[Radiance-general] Watching the Skies (aka Sky Model Bewilderment)

[Jia Hu]

Hi Randolph:

I do not know what data you have and your reseasrch aim and thus will talk
about what I know about this issue. I am sure others have better ideas.
Generally, if you have direct and diffuse irradiation data (you can get real
time data from your local weather station, check DOE EnergyPlus program),
you can try Perez model (gendaylit program in Radiance) which determines the
sky type according to the irradation value (see Perez's paper in 1990).

If you use gensky, you have to specify the sky type. On the other hand, you
can also try gensky to find a best sky model fitting your measured data.
When using gensky, it would be better to use measured illuminance values
rather than measure irradiation value. I remember someone mentioned that the
irradiation data required by gensky is only visible range (I saw a post
talking about this)?

Cheers,
Jia


On Fri, Jul 16, 2010 at 6:20 PM, R Fritz <RFritz at lbl.gov> wrote:

> I have a pile of data from an actual test room, with more coming, and a
> Radiance model under construction. Do people have an opinion as to which sky
> model might best reflect the actual skies of Berkeley, California? I've got
> some reading ahead of me, Perez and Shirley and perhaps some CIE documents,
> but I'm wondering if anyone has perhaps some thoughts or cites to share. The
> test room is, yes, in Berkeley, California.
>
> BTW, I did find the discussion of sky modeling on the list in October of
> 2003. (If anyone hasn't seen it before, look for entries titled "Sky
> Definition" in <
> http://www.radiance-online.org/pipermail/radiance-general/2003-October/date.html
> >.)
> --
>
>
> Randolph Fritz • RFritz at lbl.gov
> Environmental Energy Technologies Division • Lawrence Berkeley Labs
>
>
>
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