Wind Turbines Shed Their Gears
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Siemens erected a prototype of its machine in Brande, Denmark, in December and plans to install 10 more this year, primarily in Denmark, before beginning mass production in 2011. GE’s technology, which it acquired with the purchase of Norwegian turbine producer ScanWind last year, is being demonstrated at a test site in Norway; commercialization of its four-megawatt machine is slated for 2012.
More competition is on the way. Venture capital firm New Enterprise Associates is backing a Boulder, CO-based startup called Boulder Wind Power, which is developing a 1.5-megawatt direct-drive turbine. The firm was founded in December by Sandy Butterfield, who was chief engineer for the U.S. National Renewable Energy Laboratory’s (NREL) wind technology center, where he led a major study of the gearbox design process.
Whether gearbox failures are an industrywide problem remains a matter of some contention. NREL initiated its study in 2007, when there were several failures: a U.S.-based company, Clipper Windpower, experienced serious gearbox problems within months of installing the first of its 2.5-megawatt turbines at a wind farm in Lackawanna, NY, while gearboxes in the 30 Vestas Wind Systems turbines forming the U.K.’s offshore Kentish Flats wind farm had to be replaced after just two years of operation. NREL concluded that most wind turbine gearboxes would fail “well before” their 20-year design life.
Stiesdal says Siemens’s own studies show that gearboxes are quite reliable, overall. A 2008 analysis of Siemens machines installed from 1983 to 1989 in the U.S. found that the “vast majority” were still operating with their original gearboxes. But he does expect increased reliability from the direct-drive system, which has about half as many parts as a conventional turbine.
Direct-drive systems do introduce one potential problem, however. There are ongoing concerns regarding the future supply of the rare earth metals used to make permanent magnets. “That’s a serious issue,” says Stiesdal.
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