Design of a Turbocharged PEMFC System for Aviation

Abstract The civil aviation sector is currently being required to adopt highly efficient propulsion technologies and to use cleaner fuels to limit the emissions of commercial aircrafts. In fact, the steady growth of flights worldwide, together with the increased impact of emissions released at high altitudes, pose serious risks to the environment. In this context, this work presents the design and analysis of a Turbocharged Proton Exchange Membrane Fuel Cell system (TC-PEMFC) fuelled by pure hydrogen and specifically developed for aviation. Previous studies conducted by UNIGE-TPG highlighted the potential of TC-PEMFCs for stationary and marine applications, demonstrating their capability to provide clean energy and reach efficiencies up to 46% thanks to the pressurization of the cell. Starting from the outcomes of these studies, this paper aims at designing a TC-PEMFC suitable for aircrafts. Alternative layouts of the system are proposed and analysed, while considering the variation of ambient conditions (pressure and temperature) at different altitudes. This study considers plant configurations based on different turbochargers: a single-shaft turbocharger designed for sea level (SS-S), a single shaft turbocharger designed for cruise at 15,000 ft (SS-C), a double-shaft turbocharger designed for cruise at 15,000 ft, with (DSIC-C) or without (DS-C) intercooling between the compression stages. The on-design and off-design performance of each TC-PEMFC is simulated with a detailed MATLAB-Simulink model, both for take-off and cruise conditions, with altitudes ranging from sea level to 15,000 ft. The model is integrated with a controller designed to comply with all the constraints of the system, and the safe operation of the turbocharger and fuel cell is monitored in each operative condition. The results obtained for the SS-S solution indicate a significant limitation of the power range at higher altitudes, to maintain the required air excess ratio at the PEMFC inlet. On the other hand, the SS-C can cover a wider range of power output, at cost of a reduced turbine and compressor efficiency in the take-off phase. The adoption of a double-shaft turbocharger (DSIC-C and DS-C) makes it possible to reduce the pressure ratio required by a single machine and improves the control flexibility, but requires the installation of additional components, increasing the overall weight and volume. Advantages and limitations of each solution are analysed and compared to identify the best TC-PEMFC configuration. These results are expected to contribute to the ongoing efforts to decarbonize the aeronautical sector and demonstrate the potential of PEMFC-TCs as a viable power generation system for future low-emission aircrafts, underlining the urgent need for experimental validation to further increase the reliability of the outcome.