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@xxxxxxx]
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
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@xxxxxxxxxxxxxxxxxxxxx [mailto:bldg-sim-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of Jim Dirkes
Sent: June-28-12 11:49 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx; bldg-sim@xxxxxxxxxxxxxxxxxxxxx
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?