V7.3.1 diffuse shade on trackers - issue with tracker selection

[Debbie]

Hi PVsyst team,

I really appreciate the speed of the tracker shading analysis in this version, and the new interface for diffuse shade losses.  However, I noticed that sometimes when the central tracker is selected, or I select a custom tracker, it does not automatically select the adjacent trackers for the "shading mask".  See screen capture below.  I have found that I need to try selecting a few different trackers until I get one where the mask includes trackers on both sides.  If I run the model with the selection that does not include shading trackers on both sides, it significantly impacts the results.  I'm not sure why this happens.  Perhaps it has to do with the tilt of the trackers?  These have variable N-S tilts because of terrain.  Perhaps if the tilt between adjacent trackers varies too much they don't get selected?

Thank you,

Debbie

(example where the selected tracker did not cause the neighboring trackers to be selected)

 

[Michele Oliosi]

Hi,

On 1/13/2023 at 10:57 PM, Debbie said:

Perhaps if the tilt between adjacent trackers varies too much they don't get selected?

Yes this is likely the cause.

In fact the "central tracker and mask" algorithm will somtimes fail, depending on the details of the scene, this is why we left the option of selecting "all trackers". If your computer can run it, it is the recommended option.

We shall improve the central tracker and mask selection algorithm in the future.

[laurahin]

Were all trackers always used in past versions of PVsyst?

[laurahin]

Were all trackers always used in past versions of PVsyst?

We're having a problem where the "automatic" selection gives a bad result because it chooses a tracker on the edge of the array layout.  This can cause a difference of as much as 2% in the losses.   We suspect the issue is that we have broken arrays with many trackers, so that the number of trackers is large and it's easy for the "central tracker" selection to be on an edge.  So the new treatment may save computational time, but now we have to check the choice of "central tracker" every time we set up a project.

[Michele Oliosi]

Actually the "automatic" selection is the historical way that was used in previous versions. We added the window for people to be able to have more control on the choice of trackers, while being able to use the "old" way.

It became clear we had to propose other ways when we noticed the issue you point out.

The related help page
https://www.pvsyst.com/help/tracking_diffuse.htm