[Bldg-sim] IES-VE Energy

Joe Huang joe at drawbdl.com
Thu Feb 26 12:30:09 PST 2009


On the modeling of natural ventilation, I've not heard of anyone who's 
coupled thermal with CFD for annual simulations, and if they did I'd 
guess they're still waiting for the results!  There are, however, 
several programs (EnergyPlus, ESPr) that do link up with a multi-zone 
air-flow network program (EnergyPlus uses AirNET/CONTAM)  to  "ping 
pong" with the thermal
program.  My experience doing an earlier linking of COMIS into 
EnergyPlus showed increases in runtimes of  2-3 times (that's on top of 
the standard run times most people have seen). I also saw instabilities 
in the "ping pong" approach that made me think of more iterations 
(horrors!), but the funding got cut so I didn't pursue that.

As for eQuest handling of natural ventilation, its capabilities are 
probably the same as DOE-2.1E,  which does have a very simple one-zone 
natural ventilation model that would calculate outside air flow rates 
based on that zone's leakage are, outside temperature, and wind speed. 
This capability was available first only in the RESYS system, but later 
extended to the other systems. I wouldn't use it to design a commercial 
building with hybrid ventilation, but for rough estimates of natural 
ventilation potentials for operable windows in perimeter offices, how 
bad is it ?  Another nice thing about this natural ventilation feature 
in DOE-2 is that DOE-2 Systems first checks to see if NV can hold the 
setpoint temperature, and if not, it shuts off NV and turns on the 
mechanical system.  Voila!  The ideal natural ventilation control.  I've 
yet to see such a control available in other programs.

So, I get a little impatient when people talk about the capabilities of 
different programs in a yes-no context.

Joe Huang
White Box Technologies


Karen Walkerman wrote:
> Carol said most of it, and I definitely second the prohibitive cost 
> for a program like IES-VE for a small shop, but I've used Trace700, 
> which I assume uses an iterative algorithm (it took about 1-2 hours 
> run-time).  So maybe using an iterative algorithm gives a little more 
> accuracy, I'd guess on the order of 2-5%, BUT many of these programs 
> don't allow you the flexibility in your inputs to take advantage of 
> the iterative nature of the program.  For many systems, you don't need 
> to use an iterative program, you just need to know the hourly space 
> loads, hourly ventilation loads, and equipment operation efficiencies 
> at the given conditions.  You need just a few layers: component load 
> (walls, windows, internal loads, etc), zone loads, hvac system loads, 
> loop loads and plant loads, in order to get pretty good results.  You 
> need a few additional levels when your systems get more compliated, 
> but it doesn't require a super-complicated algorithm.
>  
> Bottom line is, many programs have their drawbacks.  eQuest is not 
> good at modeling natural ventilation, precisely because it is not a 
> CFD program.  If it were good at modeling natural ventilation, it 
> wouldn't be able to run in 1-2 minutes.
>  
> I'd love to see a program that could integrate into two simulation 
> engines, one quick engine for trouble-shooting, doing DD models and 
> running lots of alternatives, and then an interative simulation engine 
> for more complex stuff, natural ventilation, complicated HVAC system 
> configurations, etc.  Add that one to the wish-list!  Maybe we'll see 
> it in 20 years.
>  
>  
> --
> Karen
>  
> On 2/26/09, *Carol Gardner* <gems at spiritone.com 
> <mailto:gems at spiritone.com>> wrote:
>
>     It can be better because you only have to do the renaming process
>     once and then your done whereas you are going to have to do the
>     rerunning way more than once: at least 4 orientation runs, a run
>     for each energy efficiency measure, a run each time you realize
>     you forgot to do the ____(fill it in). You are way further ahead
>     using eQUEST. I'm not sure what you mean by an interactive 3D
>     viewer, I find eQUEST's 3D views really helpful but I get the
>     impression you are talking about something else. At any rate, I
>     have used IESVE and E+ and I think they both excel in ways that
>     eQUEST doesn't but IESVE is just too expensive for a single shop
>     person like me and E+ is just too slow so far. I don't rule them
>     out for use when I'm rich and they're faster, though.
>
>     Carol
>
>     Paul Carey wrote:
>
>
>         Karen and all,
>
>         I’m confused here....how can a program that takes up to 3
>         hours to rename the zones but then takes minutes to get
>         results, be better than something that takes a few minutes to
>         rename, but then takes a couple of hours to run? They are
>         about the same surely? The only advantage I can see is that
>         further iteration might be quicker in the former assuming your
>         geometry doesn’t change.
>
>         I have been using various modelling tools such as IES VE, TAS
>         and DesignBuilder as well as a few other tools when necessary
>         (Fluent & CHAM CFD etc) since the late 90s. IES is good, it’s
>         quick to produce models and excellent for dynamic natural
>         ventilation design. TAS is better at the HVAC and natural
>         ventilation design aspects than IES and I think it’s more
>         accurate, but it’s front end still lacks some of the
>         functionality of other tools. Hopefully that is being
>         addressed by their links with Bentley. My colleague, Chris
>         Yates (also on this list) has become a bit of a wiz with the
>         sketchup plug in for IES and this appears to be much better
>         than relying on the gbxml output of revit.
>
>         DesignBuilder is the tool that I use most now in both SBEM (UK
>         regulations format) and EnergyPlus for dynamic modelling. It
>         takes a lot of the best features of both IES and TAS and then
>         adds some other nice touches in terms of data application to
>         speed up the process of setting up your models. The only
>         sticking point with it is that EnergyPlus is painfully slow.
>         The main thing I’d like is for that to be changed and
>         improved. Carrying out simulations with all the lighting
>         controls and calculated natural ventilation turned on for
>         buildings with over 100 zones is nigh on impossible as I don’t
>         fancy leaving it running for a week or two. I have to carry
>         out major sub-division of models or calculate individual zones
>         then schedule up the vent based on those results or just go
>         with scheduled vent. Thankfully the reporting methodology from
>         DesignBuilder is pretty good, though I have to admit I quite
>         like some of the report wizard output by equest.
>
>         The main advantage of the commercial tools as opposed to the
>         free tools such as DOE and equest, is that they use an
>         interactive 3d model to input the building and that you can
>         interrogate much more easily for post-processing. This means
>         you gain an understanding of the building form much more
>         easily and many link with other tools for further analysis. I
>         like some of what equest has to offer, but I much prefer the
>         interactive model building tools that IES, TAS and
>         DeisgnBuilder offer. They just make it...easier...and
>         generally quicker and more efficient when you consider the
>         other studies that you can do (e.g daylighting, CFD, etc).
>
>         In terms of asking for changes – having worked for IES (and
>         with many other developers), the stock answer even to their
>         own team was...yes it’s on the list. My guess is that will
>         still be the same.
>
>         Regards
>
>         Paul
>
>                
>
>         Dr Paul Carey
>
>         Director
>
>         Low Carbon Energy Assessor
>
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>         *From:* bldg-sim-bounces at lists.onebuilding.org
>         <mailto:bldg-sim-bounces at lists.onebuilding.org>
>         [mailto:bldg-sim-bounces at lists.onebuilding.org
>         <mailto:bldg-sim-bounces at lists.onebuilding.org>] *On Behalf Of
>         *Karen Walkerman
>         *Sent:* 25 February 2009 23:06
>         *To:* Varkie C Thomas
>         *Cc:* Varkie Thomas; bldg-sim at lists.onebuilding.org
>         <mailto:bldg-sim at lists.onebuilding.org>
>         *Subject:* Re: [Bldg-sim] IES-VE Energy
>
>         Varkie,
>
>         I disagree with your statement that eQuest is not appropriate
>         for large buildings because you can't change space names to
>         match architectural names in wizard mode, and the inputs
>         created from the wizard aren't appropriate for all spaces. The
>         wizards are called "Schematic Design Wizard" and "Design
>         Development Wizard" for a reason. They aren't desinged for
>         detail, they're designed to help you make big design decisions
>         quickly. If you want the building to be modeled as closely as
>         possible to the final design, this takes some extra work.
>         Yeah, re-naming spaces is a pain, but at 5 seconds per space,
>         re-naming 1,000 spaces takes about 1.5 hours, well worth the
>         effort. If you re-name zones too, maybe it's 3 hours total.
>
>         Yeah, some things about eQuest are clumsy, like why does it
>         create one underground wall (and floor) consturction for each
>         surface, when only 4-5 are needed for the whole model? Why
>         does it re-create occupancy, lighting and micellaneous
>         equipment schedules for each shell, even if the use is the
>         same? And why does it create tons of duplicate infiltration
>         schedules? BUT... this takes an hour or two to clean up, and
>         then you have a decently flexible model that gives you
>         reasonable results in a matter of minutes. Versus a program
>         that takes 1-2 hours to run. I've done a few LEED projects in
>         Trace700 and it's painful modeling a design case and four
>         (rotated) base cases at 1-2 hours each, especially if you then
>         find you've left anything out.
>
>         I definitely agree that there are some major things missing in
>         all modeling programs, which is why I'm putting together a
>         "Master Wish List" of modeler's desires. If you have things
>         that you would like to be able to model, things you'd like to
>         be able to model more easily, or things that you can do that
>         you feel are very important, please send me your list. I
>         currently have contact info for about 10 people representing
>         various simulation programs who want to know what we want!
>         Now's our chance to have some input!
>
>         --
>         Karen
>
>
>         On Wed, Feb 25, 2009 at 2:15 PM, Varkie C Thomas
>         <thomasv at iit.edu <mailto:thomasv at iit.edu>
>         <mailto:thomasv at iit.edu <mailto:thomasv at iit.edu>>> wrote:
>
>         Graham,
>
>         The comment below stands out which might also be the reason
>         for not using EnergyPlus on large projects.
>
>         - DOE-2.2 runs much quicker. For comparable 30,000 m2
>         buildings I would say DOE-2 runs in 1 minute and IES VE with
>         an APhvac network probably 1-2 hours. If you through in
>         Macroflo it probably adds another hour of simulation time. As
>         a result *iterative trial and error debugging* has to be done
>         on a 1-2 week period.
>
>         Large building projects (1 to 10 million sqft) with up to
>         1,000 zones and 70 systems ranging in size from 10,000 to
>         200,000 cfm (pardon the English units - the USA & the Bahamas
>         are not going to switch to metric) require several iterative
>         runs to get the input errors fixed. Breaking up the project
>         into small pieces is not a solution since it affects demand
>         costs, central plants and other components. I have worked on
>         such projects using DOE2.1E and TRACE600/700.
>
>         eQUEST is not suitable for such projects either. One of its
>         limitations is that you cannot enter the space names shown on
>         architectural drawings. Others include assuming all the input
>         data and making all the decisions for you when you enter the
>         type of building. 1000 zones means 1000 infiltration schedules
>         and multiples of other building components. It is unrealistic
>         to check all the input created by eQUEST for errors. Fixing
>         everything to match the exact project data has to be done in
>         detailed edit. Detailed edit means you lose access to the
>         graphical method of creating the building model from AutoCAD
>         drawings which is the main benefit of this program.
>
>         Varkie
>
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