Multi-Variable Bifacial Photovoltaic Module Test Results and Best-Fit Annual Bifacial Energy Yield Model

Abstract

Bifacial photovoltaic cell and module technology have been well understood for many years and produced in quantity by companies, such as Sanyo/Panasonic, Hitachi, PVGS, BSolar, Yingli, and LG. While manufacturers are already producing bifacial modules, there is slow adoption into the market place due to a deficiency in standardized testing and modeling techniques used to predict the performance of bifacial systems. As such, Prism Solar conducted a multi-variable, multi-site testing program to determine the impact that common installation variables have on the yearly energy output of its bifacial solar modules. The effects of the module’s minimum height ratio, tilt angle, and ground albedo on the annual energy output were studied through direct field measurement. Based on these results, a best-fit model that links these variables to the annual energy output is presented. We believe this is the largest single collection of bifacial experiments presented to date, and one of the first general bifacial energy models publicly disclosed for general use. In addition, a comparison of the results of using this best-fit bifacial energy yield model derived by the authors with third-party bifacial data is also presented; this serves to validate the authors’ model and adds to the utility of this paper by presenting and combining multiple sources of bifacial data.