IAM Models and Photovoltaic Energy Yield Simulations

The Incidence Angle Modifier (IAM) in photovoltaic (PV) modules is a relationship between the incident ray on a surface and the normal to this module surface, which causes optical losses in PV modules and consequently in PV systems. There are different directional models that describe the behavior for different angles of incidence with an assigned normalized value. These models have been implemented in SISIFO, an open and free PV simulation software developed by the IES-UPM. A simulation exercise, extended to static and tracked PV arrays, has been carried out with the aim of understanding the impact of the IAM losses and the compatibility between the different models. To quantify the losses associated with IAM, spectral effects and the presence of soiling in the locations are ignored but they could be seamlessly incorporated into the current simulation tool. The annual IAM losses calculated with the different models allow us to find correspondences between the models studied in the impact of the annual losses on global irradiance and its components. Using these values, the annual IAM losses calculated with the different models are between 1 to 3.5% in static systems and less than 1% in tracking systems.