Re: [EnergyPlus_Support] "Surface Ext Solar Incident" (w/m^2)

["Michael J. Witte" <mjwitte@xxxxxxxx>]

The problem occurs only for exterior base surfaces which have a DOOR 
subsurface.  For an unshaded surface, the "Surface Ext Sunlit Fraction" for the 
affected surfaces is incorrectly computed as  

   (BaseSurfaceGrossArea - DoorArea)/BaseSurfaceGrossArea 

This causes the incident solar on the base surface to be reduced by this 
fraction.  The workaround is to not use DOOR subsurfaces on exterior walls.  
Describe the wall in two parts, one with the wall construction, and one with 
the door construction.  

Mike


On 16 May 2006 at 10:19, Michael J. Witte wrote:

> I agree that one would expect the same value for incident solar [w/m2] for an
> unshaded base surface and its subsurface.  The values of absorptance (thermal
> or solar) should have no impact.  This is reporting the solar that is incident
> on the surface, not the amount that is absorbed.  
> 
> I have been testing this with several different files.  One of the files shows
> exactly the same incident solar on base and subsurfaces, other files show very
> tiny differences, and others show a more significant difference.  At this 
> point, I have no answer whether this is an input issue or an algorithm
> issue.
> 
> Mike
> 
> 
> On 14 May 2006 at 18:22, Georgios Kokogiannakis wrote:
> 
> > Hi all,
> > 
> > I run an annual simulation for a building and then looked at my "Surface
> Ext
> > Solar Incident" (w/m^2) average annual results. For 2 vertical (opaque)
> > surfaces
> > that have the same orientation and nothing shades them (e.g. an external
> door
> > on
> > an external wall) I was expecting to get results that are only different
> > because
> > of their (external) thermal absorptance. However, it seems that this is
> not
> > the
> > case - am I considering something wrong here?
> > For example:
> > -External West wall with 0.5 (external) thermal absorptance gets average
> > 51.84
> > w/m2 incident solar radiation
> > &
> > -External West door with 0.65 (external) thermal absorptance gets average
> > 55.31
> > w/m2 incident solar radiation
> > 
> > I would appreciate any help so that I make this clear.
> > Thanks.
> > 
> > Georgios
> > 
> > 
> > 
> > 
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> > 
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> > 
> > Attachments are not allowed -- please post any files to the appropriate
> folder
> > in the Files area of the Support Web Site.
> > 
> > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf and press
> the
> > "search" button.
> >  
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> > 
> > 
> 
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support      
> EnergyPlus-Support@xxxxxxxx
> 
> 
> 
> 
> 
> 
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
> 
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
> 
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
> 
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf and press the
> "search" button.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 
> 


========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





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