Performance Investigation of a Solar-Driven Thermochemical Heat Upgrading System Utilizing Reversible Calcium Chloride Hydrate Reactions

The increasing need for sustainable industrial process heat has led to advances in the evolution of thermochemical thermal transformer systems designed for heat upgrading applications. The present study investigates the operation of a solar-driven solid-gas thermochemical heat transformer (SGTHT) system. In this system, CalCl₂.H2O is used in reversible hydration and dehydration reactions. A dynamic model of the proposed system is developed using the Modelica language and implements in Dymola to investigate the system’s efficiency and temperature variations under different operating conditions. The system consists of an evacuated tube solar collector (ETSC) as the heat source and a SGTHT system for heat upgrade applications. The results of the dynamic simulation show that the system is capable of increasing the temperature of heat transfer fluid (HTF) up to approximately 148°C. The heat absorption during the dehydration operation is 36.08 kWh, and the upgrading heat released during the hydration operation is 39.39 kWh. The maximum heat transfer rate of the dehydration and hydration processes
are 20.44 kW and 30.45 kW, respectively. The system achieves a total thermal efficiency of 63.24% in the SGTHT subsystem, proving its applicability for industrial process heat. Furthermore, a parametric study is conducted to evaluate the impact of the most important parameters, including condenser temperature, evaporator temperature, and the flow rate of the HTF, on the system performance. The results highlight the importance of optimizing operational conditions to enhance energy efficiency and improve heat upgrading potential. The findings confirm the potential of the proposed SGTHT system with solar-driven operation as a viable solution for upgrading low-grade renewable heat and industrial waste heat.