[Bldg-sim] eQuest - Model verification

Chuck Khuen chuck.khuen at wxaglobal.com
Mon May 2 06:15:45 PDT 2011


Nick,

Our AMY files are supposed to be complete and ready to run in eQuest (and other modeling systems).  If there is anything missing or could be improved, we want to hear about it so we can fix.  It is one of the reasons we have been giving away files early on.  For example James Dirkes’s requested to have the start day in the header be the actual day for that file, so we have coded this and it will be in our next upgrade. The processing on 2010 and 2011 is going well should have at least test AMY files for those ready end of this week (with luck).  When this is done we will have the continuous stream from current conditions back thru recent history to deep history.

Thanks for the question,

Chuck

_____________________
Chuck Khuen
Principal
Weather Analytics Inc.
www.weatheranalytics.com
781-856-5383

From: Nick Caton 
Sent: Friday, April 29, 2011 6:51 PM
To: Chuck Khuen ; Katherine Louman-Gardiner ; James V Dirkes II, PE 
Subject: RE: [Bldg-sim] eQuest - Model verification

Chuck I’m curious:

 

Are Weather Analytics’ AMY files fully compatible, complete and “ready-to-run” for users of eQuest 3.64?  Are there any fields of data for that may be incomplete or require post-processing in some fashion?  I feel like I’m hearing mixed-messages on that front…

 

Thanks very much, and don’t hesitate to copy the list in response if you feel the answer would be useful to others =)!

 

~Nick

 



 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chuck Khuen
Sent: Friday, April 29, 2011 3:14 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] eQuest - Model verification

 

As to James posting on this issue the weather data platform we are just finishing has cleaned up and localized weather input and can deliver a continuously updated stream of recent history and current conditions with direct web services access to any and all data.  In other words, we have the weather data side of the client’s desire all set.  We are very happy to cooperate with any efforts to integrate, assimilate or utilize this in a model or models.  Indeed we are looking for partners here, as we believe this is going to be an increasingly important element in the solution to upgrading existing buildings.  So if anyone wants to take on this part of the problem for Katherine, we will supply the weather data portion for free.

 

Chuck

 

_____________________
Chuck Khuen
Principal
Weather Analytics Inc.
www.weatheranalytics.com
781-856-5383

 

From: James V Dirkes II, PE 

Sent: Friday, April 29, 2011 12:02 PM

To: bldg-sim at lists.onebuilding.org 

Subject: Re: [Bldg-sim] eQuest - Model verification

 

FYI, Check out www.Weatheranalytics.com  for “AMY” (Actual Meteorological Year) data.  They’re a new player in this arena and seem to have their act together. 

 

 

The Building Performance Team
James V. Dirkes II, P.E., LEED AP, BEMP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653

 

From: Jorge Torres-Coto [mailto:jtorres-coto at mbo1.com] 
Sent: Friday, April 29, 2011 10:49 AM
To: 'Nick Caton'; 'James V Dirkes II, PE'; 'Karen Walkerman'; 'Carol Gardner'
Cc: bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] eQuest - Model verification

 

5% is a really tight number we have been forced to work with on come retro commissioning projects in the past, with 10% being the norm on an annual and monthly basis for overall building energy use.  Anything stricter than those numbers is unrealistic (again for the overall building).

 

Jorge E. Torres Coto   

4830 Viewridge Ave.

San Diego, CA 92123

p              858.751.0933

f              858.751.0937

c              858.688.6088




--------------------------------------------------------------------------------

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Friday, April 29, 2011 7:42 AM
To: James V Dirkes II, PE; Karen Walkerman; Carol Gardner
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] eQuest - Model verification

 

I know I have less experience calibrating models than some other respondents, but I’ll share my perspectives as well:

 

It is easy to adjust occupancy schedules / lighting loads in eQuest, but it requires the end-user knows the program.  If the end-user is inexperienced with eQuest or any other simulation program, then there is no “easily modifiable” model you can provide.

 

1)      Even if I manage to put in daily occupant and fan schedules based on actual use, will the model be accurate enough to take me within 1%?

 

With regard to historical modeling, showing any deadband of accuracy to known costs/consumptions is *technically* possible given enough information and time…  That said, falling within 1% of any holistic measure, even on an annual basis, before “refining the unknowns” would probably happen only by very lucky/happy coincidence.  It’s fair to say that in a relative sense, some buildings operate much more regularly and predictably than others, and for these cases you or a client might reasonably expect a tighter deadband.  Asking what is “accurate enough” is like asking “what’s reasonable,” and the answer is that it depends on what info/time you have. There are always “unknowable” variables that can play a big role in your end-results (example:  what is the actual leakiness of a 35 year old envelope?).

 

2)      We have been asked to remove plug loads (both for consumption purposes and cooling loads).  Will this be too big of an assumption to get any accuracy out of the model in the future?

 

Depends on your building, but for most buildings plug loads are a significant fraction of consumption/internal loads.  

 

3)      How do I modify the weather input file?

 

I saved the attached email from David Reddy for the next time I need to tackle “actual weather.”  My attempts thus far haven’t been terribly successful, so I have no “go-to” procedures to share just yet.  I have heard reference from those who appear in the know to macro/VBA-heavy excel spreadsheets which can automate the workflow to one extent or another, but I’ve not yet seen one with my own eyes.  I have yet to hear of any program that can “easily” incorporate recently recorded weather data.  

 

4)      Are there any other ideas I’m missing that will help us validate a model as an absolute measure of actual building energy consumption?

 

Generally:  the only “absolute measure of actual building consumption” will be the utility bills.  Something about the 1% number tells me you or your client might be trying to hammer a nail with a screwdriver… Energy models are great for looking to the past to make decisions that acknowledge the unknowns of the future, but if the real goal is to know the actual energy usage on an hourly basis – why not set up some sub-meters and track them?  While meters/bills measure energy usage and energy models can use that information to make predictions, models don’t determine bills – it doesn’t work in reverse!

 

PS:  For all the work you might put into calibrating a model with historical weather and other known data, keep perspective that your model will only ever be that accurate for behaviour in that year.  The moment anyone wants  to use this model predictively (for the future), you probably should swap back to TMY weather data and embrace the inherent unknowns.

 

~Nick



 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James V Dirkes II, PE
Sent: Thursday, April 28, 2011 7:12 PM
To: 'Karen Walkerman'; 'Carol Gardner'
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] eQuest - Model verification

 

Weighing in late on this….

If I get >80% R-squared correlation, I think I’m doing well!  

There are so many unknowns, including the normal situation that the client doesn’t know their own operating schedules, occupancy patterns, or maintenance / calibration procedures….

 

The Building Performance Team
James V. Dirkes II, P.E., LEED AP, BEMP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karen Walkerman
Sent: Thursday, April 28, 2011 3:31 PM
To: Carol Gardner
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] eQuest - Model verification

 

Also, a model that is calibrated to actual building use and weather can help to highlight building operation issues.  I have had models which were off from actual operating energy use that I was able to determine how the building was operating inefficiently.

 

In one case, I created a model of an existing building.  For this model, I made an actual count of lighting fixtures and computers.  For most of the year, there were few other electrical loads.  I based on their occupancy and use schedules, I was not quite able to calibrate the electrical energy use.  When I met with the client, I informed him that my model showed somewhat lower electrical use, equivalent to 1/3 of the computers remaining on 24-hours per day.  As it turned out, about 1/3 of the employees DID leave their computers on at all times so that they could log in remotely.

 

... I guess what I'm saying is that maybe the goal is not to get the model within 1% of the building energy use, but get the building within 1% of the model.

 

--

Karen

 

On Thu, Apr 28, 2011 at 3:20 PM, Carol Gardner <cmg750 at gmail.com> wrote:

Bill summed it up really well, Katherine. Sometimes a client will think a calibrated model must match the real building by an unrealistically high number, like 1%. I really can't imagine an instance when that would be desirable. It certainly would be costly to achieve. 

 

Usually the plan is to use the calibrated model as a tool to examine various energy saving measures/opportunities that the client may be interested in implementing. It is important to remember, in this case that you are looking at the usage between the calibrated model and the ECM model, so the 1% deviation is consistent in both and not a worry.

 

Carol

On Thu, Apr 28, 2011 at 12:03 PM, Bishop, Bill <wbishop at pathfinder-ea.com> wrote:

  Katherine,

   

  The questions I would have for you (or your client) are:

  ·         Is this an existing building, or something in the design phase?

  ·         What is the model going to be used for?

  ·         Is there something magical about the 1% number?

  ·         1% of what? Annual electrical consumption? Annual gas consumption? Both? Monthly electric/gas consumption? Monthly/annual electrical demand?

  ·         Why remove the plug loads? Even if everything else is modeled perfectly, plug loads are typically 10% or more of annual electrical consumption but can be all over the place.

  ·         “Easily adjusted” by whom? Does your client want you to hand them a model and let them make all subsequent adjustments?

   

  Even if you are an expert energy modeler, and there is monitored energy data available for the building down to the individual electrical panels or broken out by end use (lighting, plug loads, individual HVAC units etc.) you will be hard-pressed to get to within 1% on a month-by-month basis. Even 5% month-by-month is difficult. Sure, you can tweak to your heart’s content to get a model to match annual electric consumption within 1% based on prior year’s utility bills but to maintain a calibrated model to that tolerance after that would require a lot of work.

   

  I suggest searching the bldg-sim and equest-users archives for information about weather files.

   

  Oh, one more question – how much money does your client have?

   

  Regards,

  Bill

   

  William Bishop, PE, BEMP, LEED® AP | Pathfinder Engineers & Architects LLP

  Mechanical Engineer

   

  Error! Filename not specified.134 South Fitzhugh Street                 Rochester, NY 14608
  T: (585) 325-6004 Ext. 114            F: (585) 325-6005

  wbishop at pathfinder-ea.com           www.pathfinder-ea.com

  P   Sustainability – the forest AND the trees. P   

  From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Katherine Louman-Gardiner
  Sent: Thursday, April 28, 2011 1:49 PM
  To: bldg-sim at lists.onebuilding.org
  Subject: [Bldg-sim] eQuest - Model verification

   

  Hi All,

  Our client would like us to produce an eQuest model that

  a)      Can be easily adjusted to include current and recently recorded weather data

  b)      Can be easily adjusted to reflect space occupancies and lighting loads

  c)       Will reflect the actual building energy usage to within 1%

  Do any of you have experience trying to validate models like this?  

  My concern is that models are approximations, and will not account for small changes in occupancy, outdoor weather, etc.  

  I guess my questions are these:

  1)      Even if I manage to put in daily occupant and fan schedules based on actual use, will the model be accurate enough to take me within 1%?

  2)      We have been asked to remove plug loads (both for consumption purposes and cooling loads).  Will this be too big of an assumption to get any accuracy out of the model in the future?

  3)      How do I modify the weather input file?

  4)      Are there any other ideas I’m missing that will help us validate a model as an absolute measure of actual building energy consumption?

  Thank you for your help,
  Katherine

   

  Katherine Louman-Gardiner, EIT

  Mechanical Engineer

   

   

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-- 
Carol Gardner PE


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