Experimental investigation of an indirect PV/T-assisted heat pump system with condenser-integrated phase change thermal storage

Integrating photovoltaic/thermal (PV/T) collectors with heat pumps is a promising route for solar-assisted building heating, but intermittent solar input and the mismatch between heat collection and heating demand still restrict system stability. This study experimentally investigates an indirect PV/T-assisted heat pump system incorporating a condenser-integrated composite phase change thermal storage tank (CPCTST). A prototype rig was built to compare water-only storage, phase change material (PCM) storage, and heat-pump-assisted discharging. PV/T conversion performance, heat pump operation, CPCTST charging/discharging behaviour, load-side heat delivery, and useful load-side thermal exergy were evaluated to clarify the role of condenser-side latent heat buffering. Results show that the system maintained stable PV/T electrical performance under dynamic solar irradiation, with average electrical efficiencies of 17.8% to 19.5%. For the two PCM-integrated test days, the average thermal efficiencies were 45.8% and 49.1%. Under heat-pump-assisted discharging, the average heat pump coefficient of performance and net-electricity-based system coefficient of performance reached 4.6 and 8.9, respectively. Compared with water-only discharging, PCM integration extended the storage-only discharging duration from 64 min to 127 min and increased the cumulative load-side heat delivery from 3.65 kWh to 5.02 kWh. With heat-pump assistance, the cumulative load-side heat delivery further increased to 8.91 kWh. The useful load-side thermal exergy increased from 0.387 kWh in the water-only case to 0.883 kWh with PCM storage and 1.324 kWh under heat-pump-assisted discharging. The results demonstrate that condenser-integrated latent heat storage can improve heat supply continuity and support stable solar-assisted heating.