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Wind turbine: Difference between revisions
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Although there are many ways that the wind can be used to turn a turbine, this site concerns the 3-bladed horizontal-axis upwind design that is usually used. | Although there are many ways that the wind can be used to turn a turbine, this site concerns the 3-bladed horizontal-axis upwind (i.e., “facing” the wind) design that is usually used. | ||
The only major design difference among the latter is whether the generator is direct-driven or gearbox driven. The former are increasingly used in larger wind turbines for the advantage of fewer moving parts. The gearbox on wind turbines is the second most common site of mechanical failure (after the blades).<ref>“Special Report: Grinding Gearboxes”, GCube Underwriting, February 2015</ref> Direct-drive generators, however, because the rotor speed is slower, require many – up to tenfold – more magnets, about a third of whose composition is the rare earth metal neodymium. Although rare earth metals turned out to be – well after receiving the classification – not all that “rare”, their mining and processing are highly toxic and environmentally harmful, and the supply is therefore limited.<ref>https://kirbymtn.blogspot.com/2017/05/rare-earths-and-wind-turbines-yes-its.html</ref> | The only major design difference among the latter is whether the generator is direct-driven or gearbox driven. The former are increasingly used in larger wind turbines for the advantage of fewer moving parts. The gearbox on wind turbines is the second most common site of mechanical failure (after the blades).<ref>“Special Report: Grinding Gearboxes”, GCube Underwriting, February 2015</ref> Direct-drive generators, however, because the rotor speed is slower, require many – up to tenfold – more magnets, about a third of whose composition is the rare earth metal neodymium. Although rare earth metals turned out to be – well after receiving the classification – not all that “rare”, their mining and processing are highly toxic and environmentally harmful, and the supply is therefore limited.<ref>https://kirbymtn.blogspot.com/2017/05/rare-earths-and-wind-turbines-yes-its.html</ref> | ||