Simulation of Hydrogen Supply in Coupled PEM Fuel Cell/LH2 Tank Systems under Aviation-Relevant Conditions

Fuel cell-based electric propulsion systems are discussed as one technological option to achieve emission reduction of aviation industry. Especially, for short-haul and regional aircraft applications the feasibility is currently investigated. In this regard, relevant research topics are the upscaling of the polymer electrolyte fuel cell (PEMFC) technology to the megawatt range and the use cryogenic liquid hydrogen (LH2) in order to achieve acceptable energy densities. In this study, the coupling behavior of a multi-modular megawatt PEMFC system with an LH2 tank system is investigated by simulating the subsystems on the basis of a self-developed Modelica model. This PEMFC system, built from a number of individual modules, is designed to deliver the full propulsion power during all phases of the flight. The system concept is to use the heat losses from the fuel cell system for the vaporization and heating of LH2. The supply temperature and pressure of hydrogen under defined control strategies and load profiles are predicted and its effect on the fuel cell performance is investigated. The simulation results indicate that the LH2 tank pressure remains stable during the anode purge process. The LH2 tank pressure changes due to load changes have no significant impact on the fuel cell performance. Furthermore, the hydrogen supply temperature has limited influence on the fuel cell performance and durability within the observed temperature range. Overall, based on the simulation results, no operational restrictions due to pressure and temperature fluctuations in the hydrogen supply from the cryogenic storage system are to be expected.