Tailored phase change behavior of CaCl2·6H2O-based hydrated salt for low-temperature thermal energy storage

Hydrated salts have significant potential as a low cost, high latent heat phase change material for energy storage in building thermal management. However, there are also problems of inappropriate phase change temperature , subcooling and phase separation in practical applications. In this study, phase change energy storage materials based on calcium chloride hexahydrate suitable for low-carbon buildings were successfully prepared. The addition of NH 4 Cl slightly decreased the phase change temperature and latent heat. TiO 2 was used to overcome the supercooling phenomenon and increase the latent heat. The melting latent heat was increased by 2.79 % through the combined action of NH 4 Cl and TiO 2 . Thermogravimetric-Differential Thermal Analysis was used to evaluate the effect of HEC on phase separation. The optimized composite phase change material exhibited a melting phase change temperature of 22.42 °C, a subcooling degree of 0.9 °C, and an 18.16 % improvement in thermal conductivity . The latent heat recovered was 87.54 %, increasing by 6.86 %. The non-isothermal phase change behavior was studied, the effect of additives on melting and crystallization processes was analyzed, and the additives were shown to reduce the nucleation activation energy of modified calcium chloride hexahydrate. In addition, the composite phase change material maintained excellent stability after 100 heating-cooling cycles. This building energy storage material improves the energy density of calcium chloride hexahydrate and offers a new strategy for solar energy storage and integrated use in buildings. • NH 4 Cl lowers temperature to avoid a significant drop in latent heat. • TiO 2 reduced subcooling and increased latent heat to 2.79 %. • HEC mitigation phase separation, ∆W reduced from 9.32 % to 3.00 %. • The mechanisms by which additives affect melting and crystallization behavior were revealed using non-isothermal kinetics.