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

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