Experimental study on ultra-low radiation heat loss photovoltaic-thermal collector based on infrared emissivity regulation

This paper presents an ultra-low radiative heat loss design for photovoltaic-thermal collectors based on infrared emissivity regulation, addressing the significant radiative heat loss during operation. The design employs unencapsulated Interdigitated Back Contact solar cells as the absorber and a glass cover with a low-emissivity aluminum-doped zinc oxide coating, which together significantly reduce radiative heat loss. A key advantage of this design is its compatibility with modularly fabrication at the square meter scale. The effectiveness of this design in improving thermal efficiency and overall energy utilization efficiency was validated through outdoor experiments and numerical simulations. Results show that the intercept efficiency of the low-emissivity configured photovoltaic-thermal collector increased from 0.63 to 0.70, and the heat loss coefficient decreased from 5.91 to 3.05 W/(m2·K). Within an inlet temperature range of 50°C to 70°C, the thermal efficiency of the low-emissivity photovoltaic-thermal collector exhibited a relative increase of 9.9% to 40.5%, and the overall efficiency rose by 7.2% to 30.8%, with advantages becoming more pronounced under higher operating temperatures. Furthermore, annual performance simulations demonstrated significant energy gains, indicating that the proposed photovoltaic-thermal collector is particularly suitable for high-latitude cold regions.