[Radiance-general] GenCumulativeSky compiled for Mac?

[John Mardaljevic]

Hi Ji,

I was testing GenCumulativeSky.exe to get the* annual "global horizontal
radiation"* for *a single unobstructed upward sensor*.

The results is* *always *SMALLER or LOWER *than the *SUM of the "global
horizontal radiation" column in the epw file*. (For London.epw, up to 2.7%
lower; for Paris.epw, up to 1.73% lower, for Singapore.epw, up to 1.5%
lower ...)

May I ask:
1) Is the difference in this kind of magnitude acceptable?
2) is the difference related to the parameters for rtrace (I assume not, as
the sensor is unobstructed and the scene is empty...)?

I'd say those results are acceptable.  You are always going to get small differences depending on the how the skies are normalised and the cumulative map generated.  I'm not familiar with GenCumulativeSky, but my own cumulative sky approach usually gets me within 1 or 2% of the column total from the climate file.  Anything in that range I wouldn't worry about.

Best
John

John Mardaljevic
Professor of Building Daylight Modelling
School of Civil & Building Engineering
Loughborough University
Loughborough
Leicestershire
LE11 3TU, UK

Tel: +44 1509 222630 (Direct)
Tel: +44 1509 228529 (Pam Allen, secretary)

j.mardaljevic at lboro.ac.uk<mailto:j.mardaljevic at lboro.ac.uk>

http://www.lboro.ac.uk/departments/cv/staff/profile/367.html<http://www.lboro.ac.uk/departments/cv/>

Personal daylighting website:

http://climate-based-daylighting.com<http://climate-based-daylighting.com/>

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