When it rains in hills and mountains, the water becomes streams and rivers that
run down to the ocean. The moving or falling water can be used to do work.
Energy, you'll remember is the ability to do work. So moving water, which has
kinetic energy, can be used to make electricity.
For hundreds of years, moving water was used to turn wooden wheels that were attached to grinding wheels to grind (or mill) flour or corn. These were called grist mills or water mills.
Today, moving water can also be used to make electricity.
Hydro means water. Hydro-electric means making electricity from water power.
Hydroelectric power uses the kinetic energy of moving water to make electricity. Dams can be built to stop the flow of a river. Water behind a dam often forms a reservoir Like the picture of Shasta Dam in Northern California pictured on the right. Dams are also built across larger rivers but no reservoir is made. The river is simply sent through a hydroelectric power plant or powerhouse. You can see this in the picture of The Dalles Dam on the Columbia River along the border of Oregon and Washington State.
Hydro is one of the largest producers of electricity in the United States. Water power supplies about 10 percent of the entire electricity that we use. In states with high mountains and lots of rivers, even more electricity if made by hydro power. In California, for example, about 15 percent of all the electricity comes from hydroelectric.
The state of Washington leads the nation in hydroelectricity. The Grand Coulee,
Chief Joseph and John Day dams are three of six major dams on the Columbia
River. About 87 percent of the electricity made in Washington state is produced
by hydroelectric facilities. Some of that electricity is exported from the state
and used in other states.
The water behind the dam flows through the intake and into a pipe called a penstock. The water pushes against blades in a turbine, causing them to turn. The turbine is similar to the kind used in a power plant but instead of using steam to turn the turbine, water is used.
The turbine spins a generator to produce electricity. The electricity can then travel over long distance electric lines to your home, to your school, to factories and businesses.
Hydro power today can be found in the mountainous areas of states where there are lakes and reservoirs and along rivers.
Hydro-electric
generating facilities have the attraction of providing electricity without polluting the atmosphere. They harness the energy of falling water, which can occur naturally, but more often has to be engineered by the construction of large dams with lakes behind them. The advantages of hrdro-electricity have long been appreciated and today it provides 18% of the world's power. In many countries most of the suitable dam sites have already been used, thus limiting further major development of this source.
Other renewable energy sources have more potential for increased use, but also have characteristics which limit their ability to play a major role in meeting electricity needs, bearing in mind that much of the demand is for continuous, reliable supply:
Hudson River Power Plant Description.
During times of peak use, power plants
withdraw five billion gallons per day from the biologically rich tidal Hudson
River north of New York City. The facilities kill virtually all aquatic life
in this massive volume, many billions of organisms each year, by entraining
eggs and larvae into the cooling water system or impinging the larger fish on
intake screens. The mortality varies widely from year to year but typically
includes a sizable portion of the newly spawned populations. For example, in
most years the plants cumulatively entrain more than 40 percent of young
striped bass, perhaps the River’s most prominent recreational species.
Abatement of these kills would help restore the estuary’s productivity. The
Clean Water Act, which the state DEC administers under the SPDES program,
requires such facilities to employ the best technology available to minimize
adverse environmental impact. However, the Hudson River power plants use “once
through” cooling, by far the most wasteful and destructive system.
In contrast, the “closed cycle” technology used on the Hudson’s new power
plants, and on some older facilities elsewhere, could reduce water withdrawals
and thereby fish mortality by up to 97 percent. Given its vastly superior
efficiency, it is impossible to minimize adverse environmental impact without
recirculating the water by some type of closed cycle cooling.
Hydroelectric Power.
A large river which falls down a steep slope
is suitable for generating hydroelectric power.
The river is dammed at the top and the valley is flooded
creating a large reservoir (lake) of water.
The water is let out through
turbines at the bottom of the dam.
The turbines turn a generator which produces electricity.
The original source of the energy is the
Sun
which makes the
wind blow and the
rain fall.
Gravity
causes the falling water to turn the turbines.
Advantages of hydroelectric power.
1. It is renewable.
2. It is readily available.
If you need more energy,
you just let out more water through the turbines.
3. It does not cause pollution.
Disadvantages.
1. Flooding the river valley will destroy the
local habitat
for many of the species which live there.