Thermal properties characterization of chloride salts/nanoparticles composite phase change material for high-temperature thermal energy storage

Chloride salts are widely used as thermal energy storage (TES) media for high-temperature solar TES systems. Their thermal properties are crucial for the performance of TES systems. In this study, we prepared and characterized chloride salts/nanoparticles composite phase change materials (CPCMs) for high-temperature thermal energy storage. The ternary chloride salts (MgCl2:KCl:NaCl with 51:22:27 molar ratio) were used as base salt and Al2O3, CuO, and ZnO nanoparticles were dispersed into the base salt at 0.7 wt% to form various composite phase change materials (CPCMs). The thermal properties of the base salt and CPCMs were measured. The results showed that the melting temperature of the CPCMs was very close to that of the base salt. The phase change latent heat of the CPCMs was slightly lower than that of the base salt while the addition of dopant nanoparticles clearly enhanced the thermal diffusivity and thermal conductivity of the CPCMs. In particular, the thermal conductivity of the CPCM doped with Al2O3 nanoparticles showed the most obvious enhancement, which increased by more than 48%, compared to that of the base salt. Al2O3 nanoparticles could be considered as an optimal additive to improve the thermal conductivity of chloride salts. Moreover, the CPCM with Al2O3 also exhibited excellent thermal stability. These good thermal characteristics of CPCM with Al2O3 nanoparticles endow it promising applications for high-temperature TES system.