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| Tidal Power |
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| The tides are formed due to the
gravitational force of attraction between the earth, sun and moon. During
high tides sea water is trapped in a reservoir, and released later to drive
turbines, which in turn produces electricity. The block diagram given below
illustrates the transformation of energy. |
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| Tidal Power |
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| The world's first successful tidal powered electric plant, which spans the Rance River generates a peak 240 megawatts a day enough to power 16,000 homes in the United States. |
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| Today this is the only tidal power station in the world since it is very difficult to find good tidal sites. Tidal mills were used for hundreds of years in some of the European countries. |
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Schematic view of Turbines Fixed at the Bottom of a Reservoir |
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| The first small wave-energy device was built in Japan by Yoshio Masuda. Hundreds of navigation buoys use his system in the Sea of Japan. The Japanese are also testing a number of other systems from several countries. It is found that some of the most suitable conditions lie in the north west of Scotland. The most promising system in the UK has been developed at the National Engineering Laboratory. |
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| Oceans can supply energy in many other ways too. The temperature of water deep beneath a sea is lower than that at the surface. At many places this difference is as high as 25o C. This difference in temperature can be used to extract heat which in turn produces electricity. This is
known as ocean thermal energy. Small scale experiments have shown that it might be possible to build large ocean thermal energy systems but they would be quite expensive. |
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| Different seas have different concentrations of salt. When two seas meet, electricity can be produced by making use of the difference in the salinity i.e., salinity gradient. |
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| Sea vegetation is another indirect source of energy. The oceans are also a source of deuterium, an isotope of hydrogen. Two deuterium atoms and one oxygen atom form a molecule of heavy water. |
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| Heavy water is present in the oceans in the ratio 1:2000. This heavy water is also used in some nuclear reactors which generate electricity. |
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