On the design of environmentally sustainable aircraft for urban air mobility. (February 2021)

• Record Type: Journal Article
• Authors: Afonso, Frederico; Ferreira, Ana; Ribeiro, Inês; Lau, Fernando; Suleman, Afzal
• Is Part Of: Transportation research. Volume 91(2021)
• Publication Date: 2021-02
• Subjects: Life cycle assessment -- Hybrid-electric aircraft -- Biofuels -- Urban air mobility -- Conceptual design; Transportation -- Research -- Periodicals; Transportation -- Environmental aspects -- Periodicals; 354.76
• DOI: 10.1016/j.trd.2020.102688
• Languages: English
• ISSNs: 1361-9209

Abstract

Highlights: A MDO methodology is proposed to sustainably design VTOL aircraft for the UAM market. Biofuels present substantially lower GWPs than conventional fuels for the same performance. Sustainable biofuels have a lower GWP than batteries recharged from non-renewable sources. In terms of performance, the hybrid-electric solution is more competitive than the all-electric one. Abstract: Urban Air Mobility (UAM), recently envisioned as faster and flexible mean of transportation in large urban centers, faces considerable challenges inherent in its operation in densely populated cities and related environmental issues such as pollutant and noise emissions. To address the environmental challenges, the proposed concepts are either hybrid-electric or all-electric vehicles enabled with propellers that rotate at lower speeds than conventional rotorcraft configurations, such as helicopters. However, the feasibility of UAM in the near future requires significant progress on the all-electric propulsion systems since current battery technology still falls short when compared with fossil fuel in terms of specific energy density. In this work, a methodology is proposed to evaluate the environmental footprint of Vertical Take-Off and Landing (VTOL) aircraft for the UAM market. This methodology is applied to existing concepts for exploratory studies on mission critical performance and environmental parameters. All-electric aircraft were found to be feasible for the UAM segment from the performance perspective. However, further improvements in battery technology and electricity generation from renewable sources are required. Sustainable aviation fuels, such as Alcohol-To-Jet (ATJ) obtained from wheat straw, present a substantially lower environmental impact than conventional fuels while providing the same performance. These biofuels also contribute less to global warming and climate changes than batteries which: (i) are recharged from electric grids still dependable on non-renewable sources; and (ii) have a low number of recharge–discharge cycles.