Experimental evaluation of binary and ternary eutectic phase change material for sustainable thermal energy storage

Abstract

Phase change materials (PCMs) are the active source for storing thermal energy in the form of latent heat. Inorganic salt hydrate based PCMs are regarded as high energy storage materials with high thermal conductivity and low flammability compared to organic PCM, whereas the major hindrances are supercooling and corrosivity which reduces service life. This encourages examining and developing new forms for inorganic-inorganic eutectic PCM with a focus on melting point and enthalpy. In this article we design, develop, and characterize, low temperature inorganic salt hydrate eutectic PCMs, using calcium chloride hexahydrate, sodium carbonate decahydrate, sodium sulphate decahydrate and sodium phosphate dibasic dodecahydrate. Schrader equations along with the thermophysical property of salt hydrates were adopted to determine eutectic phase transition temperature and eutectic mixtures proportions. Twenty-one different combination of PCMs mixture were numerically evaluated, out of which seven eutectic mixtures with a melting temperature between 21 and 28 °C (four binary and three ternary), were experimentally synthesised and characterized. Melting point, heating enthalpy, specific heat capacity and degree of supercooling of the pure salt hydrates and their eutectic mixtures were analysed using differential scanning calorimeter. The melting enthalpy of eutectic PCMs, were 200–215 J/g; furthermore, the degree of supercooling reduces by 10–13 °C for eutectic PCMs when compared to pure PCMs. The numerical values were supplemented with experimental results and ensured the suitability of the developed eutectic PCM for low temperature energy storage application with a focus towards building cooling.