Wednesday, June 29, 2011
4:10 PM | Posted by
Anonymous |
Hydroelectric power plants capture the energy of moving water. There are multiple ways hydro energy can be extracted. Falling water such as in a penstock, flume, or waterwheel can be used to drive a hydro turbine. Hydro energy can be extracted from water flowing at the lower section of dams, where the pressure forces water to flow. Hydroelectric power generation is efficient, cost effective, and environmentally cooperative. Hydro power production is considered to be a renewable energy source because the water cycle is continuous and constantly recharged.
Water flows much slower through a hydro turbine than does steam
through a high-pressure steam turbine. Therefore, several rotor magnetic poles are used to reduce the rotational speed requirement of the hydro turbine shaft.
Hydro units have a number of excellent advantages. The hydro unit can be started very quickly and brought up to full load in a matter of minutes. In most cases, little or no start-up power is required. A hydro plant is almost by definition a black start unit.
Black start means that electrical power is not needed first in order to start a hydro power plant. Hydro plants have a relatively long life; 50–60 year life spans are common. Some hydroelectric power plants along the Truckee River in California have been in operation for over 100 years.Above figure shows a typical hydroelectric power plant.
The cross-section of a typical low-head hydro installation is shown in above figure. Basically, the water behind the dam is transported to the turbine by means of a penstock. The turbine causes the generator to rotate, producing electricity, which is then delivered to the load center over longdistance power lines. The water coming out of the turbine goes into the river.
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