well developed, and the industry is much younger. From around 2010, wave and tidal should begin to expand commercially. The growth of wave and tidal power offers significant supply chain growth opportunities for countries that failed to capture the value of the growth in the wind industry (both onshore and offshore). Europe is the dominant region, leading in all three sectors. The UK is a particularly important market, driven by a world-class natural resource, the past 3 years has seen notable successes in wind, wave and tidal energies. With more approved offshore wind capacity in the planning stage than any other country, prospects for the United Kingdom look bright. The UK is forecast to become world leader in offshore wind in 2008 and is already the leader in the wave and tidal current stream industries. The UK Energy White Paper due May 2007 is expected to increase banding to the main support system for renewables to give greater support to emerging technologies, particularly offshore renewables. This should provide a strong catalyst for growth. Whilst currently lacking, future growth in other regions should not be discounted in the long term. Interest in North America is growing and we will see large projects progressing around the end of the decade, particularly in the offshore wind sector. Greater support and structure would reap big rewards for the industry here. At present though, it lags far behind the established European market which remains the focal point for the marine renewables industry. Europe is home to the leading technology developers and superior funding packages are in place in key countries to stimulate development. Acknowledgements The author acknowledges contributions made by Peter O’Donnell (Senior Energy Specialist, Manager Generation Solar & Renewables Programs, San Francisco Environment Organization, CA, USA); Omar Siddiqui (Senior Associate, Global Energy Partners LLC, Lafayette, CA, USA); Roger Bedard (Offshore Wave Energy Project Manager, EPRI, CA, USA), Andrew Mill (Managing Director European Marine Energy Centre, UK); Mirko Previsic (Consultant— Offshore Renewables, Sacramento, CA, USA); Anthony T Jones (Senior Oceanographer, oceanUS consulting, Palm Springs, CA, USA); and Adam Westwood (Renewable Energy 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 Conference, 1997. [3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Turbine for (Canadian) Ministry of Employment and Investment, N.H. Halvorson Consultants Ltd. [4] Renewable Energy: Power for a Sustainable Future; Technology Update, Tidal Current Power Update & Wave Power Update, Oxford University Press, 2001. [5] P. Fraenkel, Renewables is the tide turning for marine current turbines? Modern Power System, Marine Current Turbines Ltd, London, UK, June 30, 2001. [6] R. Bedard, Final summary report: offshore wave power feasibility demonstration project (E2I EPRI Global WP009 – US, 2005). [7] M. Previsic, System level design, performance and costs for San Francisco Pelamis offshore wave power plant (E2I EPRI Global – 006A – SF, 2004). [8] G. Hagerman, Offshore Wave Power in the US: Environmental Issues (E2I Global EPRI – 007 – US, 2004). [9] B. Ram, Wave Power in the US: Permitting and Jurisdictional Issues (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 Wave Energy Conversion Devices. [12] E2i/EPRI WP-005-US Methodology, Guidelines and Assumptions for the Conceptual Design of Offshore Wave Energy Power Plants (Farms). [13] E2i/EPRI WP-006-HI System Level Design, Preliminary Performance and Cost Estimate – Hawaii. [14] E2i EPRI WP-006-OR System Level Design, Preliminary Performance and Cost Estimate – Oregon. [15] E2i/EPRI WP-006-ME System Level Design, Preliminary Performance and Cost Estimate – Maine. [16] E2i/EPRI WP-006-MA System Level Design, Preliminary Performance and Cost Estimate – Massachusetts. [17] E2i/EPRI WP-006-SFa System Level Design, Preliminary Performance and Cost Estimate – San Francisco, California Pelamis Offshore Wave Power Plant. 427 [18] E2i/EPRI WP-006-SFb System Level Design, Preliminary Performance and Cost Estimate – San Francisco Energetech Offshore Wave Power Plant. [19] Sea Technology Magazine August 2003, Wave Energy Conversion – The State of the Art. [20] EPRI – RE Technical Assessment Guide Ocean Wave Power Section for the years 2001, 2002 and 2003. [21] California Energy Commission – Wave Energy Resource Assessment for the State of California. [22] A.D. Trapp & M. Watchorn, EB development of tidal stream energy, Proc. MAREC 2001, 2001, 169–173. [23] A.T. Jones & A. Westwood, Economic forecast for renewable ocean energy technologies, presented at EnergyOcean 2004, Palm Beach, Florida, 2004. [24] A.T. Jones & W. Rowley, Global perspective: Economic forecast 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 tidal current generator, Proc. MAREC 2002, 2002, 1–10. [26] A.M. Gorlov, The helical turbine and its applications for tidal and wave power, Proc. OCEANS 2003, 2003, 1996. [27] P.W. Ullman, Offshore Tidal Power Generation – A new approach to power conversion of the oceans’ tides, MTS Journal, 36(4), 2002, 16–24.
  25. [28] P. Breeze, The Future of Global Offshore Wind Power, Reuter Business Insight 2004.
  26. [30]. In deep water, the wave power spatial flux (in kW/m of wave front crest) is given by significant wave height (Hs in m) and the peak wave period (Tp in s). Based on these two parameters, the incident wave power (J in kW/m of wave crest length) associated with each sea state record is estimated by the following equation: J = 0.42 × (Hs)2 × Tp (kW) It is significant to note that wave power varies with the square of wave height – that is, a wave whose height is doubled generates four times as much power. The power of a tidal current is given by the following equation: Pwater = (1/2) rAV 3 (W) where A is the cross-sectional area of flow intercepted by the turbine device (m2 ), r is the water density (kg/m3 ) and V is current velocity speed (m/s). The current velocity V varies in a precisely predictable manner as an additive function of period of the different sinusoidal tidal components. Tidal flow energy studies are in progress at EPRI and the techno-economic results are not available. Therefore, the focus is on the results of the wave energy feasibility definition study of 2004. 4.2 Wave Project Results 4.2.1 US Wave Energy Resources An ideal site to deploy, operate and maintain an offshore wave energy power plant must have many attributes. First and foremost is a sufficient native energy and energy spectra potential.1 The US regional wave regimes and the total annual incident wave energy for each of these regimes are shown in Fig. 4. The total US available incident wave energy flux is about 2,300 TWh/yr. The DOE Energy Information Energy (EIA) estimated in 2003 hydroelectric generation in USA to be about 270 TWh which is a little more than a tenth of the yearly offshore wave energy flux into the US. Therefore, wave energy is a significant resource. Figure 4. US energy resources. Source: O. Siddiqui & R. Bedard [30]. 4.2.2 Feasibility Definition Study Sites Site attributes characterized by the Project Team included offshore bathymetry2 and seafloor surface geology, robustness of the coastal utility grid, regional maritime infrastructure for both fabrication and maintenance, conflicts with competing uses of sea space and existence of other unique characteristics that might minimize project development costs (e.g. existing ocean outfall easements for routing power cable and shore crossing). Table 2 identifies the site selected in each of the five states that participated in the study, and also provides a few key characteristics of each selected site. 4.2.3 Feasibility Study: WEC Devices Twelve companies responded to EPRI’s request for information. An initial screening considered two key issues: (1) technology readiness (i.e. readiness of device for demonstration in the 2006 time period) and (2) survivability in adverse conditions (i.e. sufficiency of technical information provided by the device manufacturer to prove the survivability in storm conditions). The eight devices that passed the 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 water height (i.e. the inverse of a topographic map). 420 Table 2 Estimated Performance of Pilot Demonstration Plants HI OR CA Mass Maine County Oahu Douglas SF Cape Cod Cumberland Grid I/C Waimanalo Gardner Wastewater Well Old Beach Plant Fleet Orchard Beach S/S Average 15.2 21.2 11.21 13.8 4.9 Annual J (kW/m) Depth (m) 60 60 30 60 60 Distance 2 3.5 13 9 9 from Shore Cable Makai IPP Outflow Water Dir Drill Dir Drill Landing Pier Pipe Outflow 1Sited within the marine sanctuary exclusionary zone. Source: O. Siddiqui & R. Bedard [30]. Table 3 Estimated Performance of Pilot Demonstration Plants Length (m) Width (m) Power (kW)1 Type Rating Ocean 120 4.6 153 Floating 1 Power Attenuator Delivery Energetech 25 35 259 OWC – Bottom 2 Terminator Wave 150 260 1,369 Floating 2 Dragon Overtopping Wave 9.5 9.5 351 Bottom Point 2 Swing Absorber Wave Bob 16 15 131 Floating Point 3 Absorber Aqua-Energy 6 6 17 Floating Point 3 Absorber OreCON 32 32 532 Floating OWC 3 Ind Natural 5.4 5.4 112 Bottom Point 3 Resources Inc Absorber 1Based on Oregon average annual wave energy resource. Source: O. Siddiqui & R. Bedard [30]. These eight devices were then assessed with the objective of determining any critical issues and recommending RD&D needed to achieve technological readiness for an at sea demonstration. As a result of this assessment, the eight devices were grouped into one of three levels of development categories: • Level 1 : Development complete and full-scale testing in the ocean underway. • Level 2 : Development near complete. Only deployment, recovery and mooring issues are yet to be validated. There are funded plans for full-scale at sea testing. • Level 3 : Most critical RD&D issues are resolved. Additional laboratory and sub-scale testing, simulations and systems integration work is needed prior to finalization of the full-scale design. There are no funded 421 plans for full-scale at sea testing. At the time of EPRI’s analysis (March 2004), only one WEC device manufacturer had attained a Level 1 technology readiness status – OPD with its Pelamis device. At the time of this paper (February 2005) there are an additional four WEC device manufacturers that are close to reaching that status: TeamWorks of the Netherlands with its Wave Swing, Energetechs of Australia with its OWC, Wave Dragon of Denmark with its overtopping device, and Ocean Power Technology of the US with a floating buoy. 4.2.4 Demonstration-Scale Plant Design: Oregon Example Demonstration-scale (as well as commercial-scale) designs were based on the OPD Pelamis WEC device for the five sites listed in Table 2. The Pelamis WEC device consists of four cylindrical steel sections, which are connected by three hydraulic PCM. Total length of the device is 120 m and device diameter is 4.6 m. Fig. 5 shows the device being tested off the Scottish coast. Figure 5. OPD Pelamis WEC device. 1 nm = 1 nautical mile. Source: O. Siddiqui & R. Bedard [30]. A second San Francisco, CA design based on the Energetech OWC WEC device depicted in Fig. 6 was also tested. Figure 6. Energetech WEC device. Source: O. Siddiqui & R. Bedard [30]. The estimated performance of the single unit demonstration plant at each of the five sites is shown in Table 4. Table 4 Estimated Performance of Pelamis Pilot Demonstration Plants HI OR CA1 Mass Maine Device Rated 750 750 750 750 750 Capacity (kW) Annual 1,989 1,472 1,229 1,268 426 Energy Absorbed (MWh/yr) Annual Energy 1,663 1,001 835 964 290 Produced (MWh/yr) Average 180 114 95 98 33 Electrical Power (kW) Number of 180 114 95 98 33 Homes Powered by Plant 1Energetech 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 Example The commercial system uses a total of 4 clusters, each one containing 45 Pelamis units (i.e. 180 total Pelamis WEC devices), connected to sub-sea cables. Each cluster consists of 3 rows with 15 devices per row. The other state designs are organized in a similar manner with 4 clusters. The number of devices per cluster varies such that each plant produces an annual energy output of 300,000 MWh/yr. The electrical interconnection of the devices is accomplished with flexible jumper cables, connecting the units in mid-water. The introduction of 4 independent sub-sea cables and the interconnection on the surface provides some redundancy in the wave farm arrangement. The estimated performance of the commercial-scale plant at each of the five sites is shown in Table 5. The device rated capacity has been derated from 750 kW in the demonstration plant to 500 kW for the commercial plant. The performance assessment of the demonstration plants shows that the PCMs are overrated and reducing the rated power to 500 kW per device would yield a significant cost reduction and only a relatively small decrease in annual output (attributed to the fact that the US sites have a lower energy level than UK sites for which the device was originally developed). 4.2.6 Learning Curves and Economics The costs and cost of electricity shown in the previous section are for the first commercial-scale wave plant. Learning through production experience reduces costs – a phenomenon that follows a logarithmic relationship such that 422 Table 5 Estimated Performance of Pelamis Commercial Plants HI OR CA Mass Maine Device Rated 500 500 500 500 500 Capacity (kW) Annual Energy 1,989 1,997 1,683 1,738 584 Absorbed (MWh/yr) Annual Energy 1,663 1,669 1,407 1,453 488 Produced (MWh/yr) Average Electrical 191 191 161 166 56 Power at Busbar (kW) Number of OPD 180 180 213 206 615 Pelamis Units Needed for 300,000 MWh/yr Number of Homes 34,000 34,000 34,000 34,000 34,000 Powered by Plant Source: 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%, which is consistent with documented experience in the wind energy, photovoltaic, shipbuilding, and offshore oil and gas industries. The industry-documented historical wind energy learning curve is shown as the top line in Fig. 7
  27. [31]. The cost of electricity is about 4 cents/kWh in 2004 US dollars based on 40,000 MW of worldwide installed capacity and a good wind site. The lower and higher bound cost estimates of wave energy are also shown in Fig. 7. The 82% learning curve is applied to the wave power plant installed cost but not to the operation and maintenance part of cost of electricity (hence the reason that the three lines are not parallel). Figure 7. Electrical interconnection of demo-plant: Oregon example. Source: O. Siddiqui & R. Bedard [30]. Fig. 7 shows the cost of wave-generated electricity: low band (bottom curve), upper band (middle curve); and wind-generated electricity (top curve) at equal cumulative production volume under all cost estimating assumptions for the wave plant. It shows that the cost of wave-generated electricity is less than wind-generated electricity at any equal cumulative production volume under all cost estimating assumptions for the wave plant. The lower capital cost of a wave machine (compared to a wind machine) more than compensates for the higher O&M cost for the remotely located offshore wave machine. A challenge to the wave energy industry is to drive down O&M costs to offer even more economic favourability and to delay the crossover point shown at greater than 40,000 MW. In summary, the techno-economic forecast made by the Project Team is that wave energy will first become commercially competitive with the current 40,000 MW installed land-based wind technology at a cumulative production volume of 15,000 MW or less in Hawaii and northern California, about 20,000 MW in Oregon and about 40,000 MW in Massachusetts. This forecast was made on the basis of a 300,000 MWh/yr (nominal 90 MW at 38% capacity factor) Pelamis WEC commercial plant design and application of technology learning curves. Maine was the only state in the study whose wave climate was such that wave energy may never be able to economically compete with a good wind energy site. In addition to economics, there are other compelling arguments for investing in offshore wave energy technology. First, with proper sitting, converting ocean wave energy to electricity is believed to be one of the most environmentally benign ways to generate electricity. Second, offshore wave energy offers a way to minimize the “Not In My Backyard” (NIMBY) issues that plague many energy infrastructure 423 projects, from nuclear to coal and to wind generation. Because these devices have a very low profile and are located at a distance from the shore, they are generally not visible. Third, because wave energy is more predictable than solar and wind energy, it offers a better possibility than either solar or wind of being dispatch able and earning a capacity payment. A characteristic of wave energy that suggests that it may be one of the lowest cost renewable energy sources is its high power density. Processes in the ocean concentrate solar and wind energy into ocean waves making it easier and cheaper to harvest. Solar and wind energy sources are much more diffuse, by comparison. Since a diversity of energy sources is the bedrock of a robust electricity system, to overlook wave energy is inconsistent with national needs and goals. Wave energy is an energy source that is too important to overlook. 4.2.7 Recommendations The development of ocean energy technology and the deployment of this clean renewable energy technology would be greatly accelerated by adequate support from governments. Appropriate roles for governments in ocean energy development could include: • Providing leadership for the development of an ocean energy RD&D programme to fill known RD&D gaps, and to accelerate technology development and prototype system deployment. • Operating national offshore wave test centers to test performance and reliability of prototype ocean energy systems under real conditions. • Development of design and testing standards for ocean energy devices. • Joining the International Energy Agency Ocean Energy Systems Implementing Agreement to collaborate RD&D activities, and appropriate ocean energy policies with other governments and organizations. • Studying provision of production tax credits, renewable energy credits, and other incentives to spur private investment in ocean energy technologies and projects, and implementing appropriate incentives to accelerate ocean energy deployment. • Ensuring that the public receives a fair return from the use of ocean energy resources. • Ensuring that development rights are allocated through a transparent process that takes into account state, local, and public concerns. 5. Recent Progress in Offshore Renewable Energy Technology Development The recent progress in offshore renewable energy technology development is now examined and potential markets for tidal power, WEC, and offshore wind are considered. The analysis of market potentials for offshore renewable technology 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 and tidal current stream sectors. 5.1 Tidal Current Stream Historically, tidal projects have been large-scale barrage systems that block estuaries. Within the last few decades, developers have shifted toward technologies that capture the tidally driven coastal currents or tidal stream. The challenge is, “to develop technology and innovate in a way that will allow this form of low density renewable energy to become practical and economic” [22]. Tidal current turbines are basically underwater windmills. The tidal currents are used to rotate an underwater turbine. First proposed during the 1970s’ oil crisis, the technology has only recently become a reality with commercial prospects. Marine Current Turbines (MCT) installed the first full-scale prototype turbine (300 kW) off Lynmouth in Devon, UK in 2003. Shortly thereafter, the Norwegian company Hammerfest Støm installed their first grid-connected 300 kW prototype device. MCT, arguably the market leader is now preparing to install its new twin-rotored 1 MW device in 2007. The company has plans to install a commercial scale project off the UK coast around the turn of the decade. There are a great number of sites suitable for tidal current turbines. As tidal currents are predictable and reliable, tidal turbines have advantages over offshore wind counterparts. The ideal sites are generally within several kilometres of the shore in water depths of 20–30 m. 5.1.1 Tidal Forecasts Douglas-Westwood Ltd expect 25 MW of tidal current stream capacity to be brought online in the 2007–2011 period (see Fig. 8). The vast majority of this capacity will be in the UK where 23 MW is forecast. With several successful large-scale prototypes already tested, the period to the end of the decade will see further refinement of devices and applications for multiple-unit farms in key markets. The above forecast shows a sharp growth in 2011 from tidal current farms expected from MCT and Lunar Energy. Figure 8. Potential tidal current stream capacity 2007– 2011. Source: Douglas-Westwood Ltd
  28. [32]. 424 5.1.2 Projects Shiswa Lake Tidal Power Plant, Korea Korea has a plentiful tidal and tidal current energy resource. Under construction is a single stream style generator at Ansan City’s Shiswa Lake, which will have a capacity of 252 MW, comprised of 12 units of 21 MW generators. Annual power generation, when completed in 2008, is projected at 552 million kWh. If successful, this project will surpass La Rance (France) as the largest tidal power plant in the world. Korea is also planning a tidal current power plant in Uldol-muk Strait, a restriction in the strait where maximum water speed exceeds 6.5 m/s. The experimental plant will utilize helical or “Gorlov” turbines developed by GCK Technology [26]. Yalu River, China By creating a tidal lagoon offshore, Tidal Electric has taken a novel approach to resolve environmental and economic concerns of tidal barrage technology [27]. Due to the highly predictive nature of the ocean tides, the company has developed simulation models with performance data from available generators to optimize design for particular locations. The recent announcement of a cooperative agreement with the Chinese government for ambitious 300 MW offshore tidal power generation facilities off Yalu River, Liaoning Province allows for an engineering feasibility study to be undertaken. Tidal Electric also has plans under consideration for UK-based projects in Swansea Bay (30 MW), Fifoots Point (930 MW), and North Wales (432 MW). These projects have failed to make progress and will not go ahead in the foreseeable future. 5.2 Wave Energy The true potential of wave energy will only be realized in the offshore environment where large developments are conceivable. Nearly 300 concepts for wave energy devices have been proposed. The development process for wave energy can be looked at in three phases. First, smallscale prototype devices, typically with low capacity, will be deployed. During the second stage, outside funding from government or private investors is possible for the most promising devices. The final stage is the production of full-scale, grid-connected devices that will in some cases be deployable in farm style configurations. Modular offshore wave energy devices that can be deployed quickly and cost effectively in a wide range of conditions will accelerate commercial wave energy. In the coming decade, wave energy will become commercially successful through multiple-unit offshore projects, the first of which are now being installed. These projects clearly demonstrate the commercial future for wave energy but valuable operational experience is necessary before larger projects are built with a greater number of devices. The growth of shoreline wave energy devices is limited by the low number of available sites and high installation costs. Deployment costs for shoreline wave energy devices are very high because they are individual sitespecific projects and economies of scale are not applicable. Whereas an offshore 50-MW wave farm is conceivable, and will in time be developed, no shoreline wave energy converter can offer such potential for deployment in this way. As such, individual coastal installations are expected to be few and far between. Shoreline wave energy will, however, continue to be relevant, as the average unit capacity is generally higher than existing offshore technology. Individual devices can be very effective, especially for remote or island communities where, for example, an individual unit of 4 MW could have a big impact. Offshore locations offer greater power potential than shoreline locations. Shoreline technologies have the benefit of easy access for maintenance purposes, whereas offshore devices are in most cases more difficult to access. Improvements in reliability and accessibility will be critical to the commercial success of the many devices currently under development. 5.2.1 Wave Energy Forecast Douglas-Westwood Ltd claim there is a potential 46 MW of wave energy projects that could be installed between 2007 and 2011. The United Kingdom is expected to be the dominant player over the next 5 years, with a forecast capacity of 28.6 MW, which equates to a 62% market share. In comparison with other countries, the UK has forecast capacity every year to 2008, whereas installations elsewhere are more intermittent. Norway (6 MW) and Portugal (4.25 MW) are the next most significant markets and have several projected installations, but they lag behind the UK in terms of technology development and project deployment. The United Kingdom government has shown reasonable levels of support, which have injected many technologies with valuable grants. The result is a number of proven wave technologies with good prospects for commercial deployment and several more at an advanced prototype stage. Coupled with a world-class natural resource, the United Kingdom remains the strongest market into the next decade. Potential wave energy capacity 2007–2011 is indicated in Fig. 9. Figure 9. Potential wave energy capacity 2007–2011. Source: Douglas-Westwood Ltd [32]. 425 5.3 Offshore Wind There are 25 operational offshore wind farms in the world today. The 436 installed turbines in these projects provide a total of 919 MW. The first offshore wind turbine was installed at Nogersund off Sweden in 1990. The first offshore wind farm were installed at Vindeby off the Danish island of Lolland in 1991. The most recent project is the Beatrice Demonstration Project off Scotland. The first 10 years of the industry saw small projects being built in very shallow water near-shore locations. These wind farms in most cases used onshore turbine models with slight adaptations made. These “demonstration” projects have paved the way for the more recent projects that are of a much larger size. The biggest offshore wind farm yet installed is the Nysted development off Denmark which was completed in 2003. Just as this project dwarfs those built 10 years previously, within another decade projects will be installed that are many times greater in size than today’s offshore wind farms. The industry faces problems from increasing costs. In the last 5 years, the cost of offshore wind has increased by up to 65%. This is caused by increased turbine prices driven by the extremely strong onshore wind market (particularly in the US), and rising contractor prices based upon experiences on earlier projects. Cost reductions of approximately 25% are essential to help stimulate the industry and help strengthen it. The total global offshore wind capacity forecast for installation between 2007 and 2011 stands at 4.2 GW. The UK is the world’s largest market for the forthcoming 5-year period. A total of 2.2 GW is forecast here, representing 52% of the entire world market. The UK’s “Round 1” projects are continuing to be installed at the rate of 1–2 per year. The first of the larger “Round 2” projects are expected to enter construction at the turn of the decade, significantly boosting the UK’s capacity. The UK’s prospects are expected almost three times those of Germany, the next largest market. Germany has so far seen only minor installations, but the first significant activity is expected to begin in 2008 with the Borkum West project. Several projects are forecast for 2009 and 2010. The bulk of projects, however, will not begin construction until the turn of the decade. Long-term prospects are excellent off Germany but in the short and mid-term future the industry has much to overcome. The only activity off Denmark in the period will come with the construction and completion of the Horns Rev II and Nysted II projects in 2009 and 2010 respectively. Although the country showed initial promise for offshore development, a lack of government commitment has stunted the industry here. Long-term prospects are, however, high and a new round of licences is expected shortly for development in the next decade. Whilst the Netherlands is currently seeing a period of activity with the completion of the Egmond aan Zee project and construction of Q7-WP, it will not be until after this decade that the next projects are completed. Whilst not reflected in the above forecast, long-term prospects are good. North America is yet to install any offshore wind projects. With the onshore market in such good health, the drivers for offshore are not as strong as in Europe where the industry is reaching take-off after a period of slow but steady growth. There are currently three large offshore wind farms in North America in advanced stages of planning although it is now unlikely that they will be built this decade due to delays from drawn-out permitting processes and legal challenges. In addition to this are a number of more speculative large projects and several small scale demonstration projects that could be installed before the end of the decade. The highest profile project is Cape Wind off the coast of Massachusetts. The proposed 420 MW wind farm has courted controversy since conception. After clearing a number of regulatory and legal hurdles over a 6-year period, the project faces a ruling from US federal authorities. The Minerals Management Service (MMS) took over regulation of offshore renewables in the autumn of 2005. The MMS intend to record a decision on the project in the fall of 2008. The 144 MW Long Island offshore wind farm is being developed by FPL Energy. The MMS is due to record a decision on the project in spring 2008. The project started after The Long Island Power Authority announced in January 2003 that it was seeking developers to build an offshore wind farm off Jones Beach. The largest North American project is the 1,750 MW NaiKun wind farm off the coast of British Columbia which will be developed in five phases, the first of which is scheduled for completion in 2011. Cumulative installed offshore wind capacity is given in Fig. 10. Forecast offshore capacity 2002–2011 is indicated in Fig. 11. 6. Conclusions For the entire marine renewables sector, 4.5 GW of installed capacity is projected between 2007 and 2011. Some 98% of that capacity is in the form of offshore wind farms. The Figure 10. Cumulative installed offshore wind capacity. Source: Douglas-Westwood Ltd [32]. 426 Figure 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 percentage of the total expenditure on offshore renewables, of the order of $300 million in total expenditure between them. However, wave and tidal power currently attract higher expenditures per megawatt. This indicates higher costs of the immature developing industries. These costs will fall as time goes by and the industries progresses. The leading devices should be comparable with, and in some cases more competitive than offshore wind, by early next decade. The more well-established offshore wind sector will lead the offshore renewables industry, and will see strong growth throughout the period led by countries such as the UK, the Netherlands, Germany and Denmark. Established onshore wind supply chains in Denmark and Germany will, however, see most of the financial benefit of the growth in offshore wind for the short-term. The dominance of offshore wind does not mean wave and tidal energy are not important, they are just less well developed, and the industry is much younger. From around 2010, wave and tidal should begin to expand commercially. The growth of wave and tidal power offers significant supply chain growth opportunities for countries that failed to capture the value of the growth in the wind industry (both onshore and offshore). Europe is the dominant region, leading in all three sectors. The UK is a particularly important market, driven by a world-class natural resource, the past 3 years has seen notable successes in wind, wave and tidal energies. With more approved offshore wind capacity in the planning stage than any other country, prospects for the United Kingdom look bright. The UK is forecast to become world leader in offshore wind in 2008 and is already the leader in the wave and tidal current stream industries. The UK Energy White Paper due May 2007 is expected to increase banding to the main support system for renewables to give greater support to emerging technologies, particularly offshore renewables. This should provide a strong catalyst for growth. Whilst currently lacking, future growth in other regions should not be discounted in the long term. Interest in North America is growing and we will see large projects progressing around the end of the decade, particularly in the offshore wind sector. Greater support and structure would reap big rewards for the industry here. At present though, it lags far behind the established European market which remains the focal point for the marine renewables industry. Europe is home to the leading technology developers and superior funding packages are in place in key countries to stimulate development. Acknowledgements The author acknowledges contributions made by Peter O’Donnell (Senior Energy Specialist, Manager Generation Solar & Renewables Programs, San Francisco Environment Organization, CA, USA); Omar Siddiqui (Senior Associate, Global Energy Partners LLC, Lafayette, CA, USA); Roger Bedard (Offshore Wave Energy Project Manager, EPRI, CA, USA), Andrew Mill (Managing Director European Marine Energy Centre, UK); Mirko Previsic (Consultant— Offshore Renewables, Sacramento, CA, USA); Anthony T Jones (Senior Oceanographer, oceanUS consulting, Palm Springs, CA, USA); and Adam Westwood (Renewable Energy 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 Conference, 1997. [3] N.H. Halvorson, Evaluation of Nova Energy Ltd.’s Hydro Turbine for (Canadian) Ministry of Employment and Investment, N.H. Halvorson Consultants Ltd. [4] Renewable Energy: Power for a Sustainable Future; Technology Update, Tidal Current Power Update & Wave Power Update, Oxford University Press, 2001. [5] P. Fraenkel, Renewables is the tide turning for marine current turbines? Modern Power System, Marine Current Turbines Ltd, London, UK, June 30, 2001. [6] R. Bedard, Final summary report: offshore wave power feasibility demonstration project (E2I EPRI Global WP009 – US, 2005). [7] M. Previsic, System level design, performance and costs for San Francisco Pelamis offshore wave power plant (E2I EPRI Global – 006A – SF, 2004). [8] G. Hagerman, Offshore Wave Power in the US: Environmental Issues (E2I Global EPRI – 007 – US, 2004). [9] B. Ram, Wave Power in the US: Permitting and Jurisdictional Issues (E2I Global EPRI DOE NREL – 008 – US). [10] M. Previsic, Wave power technologies, Proc. 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