[Bldg-sim] illuminance data in TMY2 file

[Horowitz, Scott]

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