Are there any operational Ocean Thermal Energy Conversion (OTEC) plants anywhere?
Or, was this just another option that folks were scrambling to investigate during the "energy crunch of the 1970s/1980s--and it became a dead end?
As a former marine biology major at the University of Guam, I remember that researchers were finding that biofouling was a major problem. The intake pipes would quickly reduce in volume because algae, barnacles, and mussels would coat the linings and other internal areas. Another problem was how to protect the plants during tropical storms... some of the storms, such as hurricanes, typhoons, and cyclones could severely damage the main structure as well as the accessory structures of such a plant.
OTEC was an interesting concept--but it didn't go very far.
OTEC uses the temperature differential between deep water and surface water to liquify and vaporize a coolant (much in the same way a refrigerator works). The cooler water liquifies the coolant, the warmer surface water vaporizes it. When the coolant is vaporized, the gaseous form can move turbine blades of a generator--thus producing the power. Back in the late 1970s, there was a pilot plant in Hawaii. Another was being investigated on Guam.
Evidently, the interest in this method of generating power has waned and the plants are no longer working (they've probably been scrapped by now).
Hawaii was investigating all sorts of power/energy alternatives--geothermal (with all their volcanos, this would be viable in some ways), wave action/tidal (these are also in action in France, I believe), biofuel (halekoa, tangantangan--a fast-growing legume/tree that many consider a weed--shredded and used for boiler-style electricity-generating plants), and small-scale hydroelectric (dams aren't that pretty and can wipe out indigenous plants and animals in their flood area--a major concern in tourist destinations).
However, the best bet for places such as Hawaii (and other places as well) is most likely solar. I was digging around again for solar info... and I stumbled over this solar contracting and research facility -- based in Hawaii: Sopogy. Their headquarters are in Hawaii, but they also have offices here in the U.S. --one is in San Jose, California.