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[EnergyPlus_Support] Re: space cooling load calculation for each contributor?

Hi Michael,

Having just read your reply - I'm gutted :)

I've been writing a graphical viewer for ESO files and need a
standard report which breaks space loads into separate FABIC, DIRECT
SOLAR, VENTILATION and INTERNAL components (ideally I'd like to
isolate sol-air and inter-zonal gains as well, but that's for
later).  This viewer also reads the output from a few other thermal
analysis tools and this kind of report is great for passive analysis
as it shows the relative percentage contribution of each to overall
loads on each space.

I've been having trouble interpreting the different variables and had
a support forum post almost ready to go - however reading your
comment suggests that it's not practical to do in EnergyPlus.

My draft post is as follows, it might be that I've mis-understood
what you were saying...


I figured I could start with:

  Fabric Gains = 'Zone Opaque Surface Inside Face Conduction Gain'
               - 'Zone Opaque Surface Inside Face Conduction Loss'
               + 'Zone Window Heat Gain'
               - 'Zone Window Heat Loss'

  Solar Gains = 'Zone Transmitted Solar'

  Ventilation Gains = 'Infiltration-Sensible Heat Gain'
                    - 'Infiltration-Sensible Heat Loss'

  Internal Gains = 'Lights-Total Heat Gain'
                 + 'Electric Eq-Total Heat Gain'
                 + 'People-Total Heat Gain'

Looking at the ESO file, 'Zone Window Heat Gain' is always greater
than 'Zone Transmitted Solar', so it seems obvious that you subtract
the solar gains from the transmitted to get a conducted/radiant
value.  However, the 'Zone Opaque Surface Inside Face Conduction
Gain/Loss' values also appear to contain a solar element.  You would
expect some sol-air effects, but for 'Zone Opaque Surface Inside Face
Conduction Loss' as well...

The solar element in both 'Zone Opaque Surface Inside Face Conduction
Gain/Loss' is far greater than I would expect with the different
materials I have experimented with (lightweight/heavyweight,
light/dark coloured, insulated/non-insulated), and shows virtually no
time-lag effects.  If anyone is interested (or thinks I'm a nut :), I
have a bunch of graphs and stuff showing all this on both very simple
1-zone and complex multi-zone models.

Can anyone help with the following questions:

1. Am I double counting some solar effect - such as the window frame
conduction (possible included in both the Opaque and Window heat
gains) ?

2. Is this solar effect in the 'Zone Opaque Surface Inside Face
Conduction Gain' solely a sol-air gain and the apparent solar effect
in 'Zone Opaque Surface Inside Face Conduction Loss' due to
conduction losses back out of windows ? If so, am I double-counting
some losses by using 'Zone Window Heat Loss' as well ?

3. Have I missed a more obvious or better way of isolating these
various elements ?

Any help on this one would be hugely appreciated as I'm kinda stuck
at the moment...

Kind regards,

// Dr. Andrew Marsh
// -- -- -- -- -- -- -- -- -- -- -- --
// Architectural Science Research Unit
// Welsh School of Architecture (ARCHI)
// Bute Building, King Edward VII Ave
// Cardiff, CF10 3NB, United Kingdom
// Tel: +44 (0) 29 2087 6207
// Fax: +44 (0) 29 2087 4926

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
<mjwitte@g...> wrote:
> EnergyPlus does not report component loads, because the heat
balance is done as
> a combined solution and the presence of one load can affect the
impact of
> another load.  The best way to determine this breakdown is to run
> simulations, first with just the envelope, then a run adding
infiltration, then
> add ventilation, and so on until all components are present in the
run.  If you
> change the order in which you add components, you may get slightly
> answers for the incremental component loads.
> Mike

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