Experimental study on the thermal stability of a new molten salt with low melting point for thermal energy storage applications

This paper presents a new kind of KNO3-NaNO3-LiNO3-Ca(NO3)2·4H2O with certain proportion, which is potentially suitable for high-temperature thermal energy storage in concentrating solar power technology. Its primary thermophysical properties were evaluated. Thermal physical tests were conducted for the samples obtained at different stages during the tests of 1,200-h exposure to constant high temperature and thermal shock cycling for 1000 times. Results show that a comprehensive grasp of the time evolution of its thermophysical properties and their respective changes with heating time and thermal cycles were achieved. The thermophysical properties of the molten salt show good repeatability before and after the experiments, and most variations are within ± 10%. In addition, the normal temperature X-ray diffraction diagram of the candidate was measured and analyzed after 1200 h of heating and 1000 times of thermal cycling. Although part of calcium nitrates has been dissolved and formed a new solution, this phenomenon does not affect the performance of the candidates, which showed high-temperature tolerance and good thermal stability. Therefore, this new kind of molten salt thermal storage materials is a promising candidate for both heat transfer and energy storage in large-scale solar thermal power plants.