The energy of wind power comes from moving air. The natural process is the following: wind is caused by uneven heating of the earth’s surface by the sun. Since the surface of the earth consists of different types of land and water, it absorbs the sun’s heat at different speeds. An example of this uneven warming is the daily wind cycle: during the day, the air over land heats up faster than the air over water. Warm air over land expands and rises, and heavier, cooler air flows in its place, creating wind. At night, the winds reverse because the air cools faster over land than over water, and so do the atmospheric winds that circle the earth because the land near the earth’s equator is hotter than the land near the North Pole and the South Pole.
Today wind energy is mainly used to generate electricity. Wind turbines use rotor blades to harness the kinetic energy of the wind. Wind flows over the blades and creates lifting force (similar to airplane wings), causing the blades to spin. The rotor blades are connected to a drive shaft that rotates an electrical generator that generates electricity.
The generation of electrical energy from wind power has increased significantly in the last decades. Technical progress in particular contributed to this, which also enabled the costs of wind power to be reduced. In addition, many countries provide financial incentives to promote the expansion of wind turbines.
Almost 5% of global electrical power usage currently comes from wind turbines.