Heating performance of a dual-source PV/T heat pump with potential for building energy decarbonization

This study proposes a novel solar/air-source Direct-Expansion (DX) photovoltaic/thermal (PV/T) heat pump system in which a single finned PV/T unit simultaneously operates as both the solar and air evaporator, enabling compact system configuration and reduced structural complexity. A transient numerical model based on the finite-difference method was developed in MATLAB to simulate the coupled heat transfer, refrigerant thermodynamics, and system energy balance. The model was validated against published experimental data, and the relative errors for the coefficient of performance (COP) and compressor power were found to be within 10%, indicating good predictive accuracy. The system performance was evaluated under the climatic conditions of Yibin. The results show that the PV surface temperature varies from 11°C in winter to 53°C in summer, corresponding to electrical efficiencies of 13.9-15.4% and thermal efficiencies of approximately 55%. The system achieves peak outputs of about 230 W electrical power and 1181 W thermal power, with a maximum COP exceeding 5.0 in heating mode. Parametric analysis indicates that increasing the condensing pressure from 12 to 20 bar reduces the COP from 5.3 to 3.3, while higher solar irradiance increases the total energy output but also intensifies PV temperature-related losses. These results demonstrate that the proposed integrated PV/T-heat pump system can provide efficient and stable thermal and electrical energy for building heating applications, with potential for renewable-based building energy utilization.