Structural Integrity of Offshore Wind Turbines Oversight of Design, Fabrication, and Installation - Special Report 305 (2011) / Chapter Skim
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2 Offshore Wind Technology and Status
2 Offshore Wind Technology and Status
Pages 17-37
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WIND TECHNOLOGY Land-Based Wind Energy Technology Wind turbines convert the kinetic energy of moving air into electricity. Modern wind turbines emerged out of the U.S.
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Renewable sources for electricity generation, such as wind and solar energy, can be exploited only where these resources are available in sufficient quantities -- windy areas for wind, and so on. As demand increases for electricity generated from wind energy, additional sites with sufficient wind resources must be identified.
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Although their architecture mimics that of conventional land-base turbines, offshore wind turbines incorporate significant enhancements to account for ocean conditions. The modifications include strengthening of the tower to handle the added loading from waves, pressurization of the nacelles, addition of environmental controls to keep corrosive sea spray away from critical drivetrain and electrical components, upgrades to electrical systems, and addition of personnel access platforms to facilitate maintenance and provide emergency shelter.
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Cable protection Trenched cable with optical-fiber cable (connects the turbine to neighboring Driven steel pile turbines or substation) FIGURE 2-2 Horns Rev 2-MW offshore wind turbine.
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(b) FIGURE 2-3 Common offshore wind turbines: (a)
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(d) FIGURE 2-4 Four common substructure types for offshore wind: (a)
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Medium-diameter suction caissons can be used in place of piles to pin tripods to the sea floor, as shown in Figure 2.5. Approximately 20 percent of offshore installed wind turbines are on reinforced concrete gravity-base foundations, which avoid the need to use a large pile-driving hammer and instead rely on mass and a larger base dimension to provide stability and resist overturning.
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With vast stretches of open water offshore, higher wind speeds can exist at lower elevations, so offshore wind turbine towers can be shorter than their land-based counterparts for a given power output. Infrastructure mobilization and logistical support for construction of a large offshore wind plant are major portions of the total system cost.
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. The power output from all the turbines in the wind farm is collected at a central electric service platform (ESP)
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Future Technology Future wind technology may introduce novel concepts and advanced technology innovations for offshore wind energy that deviate significantly from the current technology (Musial and Ram 2010; Butterfield et al.
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U.S. Offshore Wind Energy Potential The resource potential for offshore wind power in the United States has been calculated by the National Renewable Energy Laboratory by state on the basis of water depth, distance from shore, and wind speed.
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Of the hundreds of wind projects that are navigating some layer of the permitting process, at least 52 have been given consent and at least 16 are under construction. As of March 2010, approximately 42 projects had been installed with an estimate of 2,377 MW in operation (4C Offshore 2010; Alpha Ventus 2010; C-Power NV 2010; Centrica Energy 2010; DONG Energy 2010a; DONG Energy 2010b; Japan for Sustainability 2004; NoordzeeWind 2010; Offshore Center Denmark 2010; Prinses Amalia Windpark 2010; Statoil 2010b; Vindpark Vänern 2010; Blue H USA 2009; E.ON UK 2009; EWEA 2009a; Ministry of Foreign Affairs of Denmark 2009; RWE npower renewables 2009; OWE 2008)
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Recently, some problems with corrosion have been discovered. For example, in late 2010 Siemens discovered that corrosion protection had failed for the pitch bearings in its 3.6-MW offshore wind turbines in four wind farms.1 Recently, the market has regained momentum as the industry has overcome some of these problems and is trending toward more sustained growth.
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Although Europe has been the leader in offshore wind so far, several other countries have begun looking toward offshore wind to meet their energy needs, including Canada, China, and the United States. Figure 2-10 juxtaposes installed offshore projects against proposed North American projects (reNews 2009; Daily 2008; Wired Magazine 2007; Sokolic 2008; Williams 2008; Garden State Wind 2010; AWS Truewind 2010)
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. (SOURCE: National Renewable Energy Laboratory.)
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Offshore wind turbines are produced mainly by a small number of European turbine manufacturers, although there has been some very recent activity by at least one Chinese original equipment manufacturer. The New York State Energy Research and Development Authority (NYSERDA)
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Progress in Development of U.S. Offshore Wind Facilities As of November 2010, there were no offshore wind power facilities in the United States, but it is probable that construction activities for offshore wind energy projects will begin soon.
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coast, including the Great Lakes, the Gulf of Mexico, and even the West Coast. The West Coast has much greater water depths close to shore, however, and this is likely to constrain development in the near term despite a good wind resource, because wind turbine designs for such deep waters are just entering the prototype demonstration phase (Moe, 2010; Pool 2010)
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REFERENCES Abbreviations AWEA American Wind Energy Association CEQ Council on Environmental Quality EWEA European Wind Energy Association IEC International Electrotechnical Commission NYSERDA New York State Energy Research and Development Authority OWE Offshore Windenergy Europe USDOE U.S. Department of Energy Alpha Ventus.
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2004. Japan's First Offshore Wind Turbines on Trial Run.
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2010. Deep Water Wind Turbines.
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