An experimental investigation of temperature distribution and heat loss in molten salt tanks in concentrating solar power plants

Two-tank molten salt storage systems, which increase the dispatchability of power, are widely utilized in commercial concentrating solar power plants. In the present work, a pilot solar thermal power plant was created to investigate temperature distribution and heat loss in the molten salt tank. The results showed that the molten salt had no temperature stratification at different liquid levels and operating temperature conditions except at the unprotected position near the electric heater. However, there was an obvious temperature difference in the upper atmosphere: the temperature dropped by 5.5 °C to 6.5 °C with every 400 mm increase in the height. During the cooling process, the temperature gradient in the tank foundation was basically stable. Experiments indicated that the liquid level of the salt affected the cooling rate of the molten salt significantly, while it had a little effect on the total heat loss in the tank. As the liquid level decreased from 2040 to 1039 mm, the temperature difference of the molten salt in the cooling process increased from 22.1 °C to 41.5 °C, but the total heat loss only changed by 4.3%. However, the molten salt operating temperature had a great influence on both the temperature change and the heat loss in the molten salt tank. When the operating temperature decreased from 557.7 °C to 376.9 °C, the temperature difference of molten salt in the cooling process decreased from 37.4 °C to 19.7 °C and the total heat loss in the tank decreased by 48.2%.