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

[Joe Huang]

Jim,

Sorry if I came off as a little smug.  You've actually put in words the main reason why I 
think building energy modelers have steered away from using historical weather data, which 
is simply that of  convenience, i.e., there are a lot of "typical year" weather files 
floating around, but getting hold of
a usable historical year weather file takes a little more work.

For the study that I mentioned, Dru and I did not have to do anything because the SANSOM 
data set,
available from NCDC, contained 25 years of historical weather files for 239 cities (same 
as TMY2s).

That was in 1996, and the availability of historical weather data has only increased 
exponentially since
then, although the building energy modeling community seems curiously to not have followed.
The most notable change, in my view, is NCDC's decision to put the entire ISH (Integrated 
Surface Hourly) data online in 2005, and then to make it free to all in 2011.  This means 
that the raw weather reports
from major stations around the world ( ~ 1,500 in the US) are available stretching back to 
1980.

I've been working with the ISH for many years now, and am able to generate complete 
weather files from any ISH file within seconds, and have been providing that as a service 
to customers.  Sometime later this
year, I'll be rolling out something on the Web, but for now, those interested can just 
send me an e-mail.

The idea that the ISH is of questionable quality is, in my view, rather backwards.  The 
ISH is a repository of the weather reports by the "official" weather stations around the 
world, so if you can't trust that, what can you trust?

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 11:48 AM, Jim Dirkes wrote:
>
> 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 at whiteboxtechnologies.com]
> *Sent:* Thursday, June 28, 2012 1:53 PM
> *To:* EnergyPlus_Support at yahoogroups.com
> *Cc:* Jim Dirkes; bldg-sim at lists.onebuilding.org
> *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 at whiteboxtechnologies.com  <mailto:yjhuang at whiteboxtechnologies.com>   
> www.whiteboxtechnologies.com  <http://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 muc h 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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