The main challenge for modeling the performance of bifacial PV arrays and systems is the prediction of the irradiance hitting the array from the back side. Unlike the front side irradiance, which is usually assumed to vary little with position on the array, backside irradiance varies quite a lot with position, array design, and near field objects such as combiner boxes and racking. It is also influenced significantly by the albedo of the ground surface and other nearby surfaces.
There are two primary approaches to modeling the backside irradiance:
