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PostPosted: Sat Nov 13, 2021 7:52 pm 

Joined: Mon Nov 04, 2019 4:04 pm
Posts: 5
From PVSyst help:
Backtracking on a hill
The backtracking strategy is based on the relationship between pairs of neighbour trackers. See the description of the backtracking strategy.
It requires that the tracker's array is perfectly regular, with the same width/pitch ratio, as well as altitude.
The altitude differences will necessarily be the same for all trackers (i.e. if not horizontal, the tracker array will be on a same flat E-W inclined plane).
With different and irregular altitudes like on a hill, the Backtracking strategy is geometrically impossible, neither in PVsyst nor in the reality.
I want to do a sensitivity analysis on the performance of trackers vs the East-West slope of the terrain. Since the backtracking on a hill cannot be simulated, I created a flat E-W inclined plane, descending toward East, I put down the trackers on the inclined plane with "Automatic altitude", I re-aligned the baseline slope to zero (since this changed after the Automatic Altitude" command) and I set the backtracking on.
All the trackers have the same pitch and the same elevation difference; I believed a backtracking strategy could be simulated in this case.
But I still have relevant mutual shading in the afternoon.
scene 1.jpg
scene 1.jpg [ 256.86 KiB | Viewed 1195 times ]
scene 2.jpg
scene 2.jpg [ 583.32 KiB | Viewed 1195 times ]
scene 3.PNG
scene 3.PNG [ 6.96 KiB | Viewed 1195 times ]
Do there is a workaround to avoid this? Is this simulation possible?

I also tried adding a couple of additional trackers in the same shading scene, and putting them at the same elevation and with a little higher GCR with respect to the others, and set the backtracking based on this couple, but did not work: I don't have shadows between the sample trackers but I have it for the trackers in the sloped plan... even decreasing a lot the distance between the reference trackers I still have shadows in the sloped plane.

Looking at the shading animation, we can see that the backtracking starts also in the afternoon, but too late, when the mutual rows shadow has already started

PostPosted: Sun Nov 14, 2021 2:56 am 
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Joined: Tue Oct 18, 2016 3:31 am
Posts: 448
Backtracking is based on sun height/angle for the site's location. It does not backtrack according to terrain conditions. Check your results with irradiance optimization checked under orientation menu to see if that helps.

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