Jia,
Direct and diffuse illuminance increase with solar elevation.
Direct illuminance tends to decrease with cloudiness, whereas diffuse
illuminance tends to increase with cloudiness (white clouds) up to some
point, after which it decreases (thick dark clouds). The diffuse
illuminance under a thin cloud layer is much higher than under clear skies.
The main problem with your file is that the cloud cover is obviously
incorrect. In Florida in general, and Gainesville in particular, summer
days have elevated cloudiness and many thunderstorms (e.g, one each
afternoon). This is not reflected in your data...
Chris
---------------
Hello friends,
I met a problem about the weather file. First of all, see one example, the
data are from weather file.
*DATE* *Global Horizontal Illuminance {lux}* *Total Sky Cover {.1}Opaque
Sky Cover {.1}* *Opaque Sky Cover {.1}* *5-Jan* *64100* *0* *0* *13-Jan* *
15300* *1* *1* *16-Jan* *46900* *0* *0* *18-Jan* *58500* *1* *0* *28-Jan* *
18700* *1* 1
Look at the Jan 16 and Jan. 18 illum. data and sky cover. For zero cover,
The horizontal illuminance is lower for sky cover of 0 than that for sky
cover of 1.
*My question is what factors influence the "Normal illuminance' and
"Horizontal illuminance' in the weather file? It seems that the "sky cover"
in the weather file is not the only factor according to the above example.*
I have uploaded the excel file of weather file at Problem_submittals folder
at URL:
http://groups.yahoo.com/group/EnergyPlus_Support/files/_Problem_Submittals/USA_FL_Gainesville.Rgnl.AP.722146_TMY3E.xls
I have highlighted the data in the weather file, and you can find it easily.
**
Thank you in advance.
Jia
--
Chris A. Gueymard, PhD
Solar Consulting Services
P.O. Box 392
Colebrook, NH 03576, USA
Tel. (603) 237-8550
Fax (603) 237-5314
http://www.SolarConsultingServices.com
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