[Equest-users] equest and energy plus outputs
Joe Huang
yjhuang at whiteboxtechnologies.com
Fri Apr 29 01:56:17 PDT 2011
Please note that the link for my paper should be
http://www.whiteboxtechnologies.com/downloads/SimBuild2006_EPlusDOE2_translatorF.pdf,
not what was written below. Sorry for the mistake.
Joe
Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
Joe Huang wrote:
> I did not think my previous reply to Deepika would engender so much
> traffic on this topic, but after reading through the various posts
> I feel compelled to add further comments because I think there's been
> some misunderstanding or misperceptions abou comparing results
> between two programs, in this case, specifically EnergyPlus and
> eQUEST or DOE-2:
>
> 1) Several people (some even in private e-mail) have mentioned
> looking at the BESTTEST or SP-140 test runs that are repeated
> everytime there's a new EnergyPlus release. Those simulations are
> extremely simplified test cases, mostly of one-zone models designed to
> test fundamental heat transfer algorithms - the impact of solar gain,
> wall heat loss, thermal mass - across various programs. These test cases
> do not begin to address the dynamic conditions found in any real
> building, particularly not a large commercial building.
> Unfortunately, it's
> these interactions between the transient loads and the HVAC system
> response that will color or dominate the resultant energy numbers.
> In my opinion, a far more revealing test suite would be either the CEC
> Title 24 certification test suite or even the ten DOE-2 sample runs,
> where the models are of realistic buildings with typical systems and
> operating controls (for more details on the Title-24 certification
> test suite, please see my SimBuild 2006 paper, available for download
> at http://www.wbt/downloads/SimBuild2006_EPlusDOE2_translatorF.pdf ).
> My point is that the BESTTEST/SP140 results may show that the basic
> heat transfer algorithms in the programs are (reasonably) consistent,
> but that doesn't mean the programs will show similar results when used
> to model actual buildings, particularly not commercial buildings with
> intermittent operations and complex HVAC systems and controls.
>
> 2) Several people sounded incredulous that the differences could be as
> much as 50%. I can only say that if you try it, i.e., model the same
> building (preferably not a shoebox with a window on one side :-)) with
> two programs, you will quickly appreciate the difficulty. Actually,
> from my vantage point, 50% does not sound exaggerated at all. I just
> got back from a simulation workshop in China, where differences of
> several hundred percent were reported comparing programs such as
> DOE-2.1E, TRNSYS, and DeST, a Chinese program, even though they were
> looking only at residential apartment buildings. The dirty secret in
> our field is that even if you asked two reasonably competent modelers
> to model the same building with the same program, they're apt to come
> up with quite different results. Doing it with two different programs
> just makes that match exponentially more difficult.
>
> 3) Several people (including me) have alluded to the difficulty in
> making the inputs consistent. I cannot emphasize this enough. All
> programs have hundreds of hidden defaults or assumptions that aren't
> necessarily transferable. My paper highlights nine of the most
> prominent ones found in the CEC project, e.g., DOE-2 models drapes as
> a SHADING-FRACTION, EnergyPlus models them as internal shading surface
> requiring 10 inputs; DOE-2 allows a distribution loss in the water
> loop, EnergyPlus didn't; DOE-2 degrades the wind speed in its
> infiltration calculation, EnergyPlus didn't; DOE-2 allows a thermostat
> throttling range; EnergyPlus didn't; etc., etc. (some of these
> limitations in EnergyPlus may have been corrected since 2007). Since
> I had access to both the DOE-2 and EnergyPlus source code at the time,
> I believe I did the most thorough job possible in matching inputs, but
> even so I had to "punt" in numerous places (no drapes, infiltration at
> raw wind speed, etc.) for the sake of an "apples-to-apples"
> comparison. Yet, even under these ground rules, I was still seeing up
> to 40% differences in heating loads in some cases.
>
> 4) So which are the correct, or better, results? I really can't say.
> When you look into the codes, there is room for questioning the
> solution techniques in both programs. Just by dint of having seen many
> more DOE-2 results, I tended to regard them as the "conventional
> wisdom", but then conventional wisdom could always be wrong. Maybe we
> have been overestimating the heating energies in California all these
> years. After reading through this litany of problems, some may want to
> throw up their hands and say either, "it's hopeless" or even, "who
> cares?". That to me is a wrong and dangerous response, because it
> ultimately damages the credibility of simulations. Going back to
> China, many experts there have become disenchanted and distrustful of
> simulations, and are calling for it NOT to be used for compliance
> calculations. The same can happen here, as well. So, I think we need
> to spend more effort to have a better sense of the relative
> performance of different programs, and what is the "ground truth".
> Doing a parallel set of calibrated simulations against good monitored
> data would be a good start.
>
> Joe
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 108D
> Moraga CA 94556
> yjhuang at whiteboxtechnologies.com
> www.whiteboxtechnologies.com
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
>
>
>
> Paul Diglio wrote:
>> Mizra:
>>
>> Thank you for the time it took you to send the results of your study
>> to the forum. Some of the top simulation firms in my area use Energy
>> Plus and I was confused when other people claimed a higher
>> discrepancy rate than you modeled.
>>
>> Paul Diglio
>>
>> *From:* Mirza Sajjal <Mirza.Sajjal at BuroHappold.com>
>> *To:* Pasha Korber-Gonzalez <pasha.pkconsulting at gmail.com>; deepika
>> khowal <deepika.khowal at gmail.com>
>> *Cc:* equest-users at lists.onebuilding.org; energyplus_support
>> <EnergyPlus_Support at yahoogroups.com>
>> *Sent:* Thu, April 28, 2011 5:55:09 PM
>> *Subject:* Re: [Equest-users] equest and energy plus outputs
>>
>> This was a little study I did out of curiosity last year, and the
>> results between eQUEST (v3.63) and EnergyPlus (v4.0) matched quite
>> well (~1.4% difference). All the schedules, zone areas, surface areas
>> were exactly the same (I checked), but I also chose a simple system;
>> PTAC units for the comparison. I believe when I was doing this I had
>> checked the performance curves that were being used in EnergyPlus and
>> they matched the eQUEST curves.
>>
>>
>>
>> I assume the results will begin to differ when the systems become
>> more complicated, but even then I believe if both models are
>> calibrated to match as much as possible the results shouldn’t vary
>> significantly (assuming all systems are native to the programs and
>> we’re not creating work-arounds i.e. DOAS in eQUEST using dummy zones
>> or the like).
>>
>>
>>
>> (FYI, the geometry was ported over to EnergyPlus through a tool I
>> wrote using Excel and VBA, but it’s a messy process)
>>
>>
>>
>> Following are some of the results and graphical outputs:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> *____________________***
>>
>> *Mirza Sajjal*
>> Engineer
>>
>>
>>
>> Buro Happold
>> 100 Broadway
>> New York, NY 10005
>>
>> Tel: +1 212 334 2025
>>
>> Direct: +1 212 616 0380
>>
>>
>>
>> *From:* equest-users-bounces at lists.onebuilding.org
>> [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of
>> *Pasha Korber-Gonzalez
>> *Sent:* Thursday, April 28, 2011 4:46 PM
>> *To:* deepika khowal
>> *Cc:* equest-users at lists.onebuilding.org; energyplus_support
>> *Subject:* Re: [Equest-users] equest and energy plus outputs
>>
>>
>>
>> As I understand it--Energy+ is free-ware in it's raw form. I guess
>> I was wrong to make an assumption that Deepika is using it without an
>> interface. If this is not the case it might explain such a
>> variance in results. When I model in DOE-2 raw form---it is so
>> much harder for me to manage my data and inputs in my head and
>> such----I was not born to be a programmer, and it gives me nightmares
>> from struggling to pass FORTRAN so many years ago...ugh.
>>
>>
>>
>> Therefore, I haven't looked at E+ myself for a very long time and
>> purchasing or putting out the cost for the user-interface programs is
>> not as desireable as using the eQuest free-ware. or the future
>> CANQuest free-ware (future SI version).
>>
>>
>>
>> BUT-- I know that E+ is supposed to have some great capabilities in
>> which we are limited with DOE-2 (to an extent.) Has anyone else
>> had the time and desire to compare these program engines more closely
>> recently? Also--why is it so difficult to "match" systems in eQuest
>> and E+....forgive my blase'-ness, but isn't a pkgd system a pkgd
>> system...a pkgd system??? :)
>>
>> Pasha
>>
>>
>>
>>
>> On Thu, Apr 28, 2011 at 11:39 AM, deepika khowal
>> <deepika.khowal at gmail.com <mailto:deepika.khowal at gmail.com>> wrote:
>>
>> So based on my analysis, there is a difference of about 10% in
>> results of equest and E+. I would believe that because there are
>> certain parameters which are very difficult to match.
>>
>> this seems reasonable to me.
>>
>>
>>
>> On Thu, Apr 28, 2011 at 9:09 AM, John Aulbach <jra_sac at yahoo.com
>> <mailto:jra_sac at yahoo.com>> wrote:
>>
>> I am sure EnergyPlus is a fine and well thought out program (consider
>> the sources and fine people involved). However, since I am in
>> production mode (and don't have time to create a model in two
>> different programs-who pays for THAT), I chose to migrate to eQuest
>> after DOE-2.1 A, B, C, D, and E. There are plenty of resources to ask
>> questions of, the program started out in Windows (didn't need "add
>> ons"), and gives me a 3-D rendering on the building immediately.
>>
>>
>>
>> I dealt with 20 years of "raw" DOE-2, where I didn't know what my
>> building really looked like (until Joe Huang came along with BDL
>> Draw..). So I would need at age (you guess..) to not relearn an
>> entirely new program and stick with what I had learned over the past
>> 25+ years.
>>
>>
>>
>> John R. Aulbach, PE, CEM
>>
>> Senior Energy Engineer
>>
>> *Partner** **Energy*
>>
>> 1990 E. Grand Avenue, El Segundo, CA 90245
>> W: 888-826-1216, X254| D: 310-765-7295 | F: 310-817-2745
>>
>> www.ptrenergy.com <http://www.ptrenergy.com/> |
>> jaulbach at ptrenergy.com <mailto:%7C%20jaulbach at ptrenergy.com>
>>
>>
>>
>>
>>
>>
>>
>>
>> *From:* deepika khowal <deepika.khowal at gmail.com
>> <mailto:deepika.khowal at gmail.com>>
>> *To:* Paul Diglio <paul.diglio at sbcglobal.net
>> <mailto:paul.diglio at sbcglobal.net>>
>> *Cc:* equest-users at lists.onebuilding.org
>> <mailto:equest-users at lists.onebuilding.org>; energyplus_support
>> <EnergyPlus_Support at yahoogroups.com
>> <mailto:EnergyPlus_Support at yahoogroups.com>>
>> *Sent:* Thu, April 28, 2011 8:56:34 AM
>>
>>
>> *Subject:* Re: [Equest-users] equest and energy plus outputs
>>
>>
>> As Joe and others mentioned, its really difficult to create all
>> parameters same in both softwares.
>>
>> I am still working on it .
>>
>> For ex, which system should I use in equest as equivalent to unitary
>> system in E+?
>>
>> I understand its difficult to match every input and hence, getting
>> same results is very tricky.
>>
>> Thanks all for their inputs
>>
>>
>>
>> On Thu, Apr 28, 2011 at 4:54 AM, Paul Diglio
>> <paul.diglio at sbcglobal.net <mailto:paul.diglio at sbcglobal.net>> wrote:
>>
>> I thought E+ is a free program? I would be interested to hear from
>> anyone who has used Google SketchUp and the Open Studio Plug-in to
>> generate a 3D view in E+.
>>
>> I would like to hear more about the discrepancies between eQuest and
>> E+ from those who use both programs.
>>
>> Paul Diglio
>>
>>
>>
>>
>>
>> *From:* Pasha Korber-Gonzalez <pasha.pkconsulting at gmail.com
>> <mailto:pasha.pkconsulting at gmail.com>>
>> *To:* deepika khowal <deepika.khowal at gmail.com
>> <mailto:deepika.khowal at gmail.com>>
>> *Cc:* energyplus_support <EnergyPlus_Support at yahoogroups.com
>> <mailto:EnergyPlus_Support at yahoogroups.com>>;
>> equest-users at lists.onebuilding.org
>> <mailto:equest-users at lists.onebuilding.org>
>> *Sent:* Thu, April 28, 2011 1:27:44 AM
>> *Subject:* Re: [Equest-users] equest and energy plus outputs
>>
>>
>>
>> Hmmm- an energy plus model showed 50% less energy use (EUI) than
>> eQuest? Did you use the same weather files? (i.e. convert the EPW
>> you used in E+ to .bin and use the same weather file in eQuest?)
>>
>>
>>
>> If this is truly the case, this is unsettling as a simulator.
>> Wouldn't it be safer for our clients to error on the conservative
>> side and give the eQuest results instead of the E+ results?
>>
>>
>>
>> Also--if this is the case, then what is the market advantage to
>> spending thousands of dollars on E+ software rather than use the
>> FREE-ware eQuest program??
>>
>>
>>
>> I'd appreciate any commentary to help me "see the light" of this
>> topic. And if Deepika is willing to share a visual of his energy
>> results output, I'm super curious to see what it is showing...
>>
>>
>>
>> Good question/good info...thanks,
>>
>> Pasha
>>
>>
>>
>> Korber Energy Consultants
>>
>>
>>
>>
>>
>> On Wed, Apr 27, 2011 at 7:11 PM, deepika khowal
>> <deepika.khowal at gmail.com <mailto:deepika.khowal at gmail.com>> wrote:
>>
>> Thanks Joe
>>
>> Even I realized the same thing. the total energy use in Energy plus
>> was almost 50% less than equest.
>>
>> If this is the case, who would you know that you model is working fine?
>>
>>
>>
>> On Wed, Apr 27, 2011 at 6:06 PM, Joe Huang
>> <yjhuang at whiteboxtechnologies.com
>> <mailto:yjhuang at whiteboxtechnologies.com>> wrote:
>>
>> I was involved in a two year project 2005-2007 to convert the Calif.
>> Energy Commission's Title-24 certification suite of building tests
>> from DOE-2.1E to EnergyPlus. There are some areas where it's
>> difficult to get comparable inputs due to differences or limitations
>> in the models. The differences between the two programs varied a lot
>> depending on the building, weather, and HVAC system. For the CEC
>> certification suite of 160 runs, cooling results were more
>> consistent, within 10% in most cases, with EnergyPlus almost always
>> on the high side; for heating, the differences were much greater,
>> sometimes with EnergyPlus being 40-60% lower than DOE-2.1E. I have a
>> 120-page report on this comparison, but haven't bothered to put it on
>> the Web.
>>
>> Joe
>>
>> Joe Huang
>> White Box Technologies, Inc.
>> 346 Rheem Blvd., Suite 108D
>> Moraga CA 94556
>> yjhuang at whiteboxtechnologies.com
>> <mailto:yjhuang at whiteboxtechnologies.com>
>> www.whiteboxtechnologies.com <http://www.whiteboxtechnologies.com/>
>> (o) (925)388-0265
>> (c) (510)928-2683
>> "building energy simulations at your fingertips"
>>
>>
>>
>> deepika khowal wrote:
>>
>> HI All
>> I am trying to create same model in equest and energy plus to see
>> whether i see same results and just to validate my simulation files.
>> has anyone done this before?
>> I would like to know what is the % difference in both software outputs?
>> Thanks
>> Deepika
>>
>> ------------------------------------------------------------------------
>>
>>
>>
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