Which variable is more appropriate for shading control? [closed]

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Dear unmethours members.

I am studying shaiding (venetian blind) control. During selection of input variables shading control, I found two varaibles which express solar beam's incidence.

The one is "Surface Outside Face Beam Solar Incident Angle Cosine Value". This variable indirectly expresses solar incident angle. But EnergyPlus example employs this variable for solar blocking, which is about shading control by EMS.

Another is "Surface Window Solar Horizontal Profile Angle". This directly expresses solar incident profile by projection of solar beam vector on wall. It is said that in EnergyPlus document."For a vertical exterior window, this is an angle appropriate for calculating beam solar quantities appropriate to horizontal window elements such as horizontal reveal surfaces, horizontal frame and divider elements and horizontal slats of window blinds. It is defined as the angle between the window outward normal and the projection of the sun’s ray on the vertical plane containing the outward normal." From the document, it is described for this variable to be more proper to shading control, especially Venetian blind.

However, I think that "Surface Window Solar Horizontal Profile Anlge" is hard to calculate in reality. Also, I want to know the big difference between first one that is translated to degree, and second one. In my thought, solar incident angle (translated from cosine to degree) expresses solar position in detail regarding specific surface.

(I've attached an image)

In this image, during solar beam inciding to south wall (not tilted), it is not that much different. I hope the positivie reponses that which variable is more practically appropriate to blind slat angle control.

Sincerely, thank you.