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[EnergyPlus_Support] Re: Vented PV Cavity
Dear Brent,
Thanks for your advices!
I will convert the files for the current E+ version 1.3 after I
solve my problem.
I have tried using other insulating materials instead of the heavy
concrete. In addition, I have also tried increasing the height scale
for buoyancy, effectiveness for perforations with respect to Wind
(Cv) and discharge coefficient for openings with respect to bouyancy
(Cd). However, the resulting annual electricity consumption is not
improved. The annual cooling electricity is almost the same as the
case without vented BIPV. I think attaching the exterior naturally
vented BIPV can reduce the annual cooling electricity. Besides,
better PV efficiency can be achieved.
I have uploaded the construction file (exterior wall-> WALL-1) and
OthersideConditionModel file. I am not sure I set the height scale
for buoyancy, Cv and Cd correctly. You can also see my exterior wall
construction.
Is the "SURFACE:HEATTRANSFER:EXTERIORNATURALVENTEDCAVITY" object not
preferable for vertically mounted BIPV?
I am also interested in "CONSTRUCTION WITH INTERNAL SOURCE" for
PVSpandrlPanel. But, will the efficiency be lower by using this
model because of higher temperature behind the PV panel?
Thanks.
Tony
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Griffith, Brent"
<brent_griffith@...> wrote:
>
> 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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