Skip to content

Backtracking on a hill

The backtracking strategy is based on the relationship between pairs of neighboring trackers.

PVsyst's backtracking implementation uses a common tracking angle for all trackers within an orientation group. It requires that the tracker array is perfectly regular, with the same width/pitch ratio, and set up on flat horizontal terrain.

In the case of irregular tracker heights—on a hill, for example—no single tracking angle allows a perfect backtracking strategy. There will always be either some shading or irradiance "lost" on the ground. This is illustrated in the figures below.

Backtracking_DiffAltitude

When the backtracking angle is calculated for trackers A and B (at higher altitude), a shadow on tracker C (at lower altitude) is unavoidable. Here, half the tracker is shaded.

Backtracking_DiffAltitudeB

Conversely, when tracker B is lower than tracker A, tracker C does not have an optimal tilt for collecting the full available sunlight. A better tilt would intercept more light—this corresponds to a loss due to the cosine effect.

Implementation

PVsyst does not currently implement advanced slope-aware backtracking strategies and cannot optimize individual tracker positions.

When using backtracking on a hill with PVsyst, be aware that the tracker positions might be sub-optimal and make sure to follow these steps:

  • Activate the electrical shading calculation (according to strings or module layout), as there might still be shading in your scene.
  • Run your simulation without backtracking and compare the yields. Be sure to compare the energy produced and not the PR, as explained here.
  • You may check the shading in your scene using the shading animation and tweak the backtracking angle calculation using the Backtracking Management tool.
  • Some trackers using complex tracking strategies may consume a non-negligible amount of energy to move. This is not taken into account by PVsyst by default, but it can be added to the auxiliary consumption.