Thermal Energy Storage and Performance Evaluation of a Salinity Gradient Solar Pond With Different Geometric Designs: A Numerical Comparative Study

ABSTRACT 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 influences their heat storage performance, affecting hydrodynamic behavior, heat, 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. To attain this objective, hydrodynamic, heat, and mass transfer behaviors were numerically analyzed in order to assess the impact of geometric design on the heat storage performance of SGSPs. For this purpose, three shapes of SGSP having the same area of upper free surface and depth were considered: the rectangular salinity gradient solar pond (RSGSP), the Salinity Gradient Solar Pond with One Inclined Wall (SGSP‐OIW), and the salinity gradient solar pond with two inclined walls (SGSP‐TIWs). These designs were numerically studied and compared through the resolution of the dimensionless governing equations of Navier–Stokes, heat, and mass transfer utilizing the finite‐volume method. The analysis concentrated on the time‐wise evolution of temperature, salt concentration, and velocity fields to highpoint the influence of geometric design on the heat storage performance of SGSPs. The numerical results show that the SGSP‐TIWs supplies enhanced heat storage performance compared with both the SGSP‐OIW and the RSGSP. The SGSP–TIWs increase the thermal energy stored in the HSZ by 10.8% and 15.2% compared to the SGSP–OIW and the RSGSP, respectively, at τ = 0.06. In addition, the maximum average temperature of the HSZ attained with the SGSP‐TIWs is 9.09% and 14.286% greater than those reached with the SGSP‐OIW and the RSGSP, respectively. The maximum difference in dimensionless average temperature between the UCZ and the HSZ attains 0.62, 0.66, and 0.74 for the RSGSP, SGSP–OIW, and SGSP–TIWs, respectively. Furthermore, performance correlations characterizing the effect of geometric design on the transient evolution of the dimensionless average temperature in the HSZ were developed. The numerical results confirm that the SGSP's heat storage performance can be improved by reducing both the shading area effect and the volume of salt water using two sloped walls. Besides, the SGSP‐TIWs reduce the shading area in the UCZ, NCZ, and HSZ by 88.7%, 88.45%, and 88.54%, respectively, compared with the SGSP–OIW and the RSGSP.