BIPV ventilated facade

[RM_Sintef]

Hi,
I was wondering what is the best way to modelling a ventilated facade with integrated PV panels in WUFI (1D and/or 2D). What are the most important parameters to be careful about?

I only found a discussion topic about this: viewtopic.php?p=2790#p2790
which is from some years ago and an interesting article, which unfortunately is only in German:

Bludau, Ch., Kölsch, Ph.: Verschattung von Holzflachdächern - Holz-Flachdächer: Neue Forschungsergebnisse zu Dachterrassen und Verschattung durch PV-Module. 5. Internationaler Holz[Bau]Physik-Kongress 20.–21.03.2014, Leipzig


Thanks in advance.

[Christian Bludau]

Hi,

for the ventilated facade mainly the temperature of the surface and the air exchange rate is from interest. As the PV elements probably have a dark surface, I would set the corresponding values for the radiation absorption and emission. So something like absorption index 0,8 and emission index 0,9.
Further the explicit radiation balance should be used.

Probably my paper concerning shading will not help you much, as this is handling the shading by pitched solar panels. In your case the panels are integrated, so thats not the typical shading case in my eyes, as a ventilated facade always is somehow closed by something non transparent. Thats the reason I would more handle that like a cladding or something similar.

I would set up that as follows

• Apply the PV as sd-value in the boundary conditions - tight if there are no gaps ore some effective values if there are
• Air gap with ventilation source
• Underlying assembly

For the ventilation source there is not much literature on how to set it. If the gap is well ventilated, values about 200 1/h may appear. I would calculate without ventilation, with a low value (maybe 1/h) and a high value (maybe 200/h) and see, how big is the influence on your construction. If you can find a certain value, you have to estimate, if that can appear depending on your openings.

[RM_Sintef]

Hi,

Thanks for your answer!
I will start building the model and come probably back with more doubts/questions afterwards.
Luckily, this is a real project and we have some measurement data of T and RH that we can use to compare simulation results and real data. Unfortunately, the air velocity in the air gap is not being measured, so we have to make some assumptions. I will try with your suggestions.

Could the use of WUFI 2D (instead of WUFI 1D) be of some help for modelling some parameters in this kind of simulations ?

[Christian Bludau]

If you are mainly interested in the cavity itself, WUFI Pro is sufficient. If you like to have a look on the behavior of the studs for example, you can do that with WUFI 2D.

Christian