[BLDG-SIM] strange behavior in simulating the solar radiation

[Steven.Moller at csiro.au]

Danni,
Do you see the spikes before resolving the solar beam onto the wall? If
so, you may need to test the solar altitude angle is greater than 1 or 2
degrees above the horizon AND/OR test for sunrise/sunset times.

If the unresolved data looks OK, check for angle of incidence onto the
wall.  I haven't checked the location, but you must be very close to
glancing incidence at these times.

HTH
Steve.

<><><><><><><><><><><><><><><><><><><><><><><>

Mr. Steven Moller
Building Thermal Analyst
CSIRO Manufacturing & Infrastructure Technology
PO Box 56, Highett. Vic. 3190, Australia
(Street address: Graham Rd, Highett, Vic. 3190)
Phone: +61 3 9252 6000 (Switchboard) 9252 6337 (Direct) 
Fax: +61 3 9252 6586
Email: Steven.Moller at csiro.au
Web : http://www.cmit.csiro.au 

<><><><><><><><><><><><><><><><><><><><><><><> 




>  -----Original Message-----
>  From: postman at gard.com [mailto:postman at gard.com] On Behalf 
>  Of Danni Wang
>  Sent: Tuesday, 19 April 2005 10:13 AM
>  To: BLDG-SIM at GARD.COM
>  Subject: [BLDG-SIM] strange behavior in simulating the solar 
>  radiation
>  
>  
>  I used the formula from ASHRAE Fundamentals 2001,
>  Chapter 30 Fenestration, Section Determining Incident
>  Solar Flux, Equation 10~24,  to simulate the direct,
>  diffuse, and reflect solar radiation on a south wall
>  in Sacramento in June.
>  
>  The result seems close to, or at an acceptable scale
>  of, the measured solar data (as recorded in nrel.gov
>  website) for 5~19:00 hr of a day. But there are sharp
>  spikes before 4:00 and after 20:00. The maximal value
>  of the spikes for direct radiation gets to 5000w/m2,
>  for diffuse radiation gets to 1200w/m2. This is
>  unexpected to me. I tried someone else's code and
>  result was very similar. May there be an explanation
>  for this?
>  
>  
>  Thank you very much.
>  
>  -- Danni 
>  
>  
>  		
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