Impact of Hybrid-Electric Aircraft on Contrail Coverage

Abstract

Aviation is responsible for approximately 5% of global warming and is expected to increase substantially in the future. Given the continuing expansion of air traffic, mitigation of aviation’s climate impact becomes challenging but imperative. Among various mitigation options, hybrid-electric aircraft (HEA) have drawn intensive attention due to their considerable potential in reducing greenhouse gas emissions (e.g., CO2). However, the non-CO2 effects (especially contrails) of HEA on climate change are more challenging to assess. As the first step to understanding the climate impact of HEA, this research investigates the effects on the formation of persistent contrails when flying with HEA. The simulation is performed using an Earth System Model (EMAC) coupled with a submodel (CONTRAIL), where the contrail formation criterion, the Schmidt–Appleman criterion (SAC), is adapted to globally estimate changes in the potential contrail coverage (PCC). We compared the HEA to conventional (reference) aircraft with the same characteristics, except for the propulsion system. The analysis showed that the temperature threshold of contrail formation for HEA is lower; therefore, conventional reference aircraft can form contrails at lower flight altitudes, whereas the HEA does not. For a given flight altitude, with a small fraction of electric power in use (less than 30%), the potential contrail coverage remained nearly unchanged. As the electric power fraction increased, the reduction in contrail formation was mainly observed in the mid-latitudes (30° N and 40° S) or tropical regions and was very much localized with a maximum value of about 40% locally. The analysis of seasonal effects showed that in non-summer, the reduction in contrail formation using electric power was more pronounced at lower flight altitudes, whereas in summer the changes in PCC were nearly constant with respect to altitude.

Weather Variability Induced Uncertainty of Contrail Radiative Forcing

“…For CO 2 these values are 34.3 (28,40) mW m −2 , for contrail cirrus they are 57.4 (17,98) mW m −2 , where all cited data refer to the year 2018. The corresponding contrail cirrus ERF values for 2005 are 34.8 (10,59) mW m −2 , and if we multiply these values with 0.42 −1 we obtain the corresponding values for RF, viz. 82.6 (24,140) mW m −2 .…”

“…The confidence level does not rise and the confidence interval does not shrink in spite of ongoing research. Indeed there has been progress in measurements [4], local, e.g., [5,6] and global contrail modelling [7][8][9], theories, e.g., contrail formation for hybrid-electric propulsion and for fuel cells, [10,11], the impact of new fuels has been studied experimentally [12] and in models [13], as well as new flight procedures, e.g., formation flight, [14], automatic contrail detection in satellite imagery [15] (CDA) has been extended to tracking the development of contrails [16] (ACTA), to present a selection. However, the uncertainty ranges in IPCC-type charts are not "significantly" smaller than 20 years ago.…”

Design of a Hydrogen Aircraft for Zero Persistent Contrails

“…The thickness-chord ratio is varied independently by setting the wing chord constant to maintain wing area and varying thickness. The aspect ratio is altered at a constant area by varying the wing span according to (13).…”

A Comprehensive Survey on Climate Optimal Aircraft Trajectory Planning

“…The analysis and climate-oriented optimization of H 2 -powered aircraft trajectories is missing in the literature. More efforts in the understanding of their emissions, the associated impact, and the modeling of the equations of motion and constraints are needed (e.g., see [102] for the study on the contrail coverage of hybrid-electric aircraft). When it comes to hybrid-powered vehicles, hybrid dynamical systems may be needed [103].…”