OCEAN THERMAL ENERGY CONVERSION (OTEC)
The flux of energy from the sun onto the oceans is so large that if one were to convert as little as 0.01 percent to useful purposes, it would be several times the daily amount of energy presently used by humankind. Converting any of it, however, poses substantial engineering problems. Such a project was not even considered until the early 1970s when OPEC tripled oil prices, forcing the United States to seek alternative energy sources. In recent years the idea of using the solar energy that warms the ocean as a replacement for fossil fuels has languished. William H. Avery and Chih Wu's book entitled, Renewable Energy From the Ocean ( Oxford University Press) could stimulate new interest in the subject. Much of the information that follows comes from this book.
What makes the recovery of the sun's energy possible is that water is a very efficient absorber of the light energy of the sun. Consequently, the top layer of the ocean, between 15 degrees north latitude and 15 degrees south latitude--i.e. from the Tropic of Cancer to the Tropic of Capricorn--is heated to about 28°C (82°F). The temperature is more or less constant, night and day, in all seasons, and reaches down about 300 feet. Below that level the temperature steadily decreases. At 3000 feet it measures a constant 5°C (41°F) and remains virtually at that temperature no matter how far down we go. This is water that has melted from the polar ice regions, and because cold water is heavier than warm water, it does not mix with the top