Assessment of suitable hybridization strategies of a fuel cell-battery-powered regional aircraft

Abstract

Transforming the aviation sector to electric power sources like batteries or fuel cells reduces its environmental impact by minimizing direct emissions [1]. Hybrid electric configurations using both a hydrogen powered fuel cell system and a battery system may offer superior powertrain performance over either singular energy storage method due to their respective advantages in energy density and high power capability [2]. Utilizing an optimal load distribution between the two energy sources can therefore enhance the aircraft's performance significantly. In this work multiple configurations with varying degrees of hybridization are compared using an in-house, modular hybrid simulation- and sizing tool based on thermodynamic principles, component maps and laboratory measurements [3]. An exemplary hybrid system layout is depicted in Fig. 1, where low temperature PEM fuel cell technology and Li-Ion batteries are considered for the energy conversion and storage. With this tool each configuration is individually optimized to fulfill the requirements resulting from a common mission profile focusing on system weight, efficiency and fuel consumption. The profile was developed by the DLR for an exemplary hybrid electric aircraft architecture with entry into service in 2040. Technology improvements in the next two decades are considered via estimated technology factors. Through a sensitivity analysis considering different scenarios recommendations for the degree of hybridization are derived. The results are optimized hybrid system configurations that can be used for follow-up studies.

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