In one of the latest issues of The Economist, there was an article about Ocean Thermal Energy Conversion (OTEC). This technology uses the difference between cooler deep water and warmer shallow or surface ocean waters to run a heat engine and produce electricity. An OTEC plant can be built anywhere that the ocean has a surface temperature above 25°C and is more than 1km deep.
The OTEC permit office in the US was opened between 1981 and 1994, having issued not a single OTEC permit. When oil prices went down after the 1970s, the incentive to invest in OTEC faded. Renewable energy sources are now fashionable again, and there are several companies interested in this technology, from giants such as Lockheed Martin to smaller companies like the Ocean Thermal Energy Corporation of Lancaster, located in Pennsylvania.
Lockheed Martin is doing an experiment in Hawaii in collaboration with a smaller firm, Makai Ocean Engineering, to build a ten megawatt (MW) pilot plant that should be operational by 2015. If that gives positive results, the idea is to build a 100MW power station by 2020.
Ocean Thermal Energy Corporation is working on a smaller project with the Bahamian government to build a fully commercial OTEC plant. Initially the idea is to provide cooling for a holiday resort and then to build a 10MW power station.
If you are interested in renewable energies, read also Deep Heat.