Why did you decide to write your doctoral thesis at Fraunhofer UMSICHT?

Matthias Lehmkühler: I chose Fraunhofer UMSICHT because it combines excellent scientific depth with consistent practical application. The interdisciplinary teams, close cooperation with industry partners, and excellent infrastructure allow us to work methodically. This enabled me to combine my doctoral studies with a clear contribution to the transformation of production and energy systems in industry while gaining multifaceted experience.

 

What was your topic and what was the most important result?

Matthias Lehmkühler: My doctoral thesis topic was "Superstructure optimization of a plant group for the material utilization of process gases from steel production." For this, I developed and applied a scenario-based mathematical model that combines technical plants from the steel, chemical, and energy sectors into an integrated industry area. The goal: to convert carbon-containing exhaust gases into value creation chemical products such as methanol, urea, ammonia and acetic acid using external energy or renewable hydrogen.

Key finding: The approach enables significant CO₂ reductions in the conventional steel industry and can be economically viable if key framework conditions develop favorably (including electricity prices, investment costs, and CO₂certificate prices). Flexibly operated and well-integrated production networks are particularly advantageous in this regard, as they are more resilient to price fluctuations than singular synthesis routes.

 

How did the UMSICHT Research School support you in your work?

Matthias Lehmkühler: The UMSICHT Research School helped me, especially at the beginning, to structure my daily work and adopt effective approaches from more experienced doctoral students. In the final phase, individual coaching provided me with targeted support in focusing on the writing process, setting priorities, and clearly identifying the essentials.

 

What were some important experiences you gained during your doctoral thesis?

Matthias Lehmkühler: There are a few. During my doctoral studies, I learned to deal with unpleasant issues as they arise – the sooner, the better. It is also very helpful to assign individual work packages as master theses at an early stage. Not to avoid unpleasant work, but to gain an additional perspective on my own topics. This regularly inspired me and helped me make enormous progress in my field. At the same time, after the first year, I tried not to fill my day with unimportant or unproductive tasks and appointments, but to prioritize clearly. This includes fixed focus times, which I consistently block and protect. And: writing papers – no one can take away that piece of paper once you've finished it. It creates substance for your thesis. There are many more experiences, but the most important thing at is to have these experiences yourself – behind every experience mentioned here is my initial failure to implement it sufficiently well and the subsequent learning curve.

 

Are there any anecdotes that you still like to tell?

Matthias Lehmkühler: I remember well how the external coach for text and concept consulting encouraged me when the framework for doctoral studies was in status and it was "only" a matter of filling it with content. From the beginning of last year, I worked on my dissertation every day with great focus. Another special moment was when the developed optimization model ran without errors and in an acceptable computing time for the first time. After that, I knew for sure: My approach works, I can now complete my doctoral studies! It took over a year, but that was the point of no return.

The final sprint was special: Many nights alone at the computer while my friends were out partying – but that's exactly what made it possible to finish. And a nice anecdote about the Research School is the annual Christmas market visit, where all the doctoral students could chat informally over a few hot drinks – that always did us good and brought us closer together.

 

What were the challenges? And how did you overcome them?

Matthias Lehmkühler: The biggest challenge was that for a long time I wasn't sure whether I would be able to complete my doctoral studies at all. With my first major successes in modeling and the first reliable results of the theses I supervised, my confidence returned – and I saw it through to the end.

 

What tips do you have for current and future doctoral students at Fraunhofer UMSICHT?

Matthias Lehmkühler: Define your research questions early on and start writing your thesis early. Be prepared for the fact that doctoral studies involve periods with little free time – and that the thought "I should be doing something for my doctoral studies!" is often in the back of your mind.

 

Where are you now professionally?

Matthias Lehmkühler: I continue to work as a research assistant at Fraunhofer UMSICHT in the field of Local Energy Systems (four days a week). I also work as a postdoc at the Cross-Energy Systems Chair at Ruhr University Bochum (one day a week). In addition, I teach a course at the FernUniversität in Hagen in the module "Sustainable Energy Supply."