Ocean thermal power plants, which generate electricity from the temperature difference between the tropics’ warm surface water and deep cold water, could be built on land in several hundred areas around the globe’s equatorial zones and also could be constructed as floating plants.
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A recent Electric Power Research Institute study found sites in Maine, Alaska, California and Washington that had good potential for tidal power generation with production costs ranging from 4.2 cents per kilowatt hour to 10.8 cents. By comparison, the average retail cost of electricity to U.S. consumers in May was 8.64 cents per kilowatt hour.

Wave energy also is drawing attention with Ocean Power Technologies planning to build a 50-megawatt wave park off the southern Oregon coast. The system uses buoys that drive a piston with the rise and fall of the waves to turn an electrical generator.

But development of ocean thermal energy technology has lagged since the Energy Department pulled the plug in the 1990s on an experimental 217-kilowatt demonstration plant at the Natural Energy Laboratory in Hawaii.