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Wave/Tidal Energy
by: Karina Ayala, Rachael Carleson Williams, Lidya Makonnen,
Terrell Stevenson
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Wave EnergyWHAT IS IT?Wave power devices extract energy directly
from surface waves or from pressure fluctuations below the
surface.Energy extracted from the waves is stored in
generators.Wave energy can be converted into electricity through
both offshore and onshore systems.Offshore systems are situated in
deep water, typically of more than 40 meters (131 feet).
Sophisticated mechanismslike the Salter Duckuse the bobbing motion
of the waves to power a pump that creates electricity. Other
offshore devices use hoses connected to floats that ride the waves.
The rise and fall of the float stretches and relaxes the hose,
which pressurizes the water, which, in turn, rotates a turbine.
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Oscillating water column The oscillating water column consists
of a partially submerged concrete or steel structure that has an
opening to the sea below the waterline. It encloses a column of air
above a column of water. As waves enter the air column, they cause
the water column to rise and fall. This alternately compresses and
depressurizes the air column. As the wave retreats, the air is
drawn back through the turbine as a result of the reduced air
pressure on the ocean side of the turbine.HOW DOES IT WORK?Wave
capture chamber set into rock face.Tidal power forces water into
chamber.Air alternately compressed and decompressed and
decompressed by "oscillating water column".Rushes of air drive the
Wells Turbine, creating power.
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TAPCHANTapered channel system, consists of a tapered channel,
which feeds into a reservoir constructed on cliffs above sea level.
The narrowing of the channel causes the waves to increase in height
as they move toward the cliff face. The waves spill over the walls
of the channel into the reservoir and the stored water is then fed
through a turbine.The TAPCHAN systems overcome the issue of power
on demand, as the reservoir is able to store energy until it is
required.
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Pendulor device The pendulor wave-power device consists of a
rectangular box, which is open to the sea at one end. A flap is
hinged over the opening and the action of the waves causes the flap
to swing back and forth. The motion powers a hydraulic pump and a
generator.
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Main AdvantagesThis is a non-polluting source of energyWave
turbines are relatively quiet to operate and do not affect wild
life. Main DisadvantagesWave energy requires a consistent supply of
powerful waves to fuel a community's electrical needs, but waves
are not consistent. Spills or accidental leaks caused by hydraulic
fluids in the system could also potentially harm marine life.
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Tidal EnergyWHAT IS IT?Tides of water caused by the Moon and
Sun, in combination with Earth's rotation.Practically inexhaustible
and it is classified as a renweable resource. For tidal differences
to be harnessed into electricity the difference between high and
low tides must be at least 16 feet. There are only about fourty
sites on the earth with tidal ranges of this magnitude.
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Tidal power technologies include the following...
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Barrage or damA barrage or dam is typically used to convert
tidal energy into electricity by forcing the water through
turbines, activating a generator.Gates and turbines are installed
along the dam. When the tides produce an adequate difference in the
level of the water on opposite sides of the dam, the gates are
opened. The water then flows through the turbines. The turbines
turn an electric generator to produce electricity.
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Tidal fence Tidal fences look like giant turnstiles. They can
reach across channels between small islands or across straits
between the mainland and an island. A tidal fence has vertical axis
turbines mounted in a fence. All the water that passes is forced
through the turbines. They can be used in areas such as channels
between two landmasses.
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Tidal turbine Tidal turbines look like wind turbines. They are
arranged underwater in rows, as in some wind farms.Ideal locations
for tidal turbine farms are close to shore in water depths of
65.598.5 feet.Turbines were submerged in the East River to generate
electricity from rapid tidal currents in New York City in 2007
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Main Advantages It is predictable. No waste or pollutionIt is
very cheap to maintain. Main DisadvantagesBuilding cost is
expensive.Disrupts migration of creatures in the oceanOnly produces
power for only about 10 hours a day.
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THE END...
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SOURCEShttp://www.energysavers.gov/http://www.rise.orghttp://www.technologyreview.com/energy/http://en.wikipedia.org/wiki/Tidal_powerhttp://en.wikipedia.org/wiki/Wave_power
