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RE: [EnergyPlus_Support] Re: Vented PV Cavity
Tony,
I took a look at your files. I didn't succeed at running it because it is for E+ version 1.2.2. I would recommend moving to the current E+ version 1.3.
It seems that you have set up the PV modeling correctly. The basic wall construction here is uninsulated heavy concrete. Adding the PV here is increasing the wall's solar absoptivity from 0.7 to 0.97 so this could be why the cooling loads go up. This could also be one of those non-intuitive situations where adding the first bit of insulation can actually increase cooling loads. Remember that the added PV layer will also trap more heat at night and disconnect the underlying surface from cool night sky. You might try adding a different insulating layer to test expectations.
When using the external cavity model, the Construction should describe only the underlying surface and not the air gap and actual outer layer. The models will add these to the outside of the Construction. So in your file the walls with PV actually have twp layers of glass and air gap. The Material:Air object isn't really needed for the SURFACE:HEATTRANSFER: EXTERIORNATURALVENTEDCAVITY object (unless you really want double layers of glass and air gaps). Your value for the height scale for buoyancy looks like one for horizontal orientation, for vertical you might use increase this ¼ or ½ of the PV module height.
I hope this helps...
Brent
_____
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of lnttony
Sent: Monday, July 17, 2006 1:31 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Vented PV Cavity
Dear Brent Griffith,
Thanks for your reply!
In my case, there is a 3-story building. The west-facing facades at
the 2nd and 3rd floor were attached with vented PV panels.
Files related to the PV panels were uploaded ("For enquiry to
EnergyPlus.zip"). There are 3 word document files and the related
items were highlighted in green color. The other files can be opened
with TextPad.
The surface material of the exterior wall is "glass". You can see
the details (highlighted in green color) in "construction_material
(IDF file).doc".
If there is any more information I should give you, please ask me to
do so.
Thanks again.
Best Regards,
Tony LAM
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx <mailto:EnergyPlus_Support%40yahoogroups.com> , "Griffith, Brent"
<brent_griffith@...> wrote:
>
> It is difficult to say with out seeing the file, you could up load
it.
> Did you setup the electric load center and the PV generators and
set
> them to be integrated? What is the surface material like in the
> reference case?
>
>
>
>
>
>
>
> _____
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx <mailto:EnergyPlus_Support%40yahoogroups.com>
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx <mailto:EnergyPlus_Support%40yahoogroups.com> ] On Behalf Of lnttony
> Sent: Friday, July 14, 2006 8:57 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx <mailto:EnergyPlus_Support%40yahoogroups.com>
> Subject: [EnergyPlus_Support] Vented PV Cavity
>
>
>
> Dear all,
>
> I am modeling the building integrated photovolatic (BIPV) system
for
> the building facade. The photovoltaic (PV) panels were attached on
> the exterior wall with an air cavity between them. I want the PV
> panels to serve as a solar heat barrier. But I have problem in the
> heat gain on the facade.
>
> By using "OtherSideConditionsModel", I applied "Vented PV Cavity"
as
> the type of modeling used to determine boundary conditions.
> The "SURFACE:HEATTRANSFER:EXTERIORNATURALVENTEDCAVITY" object is
> used to describe the condition. However, there is no heat gain
> reduction for the underlying surface (i.e the exterior wall), even
> the required cooling energy for the corresponding zone is higher.
>
> Is there any mistake I have made? Or, is there any part I have to
> pay attention on?
> I would be very happy if I can receive any kind advice and help.
>
> Best Regards,
> Tony LAM
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
[Non-text portions of this message have been removed]
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