Thermodynamic simulation and economic analysis of molten salt thermal energy storage system

Abstract

This research focuses on applying thermal energy storage system using molten salt as a storage medium to the steam production system of a food processing factory. Parabolic trough solar collector was installed as a heat source for a hot oil steam generator which was used to produce steam for pasteurization. Previously, only fossil-fuel boilers were used to produce steam. In this work, two tank molten salt system was considered. The system consists of a cold tank and a hot tank to be used for steam production at night or when there is no sunlight for up to 4 hours per day instead of using fossil-fueled boilers. The process flow diagram of the existing steam production system was created in Aspen Hysys. Then it has been modified with the molten salt thermal energy storage system. Hot oil (PTT-Hitemp 500) is used an intermediary for receiving thermal energy from the solar collector to the steam generator, while molten salt (60% KNO₃ and 40% NaNO₃) acts as a thermal energy storage medium. The simulation result showed that the thermal energy storage could produce saturated steam at the pressure of 6 bar and 158 °C with sufficient flow rate to meet production’s demand at 0.5 m³/hr. Economic analysis of the molten salt thermal energy storage system has been performed and key performance indicators have been evaluated. All indicators show favorable result, thus, indicating that the molten salt thermal energy storage system is economically feasible.