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When defining the backtracking strategy, PVsyst has to identify two reference trackers, to determine the relationship between them (tracker width and pitch). During the simulation, the backtracking angle calculation will be the same for all trackers, based on this reference.

"Native" PVsyst scenes with arrays of trackers

When defined within PVsyst, the 3D scenes are usually defined with arrays of trackers.  

In this case the pitch is specified in the array's definition. When there are several arrays, most of the times the GCR is the same for all arrays. If this is not the case, PVsyst will choose as reference the array with the highest width/pitch ratio (GCR).

Even if there were some arrays with a lower GCR, the backtracking will not produce mutual shadings.

Imported 3D scenes with independent trackers

In the external CAD software, the trackers are defined independently, without gathering them as arrays. Within PVsyst, this is also the case when you fill a zone.

Therefore we have to identify a pair of two reference trackers as reference for  the full backtracking calculation.

This is the objective of the tool "Backtracking management", available in the menu "Tools" of the 3D editor.

 

This identifies and lists the pitch between all neighbor trackers, and sorts them as decreasing pitch.

You have simply to select one tracker (among the higher GCR) and the tool will propose (select) the neighbour tracker to be associated (in orange).

There is a relationship between this tool and the 3D scene: the chosen reference tracker appears in green, and its neighbor in orange. This allows to visually check that the chosen tracker is really representative of the full set of trackers.

The detailed parameters involved in the backtracking calculation are shown in the frame "Heliostats parameters" on the left.

By deselecting the reference pair of trackers, one may also enter custom values.

Extended analysis

Furthermore, this tool allows refined analysis of your system.

If you have an irregular system, with some different pitches, and you are not satisfied with the "maximum pitch" choice, you can choose another pair of tables. The tool will show all the tables with a higher pitch in red. For these tables the backtracking will not be perfectly operational: there will be some possible mutual shadings. If you accept this situation, you have to activate the Electrical shading effects in your simulations.