Theoretical and experimental comparison of conventional and advanced solar pond performance

Numerical and physical experiments were carried out to compare the performance of two solar pond systems: (a) a conventional salt gradient solar pond (CSP) and (b) a salt gradient pond operated as an "advanced solar pond" (ASP). The main differences in the ASP, as originally proposed by Osdor[1], are an increase in overall salinity and the introduction of a stratified flowing layer near the bottom of the gradient zone. The increased salinity is meant to reduce evaporative heat loss and make up water requirements, while the additional flowing layer allows extra heat extraction and possibly higher temperatures to develop in the lower convective zone. A numerical study was performed to evaluate the salinity effect and the results show only a minor effect of increased salinity on heat collection efficiency. However, slightly higher collection temperatures are obtained, which may provide some benefit for heat engine efficiency. Physical experiments were performed to test the feasibility of constructing and maintaining the necessary flow system for the ASP and also to compare the performance of the ASP and the CSP under similar laboratory conditions. These tests showed that a stable stratified flowing layer could be maintained and that the ASP configuration produced higher efficiencies.