kyuminlee Posted January 2, 2018 Share Posted January 2, 2018 The help file for PVsyst 6 has the following expression for the Rsh dependence on irradiance:Rsh = Rsh(Gref) + [ Rsh(0) - Rsh(Gref) ] · exp(-Rsh exp · (G / Gref))As Rsh(Gref) is the Rsh value at the reference irradiance Gref, equating G to Gref should lead to Rsh = Rsh(Gref).However, Rsh(G=Gref) = Rsh(Gref) + [Rsh(0) - Rsh(Gref)] * exp(-RshExp) = Rsh(Gref) * { 1 + [Rsh(0)/Rsh(Gref) - 1] * exp(-RshExp) } which is not equal to Rsh(Gref) unless Rsh(0) = Rsh(Gref).For the generic module "Poly 285 Wp 72 cells", where Rsh(Gref) = 550 Ohm, Rsh(0) = 2000 Ohm, and RshExp = 5.5, the exponential expression as shown in the help file leads to Rsh(G = Gref) = 555.9 Ohm, about 1% higher than Rsh(Gref) value of 500 Ohm. Pmp-wise this is not a big effect (~0.1W), but still non-zero.I wonder if the help file description is consistent with the actual Rsh calculation within PVsyst 6? To me it would be more plausible if a separate term "RshRef" was being used internally whereRsh = RshRef + [Rsh(0) - RshRef] * exp(-RshExp * (G/Gref)) andRshRef = [Rsh(Gref) - Rsh(0)*exp(-RshExp)] /[1 - exp(-RshExp)]Then you actually get Rsh = Rsh(Gref) when G = Gref. Link to comment Share on other sites More sharing options...
André Mermoud Posted January 5, 2018 Share Posted January 5, 2018 You are quite right. PVsyst uses indeed the expression you have calculated, with a RshRef as you propose. I have to change this in the help. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now