[TRNSYS-users] Glass shading overhang with dynamic reflection coating

[David BRADLEY]

Tom and Roel,
   I would think that in such a case as this, it would be more 
appropriate (but maybe outside the scope of your project) not to use a 
workaround but to instead develop a component for TRNSYS that correctly 
models the physics of what is going on in the overhang. You could make 
the model take a window data file from Window 5 in order to deal with 
the spectral selectivity of the overhang and then pass the results on to 
the standard Type56 window model and you could also handle radiation 
augmentation on certain facades due to the overhang or to other nearby 
buildings. That said, I think Roel's comment that the Type56 window 
model assumes that the radiation falling on it has not already been 
spectrally selected is quite valid.
Kind regards,
  David


On 3/9/2013 08:58, Loonen, R.C.G.M. wrote:
> Dear Tom,
>
> Modeling and simulation of adaptable facade elements often requires the use of workaround strategies. This also seems to be the case here.
> As part of my MSc thesis "Climate adaptive building shells - what can we simulate?", I made an overview of the possibilities for performance prediction of adaptable building envelope components in TRNSYS: http://www.bwk.tue.nl/bps/hensen/team/past/master/Loonen_2010.pdf#page=57
>
> One approach to model the adaptable behavior of the shading element is to use an 'equation' to create conditional overhang dimensions (on/off) as an input to type 34. The equation can be based on solar incidence angles and could include a multi-band approach to spectral selectivity. You may want to subdivide the overhang in multiple smaller elements to approximate the semi-transparent effect by controlling the number of activated elements. So what you basically do is navigating in a look-up table with if-then-else logic to manipulate the fraction of solar energy that reaches the facade. A limitation of this method is that it disregards the impact of reflected sunlight to other zones. In addition, if the effects of spectral selectivity are (too) large, the default assumptions in the type 56 window model may no longer be appropriate.
>
> You could use the "SunSpace-Shading" example file as a starting point. Information about the use of 'equations' is available in the TRNEdit manual.
>
>
> Best regards,
>
> Roel
>
>
>
> [X]
>
> R.C.G.M. Loonen, MSc.
> PhD student
> Unit Building Physics and Services
>
> Den Dolech 2, 5612 AZ
> P.O. Box 513, VRT 6.16
> 5600 MB Eindhoven
> The Netherlands
>
> T +31 40 247 2571
> r.c.g.m.loonen at tue.nl<mailto:r.c.g.m.loonen at tue.nl>
> www.tue.nl/staff/r.c.g.m.loonen
>
>
>
>
> ________________________________
> From: De manke [onherkenbaar at hotmail.nl]
> Sent: Friday, March 08, 2013 4:19 PM
> To: trnsys-users at cae.wisc.edu
> Subject: [TRNSYS-users] Glass shading overhang with dynamic reflection coating
>
> Dear all,
>
> for the simulation of a new coating, I would like to simulate a transparent (glass) overhang above a window. The coating I'm interested in has a few important characteristics:
> - It is dynamic (it can be turned on and off)
> - It is spectrally selective (seperate between infrared and visible light reflection)
> - Its reflection value depends on the angle of incidence
> - The coating is located on this glass overhang.
>
> My question is what the best way would be to model this configuration in TRNsys. Most accurate would probably be to create an overhang above the window, of which the properties can be adjusted. I haven't found a way to create a glass overhang yet, nor a way to add a coating with the abovementioned flexibility and selectivity. Could anyone tell me whether this is possible, and if so, how I can do this?
>
>
> ***Alternative solution***
>
> If this is not possible, I may have an alternative, but again with some questions. I do have a table with transmission values of the coating for each angle of incidence, so a way to get around this might be to let TRNsys determine the percentage of the window that is shaded by the overhang at a certain time and date, and multiply this output with the reflection value that I can find in this table. If I would do so for visible light and infrared light, and combine the results, I would get a g-value with which TRNsys could calculate my cooling demand. For this method, there are a few things I wonder:
>
> - The angle of incidence can be taken from the weather data file, but how can I use this output as an input to let TRNsys select the appropriate transmission value from my table?
> - Is it possible to let TRNsys calculate the percentage of the window that is shaded, and use this as an input for the proposed multiplication with the transmission value from the table?
>
> Thanks a lot in advance to anyone who is willing to help and answer (some of) my questions.
>
> Kind regards,
>
> Tom
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David BRADLEY
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