| Summary: | This study investigates improvements in low-cost latent heat storage material calcium chloride hexahydrate (CaCl<sub>2</sub>.6H<sub>2</sub>O). Its melting point is between 25 and 28 °C, with relatively high enthalpy (170–190 J/g); however, this phase change material (PCM) shows supercooling and phase separation. In CaCl<sub>2</sub>.6H<sub>2</sub>O incongruent melting causes lower hydrates of CaCl<sub>2</sub> to form, which affects the overall energy storage capacity and long-term durability. In this work, PCM performance enhancement was achieved by adding SrCl<sub>2</sub>.6H<sub>2</sub>O as a nucleating agent and NaCl/KCl as a stabilizer to prevent supercooling and phase separation, respectively. We investigated the PCM preparation method and optimized the proportions of SrCl<sub>2</sub>.6H<sub>2</sub>O and NaCl/KCl. Thermal testing for 25 cycles combined with DSC and T-history testing was performed to observe changes in enthalpy, phase transitions and supercooling over the extended period of usage. X-ray diffraction was used to verify crystalline structure in the compounds. It was found that the addition of 2 wt.% of SrCl<sub>2</sub>.6H<sub>2</sub>O reduced supercooling from 12 °C to 0 °C compared to unmodified CaCl<sub>2</sub>.6H<sub>2</sub>O. The addition of 5 wt.% NaCl or KCl proved to effectively suppress separation and the melting enthalpy achieved was 169 J/g–178 J/g with congruent melting over 25 cycles, with no supercooling and almost no reduction in the latent heat.
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