[Equest-users] Temperature in weather data

[Stormy L. Shanks]

Ralph and all,

Interesting discussion. I agree with you for the case of using modeling for energy usage predictions. I think a lot of us in the industry who are not researchers consciously don’t do energy usage predictions. We’re mostly using modeling for relative comparisons of energy usage where we’re looking at the model’s sensitivity to one or more energy reducing strategies. Or maybe that assumption is wrong? So, I agree when you say that you wouldn’t necessarily want to use stochastic methods in the design iterations. For the case of using modeling for predicting actual energy usage, the current modeling tools are inadequate.

A basic question from someone who is not a developer of mathematical modeling methods:  If you include probabilities in the model, would your end result be an energy usage prediction with a probability distribution wide that it wouldn’t be meaningful in the end?

Stormy Shanks

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Ralph Muehleisen
Sent: Friday, July 27, 2012 3:43 PM
To: Joe Huang
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Temperature in weather data

Chris, Joe, others,

The dramatic effects of simply rounding off/ceiling the temperature data in weather files is a perfect example of why we need to, as an industry, move from deterministic energy predictions to stochastic energy predictions.

Weather and occupancy are inherently stochastic and when we couple that stochasticity with our uncertainty in so many of the actual building parameters (at least uncertainty as to their what their values will be when installed), it seems to me that far more meaningful energy predictions could be made using stochastic methods.

While you wouldn't necessarily want to use stochastic methods during much of the design iteration, stochastic estimation should be a standard procedure for comparing major iterations and for final energy predictions.

For all us researchers, there is plenty of work to be done in properly quantifying the stochasticity of weather, occupancy and other stochastic parameters and in developing uncertainty profiles for important parameters that are not stochastic.  There is also opportunities for industry to develop the wrappers to take the info and create the DOE2 wrappers.

Am I alone on this or do others feel the same way?

Ralph T Muehleisen
PhD, PE, LEED AP, INCE Board Certified, FASA
Principal Building Scientist
Argonne National Lab
9700 S. Cass Ave, Bldg 221
630-252-2547, rmuehleisen at anl.gov<mailto:rmuehleisen at anl.gov>


On Thu, Jul 26, 2012 at 2:31 PM, Joe Huang <yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>> wrote:
Chris, others,

Since as you've raised the question of how significant would be adding extra precision to the weather data in DOE-2, I was sent a copy of a recent paper by Annie-Claude Lachapelle of the Univ. of Calgary given at eSim Canada 2012 on this exact topic, "DOE2 Dry-Bulb Temperature Precision Level Impact on Sensible Economizer Performance".   With the author's permission, I've attached the paper with this post.

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<tel:%28925%29388-0265>

(c) (510)928-2683<tel:%28510%29928-2683>

"building energy simulations at your fingertips"

On 7/25/2012 10:45 AM, Joe Huang wrote:
Chris,

My attention on this issue was first raised about 15 years ago when I was working with non-US weather data , i.e., the rest of the world, that are all reported in 0.1 C. I've noticed since that US stations have also moved to the use of metric units, i.e., 0.1 C for temperature. The DOE-2 weather format is still in integer F, which leads to three unfortunate effects: (a) hourly records can be off by as much as 0.5 F, (b) clumping of the temperature distribution, and (c) statistics such as degree-days will be off by a percent or two compared to the original data. Now, one can say that all this is immaterial in the bigger picture of things, which has been the default attitude so far, but since it's really quite simple to fix, why not get it right, i.e., doesn't it feel much better to see the same temperatures in the DOE-2 outputs as in the original weather data?

BTW, all the weather data that I've looked at are records of conditions on the hour, not the average over the hour, except for solar radiation.

Joe


On 7/25/2012 9:53 AM, Chris Jones wrote:

Joe
Given that the time steps are an hour, and the fact that weather data is averaged over an hour, plus the fact that the building local will have variations from the weather station local, would an extra decimal point provide more useful information?


At 07:43 AM 25/07/2012, Joe Huang wrote:

This is not possible at present without changing the DOE-2.2 source code to read a weather input file with decimal values. When DOE-2 was first designed in the early 1980's, memory was a big concern, so the weather data was reduced to integers and then packed, which is why the DOE-2 *.BIN file is so small (146K). I have actually developed a modified file format for *.BIN where I save an extra digit of precision, i.e., temperatures to 0.1F instead of 1 F, but the source code would also need to be changed slightly to read this extra information. I've mentioned this to the developer of eQUEST/DOE-2.2 and will be experimenting with making this change to the source code. If and when it's proven to work and gets incorporated into DOE-2.2, I'll let everyone know. I welcome anyone who thinks this is a useful modification to send me an e-mail. It might spur me on to do something! Joe On 7/23/2012 2:44 AM, è”¡æ˜€èŠ wrote: > Hi, everyone: > > We know that eQUEST can edit personal weather data. > But the dry-bulb and wet-bulb temperature in weather data can only > enter integers. > Is it possible to have more precise temperature to decimal place? > Thank you very much. > > > _______________________________________________ > Equest-users mailing list > http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org > To unsubscribe from this mailing list send a blank message to > EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG<mailto:EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG> > -- Joe Huang White Box Technologies, Inc. 346 Rheem Blvd., Suite 108D Moraga, CA 94556 (o) (925)388-0265<tel:%28925%29388-0265> (c) (510)928-2683<tel:%28510%29928-2683> www.whiteboxtechnologies.com<http://www.whiteboxtechnologies.com> "Building energy simulations at your fingertips" _______________________________________________ Equest-users mailing list http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org To unsubscribe from this mailing list send a blank message to EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG<mailto:EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG> </x-flowed>

>>
Christopher Jones, P.Eng.
Suite 1801, 1 Yonge Street
Toronto, ON M5E1W7
Tel. 416-203-7465<tel:416-203-7465>
Fax. 416-946-1005<tel:416-946-1005>
email cj at enersave.ca<mailto:cj at enersave.ca>





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