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Module Low Irradiance Performance ?.

Lazare Fesnien

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When including a PV module in the PVsyst database, there is no real "validation".

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.

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

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