PV module: define low-light data

This dialog allows to define performances of your module at different (G, T) conditions.

Usually (for Rserie determination) the Relative efficiencies at 800, 600, 400 and 200 W/m² and 25°C, with respect to the STC efficiency.

On the top right of the panel, you have different options:

o Define points

Simple definition

You simply define some operating points with Irradiance, Temperature, Relative efficiency.
These data may have been defined explicitely by the manufacturer in the database.

Complete definition

When checking "Rel. efficiency from STC", you can enter the full measured data (Isc, Voc, Imp, Vmp) at different conditions, and the program will calculate the relative efficiencies with respect to the STC of the module.

o Efficiencies

Shows a plot with the points you have defined, and the model with actual parameters.
The "Rel efficiencies" mentioned on the plot are the results of the model at 800, 600, 400 and 200 W/m².

o Effic errors

Shows the differences between your operating points and the model (different colors for different temperatures).
You can now modify the Rserie and Rshunt values - and optimize Rserie - and you will see the effects with respect to your specified points.

o ISC check

If you have performed a complete definitions with (Isc, Voc, Imp, Vmp), this option allows a check of the quality of the measured data.

According to most models, the ISC values should be perfectly proportional to the irradiance.

Therefore if the Isc/G values are not identical for each measured point, this indicates an error in the irradiance measurement (for example in the calibration of the filters used for the flash-test).

In this case you have a button Linearize Isc/G, which will slightly modify the "measured" G values in order to perfectly linearize this ratio. The relative efficiencies (normalized to these corrected G values) should be more correct, as they don't include a G measurement uncertainty.

Inversely the button becomes Retrieve Gref for coming back to the original data.

Again, the o Efficiencies and o Effic errors options allow to adjust the Rshunt and Rserie with direct visualization of the effect.