The idea of using the temperature of water to make energy actually dates back to 1881 when a French Engineer by the name of Jacques D'Arsonval first thought of OTEC. The final ocean energy idea uses temperature differences in the ocean. If you ever went swimming in the ocean and dove deep below the surface, you would have noticed that the water gets colder the deeper you go. It's warmer on the surface because sunlight warms the water. But below the surface, the ocean gets very cold. That's why scuba divers wear wet suits when they dive down deep. Their wet suits trapped their body heat to keep them warm. Power plants can be built that use this difference in temperature to make energy. A difference of at least 38 degrees Fahrenheit is needed between the warmer surface water and the colder deep ocean water. The cold ocean water can also be used to cooling buildings, and desalinated water is often a by-product.
Using this type of energy source is called Ocean Thermal Energy Conversion or OTEC. It was demonstrated in Hawaii at the Open Cycle Ocean Thermal Energy Conversion (OC-OTEC) system located at the Natural Energy Laboratory of Hawaii Authority (NELHA) at Keahole Point on the Big Island of Hawaii. More info on OTEC.
