Evaluation of the Cooling Process of Thermal Storage Tanks with LiNO3-NaNO3-KNO3 Ternary Mixture as Working Fluid for CSP Plants
Abstract
The most used thermal energy storage material in concentrated solar power plants is a binary salt of 60% NaNO3+ 40%KNO3. However, the relatively high melting point of this mixture (221 °C) represents a significant risk of local solidification in the operation of these plants during standby periods. This research proposes the use of the mixture composed by 30%LiNO3+57%KNO3+13%NaNO3 due to its excellent thermal properties having a melting point of 124°C. The transient cooling process of a molten salt tank working with the proposed ternary mixture has been studied. For this purpose, a computational fluid dynamics (CFD) model has been developed and validated with experimental data. The evolution of the temperature over time at all points in the tank has been obtained, the results show that the lowest temperatures are located near the free surface of the salts. Finally, the local crystallization time of the proposed new salt has been analyzed, it is noted that crystallization times for the ternary salt of LiNO3 is much higher if we compare it with solar salt.