Analysis of heat release characteristics and optimization of high temperature thermal energy storage discharge strategies

• Discovered nonlinear impact of airflow velocity on thermal storage efficiency and temperature distribution. • Contrasted three discharge strategies’ contrasting benefits: efficiency vs. uniformity vs. simplicity. • Established practical guidelines for strategy selection balancing energy and thermal priorities. High-temperature solid thermal energy storage (TES) is the core equipment of thermal energy storage power plants. However it faces challenges such as internal temperature non-uniformity and low efficiency of heat release during operation. This research employs simulation to investigate the effects of discharge air speed on the temperature distribution and energy characteristics of the high-temperature heat storage unit, with a focus on comparing the optimization effects of three discharge strategies—constant-speed, variable-speed, and flow-direction switching—on temperature uniformity and charge/discharge performance. The results indicate that discharge air speed significantly impacts both the effective heat release and internal temperature difference. As the air speed increases from 1 m/s to 5 m/s, the effective heat release initially increases and subsequently decreases, while the internal temperature difference decreases from 256 K to 120 K. Under constant-speed discharge, the TES unit shows poor heat release characteristics and temperature uniformity, with 22.94 kWh effective heat release, 77.1% discharge efficiency and 182 K post-discharge temperature difference. The variable-speed discharge strategy achieves the highest discharge efficiency about 81.9%, but a residual temperature difference of 131 K remains. The flow-direction switching strategy minimizes the internal temperature difference to 44 K, yet yields the lowest effective heat release and efficiency, 22.69 kWh and 76.3% respectively. This research provides a reference for selecting discharge strategies in solid TES systems under different application scenarios.