How far to trust manufacturer PAN files?

[jacob]

Hello, I'm looking on opinions on what parameters in manufacturer PAN files I should be skeptical of. I'm thinking about this because I have noticed that manufacturer PAN files seem to have Iam curves that are more like a step function instead of a curve, but the one time I actually got a 3rd party test report the actual Iam curve was more inline with the PVsyst default value using the Fresnel AR coated model.

thanks

[dtarin]

IAM data is the easiest to identify. Low light data (if included) and resistances would be other items, but it is less obvious as to what is correct or not. They will have an impact on production if not properly accounted for.

[Lazare Fesnien]

Hi,

Most of the parameters are from datasheets. Some few parameters are not mentioned on the datasheets, and have to be evaluated.

The main "uncertain" parameters (not on the datasheets) are the Rserie and Rshunt.

These values determine the low-light performance of the PV module (relative efficiency as a function of irradiance, with respect to STC efficiency).

If we have independently measured data (provided by some few manufacturers), we can adjust the resistances values as function of the measurements. Otherwise PVsyst chooses a "default" value, fixed now at -3% @ 200 W/m2, which is close (or slightly below) the performance of most measurements we had received.

The problem is now that with modules of very recent technologies, the Series resistance is optimized (has a lower value), which produces a lower low-light performance.

So that with the default of -3%, PVsyst may have over-evaluated performances with respect to the reality.

We have valid low-light measurements from about 20 to 25 manufacturers. But not for all their production, just some few (usually rather old) models. The measurements received during the last 2-3 years are very scarce.

Many manufacturers now provide the PAN files by themselves to the final users. So that they can put the "uncertain" parameters as they like (usually for boosting the performances).

This is for the series resistance, but also for the IAM performance. Many manufacturers propose measurements which are – to our mind – completely irrealistic.

See our FAQ : https://forum.pvsyst.com/viewtopic.php?f=19&t=2690