Performance of Bifacial PV Arrays With Fixed Tilt and Horizontal Single-Axis Tracking: Comparison of Simulated and Measured Data

Compared with standard monofacial photovoltaic (PV) systems, the simulation of the energy yield of bifacial PV systems is more challenging since the impact of factors such as the installation height, the ground albedo, shadowing of neighbored rows, the diffuse irradiance fraction, and the PV module design is more pronounced. Therefore, many academic institutions as well as companies are currently working on the development of suitable modeling tools that allow an accurate energy yield prediction of bifacial systems. In this article, we present the results of energy-yield simulations of bifacial PV systems with fixed tilt and horizontal single-axis tracking (HSAT) in comparison to their monofacial counterparts using a tool that has been developed at ISC Konstanz. In addition, the simulated data are compared with measured results. The energy yield of fixed tilt bifacial systems is simulated as a function of the number of rows and number of modules in a row as well as a function of the installation height. The simulated data have been compared with measured data obtained using a PV system with continuously changing tilt angels. The accuracy of the simulated data is shown to be from +/-0.1% to +/-4% depending on the tilt angle of the bifacial modules. In addition, the energy yield of bifacial HSAT PV systems have been simulated and compared with measured data for a bifacial HSAT system in Chile. In this comparison, the use of ray tracing instead of the view factor (VF) concept for modeling of the rear irradiance reduced the deviation between simulated and measured gain significantly. Therefore, the approach of using VF-based calculations for the front irradiance and ray tracing for the rear irradiance was then used to evaluate different bifacial system configurations in comparison to monofacial ones. Especially, the influence of a variation of the ground coverage ratio on the energy yield for various monofacial, bifacial fixed tilt, and HSAT systems was studied.