Effect of Al2o3 dispersion on enthalpy and thermal stability of ternary nitrate eutectic salt

Abstract

The system efficiency of concentrated solar power (CSP) was determined by using the working temperature of heat transfer fluid (HTF). Initially, organic HTFs were used for this purpose, which had a maximum operating temperature of 400 °C. However, it exhibits poor thermal storage property. The use of inorganic salts which are stable at high temperature (500~600 °C) can significantly increase the system efficiency. These salts can be used as energy storage materials as well. In this paper, nanocomposite comprising of ternary nitrate eutectic molten salt having pre-defined mass dispersed with Al2O3 nanoparticles of 0.1, 0.3, 0.5, and 1 wt.% was tested. The enthalpy and melting point measurements were performed using differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) was conducted to study the thermal stability of the eutectic salt and mass loss measurement at a temperature higher than 600 ⁰C. The homogeneity and microstructure of synthesized molten salt were examined using scanning electron microscopy (SEM) imaging. The results showed that the melting point of eutectic salt was reduced by 23% with the addition of 1 wt.% of Al2O3 nanoparticles. By increasing the doping of Al2O3, the enthalpy of the mixture increased, indicating that the eutectic mixture could be used for thermal energy storage. SEM imaging analysis revealed the uniform dispersion of Al2O3 nanoparticles in the pure eutectic mixture. Based on the DSC and TGA results, both enthalpy and thermal stability of the molten salt have increased by the addition of Al2O3 nanoparticle, making it a potential candidate salt for CSP applications.