[TRNSYS-users] Error in solar radiation distribution (sumsitot) and type 56

Dear TRNSYS team and users

It is around 10 days that I have got stuck in simulation of a building. After many things that I have already checked, it seems that there is a bug in Trnsys.

Here, I am going to raise the issue in detail hoping to get some response from users and Trnsys bodies.

Project:

Modelling of a building with 3 floors without considering system (just using type 56)

Each floor has 20 zones and the plans of all 3 floors are the same.

Followed process:

In the first round the building was drawn in Trnsys3d-SketchUp and imported into the Trnsys. After importing the *.idf file, a *.tpf file was automatically generated and was working very well. The problem came up when I needed to reduce simulation time step from 1 hr to 0.2 hr. (for controller settings in the next steps of my project)

Any way, a simple type 56 for a building with 3 floors, each floor 20 zone was not working with 0.2hr simulation time step.

The error is:

“Internal error in solar radiation distribution (sumsitot) of 56.388 % at time 56.40wave length band no.3 1:total solar, 2:visual solar, 3:non visual solar”

I was checking every thing but nothing was wrong. Finally, I sent an Email for users and asked for help. Christian from TRANSSOLAR and Matt from TESS kindly replied. Matt suggested me to follow the Christian advice and Christian wrote:

“One reason for this can be that in your 3DModel you have infinitesimal small surfaces. Please check if this is the case and if so you'll have to redraw the geometry“

Then, I checked every little part of the 3D model in Sketchup and also imported model in studio but there was not such evidence.

Even though I was quite sure that there is no such a little surface I redraw the entire model several times (at least 10 times) precisely but the result was the same and after importing the *.idf file into studio exactly at 56.4 hr the error comes up every time.

In the next try I decided to draw and import building floor by floor. After drawing the first floor, it was imported to the studio. Generated *.tpf file including Type 56 ran with 0.2 hr simulation time step. The result was perfect, and I decided to check the building with 2 floors. To make the drawing I used the drawing of the first floor (previously drawn) and copy it on the top of the first floor as second floor and then import the related *.idf file into studio. Type 56 of the building with two floors was working in 0.2 hr time step perfectly without error. Then, I repeat the process and copy the drawing of the second floor and paste it as third floor in Sketchup. After importing the *.idf of the building with 3 floors, type 56 was only able to run in simulation time step 1.0 hr. when I was reducing time step to 0.5 or 0.2 the previous error came up.

All in all, this approach proved that there Christian’s expectation was not correct because if it was correct I could not run the related type 56 for the first floor and second floor without error as well.( third floor was copy and paste of second floor)

Even though it was quite clear that there is no any small surface (Christian expectation) I was thinking maybe there is some problem about connection between Sketchup and studio. Therefore, I decided to insert entire building manually in type 56. The result of manual filling type 56 was 100% similar to the importing building from Sketchup. That means, first floor and second floor was running perfectly in different simulation time step (0.2 hr , 0.5 hr and 1 hr) but just when I added the third floor, type 56 came into the same error (mentioned above) at the same time (56.4 hr).

By following these two approaches I have got sure that the error is not because of small and unattended surface (Christian expectation) and also is not because of importing *idf file from Sketchup.

This error has also detected by other users Xavier (2004) which Michaël Kummert was replied and accepted the bug in version 15.

My expectation:

1- There are limits on number of zone for each type 56.

2- Weather component (type 109) is not able to deal with some time steps.

3- There is a bug in type 56 to run model with time steps less than 1.0 hr.

4- There is a bug for solar radiation distribution within type 56.

For further detail following files are attached:

1- Folder 1 including related files of building with two floors developed in Sketchup and imported into Trnsys which works fine in different time steps (*.idf, *.tpf, *.dck and *.b17 files)

2- Folder 2 including related files of building with three floors developed in Sketchup and imported into Trnsys which is not working in time steps less than 1.0 hr (*.idf, *.tpf, *.dck and *.b17 files)

Hereby, I was wondering if anybody could help me. I am not a freelance researcher; I am a PhD student with dispread need on doing simulation. I hope you consider user situation with your kind responses.

Sorry about the long story and thanks for your time

Regards

Mehdi Shahrestani