Ocean thermal energy conversion (OTEC) uses the difference in temperature between cool ocean depths and warmer shallow or surface seawaters to run a heat engine and produce for example, electricity. It can operate with a very high capacity factor and is one of the continuously available renewable energy resources that could contribute to base load power supply. The resource potential for OTEC is considered to be much larger than for other ocean energy forms.
Systems may be either closed-cycle or open-cycle.
- Closed-cycle OTEC uses working fluids such as ammonia or R-134a which have low boiling points, and are therefore suitable for powering the system’s generator to generate electricity.
- Open-cycle engines use vapor from the seawater itself as the working fluid.
OTEC can also supply quantities of cold water as a by-product. This can be used for air conditioning and refrigeration and the nutrient-rich deep ocean water can feed biological technologies. Another by-product is fresh water distilled from the sea.