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Thermal Energy Conversion
Ocean, Thermal Energy Conversion
Water in the deep ocean is many degrees cooler than surface temperature water. The difference in temperature can be used to run a heat engine either using the water itself in an open-loop (placing warm ocean water in a low pressure system causes it to boil), or by transferring the heat energy to a closed-loop system with a heat exchanger and a low-boiling point liquid such as ammonia.

Some open-loop OTEC designs can also create desalinated water as a byproduct.

Cool deep water from oceans or deep lakes (typically at a constant 4 °C or 40 °F) can also be used for purposes of air conditioning, reducing the demand side electrical loads of buildings that are sited to take advantage of this. A similar effect can be utilized in almost any location via ground source heat sink loops.