Energy Glossary

Ocean Thermal Energy Conversion (OTEC)

The temperature difference between the surface water of tropical oceans and their deep water is roughly 30 degree centigrade. This temperatur difference can drive a turbine to provide electricity via a generator.

Using the small temperature difference of 30 degree centigrade means a low efficiency for the energy conversion of 5-10 percent. To establish a rankine cycle at the given temperatures of 35 / 5 degree centigrade the preferred working medium is ammonia (NH3).

OTEC systems may play a role for small scale power demand in rural regions near tropical oceans. A further function of OTEC systems might be cooling (with the cold water) and water deslination by condensating water on tubes cooled by the deep ocean water.

A main drawback is the high constructive effort to supply enough cold deep ocean water to the plant - OTEC systems are scientifically interesting but in the long run pv devices with cheap rechargeable batteries (which have to be developed) will be much more effective and versatile.

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