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

Abstract

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 CO2 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 CO2 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 CO2 emissions with hybrid electric aircraft in the fleet mix are about 15.9% lower than the fleet-wide CO2 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.