Sources of Energy — Science STD 10 — Question

The water at the surface of the ocean gets heated up by the Sun while the water in deep is relatively cold. This temperature difference is exploited to get energy. This can be done if the temperature difference is of the order of 293K or more up to 2km depth. The hot water of the surface is used to boil a volatile liquid like ammonia. These vapours used to run the turbine of generator. Then the cold water from the deep pumped up again used to condense these vapours again to liquid.