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Hydroelectricity generation starts with converting either the potential energy of water that is present due to the site's elevation or the kinetic energy of moving water into electrical energy. [13] Hydroelectric power plants vary in terms of the way they harvest energy. One type involves a dam and a reservoir. The water in the reservoir is ...
Castaic is an earth-fill dam with its surfaces covered with boulders and cobble-sized rocks to prevent erosion.The dam is 340 feet (100 m) high above the streambed, 425 feet (130 m) above the foundations, and 5,200 feet (1,600 m) long, containing 44 million cubic yards (34,000,000 m 3) of material. [1]
Hydropower is a flexible source of electricity since stations can be ramped up and down very quickly to adapt to changing energy demands. [31] Hydro turbines have a start-up time of the order of a few minutes. [37] Although battery power is quicker its capacity is tiny compared to hydro. [2]
The Report of the World Commission on Dams also includes in the "large" category, dams which are between 5 and 15 m (16 and 49 ft) high with a reservoir capacity of more than 3 million cubic metres (2,400 acre⋅ft). [45] Hydropower dams can be classified as either "high-head" (greater than 30 m in height) or "low-head" (less than 30 m in height).
Low-head dams and weirs do not produce harmful methane. Groynes but also weirs prevent the transport of silt (sediment) downstream to fertilize fields [5] and to move sediment towards the oceans. Low-head hydropower is typically installed close to areas where the energy is needed, preventing the need for large electrical transmission lines.
The flushing flow method involves partially or completely emptying the reservoir behind a dam to erode the sediment stored on the bottom and transport it downstream. [7] [6] Flushing flows aim to restore natural water and sediment fluxes in the river downstream of the dam, however the flushing flow method is less costly compared to removing dams or constructing bypass tunnels.
The Kajaki Dam is "an earth and rockfill embankment type dam" [4] located on the Helmand River in the Kajaki District of Helmand Province in Afghanistan, about 161 km (100 mi) northwest of Kandahar. It has a hydroelectric power station , which is operated by the Helmand and Arghandab Valley Authority through the Ministry of Energy and Water .
Moreover, run-of-the-river hydroelectric plants do not have reservoirs, thus eliminating the methane and carbon dioxide emissions caused by the decomposition of organic matter in the reservoir of a conventional hydroelectric dam. [12] That is a particular advantage in tropical countries, where methane generation can be a problem.