[Equest-users] Significan​tly Higher Heating and Cooling Energy Consumptio​n in EnergyPlus When Compared to eQUEST

Joe Huang yjhuang at whiteboxtechnologies.com
Fri May 2 15:15:21 PDT 2014


I feel compelled to respond since you mentioned me so prominently in 
your post :-)

I think you're bringing up a very germaine question, and indeed it's one 
that in my opinion needs further study, i.e.,
how does EnergyPlus compare with eQUEST or other building energy 
simulation programs in their modeling results?

The LBNL paper you cited is a summary paper from a SimBuild Conference 
in 2008 that only skimmed the findings from a
year-long effort supported by the California Energy Commission. I've put 
the full report on the Web, along with a later study
I did last year as part of an EnergyPlus Feasibility Study by AutoDesk 
done for Southern California Edison that you might find
equally interesting:


The second study was under wraps for a long time, but I received 
clearance from SCE to release it two months ago.
My part of the study is strictly the EnergyPlus to DOE-2.2 comparison 
pp. 57 -98, and I have no opinions one way or
the other in respect to the rest of the study. My task was to take 
several DEER prototypes (office, residential, and retail)
modeled in eQUEST/DOE-2.2 and convert them to EP 7.X.  Compared to what 
I saw in the 2007 study, the discrepancies
in heating energy consumption were even more striking, probably because 
all the buildings were modeled in southern
California climates.   I was getting consistently from a 5:1 to a 20:1 
difference in heating energies (DOE-2 high, EP low).

Following up on Jeff's earlier comment, diagnosing the differences 
between two simulation programs requires a lot of
time, experimentation, and often in-depth study of the source codes. In 
the 2007 paper,  I mentioned somewhere between
15 and 20 areas of modeling differences with significant effects on the 

It's been 7 years since the first study, and I've been disappointed by 
the lack of progress. Some of it is understandable, since
speaking frankly, there are a very limited number of people with 
sufficient knowledge and interest across two programs to make heads or 
tails out of these comparisons. But it is a very important issue, not 
just from technical curiosity, but because a lot of
money have been invested based on what these programs say, so if they 
give significantly different results, policy makers would
like to know what's going on and ideally, what is the ground truth?

I don't want to sound like a modern-day Cassandra, and I don't have 
enough resources or time to pursue this as a private
adventure. However, I hope that public institutions will see the need 
and benefit, and support some serious work in this area.

I know that you (Simge) or I are not the only people who've wrestled 
with this problem.  I would like to hear the experiences of
others (not you, Jeff,  I already know what you would say :-) ). Since 
all the efforts I've heard of are going from eQUEST
to EnergyPlus, not the other way around, the domain knowledge is 
probably higher on the eQUEST/DOE-2 side. Therefore,
it would be most valuable to get the EnergyPlus experts to chime in on 
the nuances of EnergyPlus modeling of which we
may be lacking.  For the same reason, you might consider posting your 
message to the EnergyPlus_Support bulletin board
as well.

See, Simge, now you got me wasting a couple of hours on a Friday afternoon!

I'm not sure when I would have time to look at your input files, but if 
I see anything I'll let you know.


On 5/1/2014 1:35 PM, Simge Andolsun wrote:
> Dear eQUEST users (Particularly Dear Joe Huang),
> Please find the attached eQUEST and EnergyPlus files. They represent 
> identical cases for comparison of the two programs. The runs are 
> conducted for Los Angeles. The heating and cooling consumption of 
> EnergyPlus file are, however, unreasonably higher than that of EQUEST. 
> It is particularly strange that heating occurs in early morning 
> time during the summer in EnergyPlus whereas no heating occurs in 
> eQUEST during these hours.
> We need our results not to deviate extremely from eQUEST when we 
> start using EnergyPlus. That is why, I am conducting this comparative 
> analyses for cases representing identical conditions. I would 
> appreciate it very much if you could examine these files and let me 
> know whether there is anything I can do to make the results of these 
> cases in the two programs as close as possible to each other.
> Dear Joe Huang,
> Please see the attached charts that show the hourly variation of 
> temperatures in the system nodes and hourly energy consumption. There 
> is definitely something weird going on in the early morning hours when 
> the system just starts working. I have read your paper in the link 
> below. Below is a section from your paper that I have paid particular 
> attention to. Might I be having a similar issue in my case?
> http://gundog.lbl.gov/dirpubs/SB06/huang.pdf.
> /"Heating to the cooling setpoint/. Temperature plots revealed that at 
> times during the shoulder seasons, /EnergyPlus /had difficulty in 
> picking between the heating or cooling season control logic. This 
> resulted in the supply air being heated to the cooling, rather than 
> the heating, setpoint during the morning hours. This problem was 
> corrected by improving the setpoint manager in /EnergyPlus/."
> Looking forward to hearing from you,
> Best Regards,
> Simge Andolsun, PhD.
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