Ocean thermal energy conversion (OTEC) is a renewable energy technology that harnesses the temperature difference between the warm surface waters of the ocean and the cold depths to produce electricity. The process uses seawater to turn solar energy into electricity by using the oceans thermal gradient, which is the temperature decline from the sun-warmed waters on the surface to the cold waters found at great depths. OTEC systems use a temperature difference of at least 20° Celsius or 36° Fahrenheit to power a turbine to produce electricity. Warm surface water is pumped through an evaporator containing a working fluid, which vaporizes and drives a turbine/generator. The vaporized fluid is then turned back to a liquid in a condenser cooled with cold ocean water pumped from deeper in the ocean. OTEC has the potential to offer global amounts of energy that are 10 to 100 times greater than other ocean energy options such as wave power.

OTEC has the potential to generate billions of watts of electricity, and it is a clean and renewable energy source. It can also be used to desalinate ocean water. However, OTEC plants require large volumes of both warm and cold water to generate electricity, and they discharge large amounts of used cold and warm water, which can have environmental drawbacks. Additionally, one of the problems that restrict OTEC is that the necessary thermal gradient is found at sea, but the power it can generate is needed on land. Despite these challenges, OTEC is a promising renewable energy technology that could provide a significant amount of electricity in the future.