Wind energy is actually a form of solar energy since heat from the sun produces temperature and density differences in air masses, which, in turn produce wind. Harnessing the wind is one of the oldest methods of producing energy and can turn a wind turbine to generate electricity.
The amount of energy a wind machine can convert to electricity depends on the speed of the wind and the amount of blade surface exposed to the wind. An alternative to the common design is the vertical axis wind turbine which looks like a large egg beater. One advantage of this type of turbine is that it can accept wind from any direction without mechanisms to turn the blades into the wind.
While the wind is free, it is often unsteady and unpredictable in many parts of the country. Another drawback is that wind speeds below about 8 miles per hour are not sufficient to produce much power, and at the other extreme, powerful gusts during storms can damage the mechanical equipment and cause rotor blades to fail. Wind turbines generally produce DC electrical power which can be stored in batteries for later use, but it is expensive. An inverter is necessary to convert the direct current produced by the wind turbine into alternating current.