Minimum saturation current

[smeredith]

In PVsyst's documentation, it's stated that due to computational problems, PVsyst requires that the saturation current of a module at STC (I0_ref) be at least 0.01 pA, or 1e-14 A.

However, after playing around with the single-diode parameters of modules in PVsyst, it seems like in reality the minimum saturation current of a module is 0.01 nA, or 1e-11 A.  This is 1000 times greater than what is stated in the documentation.  Is the value quoted in the documentation an error?  Or is there something else going on here?

Attached is a screenshot of the documentation text for reference.

[smeredith]

After posting this, I realized the documentation may be referring to the saturation current evaluated at the actual cell temp, rather than the reference value.  Is that the case?

[potentialmin]

The documentation is not necessarily wrong—it refers to the minimum runtime value of I₀(T) during the simulation, not the user-entered reference value. The difference you see is because PVsyst applies a higher minimum value to I₀\_ref internally to avoid floating-point instability during IV curve calculations.

[André Mermoud]

You mention that   "PVsyst requires that the saturation current of a module at STC (I0_ref) be at least 0.01 pA, or 1e-14 A."

 I don't see where you found this statement in the documentation.  Probably you have "added" the condition  at STC   (otherwise the documentation should indeed be corrected.

Please observe that the Io value is extremely dependent on the temperature. It varies by a factor of about 20'000 when passing from 25°C to -10°C. In the PVsyst database, we try to choose parameters which ensure that the saturation current Io(T) remains > 0.02 pA downto a temperature of -10°C. 

See the help  https://www.pvsyst.com/help/physical-models-used/pv-module-standard-one-diode-model/temperature-behaviour-correction.html#temperature-correction-on-gamma, especially the Nb2 paragraph.