shading loss % error?

[Spencer]

When you setup your sheds, say 20 at 25 degrees with a 7.3M spacing, 3 modules in landscape so 3M coil band width, with 9 diodes (3 per module), 156mm cells in the south of the UK, you would expect a figure of around 3%, which you get, when you run the simulation it comes up a7% and when you go back the shading graph is now shows 7%, which is not correct. If you load the project again the shade figure goes back to 3-4%, but then goes up again. I assume this is an error in the software?

The actual result is about right, but the radiation onto the collector gain from horizontal to 25 degrees is 21%, which is too high. I wonder if these figures are connected.

[Alexander.Nix]

I also noticed that if you run your report with no near shade model you get a higher KW/H per year than if you were to run a report with the same system with a near shade model (no shading objects) which reduces production significantly. These should match. I know there has been updates with tracking near shade models, but was that update applied to tracking systems with no near shade model?

[André Mermoud]

If you know all the results of the irradiance and shading calculations in advance, you don't need to use PVsyst.

Now I don't understand the fact that the shading drops, and then increases again, and how you obtained this. Please explain.

"I also noticed that if you run your report with no near shade model you get a higher KW/H per year than if you were to run a report with the same system with a near shade model".

I don't understand well. What is strange here ???

[Alexander.Nix]

André, I have sent you an e-mail with my phone number to discuss. I'll try to rephrase my question. I have a single axis tracker that I will be running two identical reports just to see if they match. One report will be using "Near shade model" (no shading objects except the tracker itself), and one will be using the standard "Orientation" (no shade model). I would have thought that the two report would match or at the vary least be close, but the production between the two have a delta of 44MW/H. So my question is why are they so different? If I do the same scenario with a fixed tilt system the MW/H do match. Any insight on this would be greatly appreciated.

[André Mermoud]

This is normal: even with backtracking you have a shading contribution on the diffuse.

Please see the FAQ How is calculated the Shading Loss on diffuse with tracking systems ?