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Dear Roel and David,
First of all, thanks for your quick response. I have been trying to figure out how your suggestions could help me further and that has raised some more questions, which I hope you can help me with. To start with David's assumption about creating a new component, it is correct that this is outside my project's scope. I have had a look at Windows 6, and this may indeed deal with the spectral selectivity issue. However, and please correct me if I'm wrong, I believe the window model you mention would only be useful if the coating were to be applied on the window instead of the transparent overhang (or in case of some workaround method). Therefore I think that I could use Windows 6 to calculate the SHGC/SC of the overhang (not the window), but I would have to combine it with other variables to find the Incident receiver radiation and Beam radiation on receiver that I need to use as an input for the Type 56 building. Initially, I assumed it to be not possible to change the transmission of the overhang, but in a reply by David on a question about a pergola with vegetation (http://www.mail-archive.com/trnsys-users@engr.wisc.edu/msg02046.html) I found a suggested way to do this anyway. It says that if the translucency of the vegetation is known, the incident radiation on the window (and heat gains inside) can be calculated using the Fraction of solar shading output of Type 34. In fact the heat transmission value that I would calculate with Windows 6 works the same as the translucency of the vegetation I would say, but how could I combine this with the Fraction of solar shading? I am working mostly in the Simulation studio now, but I also found an option to add your own input for a shading factor of an external shading device in TRNBuild. Would it maybe be correct if I didn't model an overhang in the Simulation studio, but instead do the following: - Let Type 34 calculate only the Fraction of solar shading - Use a lookup table to find the correct SHGC/SC/transmission value for the angle of incidence - Use the room temperature as an input for the lookup table to select either the transmission value for a coating that is turned on, or for a coating that is turned off - Use an Equation to multiply the Fraction of solar shading with the transmission value of the coating - Use the output of the equation as an input for the Shading factor of an external device that can be found in the zone manager of TRNBuild - Take the incident receiver radiation and beam radiation on receiver directly from the weather data file? I realise this doesn't take into account the reflection of sunlight into the room via the shading device, but for now this isn't my main concern. In case this sounds plausible, there is no need anymore to work with conditional overhang dimensions I reckon, but if not, Roel, could you tell me how I can use these? I can imagine that whatever the trigger may be can be used as a condition for the dimensions, but where can I input the 1 or 0 to use or not use the overhang? My apologies for the long story, and thanks in advance for helping again, I really appreciate it! Kind regards, Tom > Date: Tue, 12 Mar 2013 10:46:36 -0500 > From: d.bradley@tess-inc.com > To: r.c.g.m.loonen@tue.nl > CC: onherkenbaar@hotmail.nl; trnsys-users@cae.wisc.edu > Subject: Re: [TRNSYS-users] Glass shading overhang with dynamic reflection coating > > 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@tue.nl<mailto:r.c.g.m.loonen@tue.nl> > > www.tue.nl/staff/r.c.g.m.loonen > > > > > > > > > > ________________________________ > > From: De manke [onherkenbaar@hotmail.nl] > > Sent: Friday, March 08, 2013 4:19 PM > > To: trnsys-users@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 > > _______________________________________________ > > TRNSYS-users mailing list > > TRNSYS-users@cae.wisc.edu > > https://mailman.cae.wisc.edu/listinfo/trnsys-users > > > > -- > *************************** > David BRADLEY > Principal > Thermal Energy Systems Specialists, LLC > 22 North Carroll Street - suite 370 > Madison, WI 53703 USA > > P:+1.608.274.2577 > F:+1.608.278.1475 > d.bradley@tess-inc.com > > http://www.tess-inc.com > http://www.trnsys.com > |