Novel inorganic binary mixture for low-temperature heat storage applications

In this study, an inorganic mixture based on bischofite (industrial by-product) was developed and characterized for its application as a phase change material for low-temperature thermal energy storage. The most appropriate composition was established as 40wt% bischofite and 60wt% Mg(NO3)(2)6H(2)O. Thermophysical properties were defined and compared with those of the mixture with synthetic MgCl(2)6H(2)O. The heat of fusion and melting temperature were measured as 62.0 degrees C and 132.5kJkg(-1) for the mixture with MgCl(2)6H(2)O and 58.2 degrees C and 116.9kJkg(-1) for the mixture with bischofite. The specific heat capacity values, cycling, and thermal stability for both mixtures were also determined. For the mixture with MgCl(2)6H(2)O, the densities of the solid and liquid states were 1517kgm(-3) (ambient temperature) and 1515kgm(-3) (at 60-70 degrees C), respectively. For the mixture with bischofite, the densities of the solid and liquid states were 1525kgm(-3) (ambient temperature) and 1535kgm(-3) (at 60-70 degrees C), respectively. Both mixtures show supercooling of about 23.4 and 34.1 degrees C for the mixture with bischofite and MgCl(2)6H(2)O, respectively. In addition, it was shown that supercooling may be reduced by increasing the quantity of material tested. Thereby, it was established that an inorganic mixture based on bischofite is a promising PCM for low-temperature thermal energy storage applications.