This model computes the incidence angle modifier coefficients based on the Sandia method.

Inputs

 

Outputs

 

Algorithm

Only the beam component Θ_Eff,D is treated here. Furthermore, it was observed that the best fit of the IAM coefficients for both FSLR anti-reflective coating (ARC) and regular non-ARC modules shows an oscillation below incidence angles of 34°, as shown in Figure 32.

 

Figure 32. Comparison of Custom IAM Profile with Sandia Polynomial, Showing Oscillation for Incidence Angles Lower than 34°

 

 

To avoid this artifact, the polynomial is clipped to force the IAM to unity, as follows:

Reference

King, D. L., Kratochvil, J.A., Boyson, W.L., Measuring Solar Spectral and Angle-of-Incidence Effects on Photovoltaic Modules and Solar Irradiance Sensors. Sandia National Laboratories, Albuquerque, NM, September 1997.