[Bldg-sim] Cooling Load in EnergyPlus

Ery Djunaedy ery.mailinglist at gmail.com
Fri Mar 4 09:26:08 PST 2011


Sandeep,

This is what I call a legacy topic from the DOE2 era. You better search 
the posts in EnergyPlus support mailing list. Search for "cooling load 
component", and you will find an interesting discussion.

In summary, you will not find a cooling load component report in 
EnergyPlus nicely formatted a-la LS-C report in eQuest/DOE2.

If you try to match the total gains v.s. the cooling load for every time 
step, then you will be in for a long ride. Take the solar radiation 
gain, for example. The GAIN for a particular time step is not 
necessarily converted into cooling LOAD at the next time step. If your 
building is thermally massive, then the delay plays an important role 
and it could be hours before the solar radiation GAIN becomes an actual 
LOAD as seen by the thermostat. Do not forget about this, if you try to 
match the cooling load report with the total gains.

If you are talking about peak cooling load, then you will need to focus 
on the zone sizing report. Calculating the gains component is easy 
because the schedule is always 100% on. You just need to quantify the 
ventilation load.

Please note that the report suggested by Paul below is the convection 
report. I imagine that you would expect a conduction report? EnergyPlus 
zones technically cannot see conduction through opaque surfaces, in the 
sense of A*U*DeltaT. They can only see convection and radiation. In 
fact, if you try to match A*U*DeltaT for external wall with this report 
(Surface Int Convection Heat Rate) then you will have a hard time 
explaining. If you keep this in mind, the differences can be easily 
explained.

Cheeers,

Ery

On 03/04/2011 07:07 AM, Paul Raftery wrote:
> Hi Sandeep,
>
> A full list of the available output variables are given in the .rdd 
> file (it is one of the files output from the simulation). Simply copy 
> the relevant line from that file into your .idf (or .imf) file, rerun 
> the simulation, and the new variable(s) will be output to the .csv and 
> .eso files.
>
> e.g. Adding this line to the input file  will give you the convective 
> heat gain from all interior surfaces in your model.
> Output:Variable,*,Surface Int Convection Heat Rate,hourly; !- Zone 
> Average [W]
>
> Regards,
> Paul
>
> On 4 March 2011 13:50, Sandeep Kachhawa <sandeep.kachhawa at gmail.com 
> <mailto:sandeep.kachhawa at gmail.com>> wrote:
>
>     Dear All
>     Can we get the individual break-up of cooling load in
>     *EnergyPlus*? Internal loads (People, Equipment & Lighting),
>     Infiltration loads and Window  gains are available but the *gians
>     from Walls and Roof is missing. *Surely EnergyPlus does calculate
>     all the above loads to size the Cooling Equipment but there is no
>     such specific output.
>     Regards
>     Sandeep Kachhawa
>

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