Near Shading Losses Vertical E/W system

[RobertH]

I have a small problem concerning near shading losses for a vertical biafacial system E/W oriented.

I planned to optimize pitch distance according to near shading parameters but the numbers I get do not seem realistic. Even for high pitch distances of 25 m I still have around 5% near shading losses.

Even if I set the pitch distance on e.g. 1000 m I get near shading losses of around 1.5%.

The system has a height of 2.2 m, tilt 90°, azimuth -90°. I tried both, simulating it as unlimited sheds and modelling it in the 3D near shading scene.

I hope someone can help, thanks in advance.

Robert

[Katinka89]

Hello,

We have the same problem:
a vertical system with a pitch of 10m leads to near-shadings of -19% (that seems quite high to us).

Does anyone have any idea what this could be due to?

Thank you very much!

Janne

[Michele Oliosi]

Hi, this is actually related to the albedo component.
You can check that by setting the project settings albedo to a lower value. This will in principle decrease the near shadings proportionally, if the pitch is large enough for mutual shadings to be negligible.

Note that albedo shadings are extrapolated from the shadings at the lowest sun height, so they are very sensitive to having another row, even very far.

In the case of a bifacial system, I would not be too worried, because the loss of albedo due to mutual shadings is in principle mostly compensated by the ground reflection on the front side. This latter contribution is present in the case of the bifacial model being activated.

[laurahin]

As a follow-up question regarding bifacial modules in a vertical orientation:  Will PVsyst eventually know to treat a vertical bifacial module as having two "front" sides, such that near shading is computed for both sides?  In recent tests, I found that the only shading I could put on the back side of the module came from the standard bifacial setting "rear shading."  If I set this to zero, there is no near shading on the back side of the modules even though it occurs on the front.  (This shading comes from the neighboring rows of modules, not shading objects.)  Nevertheless, the "rear" POA irradiance is always lower than the front side irradiance, giving an asymmetry for front and rear irradiance, even on clear days.  This I cannot explain.

I do see that treatment of vertical modules is mentioned in the PVsyst v. 8 documentation, but it's not entirely clear what this will include.  Modeling vertical module configurations seems to be an important development now.

Thanks!