Equations for horizontal radiation/ illuminance under overcast sky

The integrated horizontal illuminance for a standard CIE overcast sky is 7/9 times the zenith luminance.

If you have a Perez model or something more sophisticated in mind, you may need to perform a numerical integration.

Best,
-Greg

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From: "Sotiris Papantoniou" <[email protected]>
Date: November 12, 2013 12:21:20 PM PST

Hello Radiance Group,

I want to right a code which is estimating the illuminance (or ever better radiation) in horizontal level under overcast sky. Although I have managed to find similar equations for clear sky, I haven’t managed to find any for an overcast CIE sky.

Can you lead me to any reference that can help me on this research?

Thank you

Sotiris Papantoniou
PhD Candidate
Environmental Engineering Dept.
Technical University of Crete