Study and optimization on heat storage and release characteristics of a cascaded sensible-latent heat composite energy storage heat sink

The energy storage is an effective solution for the current imbalance between energy supply and demand. In particular, the cascaded storage method can enhance the heat exchange temperature difference and heat storage efficiency. Previous research mainly focused on the combination of different phase change materials, while there was rare research on efficient cascaded conversion pathways for electrothermal direct conversion coupled thermal storage devices. This study investigated the influence of sensible and latent heat storage materials on the thermal performance, and identified the optimal volume ratios and materials types. When the volume share of Mg-Al:PW-EG=1:1, the heat storage performance was the optimal with a quantity/efficiency of heat stored as 7328.7 kJ/97.3%, leading to an increase of 458.5 kJ/6.6% than the sensible heat storage condition (Mg-Al:PW-EG=1:0) and 630.18 kJ/8.5% than the latent heat storage condition (Mg-Al:PW-EG=0:1). When the melting point and latent heat of phase change materials increased from 68.9∼79.1°C and 224.8 kJ/kg to 118.0°C and 344.9 kJ/kg respectively, the heat storage temperature rose by 162.7°C, quantity of heat stored rose by 7535.5kJ. While materials with large subcooling were not recommended for short-term heat storage, as approximately 25.6% (3309.3kJ) of stored heat and 22.4% (2505.2 kJ) of exergy were wasted when the subcooling degree was 70 °C. The findings provided solutions to support the synergistic enhancement of heat storage/release performance of the composite energy storage heat sink.