The wind has been used for centuries to pump water and grind grain, and more recently to generate electricity.
Wind energy is an indirect form of solar energy.
Winds result from an unequal heating of different parts of the Earth's surface, causing cooler dense air to circulate to replace warmer, lighter air. While some of the Sun's energy is absorbed directly into the air, most of the energy in the wind is first absorbed by the surface of the Earth and then transferred to the air by convection. Seasonal variations in the speed and direction of the wind result from the seasonal changes in the relative inclination of the Earth towards the Sun, which in turn changes the patterns of differential heating. Figure 1 Formation of winds by local heating and cooling. This air movement is complicated by a number of global scale factors such as the Earth's rotation, continents, oceans and mountain ranges and on a local scale by hills, vegetation and lakes.