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Energy From the Sea

Tidal Energy
Tidal power is classified as a renewable energy source, because tides are caused by the orbital mechanics of the solar system. The root source of the energy is the orbital kinetic energy of the earth-moon system, and also the earth-sun system. Tidal power has great potential for future power and electricity generation because of the essentially inexhaustible amount of energy contained in these rotational systems. However, there has been a controversy over whether this is a perpetual motion machine because the moon does not lose energy just because energy is extracted from tides. In fact, even if all kinetic energy in the oceans were depleted until not a single molecule is moving (which is impossible), the moon will continue to orbit the earth. This is not only because the moon is extremely large and has a vast potential energy, but also that it can orbit a large mass (in this case the Earth) forever, as long as there is no friction or change in the mass that it is orbiting. Tidal power is reliably predictable (unlike wind energy and solar power).
Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. A turbine is fixed at the opening of the dam to convert tidal energy to electricity. The efficiency of tidal power generation in ocean dams largely depends on the height of the rise and fall of the tidal swell, which can be up to 10 m.

Wave Energy

The kinetic energy possessed by huge waves near the sea-shore can be trapped to produce electricity. These waves are generated by strong winds blowing across the sea. This can be more economical where the waves are very strong.

Ocean Thermal Energy

It is the conversion of energy arising from the temperature difference between warm surface water of oceans and cold deep-ocean current into electrical energy or other useful forms of energy. It is abbreviated as OTEC.


OTEC utilizes the temperature difference that exists between deep and shallow waters — within 20° of the equator in the tropics — to run a heat engine. Because the oceans are continually heated by the sun and cover nearly 70% of the Earth's surface, this temperature difference contains a vast amount of solar energy, which could potentially be tapped for human use. If this extraction could be done profitably on a large scale, it could be a solution to some of the human population's energy problems. The total energy available is one or two orders of magnitude higher than other ocean energy options such as wave power, but the small size of the temperature difference makes energy extraction difficult and expensive. Hence, existing OTEC systems have an overall efficiency of only 1 to 3%.

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