Note on the Non-CO2 Mitigation Potential of Hybrid-Electric Aircraft Using "Eco-Switch"

Abstract

Non-CO2 effects, like ozone production and contrail cirrus formation, account for about 50-75% of aviation's climate impact, which can be effectively mitigated by re-routing flights around highly climate-sensitive areas, like ice-supersaturated regions (ISSRs). With electric drives forming no contrails and binding all life-cycle emissions to the ground, also hybrid-electric aircraft (HEA) offer the capability to mitigate non-CO2 effects by switching to full-electric mode while passing those areas. For investigating the eco-switch HEA mitigation potential, a cost-benefit assessment of eco-switch trajectories is performed for two weather situations and benchmarked against the mitigation potential of climate-optimized re-routings. We studied the impact of the HEA fuel flow and the cruising time in a full-electric operation and identified distinct weather-related differences. If the eco-switch concept is applied while passing ISSRs, we found a significant mitigation potential for all combinations of full-electric cruise times and HEA fuel flow levels. This strongly implies that the climate impact of flights dominated by contrail-cirrus is largely driven by the level of climate sensitivities along the trajectory, rather than by emission levels (aircraft design). If no ISSR is crossed, the climate impact is increasing with increasing HEA fuel flow, implying that the emission volume outweighs the local climate sensitivity.