- Tidal Energy,
- Wave Energy,
- Ocean Thermal Energy
ENERGY FROM THE SEA:-
-The difference in sea-levels gives us tidal energy. Tidal energy is harnessed by constructing a dam across a narrow opening to the sea.
-A turbine fixed at the opening of the dam converts tidal energy to electricity.
-The locations where such dams can be built are limited.
-Similarly, the kinetic energy possessed by huge waves near the seashore can be trapped in a similar manner to generate electricity.
-The waves are generated by strong winds blowing across the sea.
-Wave energy would be a viable proposition only where waves are very strong.
-A wide variety of devices have been developed to trap wave energy for rotation of turbine and production of electricity.
Ocean Thermal energy:-
-The water at the surface of the sea or ocean is heated by the Sun while the water in deeper sections is relatively cold.
-This difference in temperature is exploited to obtain energy in ocean-thermal-energy conversion plants. -These plants can operate if the temperature difference between the water at the surface and water at depths up to 2 km is 20 K (20°C) or more.
-The warm surface-water is used to boil a volatile liquid like ammonia. The vapours of the liquid are then used to run the turbine of generator.
-The cold water from the depth of the ocean is pumped up and condense vapour again to liquid.
-The energy potential from the sea (tidal energy, wave energy and ocean thermal energy) is quite large, but efficient commercial exploitation is difficult.