Enhanced light-thermal conversion efficiency of mixed clay base phase change composites for thermal energy storage

Abstract In order to improve the energy storage and conversion efficiency of phase change materials, a mixed clay sponge (MCS) containing palygorskite (Pal) and Halloysite Nanotubes (HNTs) was successfully constructed by solution polymerization. Expanded graphite (EG) was used to enhance the overall thermal conductivity and carbonized MCS with EG (mark as EG-MCS, C-EG-MCS). A series of form stable phase change materials (FSPCMs) were prepared by using them as scaffolds and encapsulated organic phase-change material 1-Hexadecylamine (HDA) by direct impregnation. By means of SEM, TEM, FTIR, XRD, XPS, DSC, TG, etc., their microstructure, chemical compatibility and thermophysical properties were systematically studied. The DSC results demonstrate that PCM composites exhibit relatively high thermal energy storage density of 214.2 kJ kg−1, 237.5 kJ kg−1 and 239.2 kJ kg−1 respectively. The reliability test shows that the PCM composites retain shape stability and almost no leakage of HDA even after 200 thermal cycles. Compared with the pure component HDA, the thermal conductivity of the as-prepared C-EG-MCS-HDA was improved from 0.147 W m−1 K−1 to 0.667 W m−1 K−1 and EG-MCS-HDA was improved from 0.147 W m−1 K−1 to 0.454 W m−1 K−1 owing to the high thermal conductivity of EG (only 6 wt%). Besides, the light-thermal conversion efficiency of EG-MCS-HDA and C-EG-MCS-HDA is 74.6%, 80.8% respectively. Therefore, the fabricated FSPCMs with high latent heat, good melting/freezing cycles reliability and high thermal conductivity, remarkable light-thermal energy conversion ability which have a broad application prospect in energy conversion and storage devices.