In the October 1978 issue of TR, William F. Whitmore invoked an idea from the 19th century: ocean thermal energy conversion, or OTEC. Exploiting the temperature difference between the sun-heated surface of tropical waters and the chilled depths thousands of feet below, Whitmore argued, could provide clean, renewable energy in the lower latitudes.

In the tropics, the oceans store an immense amount of energy from the sun. The band of surface water within 10º of the equator basks around at 80º F., while cold regions 3,000 ft. below are around 40º F. [OTEC] uses this thermal gradient, like the hot and cold terminals of a gas turbine, to generate electricity. The essence of the system is the circulation of a fluid such as ammonia or propane. Where it comes near the warm water it is brought to a boil and so expands; where it comes near the cold, it liquefies once again. In the course of its circulation from one place to another, it drives a power-generating turbine. A typical closed-loop system would include two exchangers (evaporator and condenser), a turbine, and a generator.