Dynamic Modeling and Performance Evaluation of Thermal Storage Tank With Packed Bed of Phase Change Capsules During Charging Processes

Abstract In order to address the issues of global energy crisis and environmental pollutions, renewable energies are being rapidly developed. However, solar energy and wind energy are intermittent, and energy storage should be applied to amid the imbalance between energy supply and demand sides. Thermal storage technology is an effective and potential way for large-scale and long-term energy storage, which can improve the stability and efficiency of power generation system driven by solar energy. To obtain the dynamic behaviors of thermal storage tank with packed-bed of phase change capsules, dynamic models of heat transfer fluid (HTF) and phase change capsules were developed based on a modified one-dimensional discrete concentric model. The governing equations were programed and validated. Then, the dynamic behaviors of the charging processes of thermal energy storage tank under variable operation conditions were simulated and analyzed. The effects of packed-bed characteristics, such as capsule diameter and porosity, on temperature distribution, thermal and exergy storage, energy and exergy efficiency during charging processes of thermal energy storage tank were studied. Moreover, influences of inlet temperature and mass flow rate variations of heat transfer fluid on charging behaviors was also studied to compare the dynamic variations of its energy and exergy efficiencies. These factors have affected the charging time, maximum heat storage capacity and efficiency to varying degrees. It is worth noting that the exergy efficiency of the charging process increases over time. The present work can provide insights into optimizing the operational strategies of thermal storage systems to achieve high charging efficiency.