When researching this topic, I was surprised to find out that very little research has been done in this area since the early 1980′s.  This is no doubt due to the low cost of oil and competing technologies and the what was considered the low efficiencies of this Ocean Thermal Energy Conversion (OTEC).  The question that now needs to be asked is: “Given the current cost of energy, as well as greenhouse gas and energy security concerns for all countries, is it not time to invest in OTEC for the future? 

NREL’s Definition of Ocean Thermal Energy Conversion

The oceans cover a little more than 70 percent of the Earth’s surface. This makes them the world’s largest solar energy collector and energy storage system. On an average day, 60 million square kilometers (23 million square miles) of tropical seas absorb an amount of solar radiation equal in heat content to about 250 billion barrels of oil. If less than one-tenth of one percent of this stored solar energy could be converted into electric power, it would supply more than 20 times the total amount of electricity consumed in the United States on any given day.

OTEC, or ocean thermal energy conversion, is an energy technology that converts solar radiation to electric power. OTEC systems use the ocean’s natural thermal gradient—the fact that the ocean’s layers of water have different temperatures—to drive a power-producing cycle. As long as the temperature between the warm surface water and the cold deep water differs by about 20°C (36°F), an OTEC system can produce a significant amount of power. The oceans are thus a vast renewable resource, with the potential to help us produce billions of watts of electric power. This potential is estimated to be about 10¹³ watts of baseload power generation, according to some experts. The cold, deep seawater used in the OTEC process is also rich in nutrients, and it can be used to culture both marine organisms and plant life near the shore or on land.

Below is the ocean’s thermal gradient map.  As you can see, the most promissing locations for OTEC are in equatorial waters, and offer many developing countries a source of renewable energy with zero emmissions.

From Enrel

The most promising locations for OTEC in North America are : Hawaii, the US Virgin Islands and Puerto Rico.  Here is a great video explaining how the technology works and its potential for Puerto Rico, in particular.

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