Novel inorganic binary mixture for low‐temperature heat storage applications

Summary 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 40 wt% bischofite and 60 wt% Mg(NO 3 ) 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°C and 132.5 kJ kg −1 for the mixture with MgCl 2  · 6H 2 O and 58.2°C and 116.9 kJ kg −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 1517 kg m −3 (ambient temperature) and 1515 kg m −3 (at 60‐70°C), respectively. For the mixture with bischofite, the densities of the solid and liquid states were 1525 kg m −3 (ambient temperature) and 1535 kg m −3 (at 60‐70°C), respectively. Both mixtures show supercooling of about 23.4 and 34.1°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.