Performance comparison of two metallic eutectic solder based medium-temperature domestic thermal energy storage systems

Abstract

In this study, two thermal energy storage systems based on eutectic solder (Sn63/Pb37) metallic phase change material (PCM) are compared experimentally during their charging and discharging cycles. The first system is a single-PCM system composed of a packed bed of spherically encapsulated eutectic solder capsules. The other system is a two-PCM cascaded system comprising of eutectic solder spherical capsules at the top and erythritol spherical capsules at the bottom in a storage ratio of 50%:50%. The charging experiments are conducted with three different charging flow rates to investigate the effect of the flow rate. Charging experiments are also performed with three different set charging temperatures to investigate their effect. Discharging experiments are conducted with three different discharging flow rates to investigate their effect on the thermal performance. The cascaded storage system demonstrates better energy and exergy charging rates before the bottom PCM melts. After the low-temperature PCM at the bottom melts, the temperature at the bottom of the cascaded system increases, and the single-PCM system demonstrates higher charging energy and exergy rates. Higher discharging energy and exergy rates are obtained with the single-PCM system for longer periods during discharging compared to the cascaded system. The energy and exergy storage efficiencies of the cascaded system are generally higher compared to the single-PCM system. This is possibly because of the release of latent heat during discharging in a single cycle using multiple phase change sequences.