[Bldg-sim] illuminance data in TMY2 file

[Ery Djunaedy]

Scott,

Thanks for the info. I know that the solution can be as simple as that.

This data is of course important only for the (annual) daylighting
calculation. Daysim is using this data. I suspect even EPlus or eQuest
will use this data for daylight control.

Thanks,

Ery


On Mon, Apr 6, 2009 at 5:10 PM, Horowitz, Scott <Scott.Horowitz at nrel.gov> wrote:
> Hi Ery,
>
> I don't know if this was also a problem with TMY2 or if you meant TMY3,
> but TMY3 files have the problem you observed. See the notice listed on
> this website:
>
> http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/
>
> For what it's worth, certain simulation engines (like EnergyPlus) don't
> use that data from the weather file.
>
> Hope that helps,
>
> Scott
>
> --
> Scott Horowitz
> National Renewable Energy Laboratory
> 1617 Cole Blvd.
> Golden, CO 80401
> 303.384.7560
>
>
>> -----Original Message-----
>> From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-
>> bounces at lists.onebuilding.org] On Behalf Of Ery Djunaedy
>> Sent: Monday, April 06, 2009 4:27 PM
>> To: bldg-sim at lists.onebuilding.org; radiance-general at radiance-
>> online.org
>> Subject: [Bldg-sim] illuminance data in TMY2 file
>>
>> All,
>>
>> Attached is the illuminance (global horizontal) for Boise, ID, from
>> TMY2 data. Note the valley in the graph on the left bottom corner
>> which is caused by the very low illuminance values for January (the
>> values are in the hundreds, compared to tens of thousand in February).
>> I know for a fact that in Boise January is not (much) darker than
>> December or February.
>>
>> Furthermore, the corresponding radiation data do not have that dip in
>> January. The illumination values are calculated based on the radiation
>> data, right? So if there is nothing wrong in the radiation data, is
>> this related to the model used in converting radiation data into
>> illumination values?
>>
>> I also checked another site in Idaho, it has the same dark January.
>>
>> Any thoughts?
>>
>> Thanks,
>>
>> Ery
>