Numerical study of photovoltaic/thermal performance of plate-and-tube water-based PV/T-PCM collector

This paper presented a novel design for an integrated water-based solar photovoltaic/thermal system that incorporates phase change material (PCM). The system takes advantage of the large latent heat capacity, the small temperature difference during phase change, and the long cycle life of PCMs. The impacts of the cooling water flow velocity and PCM thickness on the photovoltaic/thermal properties of the system were studied. The maximum thermal power output and photovoltaic conversion efficiency of the plate-and-tube in water-based PV/T-PCM collector were compared with those of the traditional PV, PV/T, and PV-PCM systems under consistent operating conditions by numerical simulation. The results indicated that the average photovoltaic conversion efficiency of PV/T-PCM systems respectively increased by 40.4%, 10.1%, and 9.8%, compared with the conventional PV, PV/T, and PV-PCM systems. Additionally, the all-day power output of PV/T-PCM system respectively enhanced by 205.85Wh, 71 Wh, and 50.2 Wh, in comparison to the traditional PV, PV/T, and PV-PCM systems. Moreover, increasing the flow velocity of the cooling water improved the thermal and electrical efficiencies of PV/T-PCM system. The water flow velocity increasing from 0.02 m/s to 1 m/s resulted in a maximum increase of 1.91% in the average photovoltaic conversion efficiency, 9.14% in the average photothermal conversion efficiency, and 2.12% in the all-day power generation capacity of system. The photoelectric conversion efficiency of the system initially increases and then decreases with the thickness of PCMs increasing from 30 mm to 45 mm. The system with 35 mm thick PCMs reached the highest average photoelectric conversion efficiency of 11.26%. As the increases of thickness of PCMs layer, the photothermal conversion efficiency of system enhanced. The system with 45 mm thick PCMs indicated the highest photothermal conversion efficiency of 70.7%. Optimizing arrangement of the water pipe in PV/T-PCM system could improve temperature management and result in better thermal storage efficiency.