[Bldg-sim] Errors in TMY3 Files
Joe Huang
yjhuang at whiteboxtechnologies.com
Thu Dec 24 16:45:46 PST 2020
I agree with you in principle, but have some differences in implementation -)
I think it's a shame that typical year weather files* have become regarded as the end-all
for weather data, whereas they are just meant as a snapshot. Running multiple years
clearly has its advantages, especially if you're concerned about performance under extreme
conditions, but realistically that would push up significantly the computational effort,
as well as that to digest all that data :-).
What I find lacking in using a typical year file is that you get the average performance,
but not the error bands showing how much that could vary year-to-year. Instead of
running the entire time series, I thought about selecting the years with the highest
heating and cooling consumption. Those years will vary depending on the building (a glass
box might have peak cooling in a year with a lot of sunshine, while a building with no
windows might have a year with the most cooling degree days). About 4 years ago I made a
presentation at ASHRAE where I used a modified bin method to calculate the load for a
sample building and pick these peak years.
Anyway, what I've been thinking is to provide not just the typical year, but also the peak
historical years for heating and cooling.
Joe
* I do not like to use TMY as a generic label, since TMY refers to a specific product and
methodology developed by NREL
Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://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 8:13 AM, Justin Spencer wrote:
> 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
> <mailto: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.com <mailto:yjhuang at whiteboxtechnologies.com>
> http://weather.whiteboxtechnologies.com <http://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 <mailto: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
>> <http://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.com <mailto:yjhuang at whiteboxtechnologies.com>
>> http://weather.whiteboxtechnologies.com <http://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.com <mailto:yjhuang at whiteboxtechnologies.com>
>>> http://weather.whiteboxtechnologies.com <http://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 <http://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 <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/ <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
>>>>> <http://climate.onebuilding.org> website, am I getting a TMY3 or TMYx
>>>>> version in which these issues are corrected?
>>>>
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