According to Science Daily:
Wind power is the conversion of wind energy into more useful forms, such as electricity, using wind turbines.
At the end of 2006, worldwide capacity of wind-powered generators was 73.9 gigawatts; although it currently produces just over 1% of world-wide electricity use, it accounts for approximately 20% of electricity use in Denmark, 9% in Spain, and 7% in Germany. Globally, wind power generation more than quadrupled between 2000 and 2006. Most modern wind power is generated in the form of electricity by converting the rotation of turbine blades into electrical current by means of an electrical generator.
In windmills (a much older technology), wind energy is used to turn mechanical machinery to do physical work, such as crushing grain or pumping water. Wind power is used in large scale wind farms for national electrical grids as well as in small individual turbines for providing electricity to rural residences or grid-isolated locations. Wind energy is plentiful, renewable, widely distributed, clean, and reduces toxic atmospheric and greenhouse gas emissions if used to replace fossil-fuel-derived electricity.
The intermittency of wind seldom creates problems when using wind power at low to moderate penetration levels. There are many thousands of wind turbines operating, with a total capacity of 73,904 MW of which Europe accounts for 65% (2006).
The average output of one megawatt of wind power is equivalent to the average electricity consumption of about 250 American households.
Wind power was the most rapidly-growing means of alternative electricity generation at the turn of the century and world wind generation capacity more than quadrupled between 1999 and 2005. There is an estimated 50 to 100 times more wind energy than plant biomass energy available on Earth.
Most of this wind energy can be found at high altitudes where continuous wind speeds of over 160 km/h (100 mph) occur.
Eventually, the wind energy is converted through friction into diffuse heat throughout the Earth’s surface and the atmosphere. Large-scale onshore and near-shore wind energy facilities (wind farms) can be controversial due to aesthetic reasons and impact on the local environment. It should be noted, however, that onshore and near-shore studies show that the number of birds killed by wind turbines is negligible compared to the number that die as a result of other human activities such as traffic, hunting, power lines and high-rise buildings and especially the environmental impacts of using non-clean power sources.