Characterization of calcium chloride tetrahydrate as a phase change material and thermodynamic analysis of the results

• Published in: Renewable energy 2016-09, Vol.95, p.213-224
• Main Authors: Ushak, Svetlana, Suárez, Miriam, Véliz, Sussy, Fernández, Angel G., Flores, Elsa, Galleguillos, Héctor R.
• Format: Article
• Language: English
• Subjects: Calcium chloride; Calcium chloride tetrahydrate; Chlorides; Density; Differential scanning calorimetry; Hydration; Melting points; Phase change material; Solar energy; Thermal energy storage; Thermodynamic models; Thermophysical properties
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2016.04.012

To study the feasibility of calcium chloride tetrahydrate as a phase-change material, we determined its melting point and heat of fusion using differential scanning calorimetry (DSC) in the temperature range of 0 °C-60 °C. We also determined the density and viscosity of molten calcium chloride tetrahydrate in the temperature range of 40 °C-65 °C and studied the effect of adding small quantities of LiCl, NaCl and KCl (1 mass %) on the resulting thermal and physical properties. Based on the determination of the thermophysical properties, the energy storage density was evaluated for the different systems. The CaCl2·4H2O + 1 mass % of LiCl exhibited higher values (174 J/cm3) than pure CaCl2·4H2O (156 J/cm3), and the CaCl2·4H2O + 1 mass % of NaCl (151 J/cm3). Some of the results were interpreted using thermodynamic models and functions, indicating that the addition of alkaline chlorides contributes to releasing water molecules from the hydration layer of Ca+2 ions, which appears to have a determining effect on the behavior of molten CaCl2·4H2O. •Melting point and heat of fusion of CaCl2·4H2O are 44.2 °C and 99.6 J/g, respectively.•The addition of different alkaline salts to CaCl2·4H2O reduces the melting point.•CaCl2·4H2O + LiCl exhibits a higher energy storage density than pure CaCl2·4H2O.•CaCl2 + 1 mass% of LiCl exhibits a good stability for 15 heating-cooling cycles.•CaCl2 + 1 mass% of LiCl may be a possible alternative for use as a PCM.