[TRNSYS-users] Daylight model based on NType 79

[Philipp Lezajic]

Dear TRNSYS user,

I know that using a program like radiance would be the proper approach but I hope I can get some feetback on my thoughts for determing luminace on the floor plane of a zone.

Is it possible to use NType 79 (solar (direct+diffuse) radiation absorbed at inside surface) and following simplifications:

1. solar radiation shining on the surface is NType 79 divided by solar absorptance factor of the surface
2. equal luminace distribution over the surface
3. luminous efficancy of global solar radiation ~105 lumen/W
4. luminous efficacy radiating on the floor is the same, so transmission through windows and reflection on opaque surfaces doesn´t affect the luminous efficancy of sunlight

A more detailed approach would be to use NType 80 (solar direct radiation absorbed at inside surface) and NType 81 (solar diffus radiation absorbed at inside surface) with
- luminous efficany of direct sunlight between 70-105 lumen/W depending on solar altitude
- of diffus sunlight between 110-130 lumen/W depending on cloudiness.

I am not sure if simplification No4 tolerable for reflection. Windows filter UV-light which doesnt affect luminance so for transmission it should be ok. But I dont konw how reflection on opaque surfaces alter the wavelenght spectrum of sunlight.

regards Philipp






-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20100927/1eb55acb/attachment-0001.htm>