[TRNSYS-users] Type 15-2: Relationship between data arrangements, simulation times and convergence

[Flynn Ciaran]

Hello,

I have a couple of questions concerning the relationship between the arrangement of data in TMY2 weather files, TRNSYS simulation times and convergence errors. I tried looking at the source code but I could not figure out the answer..
I am running a simulation for one year, using Type 15-2 for weather, starting at 1h on July 1st and ending at 24h on June 30th. This leaves me with two options:
1) Either I rearrange the tm2 file to start at 1h on the 1st of July and end at 24h on June 30th, and set the simulation start and stop times to 0 and 8760h respectively, or
2) Either I leave the weather file as it is and set the simulation start and stop times at 4344h and 13104h respectively.

When I use a provided weather file (e.g. CA-BC-Vancouver-718920.tm2) and set the simulation time step at 0.1h, I get the following:



Failed convergence time steps

Time steps where:
calculated total horizontal radiation > horizontal extraterrestrial radiation

Time steps where:
direct normal radiation > solar constant

Time steps where:
calculated horizontal beam radiation > total horizontal radiation

1)

7719

10664

124

3498

2)

6424

-

-

13


So my question are:

-          Why is TRNSYS giving different error messages if the same weather data are used ? (I believe that there are no other types in my file that could explain the reason for this)

-          What parameters do the radiation values calculated by TRNSYS depend on and how are they calculated?

-          What is the best approach in this situation (minimal radiation errors)?

Thanks a lot,
Ciarán





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