Numerical study on the forced convection enhancement of flat-roof integrated photovoltaic by passive components

Abstract

Photovoltaic (PV) modules installed on flat roof need to be cooled to improve the power conversion efficiency (PCE). The efficient use of natural wind for cooling is a low-cost alternative compared with the use of artificial cooling devices. In this study, a passive cooling scheme is proposed including components: curved eave and vortex generators (VGs) which is arranged on the roof to enhance the forced convective heat exchange and reduce temperature of rooftop PV module under prevailing wind conditions. The optimum arrangement of VGs was studied, temperature reduction and PCE of rooftop PV with the scheme were evaluated. The results show that the curved eaves installed on the flat-roof leading edge improved the convective heat exchange only in the airflow separation area. And the defect that surface convective heat exchange decreased along with the flow direction was improved when multi-row array VGs were arranged. The overall convective heat exchange on rooftop PV can be improved at a wide range of wind speed by scheme using curved eaves in combination with the symmetrically arranged VGs. After using the passive cooling scheme, the ratio of forced convective heat exchange on the rooftop PV upper surface to 60%, and the maximum temperature reduction is about 5.89 ℃, and PCE of PV is improved in summer. The low-cost passive cooling scheme proposed in this paper is expected to be applied to the new-built and reconstruction of flat-roof mounted PV system.