Component-dependent thermal properties of molten salt eutectics for solar thermal energy storage: Experiments, molecular simulation and applications

Abstract

Molten salts have been used in solar thermal energy storage due to their high energy storage density, low cost and excellent chemical stability. However, their application is limited by “bad days” such as cloudy days and winter because the weak concentrated solar radiation cannot melt the salt. The current study indicates that through mixing pure salts, the melting point of molten salt can be decreased significantly while the latent heat is not impaired. This is very important for solar thermal energy storage systems on “bad days” because the system using the low-melting-point salt is still possible to work on these days. The case study was performed in Nottingham, the United Kingdom and Dezhou, China respectively. The pure salt and salt mixture were used as the heat transfer fluid and energy storage medium in the solar tower power plant. It is found that by using the low-melting-point salt eutectic, the yearly operation time of the plant is increased by 75 days for Dezhou and 33 days for Nottingham. In addition, a molecular simulation was performed to reveal the mechanism underlying the component-dependent thermal properties. Mixing pure salts is proved to be a simple method to improve the utilization efficiency of the solar power plant.