Prospective Life Cycle Assessment of Future Propulsion Systems for Aviation: A Fuel-cell Based Auxiliary Unit for a Commercial Aircraft

Abstract

According to the Air Transport Action, in 2020 the aviation sector represented around 3,5 % of all anthropogenic climate impact. However, this figure is expected to grow in the future due to the increasing demand for commercial flights. Therefore, there is a need to reduce the environmental impacts of aviation in the long term and to start evaluating the environmental performance of novel lower-emission propulsion technologies. In this context, the project EXACT of the German Aerospace Center (DLR) investigates different aircraft concepts to achieve sustainable a commercial flight by 2040. One of the conceptual aircrafts considers gas turbines combusting hydrogen for propulsion, supported by fuel cells generating electric energy for auxiliary onboard power. Although this system has already been successfully demonstrated for small electric loads in commercial aircraft, there are still some challenges that need to be addressed until the technology reaches maturity and becomes competitive. For instance, the fuel cell system should have a low system mass but also be able to achieve a high efficiency. To investigate the potential environmental impacts of such emerging technologies in the future, different prospective methods are employed within the context of a life cycle assessment. Based on this specific aircraft concept, we conducted a prospective life cycle assessment for the production phase of the fuel cell-based auxiliary power unit. As the commercial aircraft is expected to enter the market in 2040, uncertainty arises and should be considered in the analysis. Thus, our contribution demonstrates the application of prospective methods and uncertainty analysis in this specific use case, by: • Describing the methodology used to conduct a prospective life cycle assessment of the production phase of a PEM fuel cell-based auxiliary power unit for a hydrogen-powered commercial aircraft • Identifying environmental hotspots in terms of climate change, resource availability, water scarcity, ecotoxicity, etc. within the production phase of the system • Depicting the approaches used to characterize the uncertainty present in the life cycle inventory data • Including parameter uncertainty of the foreground and background system in the analysis and interpretation of the results