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Re: [EnergyPlus_Support] Questions on report variables - Zone Load Components

Regarding reporting of zone load components . . .

There is currently no zone load component report in EnergyPlus  
similar to what DOE-2 had which separated the peak zone load into  
components such as conduction through walls, solar gains, internal  
loads, etc.  With the heat balance method in EnergyPlus, actual load  
components are not available which would add up to the peak sizing  
load.  For example, solar gains fall on one or more surfaces causing  
a rise in surface temperature.  Some of this rise in surface  
temperature increases the zone load immediately, but much of it is  
stored in the surface and becomes a load later, some of it may  
actually conduct back outside and never become a load, some of it may 
 radiate to another surface and become a load later.  At the same 
time  all of the other gains in the space are interacting at each 
surface.   So it is not possible to report true load components.  

It is possible to report many of the instantaneous heat gains in  
EnergyPlus.  This would not be helpful for a peak report since the 
loads components peak at different times than the gain, but it might 
be useful for a monthly summary component report.  Relevant variables 
would include:   

For windows: 

Zone Transmitted Solar[W] (transmitted solar only) 
Zone Window Heat Gain[W]  
Zone Window Heat Loss[W] 
(The previous two are net window heat gain/loss including transmitted 

For internal loads (people, lights, etc.): 

Zone-Total Latent Gain[J] 
Zone-Total Radiant Heat Gain[J] 
Zone-Total Convective Heat Gain[J] 
Zone-Total Visible Heat Gain[J] 
(the above are totals from all internal gains for the zone)

People-Radiant Heat Gain[J]
People-Convective Heat Gain[J]
People-Sensible Heat Gain[J]
People-Latent Heat Gain[J]
Lights-Total Heat Gain[J]
Lights-Return Air Heat Gain[J]
Lights-Radiant Heat Gain[J]
Lights-Convective Heat Gain[J]
Lights-Visible Heat Gain[J]
Electric Eq-Total Heat Gain[J]
Electric Eq-Radiant Heat Gain[J]
Electric Eq-Convective Heat Gain[J]
Electric Eq-Latent Heat Gain[J]
Electric Eq-Lost Heat Gain[J]

For infiltration and ventilation (only sensible loads are reported  

Infiltration-Heat Loss[J] 
Infiltration-Heat Gain[J] 
Ventilation-Heat Loss[J] 

For surface conduction: 

Surface conduction is a bit more complicated.  If you look at the  
convective gain to the zone air from the inside surface, this will  
include the effect of transmitted solar and radiant internal loads  
which will warm the inside wall surfaces.  If you look at the outside 
 surface heat balance, this includes the impact of convection from 
the  outside air or conduction from the ground along with solar 
incdident on the outside and long-wave radiation to the sky.  Since 
conduction is not  steady state, you cannot simply take conductance 
times delta T across  the surface.  It is probably best to conclude 
that surface conduction  is the remaining cooling load after 
subtracting off the solar and  internal gains.  If you wish to 
examine the surface temperatures, the  relevant report variables 
would be: 

Zone,Average,Outdoor Dry Bulb [C] 
Zone,Average,Ground Temperature [C] 
Zone,Average,Surface Inside Temperature[C] 
Zone,Average,Surface Outside Temperature[C] 
Zone,Average,Surface Int Convection Coeff[W/m2-K] 
Zone,Average,Surface Ext Convection Coeff[W/m2-K] 
Zone,Average,Opaque Surface Inside Face Conduction[W] 

The "Opaque Surface Inside Face Conduction" variable is supposed to 
be the conduction coming into/out of the inside surface heat balance, 
however, I need to check some details before I can say that for sure.

I hope this helps.  In a future release, we are planning to implement 
a heat gain component report as a standard report.

Mike Witte

On 3 Sep 2002, at 17:55, by way of Linda Lawrie wrote:

> I wonder if you can tell me which report variables (e.g. zone transmitted 
> solar, opaque surface inside face conduction, .....etc.) sum together to 
> get the zone cooling/heating capacity indicated in the zone sizing report 
> or in year simulation output.
> And there is glass solar, glass conduction, wall conduction, roof 
> conduction, underground conduction, internal conduction, people load, 
> lighting load, equipment load and infiltration load in the peak load report 
> of DOE2E. What are the report variables represent the above loads in the 
> EnergyPlus?
> Thanks!
> Lee

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