Advancing calcium-based thermochemical heat storage: Impact of a dual-reaction strategy on the system performance

Thermochemical heat storage technology offers immense potential owing to its high energy storage density and low heat loss, making it ideal for long-duration and large-scale energy storage applications. However, challenges persist in terms of the reactor scalability, heat release efficiency, and comprehensive system evaluation. This study proposes a sequential dual-reaction strategy for calcium-based thermochemical heat storage using a flexible and scalable shell-and-tube reactor. The multi-physical coupling mechanisms and key factors influencing the kinetics of a fundamental single-reaction heat release process are explored in this study. In addition to demonstrating the superior heat transfer capabilities of the shell-and-tube design, our findings revealed a significant increase in irreversible entropy generation. Under ideal constant-pressure conditions, we also identified the key parameters governing the basic single-reaction heat release process, achieving a remarkable efficiency of up to 97.01 %. To further optimize the thermochemical heat storage system, a cascaded dual-reaction heat release strategy was proposed, which reduced irreversible entropy generation by 15 % compared to the basic single-reaction process. This strategy simultaneously enhanced the rates of both energy conversion and heat transfer. Finally, the detailed examination and optimization of the multi-reaction coupling mechanisms yielded a 30.60 % improvement in the comprehensive energy efficiency evaluation metric compared to the baseline model. This study offers valuable guidance for the design and control of thermochemical heat storage systems, presenting new solutions for achieving long-term, low-entropy energy conversion.