Interview with bachelor’s student Isabella Elbe
Isabella Elbe is studying Engineering Science at the Technical University of Munich and is currently writing her bachelor’s thesis at the TUM Chair of Energy Systems. Her research is supervised by Christopher Schifflechner and Arianna Passamonti, with support from the Geothermal Alliance Bavaria (GAB). In February 2026, she attended the HTHP Symposium in Copenhagen as a scholarship recipient.
How did your collaboration with GAB begin?
My connection with GAB grew out of my bachelor’s thesis, which focuses on the thermoeconomic assessment of large‑scale heat pumps for medium‑depth geothermal district heating systems. GAB enables the supervision of my work at the chair and thereby provides the foundation for exploring this topic in depth.
The research focus also opened the door for me to participate in the HTHP Symposium in Copenhagen. There, I was able to present my research at an early stage and gain valuable feedback for the next steps.
How did you experience the HTHP Symposium in Copenhagen?
The symposium was a real highlight for me. I presented a poster and gave a short pitch, which immediately sparked lively discussions about technical concepts, modelling approaches, and new ideas for translating my simulations into practical applications. I particularly enjoyed the conversations about novel fluids and innovative design strategies, many of which were entirely new to me.
Equally enriching was the network that formed during the event. Many participants were working on projects closely connected to my own. And beyond that, the symposium offered a chance to view research outside my home university and place my work in a much broader context. That perspective is something I’m carrying with me as I continue.
What is the focus of your bachelor’s thesis?
My thesis examines which types of large‑scale heat pumps are most efficient and cost‑effective for medium‑depth geothermal district heating. Because geothermal sources in this range typically deliver temperatures between 30 and 60 degrees Celsius, heat pumps are needed to raise the heat to a usable level. I compare single‑stage, two‑stage, and three‑stage compressor heat pumps as well as different refrigerants.
Methodologically, the thesis is based on an optimisation code that I am currently developing and stabilising. The model calculates compressor sizes, efficiency indicators, and economic parameters. A key goal is to eventually provide municipalities and utilities with guidance: Which heat‑pump technology matches their geothermal resource and their local economic conditions?
What are you learning along the way?
The modelling makes it very clear how tightly technology and economics are interlinked. Electricity prices, investment costs, efficiency, and refrigerant choice all influence one another, and even small parameter changes can have major effects on the overall system. At the same time, it’s become obvious how crucial a robust code base is for drawing reliable conclusions. Debugging takes time, but it’s incredibly instructive.
Beyond that, I’m gaining a deeper understanding of real‑world market conditions and how heat‑pump technologies fit into larger energy systems. This helps me see my work not just as a theoretical exercise but as a foundation for decisions that could shape the future of district heating. That connection between theory and practice is highly motivating.
What are your plans after completing your bachelor’s degree?
Several exciting options are on the horizon. During the symposium, I was offered a potential PhD project in Ireland, where I would work more hands‑on, testing new fluids on experimental rigs and evaluating innovative heat‑exchanger concepts. The idea of experiencing research in such an immediate, tangible way is very appealing.
At the same time, I am strongly interested in the joint TUM–FAU master’s program in Geothermal/GeoEnergy, which blends geoscience fundamentals with engineering applications and maintains a strong practical focus.
Even if I choose the research project in Ireland, I look forward to staying connected with GAB, for example through events such as the Wissenstransfer. GAB’s support has certainly opened doors for me and helped build an international network early in my career.
