Ocean Thermal Energy: Back From the Deep  

IEEE Spectrum has a look at a new OTEC pilot plant in Hawaii - Ocean Thermal Energy: Back From the Deep.

The finished facility, which will be only a bit higher in capacity than existing test plants in Japan and South Korea, is quite modest by energy production standards. The plant will be able to produce at most 100 kilowatts of power—enough, when operating continuously, to supply electricity to about 80 average American homes.

The plant and its pumps will consume most of the energy produced. But Makai’s plant is geared toward research, Eldred notes, not energy generation. The facility was built primarily to design and test heat exchangers, which are among the most expensive components of an OTEC plant. With the addition of a turbine, Eldred says, Makai will be able to design an automatic control system and improve both performance and cost predictions for its commercial plant designs. The company also hopes to get a sense of how fluctuations in the temperature and pressure of ocean water will alter power output, a factor that might prove significant for wave-tossed offshore plants.

That’s likely to be where OTEC energy production winds up. A 10-megawatt plant, such as one that Lockheed Martin aims to build for China’s Reignwood Group, will require a cold-water pipe that is several meters wide. A plant floating in open water could send a pipe straight to the depth required instead of diagonally, down a long slope extending out from shore. That would make for a shorter and less expensive pipe, reduce the impact on the landscape, and cut down on the energy required to pump the cold water.

The first large-scale plant to make the leap could be New Energy for Martinique and Overseas (NEMO), says Luis Vega of the University of Hawaii’s National Marine Renewable Energy Center. The project, which is a collaboration between renewable energy firm Akuo Energy and naval defense company DCNS, both based in Paris, plans to construct a 16-MW plant about 5 kilometers off the shore of the island of Martinique.

Construction is set to start next year, and the team aims to have the plant operational in four years. When complete, NEMO should be able to supply some 11 MW of energy to the Caribbean island, with the other 5 MW powering the plant and its pumps.