Direct Sun positions in Daylight Coefficient Calculation in Daysim

daysim

#1

What is the latest number of direct contributions that Daysim considers?
It used to be 65, and then 2305. Are all the sun-positions considered now?
I can run a simulation and find this out from .dc file I believe, but I thought I should ask instead.


#2

I dont think 2305 was ever accessible through a GUI in any of the flavors of Daysim (despite the 2008 proposal). You can find the number of suns generated by your version of Daysim in a file called direct_radiance_file.tmp.rad in the daysim project directory. I checked mine (from a project a few months ago and it has 63 suns. direct_radiance_file.tmp.rad (7.1 KB)


#3

Thanks for responding Sarith. I just ran a study and I see 213 columns in .DC file. So that is 65 direct sun positions. I also checked the file you mention. Again, 65 suns are there. This makes me wonder why do you have 63?


#4

The original Daysim generates suns as per the the sunpath for a particular location, so it will keep deviating by a few suns. We do the same thing with HB[+], but take the full number of suns instead.

The 2008 DDS method and all the LBNL recommended methods such as 5 and 6 phase do away with this variability by setting 2305 (or 5165) suns irrespective of location. So, you can use the same model with different weather data without having to re-calculate the coefficient matrices.