Multifunctional System Integration of Fuel Cells aboard Civil Aircraft – Status Quo

The Advisory Council for Aviation Research and Innovation in Europe (ACARE) has imposed itself ambitious objectives concerning industrial leadership, safety and security as well as emissions reduction within civil aviation toward the years 2020 and 2050, respectively. Integration of electrochemical energy conversion technologies in form of secondary batteries, fuel cells or supercapacitors shows significant potential to reduce emissions of both contaminants and noise aboard future generations of aircraft. With its group Energy System Integration (ESI) the Institute of Engineering Thermodynamics (TT) at the German Aerospace Center (DLR) performs applied research and development with respect to innovative electrochemical energy conversion and storage technologies; thereby, research focusses on emergency and auxiliary power for more-electric civil aircraft as well as propulsion power for small all-electric aircraft. A promising approach is the multifunctional system integration of lowtemperature polymer electrolyte membrane fuel cells (LT-PEMFC) exploiting not only their electric output power but also their waste heat, process water and oxygen-depleted air (ODA) for an effective and efficient integration into aircraft system architectures. The present talk summarizes the most recent research and development results concerning multifunctional fuel cell systems (MFFCS) for emergency and/or auxiliary power generation aboard future generations of civil aircraft, with special emphasis on conceptual designs and operation strategies. Based on measurement data and theoretical studies revealing the multipurpose power demand of existing civil short- & mid-range aircraft, general requirements are derived to dimension MFFCS. It is shown that with existing fuel cell technology it is feasible to fulfill these requirements; however, novel conceptual designs for both electric and process engineering interconnection of MFFCS demonstrate the potential to optimize the dynamical behavior and/or the degradation process of the fuel cell stacks. This potential is utilized to develop optimum power point tracking method for arrays possessing several fuel cell stacks in multifunctional system integration and deduce operation strategies for MFFCS. Finally, an outlook is provided specifying and discussing the next steps for further research and development toward a practical multifunctional system integration of fuel cells in future generations of civil aircraft.