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About 71% of the earth's surface is covered by oceans. Energy can be harnessed from
- Tides
- Sea-waves
- Temperature differences in the water
We shall discuss each energy form in detail:
Tides are caused due the gravitational pull of the moon on the water in oceans and seas. The enormous movement of water between the high tides and low tides provides a very large source of energy in the coastal areas of the world. This tidal energy can be harnessed by constructing a dam or a barrage as shown in the figure given above. The energy conversion involved in the process is given below:
During high tide, when the level of water in the sea is high, sea-water flows into the reservoir of the barrage and turns the turbines. The turbines then turn the generator shaft to produce electricity.
During low tide, the sea-water stored in the barrage reservoir is allowed to flow out into the sea. This flowing water also turns the turbines and generates electricity. Thus, as the sea-water flows in and out of the tidal barrage during high and low tides, the turbines rotate continuously to generate electricity.
The tides do not possess enough energy to
generate electricity on a large scale Only few sites are suitable for building such barrages (or tidal dams)
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