[esp-r] Re: Proposed development of window shading models

[Bart Lomanowski]

Gunter, 

Thanks for the info.

> But also WIS shows a crued defect: It is NOT able to take the azimuth angle
> of
> the sun into account. A recent work from Mr. Kuhn, Fraunhofer-Institute of
> solar
> energy systems in Freiburg, Germany, has shown, that this defect may yield -
> at critical
> sun angles - to an underestimation of solar heat gain of appr. 100% !!!!!!!
> Therefore it would be the best - for my opinion -, if the new enhanced
> facade model
> (glazing AND blinds) takes into account ALL relevant angles:
> - the slope angle of the blinds
> - the sun heigt angle (or the profile angle)
> - the sun azimuth angle
> Concerning this topic, Mr. Kuhn has developed a new, enhanced algorithm (I
> assume
> based on raytracing), which considers all these angles. 

Our models do in fact take into account all the relevant angles: 

Glazings - incident angle
Venetian Blind - slat angle (tilt of the blind)
               - profile angle (projected "sun height angle" into vertical 
plane normal to facade)
               
The profile angle is a function of the solar altitude angle (sun real height 
angle) and the facade azimuth angle (difference between the solar azimuth and 
the facade orientation). Anotherwords, the profile angle takes into account the 
sun's altitude and azimuthal changes.  

>From what I can tell, Mr. Kuhn's work deals specifically with interior and 
exterior blinds due to the type of model used (i.e. the glazings are lumped 
into one layer and the blind into another). While this approach is definitely 
beneficial for performance rating of specific blind products on their own, the 
intent for the ESP-r work is to be able to specify any combination of glazings 
and venetian blinds, based on our complete (stand-alone code running) models 
considering the more standard types of venetian blinds.  

Very interesting work though, thanks for the references and contact info!

Regards,
Bart