Heat Extraction from a Large, Salt-Gradient Solar Pond

The Miamisburg Solar Pond is the largest functional, salt-gradient solar pond in the US. It provides low-cost solar energy collection and low temperature heat storage. The heat in the pond is removed by use of a copper-tube heat exchanger which has a surface area of 138 m² (1500 ft²). During the summer of 1979 the initial heat, 39,970 kW^.hr (136 million BTU), was removed for heating an outdoor community swimming pool. Based upon the performance thus far, the pond could yield 381,000 kW^.hr/yr (1300 million BTU/yr) of useful heat. An economic analysis based upon a 10-y amortization of the installation costs of the pond indicates that the cost of the heat, 1.8 cents/kW^.hr/yr ($\$$5.40/million Btu), is already below the current price for heating with fuel oil.