[Radiance-general] Asking for informations

Wed Apr 6 23:18:49 PDT 2016

Dear Séverine,

from my point of view, if your interest lies with solar >energy< gain, then
Radiance is not really best suited. Typically, what you describe is covered
by thermal building simulation tools to a quite high degree of detail
(ESP-r, EnergyPlus, IDA-ICE, TRNSYS to name a few). It would likely be quite
difficult or probably even impossible e.g. to model the secondary heat gain
through windows / glazed facades (or opaque facades, for that matter). Also,
“what goes through” is not the whole story. What happens in the building is
also of major interest to be able to decide if the gains are “useful” or
“harmful”.

Why do you think you need the ray tracing approach?

Best

Achim

Von: Séverine HUET [mailto:S.HUET at vs-a.eu] 
Gesendet: Mittwoch, 6. April 2016 15:35
An: radiance-general at radiance-online.org
Betreff: [Radiance-general] Asking for informations

VS-A.jpg

VS-A

architectes d.p.l.g / ingénierie de l’enveloppe

Hi Radiance team,

I am a student in an engineering school and I am currently doing an
internship in a design office specialized in building envelope studies. 

My work consist in developing a tool to determine precisely the solar factor
of a facade, taking into account its shading devices and its geometry which
can be complex sometimes.

My idea is to use the software Grasshopper to:

1.    Import a geometry

2.    Define the materials of the scene

3.    Create the Radiance geometry 

4.    Create two analysis grid (vertical): one before the system
“shading+facade” to determine the incident solar energy, and one inside my
building to determine the transmitted solar energy.

5.    Then, use the Ray Tracing method to calculate the solar energy on each
point

This method seems interesting for my problematic but the calculations under
the hood may be not relevant for solar energy, insofar as it is designed for
light calculations and realistic rendering.

Questions :

1)    I apology if I am missing something obvious, I have done some
researches about the “Ray tracing” method used by Radiance but I still have
some interrogations about how it works
 Is the ray divided in many rays when
it punch a surface ? What is the different between the direct light and the
diffuse light (in terms of modeling) ? Is there a way to convert R G B
radiance provided by Radiance in solar energy for instance (like it is done
for luminance) ?

2)    I must not be the first to process this kind of problematic, so I am
wondering if it exists a calculation engine derived from Radiance which can
provide the solar energy using a kind of “ray tracing” method? 

For me, in principle, it is not that complicated, I mean it is possible. The
problematic is purely geometric and mathematic. I imagine: the ray launched
is define by a wave length, an intensity and a direction (to model the
direct radiation). When it reaches a surface, the intensity took into
account is the intensity of the surface’s normal projection of the ray. Then
the ray is divided in 3 rays: one transmitted, one reflected and one
absorbed, whose proportions (in terms of intensity) and directions depend on
the material definition of the surface reached. This last can react
differently according to wavelength domain of the ray. Do the same with
diffuse rays, to model the diffuse radiation. The absorbed part of the
incident energy could be transformed in heat (Infrared radiation) according
to the emissivity of the surface.

I am sorry about the lenth of the message. I really need to understand how I
can do to determine solar energy through different kind of materials
(translucent, transparent, opaque
). I would be really thankful if you help
me! This project constitute my graduation project, it is quite ambitious
that’s why I need some guidelines.

Thank you in advance, 

Yours sincerely

Severine Huet

VS-A, architectes d.p.l.g / ingénierie de l’enveloppe

41 place Rihour / F-59000 LILLE – France

Tél : +33 (0)3.20.52.11.44 ; Ligne directe : +33 (0)3.20.52.xx.xx / Fax :
+33 (0)3.20.52.05.15

email :  <mailto:courrier at vs-a.eu> courrier at vs-a.eu  / email direct :
<mailto:S.HUET at vs-a.eu> S.HUET at vs-a.eu /  <http://www.vs-a.eu> www.vs-a.eu

Ce courriel (et ses pièces jointes) est adressé exclusivement à son
destinataire ; il n’a pas de valeur hors de ce contexte précis et peut être
confidentiel. Nous remercions d’avance les destinataires involontaires de
s’abstenir de le dupliquer de quelque manière que ce soit, et de le
détruire. Merci également de bien vouloir en avertir l’expéditeur.

This e-mail (and its attachments) is intended to be for the only use of its
recipient; the message is worthless out of this specific context and may
contain confidential information. If you have received this e-mail by
mistake, please do not duplicate it in any possible way. Thank you as well
for notifying us immediately and deleting this e-mail.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.radiance-online.org/pipermail/radiance-general/attachments/20160407/3d0f1369/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 7230 bytes
Desc: not available
URL: <http://www.radiance-online.org/pipermail/radiance-general/attachments/20160407/3d0f1369/attachment-0002.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image003.jpg
Type: image/jpeg
Size: 1361 bytes
Desc: not available
URL: <http://www.radiance-online.org/pipermail/radiance-general/attachments/20160407/3d0f1369/attachment-0003.jpg>