Ocean Thermal Energy Conversion (OTEC)The oceans harness within themselves two types of energy: thermal energy and mechanical energy. The mechanical is derived from gravity which moves the tides and waves. The thermal comes from the sun which alters the temperature of the ocean water.
Like solar panels in your calculator the surface of the ocean absorbs solar radiation. The solar panels on the calculator create electricity while the oceans surface create thermal energy. If only a small portion of this thermal energy could be harnessed, it could power the whole world.
In fact, there is so much thermal energy absorbed each day by the oceans it would equal the thermal output of 250 billion barrels of crude oil.
There are three ways the OTEC method can produce electricity.
Closed-Cycle: This system relies on low-boiling point fluids such as ammonia. The warm ocean water is used to heat up and boil the ammonia, which will turn a turbine. The turbine then produces electricity.
Open-Cycle: This system relies on a low-pressure environment to actually boil the ocean water and create steam. When warm ocean water moves into a low-pressure environment it will boil. The steam is almost pure water as the salts and other impurities are left behind. The steam then recirculates to deeper and colder areas of the ocean and condenses back to water. Just like the ammonia gas, the steam will turn a turbine.
Hybrid System: This system simply combines both Closed and Open Cycle systems.
For more info on OTEC visit The National Renewable Energy Laboratory HERE