Pitch RMS limit for bifacial 2D models - Bifacial project with different pitch distances

[Michail Katsivelakis]

Dear Team, 

In the advanced parameters section there is the Pitch RMS limit for bifacial 2D models, with a default value of 0.10m.  More specifically, working on a project with different pitch distances, the bifacial ability of panels is not able to be applied on different pitch distances. Increasing the limit mentioned above from default value to 0.4m value, the simulation is able to conducted. 

Could you please explain exactly the impact of different values of this parameter (Pitch RMS limit for bifacial 2D models) and the results that we were expecting with the default value (0.1m) in comparison to other values? How the expected P50 production is affected from this change? 

Is there any specific reason behind the selection of the default value (0.1 m) of the Pitch RMS limit for bifacial 2D models? 

Thank you in advance. 

Kind Regards

[Bruno Wittmer]

This parameter is a threshold for the RMS value of the pitch distribution that PVsyst finds in the 3D drawing.

The bifacial models in PVsyst are an approximation that is valid for identical long rows with constant pitch (spacing). If the simulation uses a 3D drawing of the PV system, then PVsyst will check if this drawing comes close to this idealization. For this purpose, it will calculate the RMS of the pitch distribution, and if it finds a value larger than the threshold, it will issue an error message, and the simulation will not be possible.

The default value of 0.1 m is not based on a specific study. The error message is meant to remind the user that the system which is being simulated, is not fully compatible with the idealized assumptions, and therefore an additional uncertainty of the bifacial contribution in the simulation results is to be expected.

So far there is no study that quantifies the increase of uncertainty in the simulation results as a function of the RMS of the pitch distribution. It will become possible to address this, once we have a more sophisticated bifacial model, which will be based on the 3D drawing. This is in work and will still require several months of development.

[MNWild]

Instead of throwing a cryptic error, may I courteously propose the software spits out a dialog box that contains all those words from your June7 response?

[laurahin]

If you adjust the RMS so that no warning is generated even though you have multiple pitches in your scene, what value of pitch will the simulation use?  I assume that PVsyst can still only use one value in its calculations.

[Michele Oliosi]

@laurahin You are right, only one pitch is being used atm: the average pitch.