Hydroelectricity, or hydroelectric power, is electricity generated from hydropower. Hydropower supplies one sixth of the world's electricity, almost 4,500 TWh in 2020, which is more than all other renewable sources combined and also more than nuclear power. Hydropower can provide large amounts of low-carbon electricity on demand, making it a key element for creating secure and clean electricity supply systems. A hydroelectric power station that has a dam and reservoir is a flexible source, since the amount of electricity produced can be increased or decreased in seconds or minutes in response to varying electricity demand. Once a hydroelectric complex is constructed, it produces no direct waste, and almost always emits considerably less greenhouse gas than fossil fuel-powered energy plants. However, when constructed in lowland rainforest areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.
The Three Gorges Dam in Central China is the world's largest power-producing facility of any kind.
Museum Hydroelectric power plant "Under the Town" in Užice, Serbia, built in 1900.
The Warwick Castle water-powered generator house, used for the generation of electricity for the castle from 1894 until 1940
Pumped-storage
Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery to end users or its storage, using for example, the pumped-storage method.
A turbo generator
Dynamos and engine installed at Edison General Electric Company, New York, 1895
Wind turbines usually provide electrical generation in conjunction with other methods of producing power.
Large dams, such as Hoover Dam in the United States, can provide large amounts of hydroelectric power. It has an installed capacity of 2.07 GW.