[EnergyPlus_Support] Re: Calculating effective SHGC

["Liam O'Brien" <liambrn@xxxxxxxxx>]

Thanks for your response. I'm not so sure it's that easy.

My objective is to calculate the solar fraction of a building from the bottom-up, by tracking every Joule of energy that enters and leaves it. So I'm really looking for the ratio of solar energy that enters the building to what is incident on the glazing - maybe not annually, but certainly  seasonally (e.g., heating season). I'm not so interested in the instantaneous SHGC.

As I mentioned earlier, the issue is that E+ reporting aggregates the convective and radiative exchanges with the inner glass surface, which includes both the effects of the sun and merely temperature differences between indoors and out. If I can disaggregate these, I'll be golden. One idea is to run two simulations and "turn off the sun", but this is not very elegant!

What would your approach be to calculating the instantaneous SHGC (based on what E+ reports)? Maybe I can extrapolate your methodology to obtain what I want.

Cheers,
Liam

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@...> wrote:
>
> 
> The effective ratio of solar heat gain to total radiation falling on the assebly will change for every simulation time step, because the wind outside will change, the zone temperature and the surfaces temperatures and thus both convective and radiative and conductive heat transfer rates will change for each time step not to mention the angle and intensity of direct radiation and diffuse radiation.
> 
> You could easily calculate it on any one timestep, possibly even plot this ever changing number over the whole year (though that would probably need a bit of EMS reporting). 
> 
> The only question is, what are you hoping to learn from it? What is your end goal with this investigation?  
> 
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Liam O'Brien" <liambrn@> wrote:
> >
> > Hi all,
> > 
> > Does anyone have any insight on a good approach for calculating the effective SHGC of a window in E+. (I'm not asking for the rated SHGC, but rather what actually happens over a year). SHGC = transmittance + absorbed solar radiation that eventually convects and radiates inwards. 
> > 
> > The transmitted part is directly reported by E+, but the absorbed part that makes its way inward is not directly reported (because the net convection and radiation are provided; not just that caused by solar radiation). 
> > 
> > Your thoughts are welcome.
> > 
> > Thanks in advance!
> > 
> > Liam O'Brien
> > Assistant Professor
> > Carleton University 
> > Ottawa, Canada
> >
>




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