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

Jeff Haberl jeffhaberl at tees.tamus.edu
Mon Apr 18 18:13:04 PDT 2005


Sounds like a bug in your incidence angle calculation, which you must shut-off for hours before sunrise and after sunset. I'd suggest you consult a solar text for more info., such as Kreith, Kreider and Goswami, or of course Duffie-Beckman.

Jeff
8=!  8=)  :=)  8=)  ;=)  8=)  8=(  8=) Blackberry  :=')  8=)  8=)  8=?

Jeff S. Haberl, Ph.D., P.E.............................jhaberl at esl.tamu.edu

Professor......................................................Office Ph: 979-845-6507

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-----Original Message-----
From: postman at gard.com <postman at gard.com>
To: BLDG-SIM at gard.com <BLDG-SIM at gard.com>
Sent: Mon Apr 18 19:12:32 2005
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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