The Effect of Adding Porous Medium Layer on the Stability of a Salt Gradient Solar Pond

Abstract

The addition of a Porous Medium Layer (PML) has been demonstrated to enhance the thermal performance of salt gradient solar pond (SGSP). However, limited attention has been given to the impact of the PML on the thermal stability of these systems. In this study, experimental study has been conducted based on a small-scale experimental solar pond. Fourthly, numerical study to investigate the effects of incorporating a PML in a large-scale SGSP has been used to examine the influence on the temperature distribution and long-term operational stability. In the experimental study, coal cinder with 0.08m thickness was added to bottom of the experimental solar pond as PML, and compared to the case without PML. It shows that the solar pond reached the highest temperature on the third day, and the maximum temperature of the saline water in the upper zone of lower convective zone (LCZ) was increased by 5.2°C by adding the PML. By examining the stability coefficient Fs, the results show that the solar pond with PML makes NCZ instable firstly, which mainly starts from the bottom of NCZ. The simulation results showed that after incorporating PML with porosities of 0.4, 0.5, and 0.6, the maximum temperature peaks at a depth of approximately 1.5m are 80.1°C, 77.9°C, and 75.9°C, respectively, and the temperature differences between the lower and upper boundaries of the NCZ with porous medium layer (porosities of 0.4, 0.5, and 0.6) and the traditional SGSP are 12.7°C, 11.7°C, and 10.8°C, respectively. The stability coefficient Fs of NCZ increases with the decreases of the porosity of PML within the porosity of this study, and the solar pond without add any PML is most stable. Therefore, the addition of the PML increased the temperature difference between the upper and lower boundaries of the NCZ and raised the overall temperature of the LCZ but weakened the stability of the SGSP. Among the three porosities tested.

Keywords: Salt gradient solar pond, porous medium, stability, porosity