Heat extraction from a salinity-gradient solar pond using in pond heat exchanger

Thermal energy extraction from a small salinity-gradient solar pond is studied in this article. The small pond has an area of 4.0 m2 and a depth of 1.1 m. Fresh water circulates through an internal heat exchanger, located in the lower convective zone, and transfers its thermal energy to an external heat exchanger. The study covers two periods of summer loading for a week and winter loading for two months. The hourly as well as daily variations of the temperatures of the storage zone, surface zone, ambient, inlet and outlet of the internal heat exchanger have been measured and analyzed. It is shown that the pond may deliver heat with a relatively high thermal efficiency in a transitional stage for a limited period of time. It can also be utilized continuously with a lower efficiency. The efficiency of the small pond in the latter case will be around 10%.