[Radiance-general] Re: Cumulative calculations of irradiance

[John Mardaljevic]

Rob,
> How would I do this with brightdata? I use a modified version of  
> Francsco's radmap to produce the aggregated image for these types of  
> analyses, but I'm interested in learning how to apply a brightdata  
> method instead. Is this faster? What is the input?

I generate the sky luminance pattern for each entry in the TMY file  
and then read-off the luminance values for points on a pre-determined  
grid.  I just keep adding to the values and then write them out in  
brightdata format (much like was done for the measured sky luminance  
patterns).  I settled on this scheme since it followed on from the  
validation.  I doubt that it is faster, or significantly so, than the  
aggregated image method.

The cumulative sun contribution is provided by a pre-determined grid  
of standard Radiance suns, where each sun contains the aggregated  
effect of all the nearby sun positions that occur throughout the  
year.  Just 150-200 or so suns provides a spatial distribution that is  
equivalent to a time-step of around 1/2 hour.  So, much better than  
creating a rad file with potentially several thousand suns (for a  
cumulative annual file).

Unfortunately, it's not code that I can share since it is part of an  
unwieldy mass of IDL procedures and scripts that only ever gets used  
in-house and is probably not fit to be let out of the door.

-John

-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)

jm at dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm