Odd cooling behavior in Multi-zone building model

[Kersasp Cawasji]

Hello all, 

My name is Kersasp and I am currently working on my Masters thesis using the BuildingSytems Library.

In your Multi-zone building example from the User Guide (pg. 22), it can be seen that the cooling systems kick on in both zones even though the ambient temperature is well below TCoolingSet of 26 deg C (as shown in attache Figure 1.png). However, the times that the cooling comes on seems to correspond with the peaks in the ambient temperature. 

On recreating this same example, I obtained the same results (as shown in Figure 2.png). I have also plotted the TOperative of building1.zone.1 for reference. 

I am unable to understand why this behavior is occurring. I believe the results should closely match those of the Simple Building example in the User guide (Pg 11), in the case where the Ambient temperature is below the TCoolingSet (shown in Figure 3). In the shown figure, we can see that the cooling system is not needlessly running until summer time, when the ambient temperature is high and cooling is required. 

In Figure 4 I have plotted the the TOperative, TAir and TAmbient for Zone 1. Clearly we can see the fluctuation of TOperative as compared to Figure 3.  

I have have a feeling that in the Multi-zone building model, some logical error takes place as an effect of adding the additional zone to the system. 

If anyone can explain this anomaly, I will be really thankful! Also any tips on how to adjust the model to overcome this will be much appreciated! I have also attached the package I was using. 

Best regards, 

Kersasp

[a.inderfurt...@gmail.com]

Dear Kersasp,

thanks for your interest in the BuildingSystems library.

The spikes in the cooing load are caused by the sun's irradiation on the building, which can drastically increase the internal loads. Thus the cooling load, that has to be removed from the building in order to keep the zone temps below their respective threshold, is also increasing.

Kind regards,

Alex

[Kersasp Cawasji]

Hello Alex, 

Thank you so much for your quick response. I really appreciate it. 

However, can you please explain why the cooling system is not activated in the initial portion of Figure 3 (the single zone example from the User Guide)? I believe that the sun's irradiance should be the same for the both examples (Figure3 and Figure 4) since the ambient data is obtained from the same weather file (Iran_Hashtgerd). 

Also, as an unrelated question, I am unable to locate the BuildingSystems_Vis3D Package. Has this package been renamed or moved? If so, where can I find a current copy of it? It will be extremely helpful in my research. 

Thank you so much!

Best regards, 

Kersasp

[Matthis Thorade]

Hi Kersasp,
at some point we decided to remove the Vis3D part, because it was still quite experimental. Users had to install a bunch of extra software, with exact versions, to get the examples running. When you search for vis3d on the github page in our repository, you will find the commits where it was removed:
https://git.io/vbaPP

We did not delete the code, instead we moved it to a new repository, but that one is currently private:
https://github.com/UdK-VPT/BuildingSystems_Vis3D
If you want access, we can discuss that. But that is really just a copy of the code that we removed, no new changes or additions.

A fork (with substantial changes) of the vis3d code is also available from OpenModelica:
https://github.com/OpenModelica/modelica3d

We are currently investigating a different approach: Starting form an IFC file, we use IfcOpenShell to generate Modelica code for the simulation, and a Unity3D model that can be viewed using a HTC Vive. Communication between Modelica and Unity is handled by MDD, here is an issue with some background:
https://github.com/modelica/Modelica_DeviceDrivers/issues/156
Unity can import a variety of 3D formats:
https://docs.unity3d.com/Manual/HOWTO-importObject.html
Some first results have been presentend at IBPSA 2017, search for BuildingSystems_VR
https://goo.gl/vL9XGV
If that approach is interesting for you, we could also discuss if and how you could use the code we have so far.

Best regards,
Matthis

[a.inderfurt...@gmail.com]

Hi Kersasp,

the single zone model has an internal volume of 9m x 9m x 3m whereas the two-zone model has a total internal volume of 1m x 0.5m x 0.5m. These are two entirely different buildings with different construction and window-to-wall ratios. Basically you can assume that the solar irradiation has a bigger effect on the building and its cooling load when to windows are bigger in comparison to the overall size of the building (big windows and small building -> high window-to-wall ratio, low internal volume -> higher cooling needs; small windows and big building -> low window-to-wall ratio, higher internal volume -> less cooling needed).

Hope that helps

Alex

[Kersasp Cawasji]

Thank you Alex. That definitely explains it better. On experimenting some more using different sized building and windows, I can see what you were talking about. Thank you so much for your help and support!

Best regards, 

Kersasp

[Kersasp Cawasji]

Hello Matthis, 

Thank you for the quick response. I had noticed the code deletions and I will try to extract the packages from there, just to try and recreate a few of the examples and possibly try to apply it to my thesis work. I am only looking for a simple geometry visualization of a 3-4 zone house (somewhat similar to the way you've done the 13 zone office building).

Would you please list out the extra software and their respective versions that I would require to recreate some of the examples? 

Thank you for the help. 

Best regards, 

Kersasp

[Matthis Thorade]

Hi Kersasp.
I tried to find out the versions and learnt that the code you find in the history is not complete, due to license issues. We will try to clarify these and hopefully open the Vis3D repo to the public, but it might take a couple of weeks. I'll post here if there are any news.
Also, note that we are switching to the Unity approach because we consider it to be easier and more scalable.
Regards,
Matthis