Fabrication and investigation of chloride salt based shape stabilization phase change composite with excellent thermal properties for medium and high temperature thermal energy storage

A novel shape-stabilized chloride salt based composite phase change material with stable thermal properties is fabricated and investigated in this work. Such composite is consisted of a ternary chloride salt of NaCl-KCl-MgCl₂ as storage medium, an expanded vermiculite as ceramic skeleton and a silicon carbide as thermal conductivity enhancer. A suite of characteristics is carried out to evaluate the composite thermal properties and stability as well as heat transfer performance. The results show that a stable physical interaction is observed among the three ingredients of salt expanded vermiculite and silicon carbide, demonstrating an excellent physical and chemical compatibility achieved in the composite. Due to the excellent wettability between the salt and expanded vermiculite, a dense structure can be attained in the composite, which could effectively eliminate the swelling effect of silicon carbide and prevent the salt leakage over the phase transition process. Owning to such a rigid structure, over 70 wt% of salt and 12 wt% of silicon carbide could be accommodated by the expanded vermiculite, giving the composite a melting temperature of 377 °C, a latent heat of 229.3 kJ/kg and a thermal conductivity of 1.66 W/m·°C. Moreover, the presence of expanded vermiculite also enhances the salt thermal stability. Compared with the pure ternary chloride salt where a decomposition temperature of 740 °C is measured, the decomposition temperature of the composite is improved to be 800 °C. The results obtained in this work indicates the chloride salt based composite with high thermal stability and splendid cycling performance that could be an effective candidate utilized in medium and high temperature thermal energy storage fields.