Hello, 

I have a question about running thermal analysis in case of a complex shading device defined in Grasshopper. 

Since Energy Plus is working only with planar surfaces (as far as I know, please correct me if I am wrong) I was wondering if there is a way to 'simplify' the process by entering some 'coefficients' in IDF file?

The paper on this link: http://www.gsd.harvard.edu/research/gsdsquare/Publications/Omidfar-...

is about how to run it in Design Builder, but to be honest, I have never used it...

''In order to model the effect of the Ornamental Hybrid Screen on the energy consumption of the space, specific performance criteria of the Screen had to be measured using DIVA, including the screen's shading coefficient and a yearly electric lighting schedule based on DA. The results were then synchronized with a thermal analysis performed in Design Builder linked with Energy Plus (Reinhart, 2010).''

Basically, I should introduce the shading coefficient in IDF Energy + file? Or I am wrong? And also, how can I calculate it? 

Regarding the lighting schedule, I know it should be defined in IDF file and I know how to do it manually, but how can I define one that is based on DA?

I hope you do not find my questions confusing, I do not have too much experience in this software, but I am willing to learn it!

Thanks everyone for help!

Danijel

 

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Hi Danijel,

> Basically, I should introduce the shading coefficient in IDF Energy + file?

In Azadeh Omidifar's paper, she calculated an hourly shading coefficient (more on that below) and used it to schedule the transmission of a shading object in EnergyPlus.

> And also, how can I calculate it? 

A good method is to set a node grid behind a shading screen in DIVA and to run a climate-based metric simulation. These simulations, besides generating overall metrics such as "Daylight Autonomy" also create hourly illuminance files (in C:\DIVA\Temp\RhinoFileName\RhinoFileName.ill). Azadeh ran the same hourly simulation with the screen and without it and used the ratio of the two to create her shading coefficient schedule. This step must be done manually.

> Regarding the lighting schedule, I know it should be defined in IDF file and I know how to do it manually, but how can I define one that is based on DA?

The method is described on this page, http://diva4rhino.com/user-guide/rhino/lighting-controls

Basically DIVA/DAYSIM creates a 8760 hour schedule file as a csv which can be linked into thermal programs such as EnergyPlus as a schedule.

Please let me know if you have any more questions.

Best regards,

Alstan

Hello Alstan,

Thanks for the reply! I am starting my thesis now, so I wanted to know if I can address thermal analyses in case of a complicated geometry shading! That is great!
Anyway, since it is still in early phase, I don't have any questions at the moment, but I think later will be messy. :)

Thanks once again!

Regards,

Danijel

Hi Alstan,


So the Shading coefficient is obtained from the solar radiation or the hourly illumination?

What do she use to calculate the ratio ?

Thank you

> And also, how can I calculate it? 

A good method is to set a node grid behind a shading screen in DIVA and to run a climate-based metric simulation. These simulations, besides generating overall metrics such as "Daylight Autonomy" also create hourly illuminance files (in C:\DIVA\Temp\RhinoFileName\RhinoFileName.ill). Azadeh ran the same hourly simulation with the screen and without it and used the ratio of the two to create her shading coefficient schedule. This step must be done manually.

> Regarding the lighting schedule, I know it should be defined in IDF file and I know how to do it manually, but how can I define one that is based on DA?

The method is described on this page, http://diva4rhino.com/user-guide/rhino/lighting-controls

Basically DIVA/DAYSIM creates a 8760 hour schedule file as a csv which can be linked into thermal programs such as EnergyPlus as a schedule.

Please let me know if you have any more questions.

Best regards,

Alstan

Hi Mohamed, 

She used the hourly solar radiation, which can be calculated in DAYSIM with a little editing of the header (.hea) file, but not from DIVA directly. If you're interested in doing this, I recently typed out some instructions to someone else which might be helpful,

If you run a DAYSIM, Climate-Based simulation in DIVA, to get W/m2 irrad. values from it, you need to browse to,
C:\DIVA\Temp\RhinoFileName\ and open RhinoFileName.hea.

You will need to edit the .hea file yourself and copy and modify the sensor_file_info line such that the file reads,

sensor_file_info 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0...
sensor_file_unit 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2...

Where sensor file unit is all 2's instead of 0's, which will make the contents of the .ill file in the simulation directory in W/m2 instead of lux. Then just re-run the RhinoFileName.bat file. When it is complete, the RhinoFileName.ill file will be in units of W/m2.

You can open this in Excel, etc. for analysis.

I believe Azadeh took the mean value across the window with the shade and without the shade and used the ratio, at each hour, to make her shading coefficient schedule.

Best,

Alstan

Hi Alstan,

Thank you.

Do you have an idea about the number of the nodes and if their location/ position can affect the results? 

Thank you.

From how I seem to understand the process based on this thread, I'd say the number and positioning of nodes would indeed modify the results, especially if the shading device to be tested exhibits localized effects (e.g. acting as light shelf in the higher part and as shielding screen in the lower...). So more nodes could, in that scenario, improve results' accuracy.+

Max

Hi Mohamed, 

I think the answer depends on what you're modeling. The nodes should be dense enough to capture the irradiance / illuminance variation behind the shading device.

Best,

Alstan

Hi, 

I am having a problem with setting up the IDF file with the coefficient schedule. Actually, it is more an Energy Plus question, but I hope you can help.

First, the .csv file should be loaded under the Schedule: File, same as the Lighting and Occupancy schedules? 

Basically, from what I can see, only one value can be set up for SHGC (WindowMaterial: SimpleGlazingSystem) or Solar Transmittance (WindowMaterial: Glazing), but not a whole schedule? Or there is another thing that should be modified? :(

If I understood right, the idea is to change the properties of the glazing with the SC, so in the EP model I do not have any shading device (shade/blind)?

Thanks everyone for help!

Danijel

Hi Danijel,

What the above conversation references is creating a shading object and scheduling its transmittance. The shading object is placed a small distance in front of the glazing. This approximates the amount, but not the direction, of light which passes through a complex screen.

I paste an example of this below.

Best,

Alstan

Shading:Building:Detailed,
        Shading Screen Object, !- Detached Shading
        ShadingTransmittance Schedule, !- Shadowing Transmittance & Schedule
        3, !-Triangle
        33.52800 , 10.66800 , 10.05800 ,
        33.52800 , 13.71600 , 0.9140000 ,
        33.52800 , 4.572000 , 0.9140000 ;

Hi Alstan,

Just to let you know that everything went fine! I've managed to apply the schedule! Thanks for all your help!

Best,

Danijel

Hi Alstan,

Is it possible to link the schedule of the shading coefficient to the viper tool or even to the diva rhino tool.

Can it be done to more than one window to the same simulation. A room with a south facing and east facing windows, and each has a different shading coefficient. 

Did you mean above to add it manually to the exported IDF file?

Thank you,

Hi Mohamed,

There isn't an automated way of doing this in DIVA -- you'd have to add it to the IDF file yourself.

Alstan

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