Comparison of Angular Reflectance Losses Between PV Modules With Planar and Textured Glass Under Singapore Outdoor Conditions

Photovoltaic (PV) modules are rated under standard test conditions with normally incident light, whereas under outdoor conditions photons arrive on a PV module surface at all angles. In this study, the angular losses of PV modules with a planar and textured front glass are investigated for the tropical conditions of Singapore. Angular reflectance for both modules is first measured using a goniophotometer. From the measurements, the angular loss factors due to the different radiation components are calculated. Then, the angular losses under Singapore outdoor conditions are determined using three transposition models: Liu and Jordan, Hay and Davies, and Perez et al. Two 60-cell PV modules with a planar and textured glass are fabricated and measured outdoors for validation of the modeling results. Outdoor measurement results show that the PV module with textured glass captures 1.4% extra light compared with the PV module with planar glass for the 6-mo period studied. Next, the annual angular loss, monthly angular loss, and typical meteorological day angular loss for both module structures are studied. For all cases studied, the PV module with textured glass has consistently lower angular losses compared with the PV module with a planar glass.