The role of environmental coupling in the performance assessment of compound parabolic concentrating photovoltaic system under windy conditions

The compound parabolic concentrator consists of two parabolic reflectors without tracking system and can be applied in the field of concentrated photovoltaic systems. Environmental coupling plays an important role in the performance assessment of compound parabolic concentrating photovoltaic (CPC-PV) system. In this study, an optical-thermal-electrical-environmental coupling (OTEEC) model was proposed to investigate thermal-electrical performance of system at different tilt angles (θ) and wind direction angles (α) through 3D numerical simulation, and compared with existing optical-thermal-electrical coupling (OTEC) model without coupling environment. Results show that since the OTEC model is not coupled with external environment and empirical correlations are used to replace real convective heat transfer, the effect of wind direction on heat transfer is ignored, which makes it unable to obtain real flow and temperature fields of the system, resulting in a large gap with the OTEEC model. Environmental coupling based on a real fluid domain around the system makes the influencing mechanism of environmental conditions on system performance different from that without environmental coupling. Under the condition of environmental coupling, temperature distribution on silicon cell (SC) layer is affected by the flow field around the system in addition to being closely related to irradiance distribution, due to the variations of θ and α. At the same θ, the combined heat transfer coefficient on tedlar-polyester-tedlar (TPT) and glass cover surfaces changes as α increases, which is different from the OTEC model that uses a fixed convective heat transfer coefficient. In addition, instantaneous electrical efficiency shows a non-monotonic trend influenced by θ and α. When θ is large, due to a large shadow area and the effect of α, localized areas need to be analyzed individually to obtain accurate thermal-electrical characteristics. Maximum differences in the SC layer's average temperature, SC layer's temperature distribution uniformity, combined heat transfer coefficients on the TPT and glass cover surfaces, and instantaneous electrical efficiency calculated with and without coupling environment over the range of θ and α variations are 10.68 °C, 11.02 %, 16.38 W/(m2·K), 8.45 W/(m2·K), and 2.12 %, respectively.