Thermal performance improvement of thermal energy storage systems by employing a contrastive experiment

The thermal storage system is widely used to reduce the mismatch between thermal energy supply and demand in time and space, and its thermal performance is a critical factor in the system's thermal efficiency. The thermal performance of the Sensible Thermal Energy Storage Unit (STESU), the Latent Thermal Energy Storage Unit (LTESU), and the LTESU integrated with Copper Foam Fin (CFF) were compared through comparative experiments. The experimental results showed that the thermal changing rate of STESU was higher than that of other units, and there was no apparent thermal stratification. However, LTESU had the lowest thermal changing rate with apparent thermal stratification. During the thermal charging process, the solid-liquid interface on the LTESU cross-section formed an inverted-triangle shape. The lower part of the PCM could not change its phase as a dead zone and failed to participate in the thermal charging and discharging. Even so, the thermal efficiency of LTESU was 18.7% higher than that of STESU. Integrating with CFF could increase the thermal charging capacity, the thermal discharging ca-pacity and the thermal efficiency by 51.1%, 55.9% and 10.8%, respectively.