Wind energy or wind power is the energy extracted from wind using wind turbines to produce electrical power, windmills for mechanical power, windpumps for water pumping, or sails to propel ships. Wind energy, as an alternative to fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation and uses little land. The effects on the environment are generally less problematic than those from other power sources.
Large wind farms consist of hundreds of individual wind turbines which are connected to the electric power transmission network. According to the recent EU analysis for new constructions, onshore wind is an inexpensive source of electricity, competitive with or in many places cheaper than coal, gas or fossil fuel plants. Offshore wind is steadier and stronger than on land, and offshore farms have less visual impact, but construction and maintenance costs are considerably higher. Small onshore wind farms can feed some energy into the grid or provide electricity to isolated off-grid locations.
Wind energy is very consistent from year to year but has significant variation over shorter time scales. As the proportion of wind energy in a region increases, a need to upgrade the grid, and a lowered ability to supplant conventional production can occur. Power management techniques such as having excess capacity storage, geographically distributed turbines, dispatchable backing sources, storage such as pumped-storage hydroelectricity, exporting and importing power to neighboring areas or reducing demand when wind production is low, can greatly mitigate these problems. In addition, weather forecasting permits the electricity network to be readied for the predictable variations in production that occur.
As of 2013, Denmark is generating more than a third of its electricity from wind and 83 countries around the world are using wind power to supply the electricity grid. Wind power capacity has expanded rapidly to 336 GW in June 2014, and wind energy production was around 4% of total worldwide electricity usage, and growing rapidly.
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