Energy and the Environment-A Coastal Perspective

In 1962, J. Hilbert Anderson and James H. Anderson, Jr. patented a closed-cycle OTEC system.  In this system, warm water is taken from the surface and pumped into a heat exchanger.  Here, a liquid with a low boiling point, generally ammonia, is vaporized.  As the vapor expands, it rotates a turbine which then generates electric energy.  Cold water from deep below the surface is pumped through a second heat exchanger which causes the vapor to condense back in to a liquid so that the cycle may be repeated (Ocean, 123eng).

Diagram of a closed-cycle OTEC device

The first successful, closed-cycle OTEC experiment occurred in 1979 when the Natural Energy Laboratory, in collaboration with others, implemented “Mini OTEC”.  This device was kept on a vessel that was moored off the coast of Hawaii.  It was the first closed-cycle OTEC to produce net electrical power at sea as it produced 50 kW.

Mini OTEC

In 1980, the US Department of Energy created and operated OTEC-1, a testing plant again off the coast of Hawaii.  This plant was designed with the focus of research.  Here, the USDOE began studying different OTEC devices and their environmental effects.

Since then, other countries have begun exploring and utilizing the closed-cycle OTEC technology.  In 1981, the Tokyo Electric Power Company produced a closed-cycle OTEC plant on the island of Nauru.  This plant was able to produce about 30 kW of net energy which was sent to the grid.  India, too, has deployed a closed-cycle OTEC device with the capacity to produce 1 MW of energy (Ocean, 123eng).

The closed-cycle OTEC concept is one that is continuing to be explored and may become more prominent as newer and better devices are produced.

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