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Hydropower or water power (from the (ギリシア語:ύδωρ), "water" ) is power derived from the energy of falling water or fast running water, which may be harnessed for useful purposes. Since ancient times, hydropower from many kinds of watermills has been used as a renewable energy source for irrigation and the operation of various mechanical devices, such as gristmills, sawmills, textile mills, trip hammers, dock cranes, domestic lifts, and ore mills. A trompe, which produces compressed air from falling water, is sometimes used to power other machinery at a distance. In the late 19th century, hydropower became a source for generating electricity. Cragside in Northumberland was the first house powered by hydroelectricity in 1878〔(【引用サイトリンク】title=Cragside Visitor Information )〕 and the first commercial hydroelectric power plant was built at Niagara Falls in 1879. In 1881, street lamps in the city of Niagara Falls were powered by hydropower. Since the early 20th century, the term has been used almost exclusively in conjunction with the modern development of hydroelectric power. International institutions such as the World Bank view hydropower as a means for economic development without adding substantial amounts of carbon to the atmosphere, but in some cases dams cause significant social or environmental issues.〔Nikolaisen, Per-Ivar . "(12 mega dams that changed the world (in Norwegian) )" (In English ) ''Teknisk Ukeblad'', 17 January 2015. Retrieved 22 January 2015.〕 == History == In India, water wheels and watermills were built; in Imperial Rome, water powered mills produced flour from grain, and were also used for sawing timber and stone; in China, watermills were widely used since the Han dynasty In China and the rest of the Far East, hydraulically operated "pot wheel" pumps raised water into crop or irrigation canals. The power of a wave of water released from a tank was used for extraction of metal ores in a method known as hushing. The method was first used at the Dolaucothi Gold Mines in Wales from 75 AD onwards, but had been developed in Spain at such mines as Las Médulas. Hushing was also widely used in Britain in the Medieval and later periods to extract lead and tin ores. It later evolved into hydraulic mining when used during the California Gold Rush. In the Middle Ages, Islamic mechanical engineer Al-Jazari described designs for 50 devices, many of them water powered in his book, ''The Book of Knowledge of Ingenious Mechanical Devices'', including devices to serve wine, clocks and five devices lift water from rivers or pools, though three are animal-powered and one can be powered by animal or water. These include an endless belt with jugs attached, a cow-powered shadoof and a reciprocating device with hinged valves. In 1753, French engineer Bernard Forest de Bélidor published ''Architecture Hydraulique'' which described vertical- and horizontal-axis hydraulic machines. By the late nineteenth century, the electric generator was developed and could now be coupled with hydraulics.〔(【引用サイトリンク】title=History of Hydropower )〕 The growing demand for the Industrial Revolution would drive development as well.〔(【引用サイトリンク】url=http://www.waterencyclopedia.com/Ge-Hy/Hydroelectric-Power.html )〕 At the beginning of the Industrial Revolution in Britain, water was the main source of power for new inventions such as Richard Arkwright's water frame. Although the use of water power gave way to steam power in many of the larger mills and factories, it was still used during the 18th and 19th centuries for many smaller operations, such as driving the bellows in small blast furnaces (e.g. the Dyfi Furnace) and gristmills, such as those built at Saint Anthony Falls, which uses the 50-foot (15 m) drop in the Mississippi River. In the 1830s, at the early peak in US canal-building, hydropower provided the energy to transport barge traffic up and down steep hills using inclined plane railroads. As railroads overtook canals for transportation, canal systems were modified and developed into hydropower systems; the history of Lowell, Massachusetts is a classic example of commercial development and industrialization, built upon the availability of water power.〔(【引用サイトリンク】title=Waterpower in Lowell )〕 Technological advances had moved the open water wheel into an enclosed turbine or water motor. In 1848 James B. Francis, while working as head engineer of Lowell's Locks and Canals company, improved on these designs to create a turbine with 90% efficiency. He applied scientific principles and testing methods to the problem of turbine design. His mathematical and graphical calculation methods allowed confident design of high efficiency turbines to exactly match a site's specific flow conditions. The Francis reaction turbine is still in wide use today. In the 1870s, deriving from uses in the California mining industry, Lester Allan Pelton developed the high efficiency Pelton wheel impulse turbine, which utilized hydropower from the high head streams characteristic of the mountainous California interior. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydropower」の詳細全文を読む スポンサード リンク
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