OTEC or Ocean Thermal Energy Conversion is a technology that has been around as a theoretical possibility since the late Nineteenth Century, and there have been a few prototype plants over the years. This week in Hawaii a small scale (50KW) plant opened. This is still more research and development than commercial scale operation but it is another step in the right direction.

I’ve blogged before about large scale marine source heat pumps. 3 weeks ago I wrote about Star Renewables and their project in Drammen Norway that is the major heat source for the town of 63,000 people, and in June 2014 I blogged about the National Trust installing a marine source heat pump at Plas Newydd in Anglesey. OTEC is in a way like a marine source heat pump, but utilizing the temperature difference between hot surface ocean waters and cold deep ocean waters to boil and chill a fluid such as ammonia with a very low boiling temperature, so generating stream and driving a turbine to produce electricity. As the diagram above shows OTEC has, at least in theory, many possible spin off uses that could be very beneficial.

OTEC works best where there is the greatest temperature difference between hot surface water and cold deep ocean water, and as the map above shows it is in the Pacific Ocean roughly between Japan and Hawaii that this technology will work best. Perhaps, unsurprisingly, the two leading research centres for this technology have been in Japan and Hawaii, and both have prioritised renewables as a major part of their energy economies. Makai Ocean Engineering built the new Hawaii plant, do check-out their website where there’s a good video explaining the technology.