Write about ocean thermal energy?

OCEAN THERMAL ENERGY :-

The water at the surface of the sea or ocean which, has considerable depth or deepness, is heated by the Sun while as we go deeper and deeper in the ocean or sea the upcoming sections become relatively colder than the previous one. This difference in temperature is used 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 293 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.