What is the reporting frequency? Maybe
you are comparing results averaged over an hour to an instantaneous hand
calculation.
From:
Sent: Thursday, July 23, 2009
11:40 AM
To:
Cc: Feng Kelvin
Subject: [EnergyPlus_Support]
Summer Design Day -- Direct Solar Radiation Calculation
Hi group,
I am using my E+ v2.2 design day to simulate a simple concrete two rooms case.
I found E+'s Direct Solar Radiation output result doesn't match with direct
normal solar radiation calculation equation: EDN = A / exp ( B /
sin(beta) )
I pick up my case at 6:00am simulation results. E+ results give:
solar altitude angle, beta = 12.049 [deg]
direct normal radiation, EDN = 201 [W/m2]
I calculate solar altitude myself by inputting building altitude, declination
angle and solar time and found the solar altitude angle, beta = 12.049 is
correct. However, when I use
EDN = A / exp ( B / sin(beta) )
where A = 1093 [W/m2]
B = 0.186
I got EDN = 449.98 [W/m2], not 201 [W/m2] calculated by E+.
Am I missing sth in this, or this has been fixed in new E+ version?
--
Best Regards
Kelvin
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