Ocean can also be used for generating energy in the following ways.
1. Tidal energy (or) Tidal power :
Ocean tides, produced by gravitational forces of sun and moon, contain enormous amount of energy. The "high tide" and "low tide" refer to the rise and fall of water in the oceans. The tidal energy can be Harnessed by constructing a tidal barrage.
During High tide, The sea-water is allowed to flow into the reservoir of the barrage and rotates the turbine, which in turn produces electricity by rotating the generators.
During low tide, when the sea level is low, the sea water stored in the barrage reservoir is allowed to flow into the sea and again rotates the turbine
Significance of Tidal Energy :
1. Tidal Power plants do not require large areas of valuable lands as they are on the bays or estuaries.
2. As the sea water is inexhaustible, It is completely independent of the uncertainity of precipitation (rainfall).
3. It is pollution free energy source, as it does not use any fuel and also does not produce any wastes.
2. Ocean Thermal Energy (OTE) :
There is often large temperature difference between the surface level and deeper level of the tropical oceans. This temperature difference can be utilized to generate electricity. The energy available due to the difference in temperature of water is called ocean thermal energy.
Condition
The temperature difference should be of 20*C or more is required between surface water and deeper water.
The warm surface water of ocean is used to boil a low boiling liquid like ammonia. The high vapor pressure of the liquid, formed by boiling, is then used to turn the turbine of the generator and generates electricity. The cold water from the deeper ocean is pumped to cool and condense the vapor into liquid.
Significance of OTE :
1.OTE is continuous, renewable and pollution free.
2.The use of cold deep water, as the chiller fluid in air-conditioning, has also been proposed.
3.Electric power generated by OTE can be used to produce hydrogen.
3.Geo-Thermal Energy :
Temperature of the earth increases at a rate of 20 - 75*C per Km, when we move down the earth surface. High temperature and High Pressure steam fields exist below the earth's surface in many places. The energy harnessed from the high temeperature present inside the earth is called geo thermal energy
1, Natural Geysers :
In some places, the hot water (or) steam comes out of the ground through cracks naturally in the form of natural geysers.
2. Artificial Geysers :
In some places, we can artificially drill a hole up to the hot region and by sending a pipe in it, we can make the hot water or steam to rush out through the pipe with very high pressure.
Thus the hot water (or) steam coming out from the natural (or) artificial geysers is allowed to rotate the turbine of a generator to produce electricity.
Significance of geothermal energy :
1.The power generation level is higher for geo-thermal than for solar and wind energies.
2.Geothermal power plants can be brought on line more quickly than most other energy sources.
3.GTE is effectively and efficiently used for direct uses such as hot water bath, resorts, aquaculture, green houses.
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