Hydroelectric Power Hydroelectric
power is America’s leading renewable energy resource. Of all the renewable power
sources, it’s the most reliable, efficient and economical. Water is needed to
run a hydroelectric generating unit. It’s held in a reservoir or lake behind a
dam, and the force of the water being released from the reservoir through the
dam spins the blades of a turbine. The turbine is connected to the generator
that produces electricity. After passing through the turbine, the water
re-enters the river on the downstream side of the dam.
Hydroelectric plants convert the kinetic energy within falling water into
electricity. The energy in moving water is produced in the sun, and consequently
is continually being renewed. The energy in sunlight evaporates water from the
seas and deposits it on land as rain. Land elevation differences result in
rainfall runoff, and permit some of the original solar energy to be harnessed as
hydroelectric power. Hydroelectric power is at present the earth’s chief
renewable electricity source, generating 6% of global energy and about 15% of
worldwide electricity. Hydroelectric power in Canada is plentiful and provides
60% of their electrical requirements. Usually regarded as an inexpensive and
clean source of electricity, most big hydroelectric projects being planned today
are facing a great deal of hostility from environmental groups and local
people. The earliest recorded use of water power was a clock,
constructed around 250 BC. Since then, people have used falling water to supply
power for grain and saw mills, as well as a host of other uses. The earliest use
of flowing water to generate electricity was a waterwheel on the Fox River in
Wisconsin in 1882. The first hydroelectric power plants were
much more dependable and efficient than the plants of the day that were fired by
fossil fuels. This led to a rise in number of small to medium sized
hydroelectric generating plants located wherever there was an adequate supply of
falling water and a need for electricity. As demand for electricity soared in
the middle years of the 20th century, and the effectiveness of coal and oil
power plants improved, small hydro plants became less popular. The majority of
new hydroelectric developments were focused on giant mega-projects.
Hydroelectric plants harness energy by passing flowing water through a
turbine. The water turbine rotation is delivered to a generator, which generates
electricity. The quantity of electricity that can be produced at a hydroelectric
plant relies upon two variables. These variables are (1) the vertical distance
that the water falls, called the "head", and (2) the flow rate, calculated as
volume over time. The amount of electricity that is produced is thus
proportional to the head product and the flow rate. So,
hydroelectric power stations can normally be separated into two kinds. The most
widespread are "high head" plants and usually employ a dam to stock up water at
an increased height. They also store water at times of rain and discharge it
during dry times. This results in reliable and consistent electricity
generation, capable of meeting demand since flow can be rapidly altered. At
times of excess electrical system capacity, usually available at night, these
plants can also pump water from one reservoir to another at a greater height.
When there is peak electrical demand, the higher reservoir releases water
through the turbines to the lower reservoir. "Low head"
hydroelectric plants usually exploit heads of just a few meters or less. These
types of power station use a weir or low dam to channel water, or no dam at all
and merely use the river flow. Unfortunately their electricity production
capacity fluctuates with seasonal water flow in a river. Around
2003 people believed almost universally that hydroelectric power was an
environmentally safe and clean means of generating electricity. Hydroelectric
stations do not release any of the usual atmospheric pollutants emitted by power
plants fuelled by fossil fuels so they do not add to global warming or acid
rain. Nevertheless, recent studies of the larger reservoirs formed behind dams
have implied that decomposing flooded vegetation could give off greenhouse gases
equal to those from other electricity sources. The clearest
result of hydroelectric dams is the flooding of huge areas of land. The
reservoirs built can be exceptionally big and they have often flooded the lands
of indigenous peoples and destroyed their way of life. Numerous rare ecosystems
are also endangered by hydroelectric power plant development.
Damming rivers may also change the quantity and quality of water in the
rivers below the dams, as well as stopping fish migrating upstream to spawn. In
addition, silt, usually taken downstream to the lower parts of a river, is
caught by a dam and so the river downstream loses the silt that should fertilize
the river’s flood plains during high water periods. Theoretical
global hydroelectric power is approximately four times larger than the amount
that has been taken advantage of today. Most of the residual hydro potential
left in the world can be found in African and Asian developing countries.
Exploiting this resource would involve an investment of billions of dollars,
since hydroelectric plants normally have very high building costs. Low head
hydro capacity facilities on small scales will probably increase in the future
as low head turbine research, and the standardization of turbine production,
reduce the costs of low head hydroelectric power production. New systems of
control and improvements in turbines could lead in the future to more
electricity created from present facilities. In addition, in the 1950’s and 60’s
when oil and coal prices were very low, lots of smaller hydroelectric plants
were closed down. Future increases in the prices of fuel could lead to these
places being renovated. Exploiting hydroelectric power resource can cost billions of dollars, for hydroelectric plants normally have ______ .