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. Although rare earth metals are not actually “rare”, their mining and processing are highly toxic and environmentally harmful, and the supply is therefore limited.