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HYDROELECTRIC POWER
Humans
have been utilizing the latent power of running water
since the beginning of recorded history. In its early
forms, a wheel was built over a swiftly flowing river or
stream, and the motion of the water pushed on the wheel,
forcing it to rotate. This motion would then be
transferred to a mechanical device, most frequently a
mill for grinding grain or a wine-press.
Today, the motion of water is normally used to turn a
turbine to produce electricity, which is called
“hydroelectric generation.” While some small power
plants are still constructed on or near fast moving
rivers (especially near waterfalls) and divert a small
portion of the water for generation, the energy of a
flowing river is often not sufficient for economic
energy production. In modern applications, a dam is
typically used instead to take advantage of the greater
potential of gravity. Contrary to common belief, water
from a dam does not flow over the dam to a turbine;
rather, water passes under or through the dam. A dam
creates a reservoir that stores potential energy, which
is released under controlled circumstances, and the
weight of the water itself creates a high pressure flow
that turns the turbines to generate electricity. Though
on-river plants are cheaper to build, dams produce far
more energy output, and remain the most viable form of
hydroelectric generation.
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Hydroelectricity is the largest source of renewable,
sustainable power in use in the world. World wide
production of hydroelectric electricity has doubled
since 1970, and currently accounts for one-fifth of the
world's electricity. Only fossil fuels are more widely
used as a source of power. It is the oldest form of
modern renewable energy, and most scientists believe
that since water is neither created or removed from the
water cycle, the net amount of water on Earth has
remained and will continue to remain constant for the
foreseeable future regardless of the level of
hydroelectric development.
There are however some concerns with the environmental
impact of hydroelectric power, particularly regarding
dam construction. The reservoir a dam creates often
destroys a large section of natural habitat, displacing
both animals and (on occasion) humans. A lake habitat
replaces a river habitat, and substantially different
flora and fauna thrive in each. If a potential reservoir
area is not sufficiently cleared prior to construction,
submerged plant material can rot and release toxic gases
into the water that can destroy fish populations.
Additionally, dams frequently block the passage of
migrating fish, such as salmon in the Northwestern
United States, which can decimate a species in a matter
of years. Some studies indicate that up to ninety
percent of a river's salmon population may be destroyed
by the construction of a dam, despite the use of fish
ladders of other accommodations. This has a trickle-down
effect on many other species, specifically predatory
animals that depend on the yearly migrations for a food
supply.
Despite these problems, hydroelectric power generation
is the most developed of all the current models, due to
its longevity. It is a non-polluting and virtually
inexhaustible supply of sustainable energy, and is far
more efficient than fossil fuels for electrical
generation (90% of potential energy is converted to
electricity, as compared with 50% for a coal burning
plant). It is easy to maintain control over production
rates, because the flow of water can simply be stopped
when electricity is not needed, meaning there is very
limited wasted productive capacity. The dam can also
help control flooding and the created lake is often used
as a recreational area, further increasing the appeal
for local residents.
Published by Carol Foss - in the hope that it will make
a difference, however small. |
