Experimental investigation and thermodynamic modeling of an innovative molten salt for thermal energy storage (TES)

A novel computational thermodynamic approach based on thermodynamic principles was applied to design and develop innovative molten salt mixtures for thermal energy storage. In this work, the eutectic composition of the NaCl-NaF-Na2CO3 ternary system was predicted based on experimental data via computational thermodynamic approach. Substitutional solution model (SSM) was used to describe the Gibbs energies for all liquid phases. Thus, a set of self-consistent thermodynamic model parameters was obtained for three subsystems and the parameters were used to predict the eutectic composition of the NaF-NaCl-Na2CO3 ternary system. Results manifested that the predicted eutectic point of the ternary system were located at T = 849 K and XNaF = 21.66 mol%, XNaCl = 41.87 mol% and XNa2CO3 = 36.47 mol%. By means of Differential Scanning Calorimetry method, the predicted results were verified experimentally and the agreement between the measured and predicted values was satisfactory. Thermal-physical properties for eutectic salt mixtures, such as enthalpies of fusion, heat capacity, density and thermal stability, were also determined experimentally via thermal analysis methods in this work. Through computational thermodynamics approach, an innovative eutectic salt was designed and developed as thermal energy storage (TES) materials at high temperatures, especially it can be serve as candidate thermal energy storage materials for next generation concentrated solar power (CSP) plants.