Preparation of inorganic molten salt composite phase change materials and study on their electrothermal conversion properties

Abstract

Due to their limitations in conductivity and shape stability, molten salt phase change materials have encountered obstacles to effectively integrating into electric heating conversion technologies, which are crucial in energy storage and conversion fields. In this study, we synthesized an inorganic molten salt composite phase change material (CPCM) with enhanced conductivity and shape stability using a gas-phase silica adsorption method. Our findings revealed the regularities in thermal properties modulation by expanded graphite (EG) within CPCM and delved into its characteristics of electric heating conversion. The study elucidated that a conductive network is essentially formed when the EG content exceeds 3 wt%. Following the fabrication of CPCM into electric heating conversion modules, we observed a correlation between the uniformity of module temperature and the quantity of EG, as well as the distribution of electrode resistance and external voltage magnitude. Building upon this observation, we proposed a strategy to adjust the module temperature field with an electric field. Comparing the proposed direct electrical heating energy storage method with traditional indirect electrical heating methods, the energy storage rate increases by 93.8%, with an improved temperature uniformity. This research offers valuable insights for the application of molten salt electric heating conversion CPCMs.

Keywords: Thermal energy storage materials; Inorganic molten salts; Composite phase transition materials; Electrothermal conversion; Physical property regulation.