A Multiobjective Approach to Evaluate Suitable Battery Technologies to Power Hybrid Medium-Range Aircraft

The development of high-performance battery systems is a critical challenge for the advancement of hybrid-electric aircraft. This work aims to develop an optimization procedure capable of correlating the performance level required by design constraints to the time framework when this performance level will be available. In practical terms, the currently available maximum energy density of a given battery technology might not be enough for developing a competitive hybrid aircraft. Still, the same technology has some potential to provide the required energy density in the near future. Hence, it becomes essential to foresee in which temporal framework the technology improvements will make possible and readily available the required performance level. In this work, we introduce a risk index that quantifies the probability that a given battery technology, characterized by a specific energy density, will not reach the required level of technological maturity within a given year. An optimization process is then developed, enabling a systematic trade-off between technological potential and associated risks, supporting strategic decision-making in the selection of energy storage solutions for hybrid-electric aviation. By quantifying the maturity risk of different battery technologies, this approach provides a structured decision support tool for aircraft designers and industries, facilitating the transition to feasible hybrid-electric propulsion systems. The risk index is correlated to key battery parameters, such as energy density and maximum discharge rate, that directly influence the feasibility and efficiency of battery technologies for aerospace applications. However, different battery technologies promise to achieve specific key parameter targets at different times, depending on advances in materials and manufacturing processes. Since many of these technologies are still developing, their future performance remains uncertain. The Dempster-Shafer theory of imprecise probabilities, a mathematical framework for modeling uncertainty and combining evidence from multiple sources, is used to account for the uncertainty associated with the evolution in time of these key parameters. This theory is instrumental because it incorporates subjective probabilities through the concepts of belief and plausibility, providing a more flexible representation of uncertainty than classical probabilistic approaches. This work is part of INDIGO, a European project aimed at reducing the impact of noise and pollution in airport areas by developing a medium-range hybrid aircraft featuring distributed propulsion, in which the outermost propellers use electrical propulsion.