[EnergyPlus_Support] Re: thermal lag in solar radiaiton.

["FCoelho" <fabio.coelho@xxxxxxxx>]

I wouldn't expect any solar radiation at night (unless its in the poles, during solstice).

You might have used it on some theoretical methods like SLR, to account for solar gains smoothed though out the day/month due to thermal mass. In energy plus the calculation is dynamic, and there's always an energy balance. Solar radiation is not lagged, you can say some of it it's "absorbed" and stored on the thermal mass of the building materials, and this energy would be re-radiated as long wave radiation, on the far infrared spectrum and this is not accounted as solar radiation.

I think the easiest way to look for the "thermal lag" you are after is looking at temperature swings, or gains of the surfaces, more noticeable on solar exposed internal walls/slabs. If you are modeling something with high internal gains during the day, (i.e. an office), you will notice this as well due to this gains. What fraction of it can be accounted for the daily solar gains?!! I don't know, you will have to make some estimation.(and I dont use EP+ that often nowadays)

If you are not comfortable with the heat transfer processes involved I recommend a heat transfer book like "heat transfer a basic approach - Neccati Ozisik" and some solar literature as well like " Solar Engineering of Thermal Processes  by John A. Duffie and William A. Beckman".

Page 236 of Input/Output reference - You can read about the Surface Output Variables available.

Page 61 of Engineering Reference - Explains the heat balance in internal surfaces.


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "mindy" <mindyyam@...> wrote:
>
> Please help.
> 
> 1. Will Energyplus show any thermal lag in calculating the solar radiation through windows? 
> 2. I am expecting some nonzero solar radiations at night (due to thermal lag) but it always shows zero. so where is this thermal lag effect? Is it even captured by Energyplus, or it just does not have that feature. 
> 
> Thanks everyone.
>




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