Bischofite as Phase Change Material (PCM) for Thermal Energy Storage (TES) Applications
Abstract
Bischofite is a by-product from the non-metallic industry which is composed by MgCl2·6H2O in approximately 95%. Both materials show similar thermo-physical properties, the temperature and the heat of fusion is 100°C and 115 kJ/kg for bischofite, and 114.5°C and 135 kJ/kg for MgCl2·6H2O. The main advantage of the use of bischofite instead of MgCl2·6H2O is the price, which is significantly lower. The present study consists in two stages: in the first one, a laboratory characterization of thermal properties such as melting enthalpy and temperature, heat capacity, as well as density, viscosity and its morphology is performed. In the second stage, the material is tested and evaluated at pilot plant scale (≈ 200 kg). Parameters such as the phase change material (PCM) charging temperatures, the HTF power, the energy balance in the system and the charging efficiency are analysed. Moreover, this PCM candidate is also compared with other materials with similar melting temperature (± 20 ºC) regarding the cost and the energy density. Finally, taking into account bischofite temperature of fusion (100 ºC), a discussion of its utilization for industrial waste heat recovery or combined heat and power (CHP) possibilities is done. Thus, the objective of this study is the analysis of the suitability of a by-product as PCM candidate for thermal energy storage (TES) applications.
Keywords
Bischofite, Phase change material (pcm), Thermal energy storage (tes), By-product, Latent heat.