Experimental study on phase change material for thermal energy storage based on ammonium alum

Through an experiment on ammonium alum, an effective method to reduce the super-cooling degree was found. The constitution of several additives and the relative preparation of the material to improve thermal characteristics were proposed. The results show that adding mass fraction 1.8% of calcium fluoride, 0.4% of carbon and 6% distilled water in the ammonium alum could inhibit super-cooling and ensure an effective heat releasing. Repetitive experiments present that after 10 cycles of melting and solidification the material still has a high melting temperature, a large phase change enthalpy and also a steady performance during the cooling process.