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. In past heat
has been successfully extracted from the Lower
Convective Zone (LCZ) from working ponds for
industrial process heat applications. Previous theoretical
studies have shown that by extracting heat from the NCZ
and LCZ together will improve the efficiency of a solar
pond to 30% from the present 20% efficiency. This paper
discusses concept designs and theoretical predictions 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. A schematic
drawing of the first method that uses pumps (forced
convection) for heat extraction has been presented. The
second method uses thermosyphon effect to transfer the
heat from different levels in NCZ to the binary fluid.
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.