Harnessing Power From the Sea

Science Fiction slowly becoming reality - this is one component amongst the many we need to keep bringing the benefits of technology to the world with a reduced environmental cost.

Renewing Efforts to Harness Power From the Sea - NYTimes.com:
"LOCKHEED MARTIN is best known for building stealth fighters, satellites and other military equipment. But since late 2006 the company has taken on a different kind of enterprise — generating renewable power from the ocean.
. . .
Lockheed and a few other companies are pursuing ocean thermal energy conversion, which uses the difference in temperature between the ocean’s warm surface and its chilly depths to generate electricity.

Experts say that the balmy waters off Hawaii and Puerto Rico, as well as near United States military bases on islands like Diego Garcia in the Indian Ocean or Guam in the Pacific, would be good sites for developing this type of energy.
. . .
In the approach that Lockheed is pursuing (with another company, Makai Ocean Engineering), the water on the ocean’s surface is used to heat a pressurized liquid, usually ammonia, which boils at a temperature slightly below that of warm seawater. That liquid becomes gas, which powers a turbine generator. Cold water is then pumped from the ocean’s depths through a giant pipe to condense the gas back into a liquid, and the cycle is repeated.

An important advantage of this method of producing energy is that it could run all the time, unlike solar plants, which cannot work at night, or wind turbines, which stop in calm conditions.

But the technology is expensive and can work in only a limited number of places, like the tropics, where there is a large difference in temperature between the ocean’s layers. This excludes many major population centers, although proponents hope that Florida and the Gulf Coast could also be markets. (Other types of ocean energy being explored would harness the tides and waves.)
. . .
Lockheed and the federal government have worked on this type of energy before, after the 1970s oil crises. In 1979, a 50-kilowatt test project was briefly run off the coast of Hawaii’s Big Island. Financing for ocean-energy projects was slashed significantly by the Reagan administration, and Lockheed abandoned its pursuit of the technology in the mid-1980s.

Proponents say that since the last attempt to develop it, the technology has improved enormously. Offshore oil platforms similar to the platforms needed for the ocean energy system have become more sophisticated, for example in their ability to withstand hurricanes and to moor in deeper water.
. . .
Robert Varley, who is helping to lead Lockheed’s efforts, estimated that just 3.5 percent of the potential energy from the warm water pumped might actually be used. “In reality that doesn’t matter — the fuel is free,” he said.

But building and operating the platform will be costly. Harry Jackson, the president of Ocees International, an engineering firm based in Honolulu also working on the technology, estimated that a test plant of the size Hawaii is planning — which is still far smaller than commercial scale — would cost $150 million to $250 million.

Some environmental groups are cautiously embracing the technology as one of many approaches that could help reduce fossil fuel consumption and thus combat climate change."