Hydroelectricity
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INTRODUCTION
Hydroelectricity
Hydroelectricity or hydroelectric power is a form of hydropower. (I.e., the use of energy released by water falling. Flowing downhill, moving tidally, or moving in some other way) to produce electricity specifically, the kinetic energy of moving water is converted to electric energy by a water turbine driving a generator. Most hydroelectric power is currently generated from water flowing downhill. But a few tidal harnesses exist that draw power from the tide. Hydroelectric power is generated at dams or other places where descends from a height, or coasts with a large tidal swing (such as a bay of fundy). Hydroelectricity is a renewable energy source. Since the water that flows in river has come from precipitation such as rain or snow, and tides are driven by a rotation of earth.
The energy that may be extracted from water depends not only on the volume but on the difference in height between the water (or source) and the water outflow. The height is difference is called the head. The amount of potential energy in water is directly proportional to the head. For the reason, it is advantageous to build dams as high as possible to produce the maximum electrical energy.


IMPORTANCE
Hydroelectric power using the potential energy of rivers, now supplies 20% of word electricity. Norway produces virtually all of its electricity from hydro, while Iceland produces 83% of its requirements (2004). Austria produces 67% of all electricity generated in the country from hydro (over 70% of its requirement). A part from a few countries with an abundance of it, hydro capacity is normally applied to peak-load demand, because it can be readily stored during off-peak hrs in fact. Pumped-storage hydroelectric reservoirs are sometimes used to store electricity produced by thermal plants for use peak hrs