A refrigerator that heats houses? Or electric cars that act as power storage units and help stabilize the energy system? What may sound unusual at first glance is, in fact, based on fundamental laws of physics. These concepts took center stage in Prof. Helge Stein’s lecture “Work, Energy & Entropy”, held on 23 September 2026, as part of the “Wissenschaft für Jedermann” lecture series at the Deutsches Museum München. In his talk, the e-conversion researcher explained how modern energy technologies work and the role they can play in achieving a climate-neutral future.
Heat pumps, battery storage systems, and electric vehicles are among the key technologies driving the energy transition. But why are they so efficient, and what physical principles lie behind them? These were the questions addressed by Helge Stein, Professor of Digital Catalysis at the Technical University of Munich (TUM) and member of the Excellence Cluster e-conversion. His lecture focused on the physical foundations of modern energy technologies and their significance for the energy, heating, and mobility transitions. “What we are currently undergoing is not only an energy transition, but also a heating transition and a mobility transition. Taken together, this can be described as the electrification of everything,” Stein explained at the beginning of his presentation.
Using vivid examples, Stein guided the audience in the Deutsches Museum auditorium, with around 100 participants on site and another 50 online, through key concepts of thermodynamics and their relevance to modern energy technologies. One focus of the lecture was heat pumps, which Stein described as a particularly efficient technology for the heating transition. “In principle, a heat pump is a refrigerator in reverse,” he explained. Both systems move heat from one place to another. While a refrigerator removes heat from its interior, a heat pump extracts heat from the air, ground, or water and uses it to heat buildings efficiently.
Another major topic was battery storage and its importance to an energy system increasingly powered by wind and solar. The TUM expert explained how modern lithium-ion batteries work, highlighted current challenges and developments in battery research, and even shared some practical advice. “Anyone who wants to maximize the lifetime of their lithium-ion batteries should try to keep them within their comfort zone,” Stein said. This comfort zone typically lies between about 10 and 80 percent state of charge. Within this range, battery aging proceeds much more slowly than at consistently very high or very low charge levels.
Looking at the integration of renewable energy sources, Stein also emphasized the potential of electric vehicles as flexible energy storage systems. The concept of vehicle-to-grid could help balance supply and demand in future electricity grids. “Cars spend most of their time parked rather than driving,” Stein noted. The energy stored in vehicle batteries could therefore be used not only for transportation, but also to support grid stability by storing surplus electricity and feeding it back into the grid whenever needed. Helge Stein’s lecture highlighted the strong interconnections between the energy, heating, and mobility transitions and demonstrated how fundamental physical principles underpin the development of sustainable technologies.
Brief profile
Helge Stein studied physics at the University of Göttingen from 2008 to 2013. In 2017, he received his doctorate in mechanical engineering from Ruhr University Bochum for his research in high-throughput methods. Subsequently, he obtained a postdoctoral position at the California Institute for Technology (USA), where he worked as a materials data engineer at the Joint Center for Artificial Photosynthesis (JCAP). In 2020, he took up a tenure-track professorship in applied electrochemistry at the Karlsruhe Institute of Technology. He was appointed Professor of Digital Catalysis at the Technical University of Munich in mid-2023.