Back-tracking with "Tracking fields" at different elevations

[ThomasP]

The real world system that is to be modelled consists of trackers at different elevations due to the slight variations in the topography of the terrain. The trackers will be following a back-tracking strategy that assumes that the terrain is perfectly flat.

To model this is in PVsyst:

1) A "Ground object" has been imported into the PVsyst shading scene from Helios based on the site survey.

2) Trackers have been grouped into "Tracking fields" consisting of 2 or 3 trackers.

3) Each "Tracking field" has been placed at different elevations depending on the elevation of the terrain under this "Tracking field".

4) Back-tracking has been enabled on all "Tracking fields".

5) Both the "Ground object" and "Tracking fields" have been defined to cast shadows.

6) The shading loss calculation is defined to be calculated according to the module layout.

In the specific case where the real world system is following a back-tracking algorithm that assumes the terrain to be flat would the above approach be suitable?

[André Mermoud]

PVsyst doesn't allow backtracking with different tracker's altitudes.

Even if you define pairs of trackers for the calculation of the backtracking angle, this doesn't ensure that you will have a valid backtracking between you pairs of trackers: you can have shades, or backtracking misorientation state without necessity.

This is not a particularity of PVsyst, but the real world.

There may eventually be a solution for keeping backtracking conditions with uneven terrain, but this implies evaluating a different orientation for each tracker, and the calculation becomes extremely complex, as all the tracker's orientations are interdependent.

A company proposes such an algorithm, which requires informatic learning techniques, and doesn't guarantee the absence of shades in any situation.

[ThomasP]

Let me clarify my question.

The real world system has trackers following a backtracking strategy calculated based on only the location of the solar farm, the time, date and the inter-row pitch (i.e. the terrain is assumed to be flat). Therefore, this is the same backtracking movement modelled in PVsyst.

The real world system however is not on a perfectly flat terrain. For a tracking system follow the above backtracking strategy this would result in a greater shading loss than what is modelled for a flat terrain. How can this extra shading loss be simulated in PVsyst?

Can "Tracking fields" that cast shadows and placed at different elevations simulate this additional shading loss that is a result of the terrain not being flat?

[André Mermoud]

You can indeed try to define an array of 2 trackers for the calculation of the backtracking angle. And add individual trackers at different locations and altitudes to your 3D scene.

In this case the backtracking will not be correct, you will have some mutual shadings. However these shadings will be calculated quite correctly by the simulation. You will have to perform the electrical shadings calculations as well (in mode "according to module strings" should be sufficient).