Good morning, I have a question about how PVsyst calculates the contribution from albedo. I have created an excel based model for irradiance, which includes direct (I_(d,surface)=I_(d,horizontal)/sin(α)*cos(θ)), diffuse (Perez) and albedo (R_surface=(ρ(1-cosβ)*G_horizontal)/2). When I compare this to PVsyst, I find minor differences with the direct and diffuse, but a significant discrepancy for the albedo contribution at sunrise and sunset. This discrepancy increases as the pitch of the module increases. Does PVsyst have extra components in the albedo calculation to the basic R_surface=(ρ(1-cosβ)*G_horizontal)/2 calc? Thanks, Tom
