Dear Joe,
No fair! You and Dru have been at the forefront energy modeling research for most of my adult life, and have a big head start.
My guess is that you spent a lot of time preparing the actual weather files for the research, however. Unless I’m missing something, the ready availability of high quality (e.g., no big hunks of missing data) actual weather data has been pretty limited until recently. With folk like Weather Analytics getting on board and making it pretty easy to get and inexpensive, it becomes a lot faster and lower cost than trying to clean some of the NOAA / NCDC data, not to mention getting good data for sites not in or near a major city.
Kudos for being way ahead of the industry curve (at least my own curve)! It’s getting easier to catch up!
p.s., Dru sent me that paper and I’ll be reading it with interest very soon.
From: Joe Huang [mailto:yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx]
Sent: Thursday, June 28, 2012 1:53 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Cc: Jim Dirkes; bldg-sim@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Food for thought....
I've always thought it was a "no-brainer" to use actual weather data whenever you're comparing simulation results to actual consumption data. Even with the earliest degree-day software such as
PRISM (Princeton Scorekeeping Method) in the 1980's, it was stressed to use the degree days
from the period of record, and not the long-term average, so I'm not sure why this (using actual
year weather data) is such a revelation.
The variation in total energy consumption of course depends a lot on the building characteristics.
Back in 1996, Dru Crawley and I wrote a paper on "Does it matter which weather data you use in energy simulations?", for the ACEEE Summer Study on Energy Efficiency in Buildings (it also appeared as two
separate ASHRAE papers at around the same time) where we took some prototypical building models (Dru did commercial, I did residential) and ran them with various "typical year" weather files and also 25 years of historical data in 10-12 US locations.
Joe
Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx
www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
On 6/28/2012 8:49 AM, Jim Dirkes wrote:
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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