[Bldg-sim] Food for thought....

[Jim Dirkes]

Thanks to all who responded so far!

The two main points so far (without reading any of the suggested articles
and for all of you who have not yet had the pleasure of modeling an existing
building) are:

.         Use actual weather data for calibrating an energy model to actual
energy use. 

o   This eliminates weather as an estimated variable and gives greater
confidence regarding your understanding of all the other variables.

.         Use TMY data (or a generic weather pattern) for savings
predictions.  

o   This eliminates the likelihood of predicting savings based on a
non-representative recent weather pattern.

 

I have lots of new reading as a result of this post and am looking forward
to it.  Interesting that this is not really a new topic, as evidenced by the
1997 and 1998 publications referenced by some of you!

I've been thinking a fair amount lately about the huge and untapped savings
potential in existing buildings, but have not figured out the right sales
pitch for the owners yet.  It seems that they have about 20 other factors
affecting their incentive for improving building operations.  I'm not giving
up, however; there is too much good to be accomplished! (not to mention
challenge, learning and income J)

 

 

From: Carolyn Balant [mailto:CBalant at mcw.com] 
Sent: Thursday, June 28, 2012 12:06 PM
To: Jim Dirkes
Subject: RE: [Bldg-sim] Food for thought....

 

I agree that if you are trying to calibrate a model to actual utility bills,
you should use actual weather data.  That is not practical for eQuest as
well as other programs so then the next best thing is to check the TMY or
weather file against the actual weather. 

 

If there is a significant difference between the TMY and the actual data,
then I would adjust the utility baseline to the TMY data.  Linear
regressions typically work well for heating applications.  For cooling, it
doesn't work as well but if you are in a dry climate it should be okay.

 

Regards 

Carolyn Balant P.Eng., LEED AP 

Senior Energy Engineer 

 

 <http://www.mcw.com> MCW Custom Energy Solutions Ltd. 

Queen's Quay Terminal 
207 Queen's Quay West, Suite 615 
Toronto, ON, Canada M5J 1A7 
Phone: (416) 598-2920 ext:315 
Fax: (416) 598-5394 

 

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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jim Dirkes
Sent: June-28-12 11:49 AM
To: EnergyPlus_Support at yahoogroups.com; bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Food for thought....

 

Dear Forums,

I am busy preparing a short talk for the Fall ASHRAE Energy Modeling
Conference.  The topic is "An Approach for Calibrating Existing Building
Energy Models to their Utility Consumption".

As part of the preparation, I will address the issue of how much difference
might result in energy conservation measure savings predictions if you use
actual weather data for the billing period versus TMY data.  

To get a rough idea  how much variation there might be, I looked at Degree
Days for a span of years.  What a variation! (for the city I'm studying at
least)

I am not yet sure how that affects total energy consumption - you'll have to
attend my presentation in Atlanta to find out J.

In the meantime, I am starting to think that existing building energy models
should use actual weather, not TMY data.  Have any of you run similar
comparisons for existing building models?



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