PVsyst Emulation
Comparisons of results from PVsyst and SolarFarmer transposition models have revealed a couple of areas where we think we know what PVsyst is doing, but we don’t agree with it.
Validating SolarFarmer’s calculations against PVsyst is desirable. However, if we chose to have our calculations deviate from PVsyst, then validating calculations will become difficult. We can’t change PVsyst’s behavior in the short term, but also do not wish to adopt calculations in SolarFarmer that we consider incorrect. It has been decided to include a “PVsyst emulation mode” in SolarFarmer that introduces the PVsyst features to the irradiance calculation, so that validations of downstream calculations can proceed without these differences coloring the results.
Details of the PVsyst emulation mode are included in the model sections in this document. It should be noted that the PVsyst behavior has been derived from reverse engineering PVsyst results so there is some uncertainty if this is exactly matching the PVsyst implementation.