Calculation of TArray

[ManPC]

Hi all,

I want to know how PVSyst calculates TArray (for monofacial and bifacial modules)

As I can see in: https://www.pvsyst.com/help/thermal_loss.htm

0) This is the formula that uses PVSyst. Is it right?

1) Tcell is TArray?

2) U = to the value introduced by the user (for instance U=29 W/m2K) , or U is calculated (ignoring the fixed value introduced by the user)? 

3) Alpha is always 0.9?

4) Ginc: Which variable is?

     Ginc = GlobInc ?

     Ginc =GlobEff ?

     Ginc = (GlobInc + GlobBak) ?

     Ginc = (GlobInc + BifacialityFactor * GlobBak) ?

5) Effic is always 10%?

 

I enclose different calculations I have made and the differences between calculations

 

Thank you in advance for your valuable support.

[Michele Oliosi]

0) right
1) Yes, in fact we iterate the formula twice, because the efficiency depends on the temperature.
2) U = Uc + Uv * WindVelocity, and the values are kept as entered by the user.
3) usually, but it may be different (it is defined in the module, you can find it under "Additional data" / "Secondary parameters"
4) GlobEff
5) efficiency is the module PV conversion efficiency, not jut 10%. See point 1, we start with the efficiency at ambient temperature, and then iterate the formula.

[JaSc]

Hello Michele,

thanks for your answer.

Could you specify which calculation method you use for step 5) ?
 

 

I found several methods but not sure which one is correct. Can I calculate it out of hourly output values?

 

Thanks for your help!

[Bruno Wittmer]

The PV module efficiency is the power generated by the PV module, divided by the power reaching the module in form of light. 

The generated power is calculated with the single diode model for the given external conditions (irradiance and temperature), while power in form of light is just the irradiance times the surface of the PV module.