Abstract: A reservoir temperature differential generator is partially submergible in a water body and a temperature differential is sensible between each of a first end, disposed above the water-air interface, and a second end submerged beneath the water surface. A volatile working fluid having a low boiling point is circulated between each of a first and second heat exchanger to effect phase change and drive a heat engine for generation of electrical energy. A plurality of sensors is included to monitor real-time environmental conditions, and thus direct a fluid circuit between a sensed maximum temperature and a sensed minimum temperature. The fluid circuit, maintained interior to the present device, is forcibly reversible between each of the first and second heat exchangers to maintain phase change of the working fluid across a maximized temperature differential in response to changing environmental conditions.