The weight and efficiency of drive trains, including a turbine's gearbox and generator, is all-important in scaling technology up to larger turbines for offshore.
GE Global Research will design and perform component testing for a 10MW direct-drive generator using a stationary superconducting component design that should reduce the risk of fluid leakage. Superconductivity means copper conductors are chilled so their resistance plummets. Therefore lighter coils that use less copper can be employed. But the refrigeration units needed to do this have so far been prohibitively heavy and costly.
GE's research is leveraging the conglomerate's decades of experience with large superconducting magnets for magnetic resonance imaging systems, says GE spokesman Todd Alhart. Not many companies can amass the global knowledge to succeed with such a project, but GE may be one of them, says Dan Shreve, a director at Make Consulting who used to work for GE. Advanced Magnet Lab of Palm Bay, Florida will also develop a superconducting direct-drive generator for large wind turbines.
Using smaller amounts of rare earths - increasingly employed in direct-drive permanent-magnet generators - is vital because of China's stranglehold on 97% of the world supply. The National Wind Technology Centre (NWTC), part of the US National Renewable Energy Laboratory, will optimise and test a hybrid design that uses a single-stage gearbox and a non-permanent magnet generator. It is not unlike a design already being tested by Multibrid-Areva in 5MW offshore turbines at the Alpha Ventus project in the North Sea. The medium-speed generator will be more reliable than the three-stage gearboxes currently employed, according to Fort Felker, NWTC director. The technology will be scalable to 10MW and useable to retrofit 1.5MW onshore turbines.
Boulder Wind Power's direct-drive architecture without iron in the core has also received funding. The project is led by Sandy Butterfield, former NWTC chief engineer. The research is interesting, says Make's Shreve, because of the small company's strong team. If the research - which is still very much in its infancy - works it could have a "massive impact" on drive trains globally, he says.
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