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

[Daniel Knapp]

Hi Joe,

Thank you for sharing this report with the list. It is very interesting to see a thorough comparison of EnergyPlus with DOE 2.2 results. I am an experienced user of eQUEST and I have been looking at EnergyPlus with some interest for future work.

Two things jumped out at me from your report, both of which you noted. One is that, as you point out on page 74, the heating load is relatively small in these climates. This would tend to amplify the effects of any discrepancies in how the heating loads are calculating and in how the plant responds to those heating loads. It would be very interesting to see the same comparison done in the same model in a different location with a much higher heating load. Would there still be a factor of 30 difference in the results in this case? The other is that it would help to see a comparison of the heating loads in the two models. Is the discrepancy coming in primarily in the calculation of the heating loads, the calculation of the energy required to meet those loads, or is it a combination of the two? 

I have to say that the more alarming result appears to be the discrepancy in results for domestic hot water. I might have expected the domestic hot water load to be the same in both the DOE 2.2 and EnergyPlus models. Are the boiler models really so different as to entirely account for such a huge difference in natural gas consumption, or are there other loads showing up in the DOE 2.2 model that don’t appear in the EnergyPlus model? 

With thanks and best wishes,
Dan



—
Daniel Knapp, PhD, P Phys, LEED® AP O+M
danielk at arborus.ca

Arborus Consulting
Energy Strategies for the Built Environment
www.arborus.ca
76 Chamberlain Avenue 
Ottawa, ON, K1S 1V9 
Phone: (613) 234-7178 ext. 113
Fax: (613) 234-0740




On May 2, 2014, at 6:15 PM, Joe Huang <yjhuang at whiteboxtechnologies.com> wrote:

> Simge, 
> 
> 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:
> 
> http://www.whiteboxtechnologies.com/download_AutoDesk_EP_feasib_rpt.htm
> 
> 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 results. 
> 
> 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.
> 
> Joe
> 
> 
> 
> 
> 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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