[Bldg-sim] Cooling Load in EnergyPlus
Ery Djunaedy
ery.mailinglist at gmail.com
Fri Mar 4 16:18:11 PST 2011
Nope, not that I know of. Before this kind of summaries is implemented
in EPlus, I think scripting is the way to get faster results. SQLite is
really a powerful result analysis tool. What you describe below can be
implemented relatively easily with some SQL statements.
We have been trying to come up with a better way to communicate this
kind of output to the client. I will share the results to this list once
we finalize how to do this in EPlus.
Thanks,
Ery
On 03/04/2011 05:04 PM, Karen Walkerman wrote:
> Thanks Ery.
>
> It helps. It's just slow. What I love about LS-C is that it's fast.
> Do you know of a way to get a grouped report for all walls within a
> particular zone. So instead of having hourly output for every wall in
> a space, you would have one for each: exterior walls, interior walls,
> etc? This would make reviewing these outputs much faster!
>
> Thanks!
>
> Karen
>
> On Fri, Mar 4, 2011 at 6:52 PM, Ery Djunaedy
> <ery.mailinglist at gmail.com <mailto:ery.mailinglist at gmail.com>> wrote:
>
> Hi Karen,
> Same here, I always use LS-C when I use eQuest. Just adding the
> ventilaton load, then you will have the peak load. Its always fun
> to compare this number with what the mechanical engineer has.
> I said earlier, in EnergyPlus it is not nicely formated like LS-C.
> It does not mean you cannot have it. You can force EPlus to show
> the numbers. The internal gains are the easy ones, the windows are
> also relatively easy, the last pieces are the opaque "conduction"
> and the ventilation load. Which is not difficult.
>
> The problem is what peak to report? You will have the peak of the
> total gains, which will happen at a different timestep then the
> peak of the cooling load. And these two, in turn is different with
> the zone sizing report.
>
> I personally use the zone sizing reports as the peak loads, and I
> will get all the details by running the designday run with
> schedules consistent with the design day schedule.
>
> Hope this helps,
>
> Ery
>
> On Fri, Mar 4, 2011 at 12:00 PM, Karen Walkerman
> <kwalkerman at gmail.com <mailto:kwalkerman at gmail.com>> wrote:
>
> Hi Ery,
>
> Thanks for this explanation. I have been struggling with this
> topic as well as I do more modeling in Energy Plus. However,
> there is one thing that you did not address above. While
> DOE2's LS-C report may not match exactly to what systems are
> seeing as far as loads, it does give an easily readable report
> which allows you to check your inputs. I review it quite
> often as a quality control check for my models. It also
> allows me to target energy saving measures, and helps me
> explain to clients why certain changes might make sense for
> their building. For example, one client might be interested
> in increasing roof insulation, but if they have a multi-story
> building with a relatively small roof, and lots of wall area,
> it makes more sense for them to reduce thermal bridging in
> their wall construction. Having a model-generated report
> makes this process much faster for me.
>
> Do you have any suggestions with regards to Energy Plus of
> ways to achieve the above goals with the currently available
> reports?
>
> Thanks.
>
> --
> Karen
>
> On Fri, Mar 4, 2011 at 12:26 PM, Ery Djunaedy
> <ery.mailinglist at gmail.com <mailto:ery.mailinglist at gmail.com>>
> wrote:
>
> 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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