Stability analysis of Calcium chloride hexahydrate inorganic phase change material

Calcium chloride hexahydrate (CaCl2.6H2O) is a potential thermal battery material that stores/retrieves energy during phase transition for thermal energy storage applications. The CaCl2.6H2O is an inorganic phase change material (PCM), salt hydrate, that is commercially available and widely utilized in several thermal energy storage applications due to its high energy density, non-hazardous nature, and cost-effectiveness. The primary issue linked with CaCl2.6H2O is phase stratification. The phase stratification is more pronounced with time and temperature which results in varying the thermal properties and phase equilibrium of the CaCl2.6H2O. This study is performed to prepare CaCl2.6H2O PCM from dry CaCl2 and investigate its thermal stability for thermal energy storage applications. The phase change equilibrium temperature and latent heat of fusion of the prepared sample were compared to the commercial product of Sigma Aldrich. The Differential Scanning Calorimetry (DSC) thermograph for the prepared sample shows the onset phase change equilibrium temperature of 30.6±0.2 ∘^{\circ}C and the latent heat of fusion is 177±2 J/g, whereas the thermal properties of the commercial CaCl2.6H2O were 30.4±0.2 ∘^{\circ}C and 184±2 J/g. The stability investigation includes thermal stress test (impact of temperature on thermal properties variation and phase stratification) and corrosion analysis (compatibility of storage tank material). The thermal stress experiment was performed for 90 days where the PCM under study was exposed to a controlled temperature environment at 50 ºC. The result reveals the sample was stable for the first 30 days and no phase stratification or variation in thermal properties was observed. Whereas, after 30 days a significant change in the thermal properties was evident. The results presented can be valuable for the research community working with CaCl 2.6H2O thermal batteries for thermal energy storage applications.