EFFECT OF REACTOR CONFIGURATION ON THE PERFORMANCE OF A CLOSED THERMOCHEMICAL ENERGY STORAGE SYSTEM

Thermochemical energy storage systems (TESS) offer higher volumetric energy density compared to sensible and latent heat storage systems. TESS utilizes endothermic dissociation reaction for thermal energy storage (charging process), and the stored thermal energy is subsequently retrieved by performing a reversible exothermic reaction (discharging process). The reactor of the TESS forms a critical system component as endothermic-exothermic reactions take place in it. The present study focuses on the effect of various reactor configurations on the performance of a potassium carbonate salt hydrate based closed TESS, with the help of numerical studies. The cylindrical and flat type of reactor configurations are commonly used for a closed TESS. The cylindrical reactor configuration offers volumetric compactness but poses challenges such as limited water vapor flow area for penetration into the salt hydrate domain. It is observed that the provision of annular passage for water vapor flow and U-tubes for heat transfer fluid (HTF) flow significantly improve the performance of a cylindrical reactor during the discharging process. Around 69 % of the reactant is consumed by the end of 60 minutes of discharging process with the provision of annular passage for water vapor flow, as opposed to only about 10 % conversion without the provision of the annular passage. On the other hand, a flat reactor configuration provides a larger area for water vapor flow but with higher reactor volume requirement. To reduce the volume requirement, a reactor configuration with multiple stacks of smaller flat reactors is recommended. The addition of metallic fins to the flat reactor results in noticeable improvement. During the discharging process of a flat reactor without fins, complete conversion is achieved in 44 minutes. Whereas in flat reactor with HTF tubes through the salt hydrate domain, complete conversion during the discharging process is achieved within 26 minutes, which is 41 % reduction in the completion time.