Hydropower

Hydropower or hydroelectric energy uses the potential energy of water flows (rivers, waterfalls, ocean currents, etc.). The kinetic energy of the water stream is converted into mechanical energy by a turbine, and then into electrical energy by a generator.

Hydropower is the first renewable source and the third general source of electricity production in the world (16.3% in 2011) behind the coal (40.6%) and gas (22.2%).

Categories of plants

A hydroelectric plant consists of a water retention (taking "over water" or dam) and a production facility.

Gravity stations

Gravity stations take advantage of the water flow and altitude. They can be classified according to the turbine flow and height of fall. There are three types of gravity stations (listed here in order of importance in the hydraulic mix):

- Over water centrals use the flow of a river and provide basic energy produced "over water" and immediately injected on the water system.

- the sluice central in large rivers with relatively steep as the Rhine or the Rhone, dams on the river or a canal parallel to the river causing suites of HF waterfalls that do not disturb the whole valley through parallel dikes to river.

- lakes central (or central of high falls) are also associated with a water reservoir created by a dam.