Wind turbine

Although there are many ways that the wind can be used to turn a turbine, this site concerns the 3-bladed horizontal-axis design that is usually used.

The only major design difference is direct-drive versus gearbox-driven generators. The former used to be primarily used in smaller wind turbines for on-site home and farm use but are increasingly used in larger wind turbines for the advantage of fewer moving parts. The gearbox on wind turbines is a common site of mechanical failure. 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. The supply of rare earth metals is limited, and their mining and processing are highly toxic and environmentally harmful.