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

[Joe Huang]

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 at whiteboxtechnologies.com
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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