[Bldg-sim] Energy consumption difference in E+ and Equest

[Jeff Haberl]

Chris,



There many layers of differences between the two codes. However, there are some ways they can be compared, this is what Standard 140 from ASHRAE has been doing for the last 20 years (i.e., Ron Judkopf and Joel Neymark at NREL). Basically, there are envelope tests, ground couping tests, systems tests, etc. Unfortunately, when all combined they can produce unpleasant differences that are hard to explain to clients. All differences, for the most part, have been cited in the previous literature, if you know where to look.



We are currently developing a test of Equest, DOE-2.1e and EnergyPlus, as well as BIM files for three platforms as part of the RP1468 project we are working on. This may help to shed some light on a few issues...bottom line, the differences are complex, but, in general, traceable to differences in specific algorithms in the three models. I might also add that one should consider several other programs when looking at differences, for example, ESPr, TRACE, HAP and TRNSYS...probably enough work to keep someone busy for years tracing the differences.



Think of it like chosing a new car...all cars will deliver you from point A to point B, but different cars have different technologies to do that, diesel, gasoline, hybrid, and come in all shapes and sizes...cars, trucks, vans, etc.



Jeff



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Jeff S. Haberl, Ph.D.,P.E., FASHRAE..............jhaberl at tamu.edu

Professor............................................................Office Ph: 979-845-6507

Department of Architecture.............................Lab Ph:979-845-6065

Energy Systems Laboratory.............................FAX: 979-862-2457

Texas A&M University.....................................77843-3581

College Station, Texas, USA, 77843..................URL:www.esl.tamu.edu

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________________________________
From: bldg-sim-bounces at lists.onebuilding.org [bldg-sim-bounces at lists.onebuilding.org] on behalf of David Eldridge [dse at grummanbutkus.com]
Sent: Wednesday, February 16, 2011 6:14 AM
To: Chris Yates
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Energy consumption difference in E+ and Equest

If you haven't done this already, I would suggest comparing the other annual end-uses for the models as well.

If cooling is the only one varying then you have some questions about specific inputs.  (equip efficiency, infiltration, etc.)

However, if all of the end-uses are varying between the two models then you'll have a wider group of inputs to consider. (internal gains, occupancy, envelope construction, etc., plus those above.)

-DSE

Sent from my iPhone

On Feb 16, 2011, at 5:07 AM, Chris Yates <chris.malcolm.yates at gmail.com<mailto:chris.malcolm.yates at gmail.com>> wrote:

Vaibhav

Sorry to nit pick... don't you mean kWh/sq.m/year?

It's difficult to say what you're discrepancy comes from without having the models.
All I can recommend is reviewing both model's results at successively deeper levels detail. You've already covered the first level of detail - the cooling consumption doesn't match.
Your next courses of action may be:

  1.  Review monthly consumption
  2.  I haven't used equest but assume you can review hourly air temps and loads, so compare these next.
  3.  Solar gain

Are your figures based on zone demand or plant? You've got quite a few layers to compare.

Cheers

Chris

On 16/02/2011 06:49, Vaibhav Jain wrote:
Hello,

We are trying to compare cooling energy consumption of a typical office building model in EnergyPlus and eQUEST. Simulation model is a simple 5 zone model with PTAC system. Climate is New Delhi. Heating consumption is near zero in both the models. We tried our best to closely match models in these two software. The result says, cooling electricity consumption/sq.m./year is about- 35 KW/sq.m./year (in Energyplus) and 100 KW/sq.m./year (in Equest). Some of the guidelines says that cooling consumption should be around 100-120KW/sq.m./year. Is this correct? Does any one has come across this phenomenon.

Why EnergyPlus is giving very less consumption as compared to Equest or references?

Thanks & regards,
Vaibhav Jain



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Chris Yates C Eng MCIBSE

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