Hydropower - Hydroelectricity

Hydroelectricity is electricity produced by hydropower. Hydroelectricity now supplies about 715,000 MWe or 19% of world electricity (16% in 2003), accounting for over 63% of the total electricity from renewables in 2005.

Although large hydroelectric installations generate most of the world's hydroelectricity, small hydro schemes are particularly popular in China, which has over 50% of world small hydro capacity.

Electricity Generation

Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. In this case the energy extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. The amount of potential energy in water is proportional to the head. To obtain very high head, water for a hydraulic turbine may be run through a large pipe called a penstock.