A wind turbine is a rotating machine which converts the kinetic energy of wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. If the mechanical energy is instead converted to electricity, the machine is called a wind generator, wind turbine, wind power unit (WPU), wind energy converter (WEC), or aerogenerator.
This article discusses electric power generation machinery. The Windmill article discusses machines used for grain-grinding, water pumping, etc. The article on wind power describes turbine placement, economics, and public concerns. The wind energy section of that article describes the distribution of wind energy over time, and how that affects wind-turbine design.
This article is about Wind energy harvesters that use the mechanical energy from the wind for milling. For machines that convert wind energy into electricity see wind turbines. Other uses, see Windmill (disambiguation).
A windmill is a mill powered by the wind. It reduces a solid or coarse substance into pulp or minute grains by crushing, grinding, or pressing. The term windmill is also sometimes used to refer to Wind energy conversion systems as windpumps and windturbines.
Wind power is the conversion of wind energy into a useful form of energy, such as electricity, using wind turbines. At the end of 2008, worldwide nameplate capacity of wind-powered generators was 121.2 gigawatts (GW). In 2008, wind power produced about 1.5% of worldwide electricity usage; and is growing rapidly, having doubled in the three years between 2005 and 2008. Several countries have achieved relatively high levels of wind power penetration, such as 19% of stationary electricity production in Denmark, 11% in Spain and Portugal, and 7% in Germany and the Republic of Ireland in 2008. As of May 2009, eighty countries around the world are using wind power on a commercial basis.
Large-scale wind farms are connected to the electric power transmission network; smaller facilities are used to provide electricity to isolated locations. Utility companies increasingly buy back surplus electricity produced by small domestic turbines. Wind energy as a power source is attractive as an alternative to fossil fuels, because it is plentiful, renewable, widely distributed, clean, and produces no greenhouse gas emissions. However, the construction of wind farms is not universally welcomed due to their visual impact and other effects on the environment.
Wind power is non-dispatchable, meaning that for economic operation, all of the available output must be taken when it is available. Other resources, such as hydropower, and standard load management techniques must be used to match supply with demand. The intermittency of wind seldom creates problems when using wind power to supply a low proportion of total demand. Where wind is to be used for a moderate fraction of demand such as 40%, additional costs for compensation of intermittency are considered to be modest.
Wind power is the conversion of wind energy into a useful form of energy, such as electricity, using wind turbines. At the end of 2008, worldwide nameplate capacity of wind-powered generators was 121.2 gigawatts (GW). In 2008, wind power produced about 1.5% of worldwide electricity usage; and is growing rapidly, having doubled in the three years between 2005 and 2008. Several countries have achieved relatively high levels of wind power penetration, such as 19% of stationary electricity production in Denmark, 11% in Spain and Portugal, and 7% in Germany and the Republic of Ireland in 2008. As of May 2009, eighty countries around the world are using wind power on a commercial basis.
Large-scale wind farms are connected to the electric power transmission network; smaller facilities are used to provide electricity to isolated locations. Utility companies increasingly buy back surplus electricity produced by small domestic turbines. Wind energy as a power source is attractive as an alternative to fossil fuels, because it is plentiful, renewable, widely distributed, clean, and produces no greenhouse gas emissions. However, the construction of wind farms is not universally welcomed due to their visual impact and other effects on the environment.
Wind power is non-dispatchable, meaning that for economic operation, all of the available output must be taken when it is available. Other resources, such as hydropower, and standard load management techniques must be used to match supply with demand. The intermittency of wind seldom creates problems when using wind power to supply a low proportion of total demand. Where wind is to be used for a moderate fraction of demand such as 40%, additional costs for compensation of intermittency are considered to be modest.

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