Trackers

Trackers refer to single-axis trackers. Similar to rack systems, a tracker system is like a family of trackers of different lengths.

Single-axis trackers in SolarFarmer are placed on a flat (but not necessarily horizontal) plane over the terrain - if the terrain is undulating, some trackers will be higher than others. The acceptable tolerances of the height of the tracker axes are controlled in the properties described below.

Tracker System Properties

Again, the Module Length and Module Width properties should be the same as the module specification that you intend to use with the tracker system. Click the 'Use a module specification to set module dimensions...' button to use the dimensions of an existing module specification.

Here you define the axis settings:

  • Min/max heights above ground - the minimum and maximum heights that the axis can be from the ground. As described above, as the trackers are all laid out in a flat plane, some may be higher than others. These parameters control the acceptable tolerances.

  • Max rotation angle - the maximum rotation angle (in degrees) from the horizontal that the tracker panels can rotate around the axis (up to 90°).

  • Max tilt along axis - the maximum angle between the axis (along the length of the trackers) and the horizontal that the trackers can be laid out. If the terrain is undulating the resulting plane may be at a steeper angle than is allowed.

You also define whether the backtracking algorithm should be used for this tracker system, along with some frame and module spacing values.

There is a cross-section diagram that is updated as up you update the properties to help you understand why validation issues arise -- for example it makes it easier to see if the tracker will hit the ground with the current settings:

Tracker Specifications

Press the 'Add' button to add a new tracker specification to the tracker system family.

You must add at least one Tracker Template (in the Tracker Template Properties panel in the bottom left) to the tracker system. Once you set the Length of tracker row property of this tracker template (the number of modules along the length of the tracker) you will see a visual representation of the currently selected tracker specification in the panel on the right.

Backtracking Options

You can choose to enable backtracking (when using the default tracker rotation algorithm) by checking the Enable backtracking check box:

Backtracking aims to minimize row-to-row shading between the rows of trackers when the sun is lower in the sky (early morning and late afternoon). Rather than continuing to follow the sun (which would lead to shading the trackers behind) the trackers go back the other way, avoiding shading. Both the distance between rows of trackers and the size of the trackers affect when and by how much the trackers backtrack.

The side-slope (shown in the layout regions table for a tracker layout region) can be integrated into the algorithm to maximize the efficiency of the backtracking angles. You can enable/disable this with the Use slope-aware backtracking option.

Tracker Rotation Algorithms

Default Standard Algorithm

There is a built-in standard tracking algorithm that will be used by default by SolarFarmer. This is based on two papers:

This calculates the rotation angle for optimum tracking. Backtracking can be enabled to reduce shading effects when the sun is lower in the sky near sunrise and sunset.

Custom Tracker Rotation Algorithms

SolarFarmer also allows you to specify your own rotation angles should you wish.

This is accomplished by the scripting functionality in SolarFarmer. See the Using custom tracker rotations example in the API and Scripting documentation for an example of how to do this.