Estimating the maintenance-related material cost for battery-powered aircraft propulsion systems

Abstract

The transformation of the aviation industry into a more sustainable ecosystem is currently facing the challenges of a continuous growth in passenger volumes and increasing emissions on a global level. In order to reduce emissions and meet ambitious regulatory requirements, great efforts have been made in recent decades to improve fuel efficiency, e.g., by improvements in engine performance. However, since these legacy engine technologies have almost reached their fuel efficiency limits today, a further reduction of aviation’s climate impact likely requires revolutionary propulsion technologies - such as the electrification of the drive train through battery systems. Additionally, besides technological challenges of battery storage (e.g., a low gravimetric energy density), a potential adoption of these propulsion concepts requires a substantial reduction of uncertainties regarding operational availability and maintenance cost. While the mitigation of reluctance from aircraft manufacturers and operators requires an estimation of maintenance cost in early design stages, currently available methods are predominantly based on historical data of conventional aircraft configurations – limiting their applicability to new system designs. With this work, we address parts of that knowledge gap by estimating the expected changes in material cost and part replacements for the maintenance of battery-powered propulsion systems. For this purpose, we establish a cost estimation method, which is based on reliability metrics and spare part prices for the corresponding drive train components. By using a conventional A320 as a reference, we carry out a comparative analysis for an All-Electric Aircraft (AEA) and Hybrid-Electric Aircraft (HEA) propulsion system. A special focus is given to the battery storage unit as the main cost driver, where we apply a semi-empirical degradation model. This work allows us to (a) assess the expected changes in material cost to shed some light on the economic viability of AEA and HEA concepts for operators, (b) identify essential degradation drivers of battery cells to derive design and operating recommendations, and (c) discuss a trade-off in HEA design with regard to maintenance cost. Since the established method is transferable to different technology concepts, our work will provide a valuable contribution to the assessment of economic viabilities for alternative propulsion systems in early design stages. Furthermore, the results allow aircraft designers and operators to gain insights into the maintenance characteristics of battery systems in aviation, building the foundation for a potential technology integration.