All projects of the Otto Hahn Group Portable Energy Systems (PoES) deal with the analysis, the optimal design and the operation of portable electrical energy systems like fuel cells and batteries. The Portable Energy Systems group focuses on generating in-depth knowledge on the processes occurring and interacting with each other in energy systems and on limitations and stability issues of the systems by combining rigorous model-based analysis and experimental validation. The gained knowledge might be subsequently used to develop improved energy system concepts or operating modes. Although the processes within the contemplated energy systems differ, all are open systems with matter and heat being exchanged with the environment. As such they show a certain dependence on environmental conditions which may lead to malfunctions and even instability during operation; such limitations are a central research topic of the group.

The group's current research projects are Small Fuel Cell Systems, Alkaline Electrochemical Cells, and Analysis and Diagnosis of Fuel Cell State. In the Small Fuel Cell Systems project, the media management of fuel cell systems is investigated at various hierarchical levels. Studies of complete systems are complemented by detailed investigations on key system components and their stabilizing effect in the system. Joint research with the MPI's research groups has been conducted on energy harvesting (ESB group: Dr. Grammel) as a part of the institute's Vision 2015+ initiative and on hybrid control for energy systems (SCT group).
The Alkaline Electrochemical Cells project investigates promising and potentially low-cost alkaline fuel cells and batteries for which there is a lack in quantitative understanding of the processes occurring inside the cells. The studies analyze, quantify and mitigate the performance-limiting processes and the cells' sensitivities to environmental conditions. External partners (Univ. Newcastle, UC Irvine, MLU Halle-Wittenberg, Karl-Winnacker-Institute) participate in the project with their expertise on cell material.
Finally, the project Analysis and Diagnosis of Fuel Cell State uses the knowledge on fuel cell processes and their dynamics for diagnostic purposes on the fuel cell state during operation. The developed methods deliver important information for the control of fuel cell systems and help to reduce the number of external sensors.