Mankind has been harnessing wind energy for hundreds of years, using windmills to convert the wind into mechanical energy, in order to pump water or grind grain. The modern method uses Wind Turbine Generators (WTGs) to produce electricity from the wind. These WTGs are mounted on towers above ground, and sometimes off-shore, and catch the wind on propeller-shaped blades. The blades are mounted on a rotor, which transfers the energy via a driveshaft and/or gearbox to a generator. The generator spins to create electricity. There can be single installations, wind farms with numerous WTGs, or something in-between.
The electric power generated by wind farms can be used for a rural, off-grid facility (which is not connected to a power grid that supplies electricity) or it can feed excess power back to the utility power grid.
Currently, all US wind energy facilities are land-based, but several off-shore projects are in the pipeline. The capacity of a WTG or a wind farm to produce electricity is measured in kilowatts (kW), megawatts (MW) or, in some very large installations, gigawatts (GW). Small wind turbines are defined as having a generating capacity of up to 100 kW, with up to a 60 foot rotor diameter.
