Does somebody know how to produce a rendering highlighting annual sunhours or luxhours, if possible combined with a file with cloudiness factors of a Test Reference Year for a certain location ???
I don't even know where to start !
Jochen
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There are several annual daylight simulation tools that use Radiance. Two of these are DAYSIM (http://irc.nrc-cnrc.gc.ca/ie/light/daysim.html) and the Dynamic Lighting System (http://www.iesd.dmu.ac.uk/~pcc/dls/). They both use similar techniques (daylight coefficients), but run in different ways. Both are free to download.
I haven't used DLS, but have DAYSIM, and it's a pleasure to use. it can give you daylight illuminances at given points for every hour (or more often) of the daylit year. you can also set a threshold level and it will provide daylight autonomies at the given points. daylight autonomy describes how often the natural illumination at a point exceeds the threshold value. with the hourly (or more often) daylight illuminances, you can calculate your annual luxhours.
John Mardaljevic's web site (http://www.iesd.dmu.ac.uk/~jm/) also describes an algorithm for predicting solar penetration. this will give you annual sunhours, or equivalent. the algorithm isn't yet available, but contact John if you'd like more info.
good luck!
Phil.
Phillip Greenup
Specialist Engineer
Arup Australasia
Level 10, 201 Kent St
Sydney NSW 2000
Ph (02) 9320 9426
Fax (02) 9320 9321
Does somebody know how to produce a rendering highlighting annual sunhours or luxhours, if possible combined with a file with cloudiness factors of a Test Reference Year for a certain location ???
I have done such kind of RADIANCE calculations by using "annual mean skies" models produced from hourly beam and diffuse irradiance data (obtained from the METEONORM software). Here is a stereographic projection showing the annual mean sky for Fribourg (Switzerland) using a falsecolor scale that maps the radiance values:
Fribourg_msky00.tif radiance_scale.tif
The sky vault is subdivided in 145 zones as defined by the CIE.
The corresponding RADIANCE scene file (F00.rad) is attached hereafter with the generic treg_sky.rad file. As indicated at the beginning of the file, the mean radiance values are computed over the daylit hours only. If you make a RADIANCE simulation under such a sky model (using rpict option -i), you get mean irradiance values in [W/m2]. If you want irradiation values in [Wh/m2], you just need to multiply the results by the number of hours indicated at the beginning of the file.
Note that in this sky model, the red, green and blue channels contain respectively diffuse, direct and total mean radiance values. To extract one of this component filter your picture like that:
to get the direct irradiance only: pcomb -e 'lo=gi(1)' original_picture.pic >direct_only.pic
or to get the total irradiance: pcomb -e 'lo=bi(1)' original_picture.pic >total.pic
Of course, due to this "unusual" way of using the RGB channels, it is not possible to use such a sky model with coloured materials. Such models have to be used with "gray" surfaces where the r,g,b materials parameters are the same (=surface overall reflectances).
With a similar approach I also prepared a mean sky model for daylighting studies (F00dl.rad). For such a model only the working hours (from 8am to 6pm) are averaged. The daylight saving time period is also considered. Again if you make a RADIANCE simulation under such a sky model (using rpict option -i), you directly get mean illuminance values in [lx].
If you want light exposure values in [lx hours], then just multiply the results by the number of hours considered in the model. The model uses the same RGB channels separation as explained above.
