Tidal Power Plants Work
The rise and fall of the sea level
can power electric-generating equipment. The gearing of the equipment is
tremendous to turn the very slow motion of the tide into enough displacement
to produce energy.
Tidal energy traditionally involves
erecting a dam across the opening to a tidal basin. The dam includes a
sluice that is opened to allow the tide to flow into the basin; the sluice
is then closed, and as the sea level drops, traditional hydropower technologies
can be used to generate electricity from the elevated water in the basin.
Some researchers are also trying to extract energy directly from tidal
The energy potential of tidal basins
is large — the largest facility, the La Rance station in France, generates
240 megawatts of power. France is the only country that successfully
uses this power source. French engineers have noted that if the use of
tidal power on a global level was brought to high enough levels, the Earth
would slow its rotation by 24 hours every 2,000 years.
Tidal energy systems can have environmental
impacts on tidal basins because of reduced tidal flow and silt buildup.
Using the Energy of the Ocean
There are three basic ways to tap
the ocean for its energy. We can use the ocean's waves, we can use the
ocean's high and low tides, or we can use temperature differences in the
water. Let's take a look at each.
Kinetic energy (movement) exists in the moving waves of the ocean. That
energy can be used to power a turbine. In this simple example, to the right,
the wave rises into a chamber. The rising water forces the air out of the
chamber. The moving air spins a turbine which can turn a generator.
When the wave goes down, air flows
through the turbine and back into the chamber through doors that are normally
This is only one type of wave-energy
system. Others actually use the up and down motion of the wave to power
a piston that moves up and down inside a cylinder. That piston can also
turn a generator.
Most wave-energy systems are very
small. But, they can be used to power a warning buoy or a small light house.
Another form of ocean energy is called
tidal energy. When tides comes into the shore, they can be trapped in reservoirs
behind dams. Then when the tide drops, the water behind the dam can be
let out just like in a regular hydroelectric power plant.
In order for this to work well, you
need large increases in tides. An increase of at least 16 feet between
low tide to high tide is needed. There are only a few places where this
tide change occurs around the earth. Some power plants are already operating
using this idea. One plant in France makes enough energy from tides to
power 240,000 homes.
Ocean Thermal Energy
The final ocean energy idea uses temperature
differences in the ocean. If you ever went swimming in the ocean and dove
deep below the surface, you would have noticed that the water gets colder
the deeper you go. It's warmer on the surface because sunlight warms the
water. But below the surface, the ocean gets very cold. That's why scuba
divers wear wet suits when they dive down deep. Their wet suits trapped
their body heat to keep them warm.
Power plants can be built that use
this difference in temperature to make energy. A difference of at least
38 degrees Fahrenheit is needed between the warmer surface water and the
colder deep ocean water.
Using this type of energy source
is called Ocean Thermal Energy Conversion or OTEC. It is being used in
both Japan and in Hawaii in some demonstration projects.
and Wave Power
Tidal power operates by building
a barrier across a river estuary. The tidal flow drives turbines to produce
Power - History
Tidal mills were built in the eighteenth
century when their major competition was windmills
There are four main ways in which
we use water to create electricity.
History of Oceanography
Although oceanography has been recognized
as a formal scientific discipline for only 150 years, the quest for this
understanding and its practical application to commerce and war - often
unwitting - goes back much further.
A portion of the information on this
page and graphic was provided by the California Department of Energy
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