Randall D. Knight — Heat Engines and Refrigerators: Problem 43

There has long been an interest in using the vast quantities of thermal energy in the oceans to run heat engines. A heat engine needs a temperature difference, a hot side and a cold side. Conveniently, the ocean surface waters are warmer than the deep ocean waters. Suppose you build a floating power plant in the tropics where the surface water temperature is \(\approx 30^\circ\text{C}\). This would be the hot reservoir of the engine. For the cold reservoir, water would be pumped up from the ocean bottom where it is always \(\approx 5^\circ\text{C}\). What is the maximum possible efficiency of such a power plant?