Wind power

Wind power is the conversion of wind energy into a useful form, such as electricity, using wind turbines. At the end of 2007, worldwide nameplate capacity of wind-powered generators was 94.1 gigawatts.[1] Although wind produces only about 1% of world-wide electricity use, it is growing rapidly, increasing more than fivefold globally between 2000 and 2007.

In several countries it has achieved relatively high levels of penetration, accounting for approximately 19% of electricity production in Denmark, 9% in Spain and Portugal, and 6% in Germany and the Republic of Ireland in 2007.
Wind energy has historically been used directly to propel sailing ships or converted into mechanical energy for pumping water or grinding grain, but the principal application of wind power today is the generation of electricity. Large scale wind farms are typically connected to the local electric power transmission network, with smaller turbines being 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 favoured by many environmentalists as an alternative to fossil fuels, as it is plentiful, renewable, widely distributed, clean, and produces lower greenhouse gas emissions, although the construction of wind farms is not universally welcomed due to their visual impact and other effects on the environment. 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, additional costs for compensation of intermittency are considered to be modest.

Wind turbine

A wind turbine is a rotating machine which converts the kinetic energy in 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 then 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. Windmill 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. See environmental concerns with electricity generation for discussion of environmental problems with wind-energy production.