Shading effect - Fixed Tilted Plane vs Unlimited sheds

[mary08]

I am using PVsyst V6.17 and I wonder which is the difference between using “Fixed Tilted Plane + Linear Shading” or “Unlimited sheds” regarding the shading effect.

I have simulated the plant with this two options, by means of the same number of sheds, and I have obtained shading losses of 1.9% for the first option (“Fixed Tilted Plane + Linear Shading”) and losses of 2.3%for the second option (“Unlimited sheds”). I would like to know how the program manages to obtain these results.

Thank you very much.

[André Mermoud]

These are quite different calculations.

The "Unlimited sheds" option uses a simple analytic shading factor calculation, which supposes that the sheds are very wide (neglects the edge effects).

The 3D shadings are based on the full 3D geometry calculation, but can use (according to your choice) a pre-calculated shading factor table, which may induce interpolation uncertainties.

Both use also an integral for the diffuse and the albedo, which also depend on these calculation modes.

The difference between both calculatioons is 0.4% in your case, which may be considered as acceptable.

We usually observe a little bit lower difference, but please check that you did use the exact similar geometry (i.e same "inactive bands" for example).