Public defence in the field of Systems and Operations Research, M.Sc. Zichan Xie

Title of the thesis: Dynamic Modeling of District Heating Network Based on Discrete Event Simulation

Thesis defender: Zichan Xie
Opponent: Professor Henrik Saxén, Åbo Akademi 
Custos: Professor Risto Lahdelma, Aalto University School of Science

Heating and cooling are vital to our daily lives, accounting for nearly half of the EU's energy consumption. While district heating (DH) systems offer an efficient way to integrate renewable energy and reduce emissions, they currently supply only 8% of global heat demand. A major challenge is the lack of real-time monitoring and smart control, which limits system efficiency and sustainability.
In this research, we developed a fast, accurate, and flexible simulation model for DH networks. Our innovative approach uses variable time steps within a discrete event simulation (DES) framework. By dynamically adjusting calculations and focusing only on critical system changes, the model achieves both computational efficiency and reliability.
The DES model was validated using measurements from three real applications: a single pipe, a tree-shaped network, and a meshed network. Key results demonstrate that our model can simulate an 85-day operation of a meshed DH network with 186 pipes in just 0.29 seconds, while maintaining temperature deviations as low as 1.15 K across 80 substations.
This high-performance DES model provides operators with a powerful tool for:
•    Real-time system monitoring and operational state detection
•    Fault diagnosis and operational troubleshooting
•    Network updating and performance evaluation
•    Control strategy testing and improvement
•    Renewable energy integration planning
The model's combination of accuracy and computational efficiency enables rapid scenario analysis and system optimization, supporting smarter decision-making for DH network operations.

Key words: Discrete event simulation; Lagrangian method; Variable time step; Dynamic hydraulic-thermal simulation; District heating network

Thesis available for public display 10 days prior to the defence at Aaltodoc.