When I started my career as a lecturer in Ocean Science way back in 1993 one of the topics that students often wanted to research for their final year project was Ocean Thermal Energy Conversion (OTEC). This is the name give to the potential to utilise the routine difference in temperature between warm surface ocean waters and the colder water found at depth. The basic idea is to use the warm surface water to heat a specially selected low boiling point fluid (such as ammonia) until it boils and then use the resulting high pressure gas to drive a turbine to generate electric power. The gas is then cooled using cold water pumped up from the deep ocean (at least one kilometre down) to turn it back into a liquid before repeating the whole process all over again (and again, and again…). The principal barriers to generating power in this way are the enormous technical difficulties involved in pumping the cold water up to the surface, building a robust and stable platform to complete the whole process at sea and transmitting the power from the point of generation to the point of use. After a few years in my job OTEC seemed to disappear off the radar as oil prices fell and I haven’t encountered it for 15 years or so. It was interesting then, to read a recent article in New Scientist about the latest attempts to use OTEC. These are based around US military bases in Hawaii and Diego Garcia along with several pilot projects in the far east (e.g. India and Indonesia). The technology still has a long way to go before it realises the kind of potential that its proponents claim it has, but the threat of rising oil prices and a drive for energy independence seems likely to sustain recent interest in OTEC over the coming years. The full New Scientist article appeared in Issue 2683 (22 November 2008).
Tim O'Hare 