Wind on the Lakes
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ince wind power must go where the wind is, much attention so far in the United States has focused on the Great Plains. But the nation’s highest winds are not on the Plains; they are over shallow waters all around the coast and on the Great Lakes. There is currently no operating offshore U.S. wind farm. But the technology is proven. By the end of 2009, 2 GW of power was being generated by offshore wind worldwide, largely in Denmark. This is predicted to increase to approximately 20 GW by 2015 and to 100 GW by 2025. China, Sweden, Belgium, the Netherlands, Germany, and the United Kingdom have also built offshore wind turbines, and several manufacturers now sell turbines specifically for this market. Although some plans for U.S. marine coastal wind power are close to being realized, using this technology in the Great Lakes has not yet been afforded the attention it is due. With technical, legal, and environmental challenges still blocking the way, it is not clear that this will change soon. But the arguments in favor are becoming harder to ignore.
Why the lakes? Recent requirements for siting turbines farther from residences are reducing the number of available sites for land-based
MRS BULLETIN
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Making wind work
Regional Initiative •
the various Great Lakes wind projects succeed or fail,” said Guy Meadows of the University of Michigan, who is attempting to understand these loading mechanisms with funding from DOE. But “ice is not a deal breaker,” according to Donny Davis of the Lake Erie Energy Development Corporation (LEEDCo). A wind farm in Lake Vanern in Sweden, which freezes in the winter, began operation in May 2010 with turbines about 7 km from the shore.
Most turbines consist of a tall (80–100 m) tubular steel tower with a three-blade rotor mounted on top, attached to a nacelle, a hollow shell of fiberglass or steel that contains the inner workings of the machine. Offshore turbines typically have a capacity of 3–5 MW, although Vestas and Siemens are developing 5–7 MW machines, and 20 MW is thought to be feasible. The bigger the machine, potentially the cheaper the power it produces. Most of the experimentation with new materials focuses on the blades. They usually have a skin of fiberglass or carbon-fiber-reinforced plastic surrounding a core that is either hollow or filled with plastic foam or balsa wood. The rotors have typical diameters of about 80 m; General Electric’s latest 3.6 MW turbines have a 110-m span, while that of the 7-MW turbines under development at Vestas is 164 m (hence the model name V164), with tip speeds of around 200 mph. Fiber-reinforced plastic blades are plagued by various defects, such as delamination of fiber and resin, wrinkles, and misaligned fibers. Some of these can be taken into consideration in the design’s safety margins, but they can be the most serious factors limiting a turbine’s lifetime. There is still room for new materials, since laminated fiber-reinforced plastics can have low tensile and shear strength for out-of-plane deformations and cannot be recycled. A
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