Performance Evaluation of a Salinity Gradient Solar Pond with Different Geometric Designs: A Numerical Study

Salinity gradient solar ponds (SGSPs) are innovative systems that harness solar energy through thermal stratification, leveraging varying salinity levels to store solar energy as thermal energy. The geometric design of these SGSPs profoundly impacts their heat storage performance, affecting hydrodynamic behavior, heat transfer, and mass transfer processes. This work aims to conduct a comparative numerical study to evaluate how different geometric designs influence the heat storage capabilities of SGSPs. In order to attain this objective, hydrodynamic, heat and mass transfer behaviors were studied numerically to see the impact of geometric design on the SGSP’s heat storage performance. For gathering this knowledge, three designs of SGSP having the same area of upper free–surface and depth, namely, Rectangular Salinity Gradient Solar Pond (RSGSP), Salinity Gradient Solar Pond with One Inclined Wall (SGSP-OIW), and Salinity Gradient Solar Pond with Two Inclined Walls (SGSP-TIWs) were studied and compared numerically through the resolution of the dimensionless governing equations of Navier–Stokes, heat and mass transfer by utilizing finite-volume method in order to see the impact of SGSP’s design on the time–wise evolution of temperature, salt concentration and velocity fields. Numerical results showed that the SGSP-TIWs supplied better heat storage performance than both SGSP-OIW and RSGSP. The SGSP–TIWs increased the thermal energy stored in the HSZ by 10.8% and 15.2% as compared to the SGSP–OIW and RSGSP, respectively, at τ = 0.06. Also, the SGSP-TIWs enhanced the maximum average temperature of HSZ by 9.09% and 14.286% than that of SGSP-OIW and RSGSP, respectively. The maximum difference of dimensionless average temperature between UCZ and HSZ in the RSGSP, SGSP–OIW and SGSP–TIWs is 0.62, 0.66 and 0.74, respectively. Performance correlations for the effect of geometric design on the transient evolution of dimensionless average temperature of HSZ are also developed. The numerical results confirm that the SGSP’s heat storage performance can be improved by reducing both the shading area’s effect and volume of salt water through the use of sloped walls. Besides, the SGSP-TIWs reduced the shading area of UCZ, NCZ and HSZ by 88.7%, 88.45% and 88.54%, respectively, as compared to the SGSP–OIW and RSGSP.