[Equest-users] equest and energy plus outputs

[Varkie C Thomas]

DOE2 and EnergyPlus
 
I would like to see the results of DOE21E (or eQUEST / DOE22) and EnergyPlus compared with the following two projects.  They are similar to real projects but modified and simplified for teaching purposes.
 
Middle School & Community Center (150,000 sf approx.) 
http://bepan.info/proj-bldgs/p12-middle-school
 
High-Rise - Multi-Use Building (1,000,000 sf approx.)
http://bepan.info/proj-bldgs/p13-high-rise-bldg
 
Has a building of the size and scope of the 160-storey Burj-Dubai (Burj-Khalifa project analyzed by TRACE) been analyzed with EnergyPlus? See facts and figures
http://www.burjkhalifa.ae/the-tower.aspx
 
How about a full university campus with one central plant?
 
In my opinion EnergyPlus needs to remove (or make optional) the features that increase execution time.  See attachment USDOE Energy-Programs - DOE21E and EnergyPlus
 
Why should a private firm develop an interface to EnergyPlus after USDOE left all the developers of interfaces to the DOE21E stranded?  There is no money to be made from the engineering software business.  Development costs of graphics and forms interface costs are much higher than engineering analysis, but small compared to the marketing, support and training costs.  There are few customers for engineering software and they expect to pay about $50 to $500 which is typical of commercial software products.
 
Varkie
 
=================================================
 
>From Joe Huang <yjhuang at whiteboxtechnologies.com> 
Sent Thursday, April 28, 2011 8:12 pm
To Paul Diglio <paul.diglio at sbcglobal.net> 
Cc energyplus_support <EnergyPlus_Support at yahoogroups.com> , equest-users at lists.onebuilding.org 
Subject Re: [Equest-users] equest and energy plus outputs

 
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 about 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"

-------------------------------------------------------
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"
=============================================
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?

>

>
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
>
_______________________________________________  




 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20110429/a750910c/attachment-0002.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: USDOE Energy-Programs - DOE21E and EnergyPlus.pdf
Type: application/pdf
Size: 100120 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20110429/a750910c/attachment-0002.pdf>