Shading Bug

Hello Paul,

The 3D shading calculator is producing some very weird results which don't make any sense. I have uploaded the file along with a few screenshots. I have tried deleting subarray 1, duplicating subarray 2 and changing it to one, closing the 3D calculator, and restarting SAM. I had this issue on another file and one of the above methods worked.

Here is the information about the version I am using:

Version 2016.3.14, 64 bit, updated to revision 4

SSC Version 160: Windows 64 bit Visual C++ Sep 22 2016 03:34:19
wxWidgets 3.0.2 on Windows 7 (build 7601, Service Pack 1), 64-bit edition
Internet connection method: none
Display: 1920 x 1080, magnification 1x

Cheers,
David

Hi David,

Thank you for including those files with your question.

Based on the name of the weather file you used, I assume you are modeling a system in Australia on the Sunshine Coast near Brisbane, so I used the Brisbane weather file that comes with SAM for my tests.

In your 3D shading scene, you defined two active surfaces, and each one is a separate subarray. If you do that, you should also define two subarrays in SAM on the System Design page so that the 3D shade calculator can correctly assign the shading losses to the correct subarray.

If the location is in Australia, I would expect an azimuth value around zero rather than around 180 degrees so that the array is facing the equator. I think that might make the diurnal shading results look more reasonable.

Does that help?

Best regards,
Paul.

Paul,

I see my failure to activate the 2nd subarray, but that didn't fix the radical shading issues. The location about at the edge of the Tropic of Capricorn, so while you are correct that it should point north for optimal operation, the cost of solar panels here is such that it makes more sense to install more panels than install tilt frames and less panels.

Regardless of the azimuth, the tilt is only 5 degrees, so the shading should not be as bad as what the calculator shows. The panels are on the same azimuth and tilt, so their results should be around the same, but they are nowhere close. In addition to this, subarray 2 is lower than subarray 1, so if anything, it should have more shading on it due to the building beside it. However, subarray 1 is totally shaded in the afternoon for the entire year except for when it suddenly drops from to 7% shading from 100% shading a couple of random times in the afternoon.

I have modeled this all in sketchup and the results for subarray 1 do not make any sense, and I believe could only be attributed to a bug. I will email you the SAM model I remade from scratch to get away from this bug, and the shading is showing a reasonable result.

Regards,
David

Hi David,

There is a bug in the 3D shade calculator that is caused by overlapping objects in the scene. If any two objects overlap, the shade analysis algorithm does not work properly.

I think you can fix your shading scene by making the boxes you used for the towers on the roof shorter so they extend to the roof instead of through the roof all the way to the ground.

Please try that and let me know whether that seems to solve the problem.

Best regards,
Paul.

From my quick test, it seems to have worked. I will keep an eye out for it in any new files I create.

Thanks Paul!