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Hyrdroelectric power
uses the energy of moving water to make electricity. Fuel for a hydro
plant is renewable and costs nothing. Another benefit is that hydro plants
do not harm effect the air quality.
Hydro plants
generated 33 percent of the nation's electricity in the 1920s. Today
they generate more electricity than 60 years ago, but account for only 13
percent. The percentage is smaller because total electric generation
from other sources is greater.
In a hydropower
system, dams on a river capture its power, directing the fast-flowing
water through turbines, turning generators and producing electricity. The
head or difference between the water levels above and below the turbine,
and the rate of water flow determine the amount of power generated.
Run-of-the-river
plants use the natural flow of the stream. This greatly limits their
potential to produce electricity in a controlled manner because the flow
usually varies during the year. To avoid this, some dams store water
upstream in a reservoir and then release it as needed.
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