Very simply, the direct normal solar radiation in the weather file that is used by E+ is actual site direct normal (measured or calculated) that includes the
effects of cloud cover already. All E+ has to do is calculate solar angles and reflections. So a surface normal to the direct beam gets 100% of the value. As the surface turns away from the direct beam, the beam radiation is reduced.
Ned Lyon, P.E. (MA, WV)
Staff Consultant
SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct
617.285.2162 mobile
781.907.9009 fax
www.sgh.com
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Thursday, June 16, 2016 9:06 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] how E+ calculates solar gain
At 10:05 AM 6/7/2016, allinson_louis@xxxxxxxxxxx [EnergyPlus_Support] wrote:
I've been trying to understand how E+ calculates solar gains from the epw weather file, but am struggling to find the right section in the engineering reference guide
I want to understand how direct normal radiation is used by energy plus. This is the 15th value in the epw file
does E+ adjust this value for the weather eg cloud cover? or is this value be used "as is" ie the value is a recorded value from a weather station?
E+ does no adjustment of values from the weather file -- except interpolation to the timestep if weather file is hourly and simulation is requested at sub hourly timesteps.
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Posted by: "Edward G. Lyon" <EGLyon@xxxxxxx>
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