Environmental Engineering Reference
In-Depth Information
For hydroelectric power generation, a dam is built across a river that has a large change in elevation (which
creates more water energy). The dam stores water behind it in the form of a lake or reservoir. The water intake
is near the bottom of the dam (see the figure below). Gravity pulls the water through the penstock. Lower in
the penstock is a turbine propeller, which is turned by the moving water. The shaft of the turbine is connected
to the generator. The shaft turns the generator, and the generator produces the electrical power. Power lines
carry the electricity to the power grid. The water continues past the propeller and into the river on the down-
stream side of the dam.
Source: Tennessee Valley Authority
Advantages and Disadvantages of Hydroelectric Power (Dams)
Advantages
Disadvantages
There is flooding of land behind dams, sometimes in-
cluding towns.
No fossil fuel is needed.
Dam reservoirs can store rainwater for use in the case
of drought.
Dams disrupt natural seasonal changes in rivers, and
ecosystems can be destroyed.
Hydroelectric plants are relatively inexpensive to main-
tain.
Impacts downstream water flow, often diminishing
available water.
Hydroelectric is a renewable energy source because
the Earth's water cycle replenishes upstream flow.
Silt accumulates and prevents mineral-enriched sedi-
ment to reach farmlands.
