High-performance composite molten salt thermal energy storage material based on resources recovery from waste salt for concentrated solar power applications

Due to wide operating temperature range and low cost, chloride molten salts have been extensively considered as potential heat transfer medium for concentrating solar power. In this work, composite energy storage material with molten salt and carbon sphere is efficiently prepared by waste salt, and its enhancement mechanism of thermal property is investigated. By hydrothermal reaction and carbonization, the organic pollutants in waste salt can be changed to carbon spheres, which exhibit high graphitization degree and excellent light absorption property. After preparation of waste salt-based composite molten salt, the latent heat of Salt-2.0 % can reach 221.1 J/g. With the increase of carbon sphere content, the specific heat capacity of composite molten salt shows 27.2 % higher than pure molten salt. And the thermal conductivity can increase to 0.44 W/(m·K) with 2.0 wt% carbon sphere content, representing an improvement of 15.8 %. According to molecular dynamics research, the simulated thermal properties agree well with experimental data, and the enhancement of thermal conductivity is attributed to the synergistic effect of system potential and kinetic energy increment. After continuous service, the composite molten salt has excellent thermal stability, which is used as low-cost and high-performance energy storage material for solar power applications.