Experimental investigation and optical visualization of a salt gradient solar pond integrated with PCM

The thermal performance of a solar pond is affected by the amount of heat lost to the ground through the lower convective zone (LCZ) in which the heat is stored. Studies are focused on decreasing the heat losses, to maximize the energy stored and guarantee the stability of the thermohaline system over time. Phase change materials (PCMs) can help to achieve all these goals, since they work as thermal energy storage (TES), exploiting the latent heat absorbed during the solid-liquid phase change. This paper presents an experimental application of PCMs in the LCZ of a small solar pond. The paraffin wax was enclosed in aluminium cylinders which have been arranged on the bottom. The temperature of the solution in deep is monitored both with and without the PCM. The stability of the pond is analyzed through a laser shadowgraph technique, to visualize the effect of the thermal convection on the interfaces. Results show that the LCZ of the solar pond with PCM is around 3 °C colder than the reference case after a 6-h heating period. The shadowgraph analysis proves that the thermal convection in the reference case is stronger and damage the interface until break. The monitoring of the solar pond with PCM shows an improved stability