Calibrating the Energy Model

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Hello,

I am tasked with calibrating my energy model in Trace 700 to existing utility data. We have been successful in getting the correct weather data (only calibrating to the actual weather year of 2012) and have achieved the correct basic profile shape. We are looking at electric, purchased hot water, and purchased chilled water (it's a campus loop system). Chilled water is almost spot on, but hot water and electric have significant offsets.

We are focusing on the hot water side for now. In summer, actual data show some but very little usage (700-1000 therms in June through August) but our model shows no usage in this months. We must be missing reheat in there somewhere is our thought, but not sure where since we've accounted for all equipment.

Does anyone have experience fixing issues like this or calibrating models in general? (See pics and Trace file for additional info.)

On a separate note, I realize there was recently a webinar on the 7 steps for calibrating models. Did anyone attend and is it worth the $200 to buy it?

Thanks for your help,

Annie

Hot Water Comparison
Electric Use Comparison
asmith's picture
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Joined: 2013-03-08
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Hey Annie-
I have all sort of experience calibrating models in TRACE 700. I would pitch the webinar, but that's not exactly fair since I was the presenter.

Given your issue, it's probably something that the webinar would help with. (I sent you a private message)

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Bob
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Please give me a little more to go on...such as system type, are you modeling domestic hot water in the Misc. Accessories? It seems that either your controls are running pumps when they don't need to due to a call from the DDC, if it's a VAV system-the AHU might not be resetting discharge based on OAT...thus causing the VAV's to reheat the air, look at your modelled coil temps, and compare actual VAV min's to modelled, economizer setrpoints as well....lots of variables to look at.

Be Sustainable -- Never let today use up tomorrow!.

Bobba_Fett's picture
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Just going from your graphs it is hard to tell what the actual problem is by not knowing the systems.  There are a few tips I can give you for how to analyze the overall results though.

You are missing summer time heating and are always under predicting winter heating.  This could be as simple as the domestic hot water loads being improperly modeled or reheat as you mentioned.  Usually a walkthrough of the building and establishing the system type, year of construction, BMS controls will let you know if something might be up.

The electricity is constantly modeled below the actual building.  As you said, there may be onsite equipment that you may not have accounted for in your model.  You need to look through all the energy using equipment to make sure you have it accurately modeled.  Basically the answer is you have to go onsite and do a walkthrough with the building operator and find these things that are causing the building to not operate efficiently like they are in the model.

Finally, operation schedules are a big deal for model calibrations.  You need to establish what a typical day is for your building because the model energy use can swing wildly one way or the other if these change.  

ASHRAE's "Procedures for Commercial Building Energy Audits" is a very useful resource for conducting walkthroughs and Level I, II, and III energy audits as well as provides excel templates for "checkoff" items while you are in the building.

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