OTEC or Ocean Thermal Energy Conversion is probably one of the most promising energy technologies for tropical countries. It utilizes warm surface water to "evaporate" a refrigerant and cold deep ocean water to condense it. The evaporation of the refrigerant produces a high pressure gas that can drive a turbine. So far literature has reported less than 20% efficiency but this may be due to the fact that this technology didn't get much support by developed countries.
An attractive feature of OTEC is the potential for the infrastructure to support refrigeration, desalination, hydrogen production while producing power. OTEC can also be installed in mobile platforms or ships. In my opinion, these features are too attractive to be ignored. Considering that developed countries don't have much of the ocean thermal gradient resource, its up to developing, equatorial countries like the Philippines to develop this resource . Developed countries ought to pitch in too because of their "carbon debt".
A typical open cycle plant design.
Map of OTEC potential sites
Illustrations taken from www.nrel.gov/otec
Knowing of your interest in OTEC as a renewable energy technology with vast potential, I invite you to check in now and then with my blog -- http://HawaiiEnergyOptions.blogspot.com All signs point to an announcement that could come at any time about a small OTEC plant that would be the beginning of the OTEC revolution in the 50th state. Aloha ~ Doug Carlson