Revision history [back]

Hello,

I am running a District Energy System in Modelica/Dymola using the geojson to modelica translator and Modelica buildings library. My model has 150 buildings attached to the District HW and CHW loops.

I am having an issue with cooling plant operation.

Whenever the cooling plant is enabled, I get massive reduction in Integrator time step. I have traced the issue down to the calculation of energy balance for the fluid volume inside the cooling tower.

From what I can tell, the solver hits major errors whenever the value of the energy balance in the cooling tower fluid volume changes significantly. The strongest driver of changes to the energy balance is the outside air temperature.

I cannot figure out how to deal with this issue... theres nothing I can do the reduce the oscillations in outside air temperature. How can I reduce the sensitivity of the energy balance equation to these changes?

Thanks, Graham

Hello,

I am running a District Energy System in Modelica/Dymola using the geojson to modelica translator and Modelica buildings library. My model has 150 buildings attached to the District HW and CHW loops.

I am having an issue with cooling plant operation.

Whenever the cooling plant is enabled, I get massive reduction in Integrator time step. I have traced the issue down to the calculation of energy balance for the fluid volume inside the cooling tower.

From what I can tell, the solver hits major errors whenever the value of the energy balance in the cooling tower fluid volume changes significantly. The strongest driver of changes to the energy balance is the outside air temperature.

I cannot figure out how to deal with this issue... theres nothing I can do the reduce the oscillations in outside air temperature. How can I reduce the sensitivity of the energy balance equation to these changes?

Thanks, Graham