Development of a comprehensive method to estimate the optical, thermal and electrical performance of a complex PV window for building integration
Xue Li, Yanyi Sun, Xiao Liu, Ming Yang, Yupeng Wu
Abstract
Increasing concerns over energy consumption and greenhouse gas emissions in buildings have contributed to the emerging of innovative PV glazing technologies to improve the building energy performance. However, some of these glazing systems have complex structures, making it challenging to investigate their optical, thermal and electrical performance for estimating their energy saving potential in buildings. In this research, a validated Computational Fluid Dynamics (CFD) combined with a ray-tracing model has been developed to accurately predict the optical, thermal and electrical performance of complex PV glazing systems under varying incident angles. A ray-tracing model is developed to calculate the light transmittance of the window as well as the solar energy absorbed by each solid-element and PV cells. To estimate the temperature profile (e.g., PV temperature and window temperature) and secondary heat of the window, ray-tracing results of solar flux absorbed by each layer are transferred into a validated CFD model as boundary conditions. Using the CFD combined ray-tracing calculation illustrated above, the Solar Heat Gain Coefficient (SHGC) of the complex PV window can be obtained. Furthermore, a PV modelling algorithm is developed to predict the power output based on the simulated PV temperature. This procedure is implemented to investigate a Crossed Compound Parabolic Concentrator Photovoltaic (CCPC-PV) window, which serves as an example of a complex PV glazing system in this study. The developed optical, thermal and electrical models have been validated through experimental tests. Additionally, new configurations have been designed to explore the impact of the pitch between adjacent optics on the SHGC and power output of the window. The results show that the original window (1.77 mm-pitch) possesses the maximum PV temperature of 64.73 °C and the maximum window inside surface temperature of 61.58 °C under National Fenestration Rating Council (NFRC) standard. Meanwhile the PV efficiency is 15.21 % and the SHGC is 0.463. The SHGC value of this innovative PV window is notably lower than that of a conventional double-glazed window with a SHGC value of 0.813, which reduces the possibility of overheating issues, especially during the summer.