[TRNSYS-users] variable time step?

[David BRADLEY]

Fred,
   TRNSYS does not allow for a variable timestep. The advantage of a 
variable timestep is of course that when not much is going on in a 
building or in the system the simulation could speed up by taking a 
bigger timestep and potentially get done faster. We had considered 
adding such a capability at one point but decided that since Trnsys 
allows (forces?) users to define their own controllers a lot of the 
time, it would be very difficult to create an algorithm in the kernel 
that would decide on an appropriate timestep and not create havoc in the 
controllers. The integrator issue isn't  too hard - as long as you know 
what the current timestep is, its not too hard to handle internally. The 
issue is more about agreement between the algorithm that sets the 
timestep and the components that control the equipment.
Best,
  David


On 1/26/2011 00:04, Fred Betz wrote:
> I'm at a conference this week and someone mentioned using a variable time step in simulations (not TRNSYS) and I was wondering if this was possible in TRNSYS.
>
> I know you can make the time step a variable in the deck.
>
> I could see using this if you want to carefully control startup and shutdown of a device, but while the device is running or not running, you could have a larger time step. This would speed up the overall run time.
>
> It would probably play havoc on the printegrator.
>
> Just wanted to start a discussion about this topic to see if it's been done successfully and when.
>
> Fred
>
>
> FRED BETZ  PhD., LEED AP
> SUSTAINABLE SYSTEMS ANALYST
>   
> AEI | AFFILIATED ENGINEERS, INC.  
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David BRADLEY
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