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[EnergyPlus_Support] Re: weather file radiation

hello Ned

yeah you're right, the excel program doesn't account for cloud cover 
corrections, something I'll have to figure out...seems like I could 
get sky clearness factors (1-10, 10 full covered), do you think I 
should aply those directly as a percentage of the global radiation( 
ed. 8/10, 9/10). or should that affect only either the duffuse or 
direct components?...

but .. yes.. that could still be a mere approximation as you well 
point out

as for the model used itself I searched and found this url 
http://www.nrel.gov/docs/legosti/old/761.pdf as referenced by the 
author of the excel file.

best regards 

hector huerta

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Edward Lyon" 
<eglyon@s...> wrote:
> The problem with these calculations for energy modeling is that 
they give you a perfect clear day solar value for any time period 
you calculate.  If you had additional sky weather data for cloud 
cover, you could try to apply some cloud cover corrections.  
However, correcting the solar data with a cloud cover algorithm is 
still not as good as measured solar data, it can be as much as 50% 
off.  I know these cloud algorithms have been applied to some of the 
canned weather files we use that do not have direct solar 
measurements, but I have not seen the source equations yet. 
> Ned Lyon
> Senior Staff Engineer
> Simpson Gumpertz & Heger Inc.
> 41 Seyon Street
> Building #1, Suite 500
> Waltham, MA  02453
> Phone:  781-907-9000
> Fax:  781-907-9009
> >>> edhugar@y... 02/06/03 11:28AM >>>

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