[Bldg-sim] Errors in TMY3 Files

Justin Spencer jspencer17 at gmail.com
Thu Dec 24 08:13:04 PST 2020


My personal opinion is that while TMYs are nice, given computing power
available today and the new problems we are going to need to solve, where
the value of energy changes by orders of magnitude and extreme conditions
matter, we should be considering running with many years of weather data
instead. I’ve had some projects where we did this, but my business is all
about grid impacts of aggregations of buildings, which is a little
different use case than most. My sense is that you generally work with TMY
and then move to running the weather decades and perhaps then focusing on
the weather year with your design shortage condition, before returning to
the weather decades. Maybe we will still slice 2020 out, just because.

Happy holidays!

On Thu, Dec 24, 2020 at 6:46 AM Joe Huang via Bldg-sim <
bldg-sim at lists.onebuilding.org> wrote:

> :-)
>
> Presenting metadata or applying checksums would pick out arithmetic or
> unit errors like what happened in the original TMY3s, but better
> documentation of the data and their provenance is the key to making sense
> of a weather file.  This thread has been talking about mistakes in the
> TMY3s, but I give credit to NREL for developing the TMY2/TMY3 format that
> added flags to every data element and included the actual time stamp.
>
> Joe
>
> Joe Huang
> White Box Technologies, Inc.346 Rheem Blvd., Suite 205A
> Moraga CA 94556 <https://www.google.com/maps/search/346+Rheem+Blvd.,+Suite+205A%0D%0AMoraga+CA+94556?entry=gmail&source=g>yjhuang at whiteboxtechnologies.comhttp://weather.whiteboxtechnologies.com for simulation-ready weather data
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
>
> On 12/24/2020 3:28 AM, Chris Yates wrote:
>
> Like glazing, I'm often a bit lost when it comes to rooting out the right
> weather file. In one instance, this has even led to purchasing the same
> data twice from CIBSE!
>
> I've thought that either better presentation of metadata or applying
> checksums to weather files could get around this.
>
> Chris
>
> On Tue, Dec 22, 2020 at 1:11 AM Joe Huang via Bldg-sim <
> bldg-sim at lists.onebuilding.org> wrote:
>
>> I forgot to mention as an aside I noticed that NREL had taken the
>> (revised) TMY3 files offline several months ago.  However, these TMY3s in
>> EPW and BINM formats are still available on my Web site at
>> weather.whiteboxtechnologies.com/TMY3.   I'm also in the process of
>> adding the *.CSV format to the files now that they're gone from the NREL
>> Web site.
>>
>> Joe
>>
>> Joe Huang
>> White Box Technologies, Inc.346 Rheem Blvd., Suite 205A
>> Moraga CA 94556 <https://www.google.com/maps/search/346+Rheem+Blvd.,+Suite+205A%0D%0AMoraga+CA+94556?entry=gmail&source=g>yjhuang at whiteboxtechnologies.comhttp://weather.whiteboxtechnologies.com for simulation-ready weather data
>> (o) (925)388-0265
>> (c) (510)928-2683
>> "building energy simulations at your fingertips"
>>
>> On 12/21/2020 3:55 PM, Joe Huang wrote:
>>
>> Interesting to see my work described by someone who was never involved.
>> The original driver for doing that work was to correct the decimal mistake
>> in some of the illuminance data that NREL had noted in 2005 but never
>> corrected because the original developers had retired. The reporting of
>> precipitation was an additional improvement I offered to NREL, and actually
>> ended up the lion's share of the work because it required reprocessing all
>> the source weather files.  Neither of these corrections/improvements should
>> affect any other weather set developed from scratch.  i have always been
>> careful to not infringe on NREL's branding of TMY for a number of reasons,
>> one of which has just been shown that all TMYs are assumed to be related.
>>
>> Joe
>>
>> Joe Huang
>> White Box Technologies, Inc.346 Rheem Blvd., Suite 205A
>> Moraga CA 94556 <https://www.google.com/maps/search/346+Rheem+Blvd.,+Suite+205A%0D%0AMoraga+CA+94556?entry=gmail&source=g>yjhuang at whiteboxtechnologies.comhttp://weather.whiteboxtechnologies.com for simulation-ready weather data
>> (o) (925)388-0265
>> (c) (510)928-2683
>> "building energy simulations at your fingertips"
>>
>> On 12/21/2020 3:04 PM, Linda Lawrie via Bldg-sim wrote:
>>
>> the TMY3 files on climate.onebuilding.org have been corrected from the
>> document posted by Joe Huang on the tmy3 site.  But I think that was for
>> precipitation.
>>
>> the TMYx files would never have had this problem as they come from a
>> different source of our creation for the TMYx files.
>>
>> And, as I remember, the illuminance problem was corrected by NREL at some
>> point after their first post.
>>
>> ------
>> Linda
>>
>> FIBPSA, FASHRAE
>> http://climate.onebuilding.org - free repository of climate data for
>> building simulation
>> Climate.onebuilding is a FREE service not supported by any outside
>> organization or government agency.
>>
>>
>>
>> Does anyone know if the errors described in TMY3 files in this post from
>> Joe Huang on Jan 14 2015 still exist in files on the
>> http://climate.onebuilding.org/ website? And were these errors also
>> fixed in TMYx files?
>>
>> Specifically I’m interested in this issue:
>>
>>
>> 1) Illuminance. The TMY3s contain values for Global Horizontal, Direct
>> Normal, Diffuse
>> Horizontal, and Zenith Illuminance that are calculated based on the sun
>> position and solar
>> radiation. Although the documentation states that the units are 100 lux
>> for the first
>> three illuminances, and 10 candela/m2 for the Zenith Illuminance, all the
>> TMY3 files used
>> these units only for the period Jan. 2-31, and for the rest of the year
>> used units of lux
>> and candela/m2, respectively. NREL put out a notice in August 2008 (see
>> the link listed
>> earlier) informing users of this discrepancy and promising a corrected
>> version that didn't
>> make it out until now! In this revision, we've decided to keep the units
>> in the original
>> TMY3 documentation, i.e., 100 lux or 10 candela/m2, which is the same as
>> what was in the
>> TMY2, and avoids the superfluous five-digit precision.
>>
>> If I use a TMY3 or TMYx file from the climate.onebuilding.org website,
>> am I getting a TMY3 or TMYx version in which these issues are corrected?
>>
>>
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