Project design > Bifacial Systems > 2D Bifacial model conditions

The 2-dimensional models for the bifacial contribution are naturally applicable to the "unlimited sheds" and "unlimited trackers" situations. Nonetheless, they may also be used in conjunction with a 3D scene, under some conditions ensuring the regularity of the arrangement of tables or trackers. If these conditions are not fulfilled, PVsyst will display the error message "your PV system is not suited for the bifacial 2D model computation".

"Fixed tilted plane" orientation with shading scene

•The (horizontal) pitch between the tables has to be regular enough. PVsyst internally computes the RMS deviation on the pitches between all neighboring tables in the scene. The resulting value must then lie below a threshold set by default at 0.4 m. The threshold can be modified in the advanced parameters, by changing the value "Pitch RMS limit for bifacial 2D models". The threshold is four times the value of the advanced parameter.

•The table heights must be homogeneous across the whole scene. PVsyst will require tables to have a difference in heights of at most 1 cm or 1%. Note that the height can be found in the PV table edition window, or under "width" in the window "List and management of objects".

•There must only be one single orientation. In some cases, it is possible to group orientations by increasing the tolerance in the "Orientations management tool".

"Tracking, horizontal axis N-S" orientation with shading scene

•The (horizontal) E-W pitch between the trackers has to be regular enough. PVsyst internally computes the RMS deviation on the pitches between all neighboring trackers in the scene. The resulting value must then lie below a threshold set by default at 0.4 m. The threshold can be modified in the advanced parameters, by changing the value "Pitch RMS limit for bifacial 2D models". The threshold is four times the value of the advanced parameter.

•The tracker widths must be homogeneous across the whole scene. PVsyst will require tables to have a difference in widths of at most 1 cm or 1%. Note that the width can be found in the tracker edition window, or in the window "List and management of objects".

•The average axis tilt must lie below a threshold given by default of 2°. The threshold can be modified directly in the advanced parameters, by changing the value "Max. tilt axis for the bifacial 2D model".

Note on modifying the thresholds

The different limits set by default ensure that the model is applied only in situations where its results will be accurate. Although it is possible to circumvent some of these limits, this will also mean that the bifacial contribution to your PV production may suffer from some inaccuracies, due to working with an idealized model using only average values.