Optimization of Preparation Method, Nucleating Agent, and Stabilizers for Synthesizing Calcium Chloride Hexahydrate (CaCl2.6H2O) Phase Change Material

Journal Article · Fri Oct 21 00:00:00 EDT 2022 · Buildings

DOI:https://doi.org/10.3390/buildings12101762· OSTI ID:1894417

Thakkar, Jay; Bowen, Nicholas; Chang, Allen C.; Horwath, Peter; Sobkowicz, Margaret J.; Kośny, Jan

This study investigates improvements in low-cost latent heat storage material calcium chloride hexahydrate (CaCl2.6H2O). 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 CaCl2.6H2O incongruent melting causes lower hydrates of CaCl2 to form, which affects the overall energy storage capacity and long-term durability. In this work, PCM performance enhancement was achieved by adding SrCl2.6H2O 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 SrCl2.6H2O 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 SrCl2.6H2O reduced supercooling from 12 °C to 0 °C compared to unmodified CaCl2.6H2O. 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.

• Sponsoring Organization: USDOE
• Grant/Contract Number: EE0009156
• OSTI ID: 1894417
• Journal Information: Buildings, Journal Name: Buildings Vol. 12 Journal Issue: 10; ISSN 2075-5309
• Publisher: MDPI AG
• Country of Publication: Switzerland
• Language: English