Experimental analysis of charging and discharging processes, with parallel and counter flow arrangements, in a molten salts high temperature pilot plant scale setup

Despite the fact that there are some commercial concentrated solar power plants worldwide, there is currently a lack of experimental reports about the operational characteristics of this type of plants. Therefore, a two-tank molten salts thermal energy storage (TES) pilot plant at the University of Lleida (Spain) was used to analyze charging and discharging processes under real conditions. In this facility, 1000 kg of molten salts are used as TES material and Therminol VP-1 is used as heat transfer fluid (HTF). This facility is equipped with measurement equipment which allows an exhaustive analysis of the processes. In this study, the fact of varying the flow arrangement in the heat exchanger (parallel and counter flow arrangements) and the temperature difference between the molten salts and the HTF have been studied and discussed in terms of temperature profiles, energy and power stored/released from/to both HTF and molten salts, efficiencies and effectiveness. The best working conditions found were counter flow arrangement with a temperature grading of about 65 °C.