Modelica-based modeling and simulation of district cooling systems: A case study

Kathryn Hinkelman, Jing Wang, Wangda Zuo, Antoine Gautier, Michael Wetter, Chengliang Fan, Nicholas Long

Research output: Contribution to journalArticlepeer-review

16 Scopus Citations


While equation-based object-oriented modeling language Modelica can evaluate practical energy improvements for district cooling systems, few have adopted Modelica for this type of large-scale thermo-fluid system. Further, to our best knowledge, district cooling modeling studies have yet to include hydraulics in piping networks alongside plant models featuring realistic mechanical systems and controls. These are critical details to include when looking to make energy and control improvements in many physical system installations. To fill these gaps, this study released new open-source district cooling models at the Modelica Buildings Library and leveraged these models for a real-world case study at the University of Colorado Boulder. The site includes six buildings connected to a central chiller plant featuring a waterside economizer. Several energy saving strategies are pursued based on the validated model, including control setpoint optimization, equipment modification, and pump setpoint adjustments. Results indicate that a combination of the studied measures can save the campus annually 84.6 MWh of energy, 8.9% of electricity costs, 58.0 metric tons of carbon dioxide emissions, while the waterside economizer cuts down chillers’ run times by 201 days/year, reducing maintenance costs and extending chiller life.

Original languageAmerican English
Article number118654
Number of pages15
JournalApplied Energy
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2022 Elsevier Ltd

NREL Publication Number

  • NREL/JA-5500-82277


  • Case study
  • District cooling
  • Modelica
  • Modeling and simulation
  • Optimization
  • Waterside economizer


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