[Equest-users] Temperature in weather data

Ralph Muehleisen rmuehleisen at anl.gov
Sat Jul 28 10:52:46 PDT 2012


Great conversation everyone.

I guess I should have started my discussion by differentiating building
design from analysis.  I definitely see a place where actual energy
predictions and characterization of uncertainty is of prime importance -
retrofits.

While designing low energy new buildings is great, if we want to really
impact the building energy and carbon footprint we need to retrofit the
existing building stock as much as possible.

Since most owners look at this as an investment, we really need to given
them information like other investments and provide risk analysis.  That
means probabilistic energy savings predictions and, when coupled
with probabilistic cost and future energy costs, a
true probabilistic return on investment and value added to the building.
 Then owners and financiers can look at a retrofit just like any other
investment, and (I hope) pull the trigger on more retrofits than they are
currently doing.

I'm not sure of a way to generate real ROI probability without stochastic
analysis.  The underlying model doesn't necessarily have to reflect the
true physics (or even full systems of the building) as long as it captures
the monthly energy use right and enough of the physics that when we make
changes to the building, the model correctly reflects the energy savings
and uncertainty in that savings.





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



On Fri, Jul 27, 2012 at 8:50 PM, Joe Huang <yjhuang at whiteboxtechnologies.com
> wrote:

> **
> Ralph, others,
>
> I think it all depends on the purpose of the simulation. Leaving aside the
> issue of design sizing for the moment, use of energy simulations to
> predict, or more often, match observed energy usage is typically concerned
> with annual or long-term energy usage.  In that case, stochastic variations
> around a mean doesn't provide much useful information, because the concern
> is not variability, but bias, in the results. It reminds me of when I saw
> that the uncertainty given for the modeled solar illuminance in the TMY2
> weather files was less than 3%. That seemed wrong to me, since I know that
> for any particular hour the differences between modeled and measured solar
> could be quite large.  However, when I read the documentation, it made
> sense because the uncertainty indicates not the stochastic variability, but
> the "mean bias error", i.e., systematic variations, between the modeled and
> measured solar.
>
> How does that relate to the value of stochastic modeling?  If we're only
> concerned in getting the annual totals to match, then whether or not we
> capture the stochastic variations from hour to hour seems to be minor
> importance.  I'm also having difficulties in understand what
> additional information is output from "stochastic modeling", except having
> error bars on each hour, which undoubtedly will be large.
>
> My last comment is that although weather patterns are stochastic, the data
> on the weather files is quite deterministic, if we allow that the weather
> stations are doing a reasonably good job in measuring temperatures, wind
> speeds, etc.  The question of adding precision to the DOE-2 weather files
> is not an issue of stochastic behavior, but simply that of round-off errors.
>
>
> Joe
>
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 108D
> Moraga CA 94556yjhuang at whiteboxtechnologies.comwww.whiteboxtechnologies.com
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
>
>
> On 7/27/2012 1:42 PM, Ralph Muehleisen wrote:
>
> 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
>
>
>
> On Thu, Jul 26, 2012 at 2:31 PM, Joe Huang <
> 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 94556yjhuang at whiteboxtechnologies.comwww.whiteboxtechnologies.com
> (o) (925)388-0265
> (c) (510)928-2683
> "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 > -- Joe Huang White Box
> Technologies, Inc. 346 Rheem Blvd., Suite 108D Moraga, CA 94556 (o)
> (925)388-0265 (c) (510)928-2683 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 </x-flowed>
>
>
> >>
> Christopher Jones, P.Eng.
> Suite 1801, 1 Yonge Street
> Toronto, ON M5E1W7
> Tel. 416-203-7465
> Fax. 416-946-1005
> email cj at enersave.ca
>
>
>
>
>
> _______________________________________________
> Equest-users mailing listhttp://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
>
>
> _______________________________________________
> 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
>
>
>
> _______________________________________________
> 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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20120728/baef8c5f/attachment-0002.htm>


More information about the Equest-users mailing list