Sabtu, Disember 08, 2007

Electricity Generation

Main article: Electricity generation Most hydroelectric power comes from the potential energy of dammed water driving a water t... thumbnail 1 summary
Main article: 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.
Pumped storage hydroelectricity produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped storage schemes currently provide the only commercially important means of large-scale grid energy storage and improve the daily load factor of the generation system. Hydroelectric plants with no reservoir capacity are called run-of-the-river plants, since it is not then possible to store water. A tidal power plant makes use of the daily rise and fall of water due to tides; such sources are highly predictable, and if conditions permit construction of barrages and reservoirs, can also be dispatchable to generate power during high demand periods.
Less common types of hydro schemes use water's kinetic energy or undammed sources such as undershot waterwheels, the relatively recent field of hydrokinetics.






The source:

Tiada ulasan