A summer view from the dock at Great Cranberry Island across to Mount Desert Island. |
Ocean thermal energy conversion, sometimes called OTEC, is a form of ocean energy extraction that is subtle yet potentially significant. The temperature difference between warmer shallow water and cooler deep water can drive a heat engine, usually using the Rankine cycle. The basic concept isn't new; the idea appears to have been first proposed in France in 1881, with the first operating plant (22 kW) built in Cuba in 1930. Since then, a number of small projects have been developed, mostly as research or demonstration projects, but the technology hasn't seen widespread adoption. Cost is the key driver here; because OTEC facilities generally have a high cost per unit of power produced, interest in OTEC tends to follow cost spikes in oil and energy pricing.
It may not mean energy prices are on the rise, but the U.S. Naval Facilities Engineering Commission has issued a total of $12.5 million in contract and grant funding to Lockheed Martin Corp. to design and commercialize a 10 MW pilot project off the Hawaiian coast of Oahu. $8.1 million of this money was awarded in 2009, with the remaining $4.4 million grant coming in last month. Hawaii is already home to an OTEC facility: the Natural Energy Laboratory of Hawaii Authority at Keahole Point. Hawaii is ideal for OTEC: larger temperature differences mean greater efficiency (important, where the theoretical maximum efficiency may only be about 7%). It will be interesting to see if the proposed new OTEC plant is built, as well as what we learn from the experience. Will commercial-scale OTEC soon make economic sense? What will it take to get there?
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