New error message from Near Shadings: "the axis tilts difference (6.0°) is too high."

[Michael Mc]

I utilize PVCASE outputs for shading scenes with trackers following the terrain. Since the new update, my shading scenes now receive this error.

"Several tracking fields defined in this scene. Field "Tracker #116" incompatible with field "Tracker #2068": the axis tilt difference (6.0°) is too high."

I'm receiving this error on the same shading scenes that did not receive this error before the latest update.

Is there anyway to resolve this issue?

[Stéphane]

Hello,

In the welcome screen of PVsyst you need to go to menu “Settings > Edit advanced parameters”.

Then search for “spread” and modify the following value:

 

Please keep in mind that the default value is 4° so increasing it can lead to results that are not entirely accurate, but at least you will be able to run the simulation. 

I hope this helps.

[Vamsee]

Hi Team,

This error seems to be there for every shading scene we do in version 7.4. When we use the same shading scene without any changes to the settings in version 7.3 the simulation runs.

Further if we are changing the default settings in the “Settings > Edit advanced parameters” we are getting very erratic results. Please can you rectify this bug. Further checking these tables manually is also a big challenge. 

When using version 7.4. 

 

When using version 7.3 (no change in any settings)

Edited January 4 by Vamsee

[Michele Oliosi]

This error message was meant to be present in the previous versions of PVsyst but a bug prevented it from appearing. This has been fixed in the latest version of PVsyst, that’s why you see the error message now.

 

To get rid of the error message, you can go to the advanced parameters, search for “spread” and modify the following value:

 

I hope this helps. Note that cases which have a very large tilt spread may induce a certain uncertainty in the transposition calculation.

[Vamsee]

Hi Michele,

If we change the axis tilt spread, we are getting very erratic results. Moreover, when we are using terrain following trackers we expect the tilt spread would not be even, the comparison is being done with far East tracker with far West tracker table which its expected to have this difference. Thats the sole reason we are doing the 3D shading to assess the impact on the EYA and electrical shading. Again, sometime even without changing this parameter the shading scene is running. Please can you look in to this issue.

[Michele Oliosi]

Hi,

The axis tilt spread does not impact the simulation results. It just lets you choose what is the maximum tilt difference in your scene.

If you don't want to see the error, you can just put a large value in the advanced parameter. Note, however, that the more differences you have in tilt in your scene (independent of the advanced parameter choice), the less the transposition calculation will be precise because of the averaging error.

[Rick]

Ability to model terrain following trackers more accurately is a major industry need right now.  Is PVsyst working on a solution for this?

[Michele Oliosi]

15 hours ago, Rick said:

Is PVsyst working on a solution for this?

We have some improvements that will help on our roadmap. In particular, in version 8, it will be possible to define multiple tracker orientations. This will be useful in case there are few distinct slopes (+ small variation, that will be averaged upon).

[laurahin]

On 1/12/2024 at 12:36 AM, Michele Oliosi said:

 

On 1/4/2024 at 7:44 AM, Michele Oliosi said:

To get rid of the error message, you can go to the advanced parameters, search for “spread” and modify the following value:

If the answer to this problem is to turn the error off, why have the message at all?  Maybe it should be a warning and not a prohibitive error?

Laura H.

Edited February 17 by laurahin

[Michele Oliosi]

On 2/17/2024 at 2:28 AM, laurahin said:

Maybe it should be a warning and not a prohibitive error?

100% agreed. We have a ticket to address this.

[jonipa]

On 1/12/2024 at 9:36 AM, Michele Oliosi said:

Hi,

The axis tilt spread does not impact the simulation results. It just lets you choose what is the maximum tilt difference in your scene.

If you don't want to see the error, you can just put a large value in the advanced parameter. Note, however, that the more differences you have in tilt in your scene (independent of the advanced parameter choice), the less the transposition calculation will be precise because of the averaging error.

How is the GlobInc parameter calculated in theses cases of large tilt spread? Is it the incident radiation on the average tilt plane? Is the average tilt plane calculated as a weighted average?

[Michele Oliosi]

PVsyst uses the average plane orientation for transposition calculations in an “averaged orientation” such as with trackers on a complex topography.

[JNutter]

Hello,

Understanding that it appears that this is something in the works for Version 8, what is the current recommendation regarding modeling sites with significant sloping and/or variations in topography. Do you recommend relaxing the "Tracking: maximum axis tilt spread" and "Max. tilt for the Bifacial 2D model"?

Additionally, can you provide some detail on how PVsyst determines the "averaged orientation" and do you have any recommendation for analyzing the uncertainty introduced by modifying the tilt limitations?

[Michele Oliosi]

Yes, it is okay to relax the corresponding thresholds. Indeed, there is no alternative, currently. However, please be aware that the uncertainty will depend on how good the “average geometry” is a good approximation.

The averaged orientation is currently an average of the axis azimuths and tilts, done separately. This works well for small angle differences, but is not so robust for large differences in either tilt or azimuth. For fixed tilts, the same is true for the plane azimuths and tilts.

Modifying the tilt limitations does not increase the uncertainty per se. What increases it is if the 3D scene is a situation that does not match the “average geometry” well. We do not have any general use tools to estimate the increase in uncertainty related to the averaging, at the moment.