Performance of bifacial PV modules under different operating conditions in the State of Minas Gerais, Brazil

Abstract

Brazil's cumulative photovoltaic (PV) installations have now surpassed 32 GWp. The fastest growing and most prevalent PV technology is the bifacial photovoltaic module, which is now being incorporated in more than 2/3 of new power plants. These modules collect solar radiation on both front and rear sides, providing gains in electricity production compared to traditional monofacial modules. The market acceptance and quality control of this technology requires standard methods to accurately determine the nominal power of the bifacial modules. But the specification of energy production from the bifacial backside is complicated due to critical factors that include the albedo, the separation, height, and positioning of the modules, the shading of the rear surface, and the specific geographic and climate conditions. This paper addresses these issues in determining the performance of bifacial PV modules in the tropical conditions of the State of Minas Gerais, Brazil. Specifically, the bifacial gain for modules and systems is evaluated, assessing the effects of albedo, site maintenance, climate/environmental conditions, thermal behavior, and back-surface shading. The special cases of tracking versus non-tracking systems are evaluated showing specific attention needs to the albedo changes and rear module shading constraints. These studies are performed on real power plants having different operating conditions (e.g., tracking, non-tracking, ground cover). The methodology includes I-V characterization of modules and string and thermal imaging/mapping under existing climate and meteorological conditions. Correlations with experimental albedo conditions is a special concern with these studies. These results are further compared to controlled laboratory measurements to establish information needed to better evaluate the developing standard for actual local operating conditions. This case study provides evaluation of the quality of the both the bifacial PV products being used and their installations in the rapidly emerging Brazil PV markets.