Investigation of the unsteady thermal storage performance of metal foam dual-phase change unit thermal storage tanks in solar thermal utilization systems

The adoption of metal foam thermal energy storage (TES) tanks in solar thermal utilization systems is crucial for enhancing energy supply stability. In this study, to investigate the transient thermal storage performance of TES tanks, a model of a solar thermal utilization system integrated with solar collectors and TES tanks was established. The model was validated through a literature review and experiments. The effects of initial temperature variation of solar collectors and the addition of metal foam on the transient heat transfer characteristics and thermal efficiency of TES tanks were analyzed. The results indicate that the porous structure of metal foam restricts natural convection, thereby improving temperature drift caused by displacement due to phase change material density variation. Maintaining the same initial temperature of solar collectors, filling metal foam can avoid the occurrence of melting dead zones at the bottom of pure paraffin phase change units, leading to an enhancement in the thermal efficiency of TES tanks and a reduction of 48.44% in phase change completion time. Additionally, a low initial temperature of the solar thermal collection system contributes to improving the thermal efficiency of metal foam composite TES tanks.