Bridging the Gap: Insights into Backtracking-Angle Related Discrepancies between Estimates and Actual Performance in Large-Scale Photovoltaic Plants

Energy yield overestimation in large-scale photovoltaic (PV) simulations is a recurring issue that affects the accuracy of performance predictions. Analysis of SCADA data from four single-axis PV plants in different regions revealed systematic deviations between simulated and measured tracker angles during backtracking periods, prompting an investigation into the role of the estimated tracking irradiation gain (TIG) in these discrepancies. These deviations seemed to be linked to empirical corrections implemented to mitigate shading caused by terrain unevenness, which introduces elevation differences between tracker rows. While these adjustments reduce shading losses, they also modify the trackers' optimal tilt, lowering incident irradiance and ultimately reducing energy yield. A reverse-engineering approach was used to derive an equivalent correction model, based on a theoretical reduction in the effective inter-row spacing. When implemented in simulation tools, this correction produced TIG values 7–10% lower than those predicted under ideal flat-terrain conditions, leading to annual energy yield overestimations of around 3%. The results underscore the importance of accounting for realistic tracking behavior in energy yield simulations to improve both technical accuracy and the financial predictability of PV projects.