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

Danni Wang liuwang94710 at yahoo.com
Mon Apr 18 17:12:32 PDT 2005

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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