Discrepancy in temperature coefficient of voltage

[Aparna]

Hi

I encountered this issue while examining a PAN file provided by a manufacturer. The PAN file was imported into PVsyst version 5.68. The PVsyst screen for PV module definition shows the value for muVoc as -153mV/C whereas the print out of the PAN file from PVsyst shows the value of muVoc as -123mV/C.

An explanation for this discrepancy would be very helpful. Has anyone else encountered such a problem?

Thanks,

Aparna

[André Mermoud]

The nuVco may either be the result of the one-diode model (and it depends itself on the temperature), or you can specify the value given by the manufacturer.

See our FAQ How to adjust the Voc temperature coefficient ?

[Aparna]

Thank you for you response.

The issue I am facing is that the PVsyst screen display and the pdf of the same PAN file are showing two different values of temperature coefficient of voltage. I will attach my screenshots here.

Could you please tell me why this is happening?

[Jen H]

I've faced a similar problem when using PVsyst 6.37

I have to identical pan files but they originate from different sources. In PVsyst, it says that muVoc for both of them should be, as expected, identical. However, when I "copy to table" and export the pan file details into a spreadsheet, the mu.Voc values are different. I attach the an image of the pan file details spreadsheet and PVsyst screenshots for reference.

 

spreadsheet and screenshots

Did either of you find out the reason for this? I'd be curious to know :) Thanks!

[André Mermoud]

In both module, you have the same parameters (namely Rserie and Rshunt) and therefore the muVco calculated by the model is identical.

NB: The muVco value slightly varies with these parameters, especially Rserie.

But in your export to EXCEL, the column muVco corresponds to the value specified by the manufacturer. This value may have been specified differently.

See our FAQ How to adjust the Voc temperature coefficient ?

[Jen H]

Ah, thank you for clearing that up!