Thermal integration of direct-indirect thermochemical reactors and charging-discharging thermal management strategies for solar thermal storage systems

Abstract

The integration of solar thermal energy into energy systems necessitates efficient thermal storage technologies. This study focuses on the development of a combined direct-indirect thermochemical reactor using the Ca(OH)₂/CaO system, aimed at enhancing heat transfer and optimizing the thermal charging/discharging processes. A multi-physics model incorporating fluid flow, heat transfer, mass transfer, and chemical reaction was established to analyze the dehydration and hydration reactions under varying conditions. The systematic investigation of the effects of key parameters, including porosity and thermal conductivity, on reaction efficiency was conducted. Specifically, increasing the thermal conductivity from 2 W/m·K to 4 W/m·K reduced the reaction time by 40 min. Additionally, enhancing the porosity from 0.6 to 0.8 led to a reduction in reaction time by 30 min. Furthermore, the utilization of metal foams and heat sinks to augment heat transfer significantly improved reactor performance. The implementation of metal foam decreased the reaction time from 100 min to 60 min (a 40 % improvement), while the addition of fins resulted in approximately a 50 % increase in efficiency. These findings underscore the importance of material properties and reactor design in enhancing the performance of thermochemical energy storage systems, offering valuable insights for future applications in solar thermal energy utilization.