| Tidal power traditionally involves
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| | low tide to high tide is needed. There
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| erecting a dam across the opening to a
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| | are only a few places where this tide
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| tidal basin. The dam includes a sluice
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| | change occurs around the earth. Some
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| that is opened to allow the tide to flow
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| | power plants are already operating using
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| into the basin; the sluice is then
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| | this idea. One plant in France makes
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| closed, and as the sea level drops,
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| | enough energy from tides to power 240,000
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| traditional hydropower technologies can
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| | homes.
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| be used to generate electricity from the
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| | 3. Ocean Thermal Energy
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| elevated water in the basin. Some
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| | The final ocean energy idea uses
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| researchers are also trying to extract
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| | temperature differences in the ocean. If
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| energy directly from tidal flow streams.
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| | you ever went swimming in the ocean and
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| There are three basic ways to tap the
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| | dove deep below the surface, you would
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| ocean for its energy. We can use the
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| | have noticed that the water gets colder
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| ocean's waves, we can use the ocean's
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| | the deeper you go. It's warmer on the
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| high and low tides, or we can use
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| | surface because sunlight warms the water.
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| temperature differences in the water.
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| | But below the surface, the ocean gets
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| 1. Wave Energy
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| | very cold. That's why scuba divers wear
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| Kinetic energy (movement) exists in the
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| | wet suits when they dive down deep. Their
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| moving waves of the ocean. That energy
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| | wet suits trapped their body heat to keep
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| can be used to power a turbine. In this
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| | them warm.
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| simple example, the wave rises into a
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| | Power plants can be built that use this
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| chamber. The rising water forces the air
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| | difference in temperature to make energy.
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| out of the chamber. The moving air spins
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| | A difference of at least 38 degrees
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| a turbine which can turn a generator.
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| | Fahrenheit is needed between the warmer
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| When the wave goes down, air flows
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| | surface water and the colder deep ocean
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| through the turbine and back into the
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| | water. Using this type of energy source
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| chamber through doors that are normally
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| | is called Ocean Thermal Energy Conversion
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| closed.
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| | or OTEC. It is being used in both Japan
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| This is only one type of wave energy
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| | and in Hawaii in some demonstration
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| system. Others actually use the up and
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| | projects.
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| down motion of the wave to power a piston
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| | Some of the oldest ocean energy
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| that moves up and down inside a cylinder.
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| | technologies use tidal power. All coastal
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| That piston can also turn a generator.
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| | areas consistently experience two high
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| Most wave-energy systems are very small.
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| | and two low tides over a period of
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| But, they can be used to power a warning
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| | slightly greater than 24 hours. For those
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| buoy or a small light house.
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| | tidal differences to be harnessed into
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| For more information see: Ocean Energy
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| | electricity, the difference between high
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| Potential
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| | and low tides must be at least five
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| 2. Tidal Energy
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| | meters, or more than 16 feet. There are
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| Another form of ocean energy is called
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| | only about 40 sites on the Earth with
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| tidal energy. When tides comes into the
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| | tidal ranges of this magnitude. If there
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| shore, they can be trapped in reservoirs
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| | is one thing we can safely predict and be
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| behind dams. Then when the tide drops,
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| | sure of on this planet, it is the coming
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| the water behind the dam can be let out
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| | and going of the tide. This gives this
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| just like in a regular hydroelectric
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| | form of renewable energy a distinct
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| power plant. In order for this to work
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| | advantage over other sources that are not
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| well, you need large increases in tides.
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| | as predictable and reliable, such as wind
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| An increase of at least 16 feet between
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| | or solar.
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