Thermodynamic performance under variable cutoff temperature and cyclic stability of packed-bed thermal energy storage tank

Abstract This study investigates the dynamic characteristics of a packed-bed thermal energy storage system under unsaturated operating conditions, with a focus on the impact of cutoff temperature thresholds on thermodynamic performance. The charging and discharging behaviors were compared under different cutoff temperature bias (∆T). Results demonstrate that as ∆T increases from 10 K to 130 K, the system’s thermal efficiency decreases from 0.98 to 0.85. Notably, compared with the ∆T=10 K scenario, the complete charge-discharge cycle period extends by over 20 %, while the corresponding thermal efficiency improvement remains below 3 %, revealing a significant economic inflection point in temperature threshold configuration. This finding highlights the necessity for developing rational temperature threshold control strategies in engineering applications. Regarding the evolution of thermodynamic behaviors under multi-cycle operations, the analysis reveals that after initial dynamic adjustments, the system’s thermal boundary conditions and heat transfer mechanisms reach a dynamic equilibrium, establishing a stable periodic thermodynamic cycle pattern. These findings provide crucial foundation for developing long-term performance prediction models, offering valuable guidance for both optimal design and operational control of thermal energy storage systems.