Annular vertical cylindrical thermochemical storage system with innovative flow arrangements for improved heat dispatch towards space heating requirements

Abstract

Thermochemical energy storage is a potential solution for low-temperature seasonal energy storage systems and for improving renewable solar thermal energy share in the global energy mix. Such systems can help in meeting the heating requirements in the Indian Himalayan region in an environment-friendly manner. A few studies have attempted to understand the performance of strontium bromide hexahydrate-monohydrate-based storage as a thermochemical energy storage medium. The present study evaluates the performance of the vertical cylindrical annular reactor configuration, considering innovative radial airflow configurations. A two-dimensional axisymmetric model has been developed to study the effect of the various geometrical and operating parameters. During the charging (dehydration) process, the outward flow configuration exhibits substantially higher exergy efficiency as against the inward flow counterpart, with the difference being more pronounced (∼6–8%) at lower aspect ratios (0.5–1.0). The flow work requirement is higher for the outward flow during the hydration (discharging process), resulting in better performance for the inward flow counterpart. Upon increasing the volumetric air flow rate, the pressure drop across the reactive bed is found to increase substantially, leading to lower exergy efficiencies for higher flow rates. During the hydration process, the exergy efficiency for the inward flow becomes almost constant (∼15%) for a relative humidity level exceeding 60%, whereas that for the outward flow gradually increases to reach ∼ 5% for an 80% relative humidity. The ratio of thermal energy stored to the flow work required is higher for the outward flow. The energy output to flow work ratio is about 35% higher for the inward flow for the aspect ratio of 4.