Dynamic heat storage and release characteristics and flow control optimization of photovoltaic/thermal-heat pump coupled packed bed thermal energy storage system (PV/T-HP-PBTES)

Integrated photovoltaic/thermal-heat pump (PV/T-HP) and packed bed thermal energy storage (PBTES) systems offer promising solutions for mitigating the temporal and spatial mismatches between energy supply and demand. However, research on the dynamic thermodynamic behavior and coordinated optimization of such coupled systems remains limited. This study aims to address this gap by developing a comprehensive model that simulates the cyclic heat storage and dynamic heat release of a PV/T-HP-PBTES system integrated with a radiator. The model is employed to evaluate system performance and to formulate a novel dynamic flow control strategy for the heat release phase. The findings reveal that solar irradiance and ambient conditions significantly influence the coefficient of performance (COP) of the PV/T-HP subsystem. During the peak solar radiation period (11:00–14:00), the subsystem achieves full energy self-sufficiency, demonstrating off-grid capability. Meanwhile, in the PBTES subsystem, the exergy storage power peaks during the phase change stage, while the exergy release power reaches its maximum at the onset of the discharge phase. Moreover, for the coupled system, designed for a 1420 m2 residential building, the COP during typical daily cyclic operation is 12.93, with a total heat storage of 358.47 MJ and an exergy storage of 50.99 MJ, corresponding to an 87.6 % reduction in electricity operating costs compared with a conventional air-source heat pump. Additionally, implementing a dynamically increasing heat transfer fluid flow strategy increases the effective heat release time to over 2 h, which is 172.5 % longer than that under constant flow conditions, with the parabolic flow mode performing best. This study provides a theoretical foundation and practical optimization approach for engineering applications of PV/T-HP-PBTES systems.