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Wind power - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Wind_power Wind power From Wikipedia, the free encyclopedia Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electrical power, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships. Large wind farms consist of hundreds of individual wind turbines which are connected to the electric power transmission network. For new constructions, onshore wind is an inexpensive source of electricity, competitive with or in many places cheaper than fossil fuel plants. [1][2] Small onshore wind farms provide electricity to isolated locations. Utility companies increasingly buy surplus electricity produced by small domestic wind turbines. [3] Offshore wind is steadier and stronger than on land, and offshore farms have less visual impact, but construction and maintenance costs are considerably higher. Wind power, as an alternative to fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during Burbo Bank Offshore Wind Farm, at [4] operation and uses little land. The effects on the environment are the entrance to the River Mersey in generally less problematic than those from other power sources. As of North West England. 2011, Denmark is generating more than a quarter of its electricity from wind and 83 countries around the world are using wind power to supply the electricity grid. [5] In 2010 wind energy production was over 2.5% of total worldwide electricity usage, and growing rapidly at more than 25% per annum. Wind power is very consistent from year to year but has significant variation over shorter time scales. As the proportion of windpower in a region increases, a need to upgrade the grid, and a lowered ability to supplant conventional production can occur. [6][7] Power management techniques such as having excess capacity storage, geographically The Shepherds Flat Wind Farm is a distributed turbines, dispatchable backing sources, storage such as 845 megawatt (MW) wind farm in the pumped-storage hydroelectricity, exporting and importing power to U.S. state of Oregon. neighboring areas or reducing demand when wind production is low, can greatly mitigate these problems. [8] In addition, weather forecasting permits the electricity network to be readied for the predictable variations in production that occur. [9][10] Contents 1 History 1.1 Mechanical power 1.2 Electrical power 2 Wind energy 2.1 Distribution of wind speed 1 of 30 6/1/2013 10:49 AM Wind power - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Wind_power 2.2 High altitude winds 3 Wind farms 3.1 Feeding into grid 3.2 Offshore wind power 4 Wind power capacity and production 4.1 Growth trends 4.2 Capacity factor 4.3 Penetration 4.4 Variability 4.5 Predictability 4.6 Reliability 4.7 Integration with other sources 4.8 Energy storage 4.9 Capacity credit and fuel savings 5 Economics 5.1 Cost trends 5.2 Incentives and community benefits 6 Environmental effects 7 Politics 7.1 Central government 7.2 Public opinion 7.3 Community 8 Small-scale wind power 9 See also 10 Notes 11 References 12 External links History Main article: History of wind power Mechanical power Sailboats and sailing ships have been using wind power for thousands of years, and architects have used wind-driven natural ventilation in buildings since similarly ancient times. The use of wind to provide mechanical power came somewhat later in antiquity. The windwheel of the Greek engineer Heron of Alexandria in the 1st century AD is the earliest known instance of using a wind-driven wheel to power a machine. [11][12][13] Medieval depiction of a wind mill The first windmills were in use in Persia at least by the 9th century and possibly as early as the 7th century. [14] The use of windmills became widespread across the Middle East and Central Asia, and later spread to China and India. [11] By 1000 AD, windmills were used to pump seawater for salt-making in China and Sicily. [15] Windmills were used extensively in Northwestern Europe to grind flour from the 1180s, [12] and windpumps were used to drain land for 2 of 30 6/1/2013 10:49 AM Wind power - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Wind_power agriculture and for building. [16 ] Early immigrants to the New World brought the technology with them from Europe. [16] In the US, the development of the water-pumping windmill was the major factor in allowing the farming and ranching of vast areas otherwise devoid of readily accessible water. [17] Windpumps contributed to the expansion of rail transport systems throughout the world, by pumping water from water wells for steam locomotives. The multi-bladed wind turbine atop a lattice tower made of wood or steel was a century a fixture of the landscape throughout rural America. [18] In 1881, Lord Kelvin proposed using wind power when coal ran out, as "so little of it is left". [19] Solar power was also proposed, at about the same time. [20] Electrical power In July 1887, a Scottish academic, Professor James Blyth, built a cloth- sailed wind turbine in the garden of his holiday cottage in Marykirk and used the electricity it produced to charge accumulators which he used to power the lights in his cottage. [21] His experiments culminated in a UK patent in 1891. [22] In the winter of 1887–1888 US inventor Charles F. Brush produced electricity using a wind powered generator which powered his home and laboratory until about 1900. In the 1890s, the Danish scientist and inventor Poul la Cour constructed wind turbines to Trends in the top five countries generate electricity, which was used to produce hydrogen and Oxygen generating electricity from wind, by electrolysis and a mixture of the two gases was stored for use as a 1980-2012 (US EIA) fuel. [22] La Cour was the first to discover that fast rotating wind turbines with fewer rotor blades were the most efficient in generating electricity and in 1904 he founded the Society of Wind Electricians. [23] By the mid-1920s, 1 to 3-kilowatt wind generators developed by companies such as Parris-Dunn and Jacobs Wind-electric [19] found widespread use in the rural areas of the mid-western Great Plains of the US but by the 1940s the demand for more power and the coming of the electrical grid throughout those areas made these small generators obsolete. [24] Blyth's "windmill" at his cottage in Marykirk in 1891 IN 1931 the French aeronautical engineer, George Darrieus was granted a patent for the Darrieus wind turbine which uses vertical-axis airfoils to create rotation [25] and a 100 kW precursor to the modern horizontal wind generator was used in Yalta, in the USSR. In 1956 Johannes Juul, a former student of la Cour, built a 200 kW, three-bladed turbine at Gedser in Denmark, which influenced the design of many later turbines. [23] In 1975 the United States Department of Energy funded a project to develop utility-scale wind turbines. The NASA wind turbines project built thirteen experimental turbines which paved the way for much of the technology used today. [23] Since then, turbines have increased greatly in size with the Enercon E-126 capable of delivering up to 7.5 Megawatts (MW). [nb 1][26] Wind turbine production has expanded to many countries and wind power is expected to grow worldwide in the twenty-first century. 3 of 30 6/1/2013 10:49 AM Wind power - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Wind_power Wind energy Wind energy is the kinetic energy of air in motion, also called wind. Total wind energy flowing through an imaginary area A during the time t is: [27] where ρ is the density of air; v is the wind speed; Avt is the volume of air passing through A (which is considered perpendicular to the direction of the wind); Avt ρ is therefore the mass m passing per unit time. Note that ½ ρv2 is the kinetic energy of the moving air per unit volume. Power is energy per unit time, so the wind power incident on A (e.g. equal to the rotor area of a wind turbine) is: [27] Wind power in an open air stream is thus proportional to the third power of the wind speed; the available power increases eightfold when the Advertisement for a wind-powered wind speed doubles. Wind turbines for grid electricity therefore need to electric system, 1897 be especially efficient at greater wind speeds. Wind is the movement of air across the surface of the Earth, affected by areas of high pressure and of low pressure. [28] The surface of the Earth is heated unevenly by the Sun, depending on factors such as the angle of incidence of the sun's rays at the surface (which differs with latitude and time of day) and whether the land is open or covered with vegetation. Also, large bodies of water, such as the oceans, heat up and cool down slower than the land. The heat energy absorbed at the Earth's surface is transferred to the air directly above it and, as warmer air is less dense than cooler air, it rises above the cool air to form areas of high pressure and thus pressure differentials. The rotation of the Earth drags the Map of available wind power for the atmosphere around with it causing turbulence. These effects combine to United States. Color codes indicate cause a constantly varying pattern of winds across the surface of the wind power density class.