Question about Single Diode Model

[Liam Hanna]

I am trying to import a .PAN file into a script and calculate Voc at a user specified irradiance and temperature. I am struggling with two of the inputs for the single diode function: mu_gamma and I_o_ref. Where do these two values come from? I am not seeing them in the PAN file, do they need to be calculated separately? Thanks

[cwh...@sandia.gov]

In the PAN file, do you see muGamma? I don't know which line provides I_o_ref (PVsyst documentation calls it IoRef). I suspect PVsyst infers IoRef from the Voc value in its PAN file.

Cliff

[Liam Hanna]

No I do not see muGamma. Attached is a PAN file for reference. How would you infer ioref from Voc?

PVObject_=pvModule
  Version=7.26
  Flags=$00100043

  PVObject_Commercial=pvCommercial
    Comment=www.firstsolar.com   (USA)
    Flags=$0041
    Manufacturer=First Solar
    Model=FS-6470A-P/FS-6470A-P-I Sep2021
    DataSource=Manufacturer September. 2021
    YearBeg=2021
    Width=1.245
    Height=2.024
    Depth=0.049
    Weight=35.0
    NPieces=0
    PriceDate=21/09/2021 00:00
    Currency=EUR
    Remarks, Count=5
      Str_1=Frame: anodized aluminum frame
      Str_2=Laminate: glass-polyolefin-glass laminate
      Str_3=.
      Str_4=.
      Str_5=.
    End of Remarks=.
  End of PVObject pvCommercial

  Technol=mtCdTe
  NCelS=264
  NCelP=1
  NDiode=1
  GRef=1000
  TRef=25
  PNom=470.0
  PNomTolLow=0
  PNomTolUp=5
  Isc=2.61
  Voc=224.3
  Imp=2.458
  Vmp=191.1
  muISC=1.044
  muVocSpec=-628.0400000000001
  muPmpReq=-0.32
  RShunt=14000
  Rp_0=14500
  Rp_Exp=5.5
  RSerie=3.641
  Gamma=1.198
  D2MuTau=0.15
  VMaxIEC=1500
  VMaxUL=1500
  Absorb=0.9
  ARev=3.2
  BRev=3.92
  RDiode=0.01
  VRevDiode=-0.7
  AirMassRef=1.5
  CellArea=87.7
  SandiaAMCorr=50.0
  RelEffic800=0.28999999999999027
  RelEffic600=0.029999999999996696
  RelEffic400=-1.2800000000000034
  RelEffic200=-5.600000000000005

  PVObject_IAM=pvIAM
    Flags=$00
    IAMMode=UserProfile
    IAMProfile=TCubicProfile
      NPtsMax=9
      NPtsEff=9
      LastCompile=$B18D
      Mode=3
      Point_1=0,1.0
      Point_2=30,1.0
      Point_3=55,0.99
      Point_4=60,0.98
      Point_5=65,0.96
      Point_6=70,0.92
      Point_7=75,0.85
      Point_8=80,0.72
      Point_9=90,0.0
    End of TCubicProfile
  End of PVObject pvIAM

  OperPoints, list of=4 tOperPoint
    Point_1=False,800,25.0,0.28999999999999027,0.00,0.000,0.000,0.00
    Point_2=False,600,25.0,0.029999999999996696,0.00,0.000,0.000,0.00
    Point_3=False,400,25.0,-1.2800000000000034,0.00,0.000,0.000,0.00
    Point_4=False,200,25.0,-5.600000000000005,0.00,0.000,0.000,0.00
  End of List OperPoints
End of PVObject pvModule

[cwh...@sandia.gov]

That's a thin-film module, so PVsyst says it uses the D2MuTau value in some manner to determine muGamma. Unfortunately, the PVsyst help files are not explicit on what's being done. I think you could assume muGamma = 0; usually, the temperature adjustment to the diode factor is quite small.

To get IoRef, solve for Io in the diode equation setting voltage to Voc, current to 0, IL to the reference photocurrent (I'm not clear where that is in this PAN file), Rsh and Rs to their reference values (RShunt and Rserie). If you have to compute reference photocurrent, you can do that as Isc * (1 + Rserie/Rshunt).

I'm becoming less and less confident that I understand these PAN files.

Cliff