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.
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.
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.