Experimental study of the effect of fallen leaf shading on the polarization characteristics of photovoltaic modules

Abstract

Coverings have an important impact on the output and safety of photovoltaic (PV) modules. However, due to the complex on-site environment and difficult identification, it is difficult to obtain timely and effective cleaning. In this paper, the optical polarization characteristics of fallen leaf are studied to find the difference for the PV modules with or without fallen leaves covered, which is one of the typical coverings, based on the basic theory of polarization imaging. Firstly, a polarimetric imaging platform with a SALSA camera for PV modules is built. Then, several experiments are conducted and the corresponding images of PV modules shaded by heather or camphor leaves are obtained. Finally, shaded by the impacts on the polarization characteristics of the PV module from fallen leaves, the waveband of the incident light, and the observation angle are analyzed. The results show that the optical polarization characteristics of PV modules at bands of 420 nm and 546 nm are significantly different from others, wherever there existed shading leaves or not; The degree of polarization decreases and then increases with the observation angle from 0° to 70° at 9:00–12:00 a.m. on sunny days; At 0° observation angle, the stokes parameter S_{0} of PV modules with or without fallen leaves has the greatest difference. HighlightsThe influence of fallen leaves on the polarization characteristics of PV modules is studied.The polarization characteristic parameter with the largest difference between the PV modules with and without fallen leaves is obtained.This parameter is more conducive to detecting fallen leaves on the surface of PV modules.