Wonsun Song

Friday, October 18, 2024, 8:00 - 9:00

Room 01-012, Georges-Köhler-Allee 102, Freiburg 79110, Germany

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This thesis investigates the mathematical modelling and optimization of a renewable energy system comprising thermal energy storage using water as a medium, a heat pump, heating loads, an electricity grid, and photovoltaics. Using this system, we address the challenges of increasing renewable energy integration, seasonal energy mismatches, and the importance of the heat transition. In particular, we explore sector coupling — the conversion of electricity to heat via the heat pump, with seasonal heat storage acting as a buffer to mitigate these mismatches, providing a pathway toward carbon-neutral energy systems.

We develop different models for thermal energy storage systems, ranging from fully-mixed to detailed stratified models incorporating temperature and mass flow dynamics. In addition, we apply a multi-node lumped capacitance method for heat transfer between the storage and the ground for the Underground Thermal Energy Storage (UTES) system. In a case study of the heating system in Dietenbach, Freiburg, we evaluate various configurations using the fully-mixed model. In the economically optimized configuration, the projected heating cost per household ranges from 121 EUR to 240 EUR per year, excluding annuity and operational costs.

This thesis highlights the economic and environmental benefits of seasonal thermal energy storage systems. From a control engineering perspective, we lay the groundwork for further research into the optimal control of seasonal thermal energy storage systems and provide a practical example of the averaging method in real-world applications.