A horizontal structure defines an expansive floating solar pond underlain by an open-ended chamber, and a distributed network of heat engines produce electricity based on the temperature differential between the heated solar pond water and ambient seawater. Each heat engine includes a heat exchanger disposed near the bottom of the solar pond, a working fluid boiler at least partially submerged in the solar pond, a turbine-generator, and a working vapor condenser disposed under the solar pond in the open-ended chamber. A heat exchange fluid is circulated through the heat exchanger and the boiler to vaporize working fluid for powering the turbine-generator, and cold ambient seawater is passed through the condenser to condense working vapor downstream of the turbine-generator. Warmed seawater from the condenser is exhausted into the open-ended chamber, where it is naturally retained by convection to minimize heat transfer from the solar pond to the ambient seawater.