Heat extraction from gradient layer using external heat exchangers to enhance the overall efficiency of solar ponds

Abstract

A salinity gradient solar pond is a combined solar collector and thermal energy storage system, and in past heat has been successfully extracted from the lower convective zone (LCZ) in working ponds. This paper discusses possibility of heat extraction from the non convective zone (NCZ) using an external heat exchanger. Here, two methods of heat extraction from different levels within the NCZ using external heat exchanger are presented. The first method uses thermosyphon effect to transfer the heat from different levels in NCZ to the binary fluid. The second method uses pumps (forced convection) for heat extraction. This paper presents theoretical modeling and experimental results for thermosyphon based heat extraction method. Later theoretical predictions and experimental results have been compared. This investigation shows good prospects for application of this system for heat extraction from NCZ of large solar ponds. By extracting heat from the NCZ the efficiency of a solar pond could be increased up to 30%.