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How can I define a tracking system with backtracking on a hill?
https://forum.pvsyst.com/viewtopic.php?f=20&t=2416
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Author:  AndrĂ© Mermoud [ Fri Apr 22, 2016 11:06 am ]
Post subject:  How can I define a tracking system with backtracking on a hill?

In PVsyst, besides defining arrays of trackers, you can also define independent trackers (i.e. several objects with one only tracker), that you can distribute (in X,Y Z) as you like on your ground.
However these trackers have the constraint of having the same tracking parameters (i.e. same axis orientation, same tracking limits, etc).
PVsyst will compute the irradiance equally for each tracker (the orientation of all trackers is the same at a given time).

Backtracking with not regular systems
Now the backtracking strategy is closely related to the relative position between trackers.
In PVsyst, you can define it only if you have a set of at least 2 trackers (within a same tracking object) for calculating the backtracking angle with respect to the tracker's width and the pitch.
If you have uneven disposition (different pitches and/or altitudes), this backtracking angle will not be valid for the other trackers.
Therefore in this situation - and for the restriction of a same orientation for each tracker - the backtracking strategy doesn't make sense. A "normal" tracking system with mutual shadings will usually have better performances.

Backtracking calculation limitations
The backtracking calculations are a complex geometric calculation. Up to now we have only elaborated the algorithm for specific cases.
- With Tilted axis systems, the trackers should be organized in a "rectangular" way (i.e. no shift of one tracher with respect to its neighbour), and at the same altitude.
- With Vertical axis, we have not found the right algorithm up to now.
- With 2-axis trackers, the algorithm only acts on the azimuth backtracking. In this configuration there are several possible backtracking strategies, we have not implemented them up to now.
- The backtracking is correct within the tracking frames, but not from frame to frame.

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