[Bldg-sim] eQuest - Model verification

Karen Walkerman kwalkerman at gmail.com
Thu Apr 28 12:30:51 PDT 2011


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
>>
>>
>>
>> [image: Top 100 Rochester 2010]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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