Predicting Fleet-level Carbon Emission Reductions from Future Single-Aisle Hybrid Electric Aircraft

With rising concerns over commercial aviation’s contribution to global carbon emissions, there exists a tremendous pressure on the aviation industry to find advanced technological solutions for reducing its share of CO
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emissions. A potential solution to mitigate this global emissions crisis is to operate fully-electric aircraft; however, the current battery technology is forcing the industry to explore partially electrified aircraft as a possible mid-term solution. There exist a number of studies that look at the potential CO
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emissions benefits possible from hybrid electric and turboelectric aircraft. Although these studies show encouraging results about the potential reduction in carbon emissions at an aircraft level, none of the studies – to the authors’ best knowledge – discuss the potential fleet-level impacts of introducing these partially electrified aircraft in an airline fleet. This paper focuses on predicting the fleet-level environmental impacts of a notional, future single-aisle parallel hybrid electric aircraft with a 900 nautical mile range. The work demonstrates an approach to make these predictions by modeling the behavior of a profit-seeking airline (with a mixture of conventional all Jet-A fuel burning and hybrid electric aircraft in its fleet) using the Fleet-Level Environmental Evaluation Tool (FLEET). FLEET’s model-based predictions rely upon historically-based information about US-touching airline routes and passenger demand served by US flag-carrier airlines from the Bureau of Transportation Statistics to initiate model-based predictions of future demand, aircraft fleet mix, and aircraft operations. Using a simplistic model for representing the behavior of a single-aisle parallel hybrid electric aircraft, the FLEET simulation predicts the changes in the fleet-wide carbon emissions due to the introduction of this new aircraft in an airline fleet in the year 2035. By 2065, FLEET results predict that the fleet-wide CO
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emissions with hybrid electric aircraft in the fleet mix are about 15.9% lower than the fleet-wide CO
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emissions of a conventional (all Jet-A fuel burning) aircraft-only airline. Because of the reduced range capability of the hybrid electric aircraft relative to a conventional aircraft of similar size, the simulation results indicate that the airline changes the usage, acquisition and retirement of its conventional aircraft when hybrid electric aircraft are available; this is most notable to serve passenger demand on certain predominantly single-aisle service routes that cannot be flown by the future single-aisle hybrid electric aircraft.