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RES: [EnergyPlus_Support] Re: The best way to represent the trees
The take home message here is to make sure you can visualise a ray tracing through the object used for shading.
Which object you use to shade may impact on how many times your ray will be "hindered" as it passes across surfaces because some objects like the shading surfaces (as Lina pointed out) will hinder the ray regardless whether the incoming direction of the ray is on the "back" of the surface or the "front" (as defined by the normal positive vector of the surface, i.e. the order of the verticies) where as others like a "roof" surface will shade in one directions only.
Jean
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Joe Huang wrote:
>
> Ah, modeling trees in building energy simulations.
>
> What I've done (with DOE-2, but it's equally doable in EnergyPlus) is to model them as
> five BUILDING-SHADES making up a box, and give the shades a transmittance schedule
> depending on when the leaves fall. The second slide in the attached PPT is from an ASHRAE
> presentation I gave in Dallas two weeks ago that happened to have some trees modeled
> around a house. The only thing to watch out for, in my case at least, was to set the
> transmissivity at the square root of the intended value, since the solar radiation always
> passed through two building shades. If building-shades in EnergyPlus are one-way, then I
> guess even this detail is unnecessary.
>
> If you're not satisfied with how clunky a square tree looks, you can also input polygons
> to make a sphere. About ten years ago, I wrote some awk scripts to do that for modeling
> building domes in Egypt, that I reported in DOE-2 User News Sept-Oct 2002 (see second
> slide attached). Of course the script just does the top hemisphere, but extending it below
> shouldn't be a problem. The article is available at
> www.whiteboxtechnologies.com/downloads/02_09_Usr_News_YJH_modeling_domes.pdf , which
> contains the awk script. If anyone tries to modify it, like putting it in another
> language, outputting the vertices in E+ IDF format, doing the lower hemisphere, etc., let
> me know how it turns out.
>
> Joe
>
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 108D
> Moraga CA 94556
> yjhuang@...
> www.whiteboxtechnologies.com
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
>
>
> On 2/14/2013 2:51 AM, Fabiano Domingues Ferreira wrote:
> >
> > Thanks Jean!
> >
> > **
> >
> > *Fabiano Ferreira*
> >
> > *De:*EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] *Em
> > nome de *Geert Bellens
> > *Enviada em:* Thursday, February 14, 2013 7:53 AM
> > *Para:* EnergyPlus_Support@xxxxxxxxxxxxxxx
> > *Assunto:* RE: [EnergyPlus_Support] Re: The best way to represent the trees
> >
> > Jean,
> >
> > very helpfull ! I was looking for such a reference.
> >
> > Geert
> >
> > *Van:*EnergyPlus_Support@xxxxxxxxxxxxxxx
> > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] *Namens *Jean marais
> > *Verzonden:* 14 February 2013 08:09
> > *Aan:* EnergyPlus_Support@xxxxxxxxxxxxxxx
> > *Onderwerp:* [EnergyPlus_Support] Re: The best way to represent the trees
> >
> > Remember that a shading surface only shades in one direction, unless the newer versions
> > of eplus changed that. So you'll need an opposite face.
> >
> > I did this once:
> >
> > The 3 large horse chestnut trees (Aesculus hippocastanum) onsite are also modelled
> > having 17,5% transmission during summer and 73% transmission in winter. Transmissions
> > are based on the table ââ?¬Å"Solar Modifying Characteristics of Various Species of Treesââ?¬Â?
> > in ââ?¬Å"Landscape architectural graphic standardsââ?¬Â? By Leonard J. Hopper, 2007. The trees
> > are modelled for the daylighting simulation and in the energy simulation for both design
> > and baseline case models together with component blocks representing neighbouring buildings.
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx ,
> > Fabiano Domingues Ferreira wrote:
> > >
> > > Hi,
> > >
> > >
> > > I'm working in a project that I'm trying to model the trees. Follow attached the
> > geometry in 3D showing the way that I represent and bellow the transmittance schedule
> > that I have adopt.
> > > Does anyone know the best way to represent the trees?
> > >
> > > Schedule:Compact
> > >
> > > Transmittance schedule for Building 1 - Trees
> > >
> > > Any Number
> > >
> > > Through: 03/21
> > >
> > > For: Alldays
> > >
> > > Until: 24:00
> > >
> > > 0.3
> > >
> > > Through: 06/21
> > >
> > > For: Alldays
> > >
> > > Until:24:00
> > >
> > > 0.6
> > >
> > > Through: 09/23
> > >
> > > For: Alldays
> > >
> > > Until:24:00
> > >
> > > 0.8
> > >
> > > Through: 12/21
> > >
> > > For: Alldays
> > >
> > > Until:24:00
> > >
> > > 0.2
> > >
> > > Through: 12/31
> > >
> > > For: Alldays
> > >
> > > Until:24:00
> > >
> > > 0.3
> > >
> > >
> > >
> > >
> > >
> > > Thanks,
> > >
> > > Fabiano Ferreira
> > >
> > >
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