Backtracking results in near shading losses

[Funerus]

Hello everyone,

 

I've been recently introduced to the concept of backtracking. Based on what I understood, the trackers are tilted in reverse to solar tracking to avoid mutual shadings between PV rows when the solar elevation is low. In that case, I would expect that the near shadings losses would be 0 (assuming that there aren't any other surrounding obstacles in the scene such as trees).

I simulated a project with bifacial PV modules in a N/S horizontal single axis tracker configuration. The elevation of each tracker row does slightly differ as indicated by the topography. However, currently, we cannot simulate such a scenario, thus we assume that all trackers are of the same elevation, orientation, and size. Considering this brief explanation, what could be the issue causing the near shadings looses to be non-zero when using backtracking?

 

If interested, I can share additional details,

Any feedback is welcome,

Regards

[dtarin]

Diffuse shading

[Funerus]

Thanks dtarin!

I thought that near shadings consisted only of beam irradiance losses, but now that I see the loss diagram there isn't any quantity indicating diffuse shadings; thus, they must be combined. 

[dtarin]

Near shadings consists of beam, diffuse, circumsolar, and albedo losses. @PVsyst, circumsolar is missing from the help menu, see attached.