Water present at the surface of sea is continuously being heated due to sunlight but, the water present in the deep sea level is quite cold because sunlight is unable to penetrate deep into the water. So this difference in the different levels of water in the sea can be utilised efficiently to create electricity. A plant where electricity is created from this source is called as OTEC- ocean thermal energy conversion plant. The minimum temperature difference required for an OTEC to function is 20^oc.