Using Measured Data for Bifacial Tracker projects

[BGiolitti]

Hello,

Which are the best irradiance values to accurately model a bifacial tracker system (grid connected) with measured data? We will have the following:

Global Horizontal Irradiance

Diffuse Horizontal Irradiance

Plane of Array Irradiance (front side tracking)

Back of Array Irradiance (rear side tracking)

Can a bifacial tracker system (grid connected) be modelled using measured Plane-of-Array irradiance?

Thank you

[André Mermoud]

You can indeed import the POA measured on your trackers. But be careful: this measurement is subject to the same mutual shadings on the diffuse part than the value calculated by the simulation (linear shading loss on the loss diagram). So this measurement is not really suited for a good simulation.

The best way is to use the measured Global horizontal. If you have also the diffuse at disposal, this is indeed the top for the accuracy of the transposition models.

Now the Rear side irradiance measurement is extremely delicate, as the reflected irradiance is not homogeneous behind the tracker.

In the present time this measurement is not useable as input for the simulation.

The relationship between this value and the GlobBack calculated by PVsyst is not well established.