Robust Environmental Life Cycle Assessment of Electric VTOL Concepts for Urban Air Mobility

Abstract

Under which scenario is Urban Air Mobility more sustainable than ground-based mobility? To answer this question, we provide a Life Cycle Assessment of three electric Vertical TakeOff and Landing concept aircraft, including a quantification of uncertainties in the concept's material composition. We conduct a Cradle-to-Gate analysis of the concepts and extend it by a Wellto-Shaft analysis of Urban Air Mobility operation, including all relevant upstream greenhouse gas emissions due to battery use, again including input uncertainties. As for aviation systems in general, we show that the impact of power demand in operation is most significant and exceeds emissions from production by orders of magnitude. We thus provide sensitivity analyses of the results for each of the most influential quantities. We report an optimum flight speed for minimum greenhouse gas emissions and a quantification of the impact of hover flight. Finally, we compare and quantify the impact's sensitivities on influential factors like the region of operation, and mission design within reasonable ranges. From the sensitivity analyses, we conclude that only very lightweight vehicles for Urban Air Mobility can be more sustainable than traditional, fossil-fueled ground-based transportation, given a maximum seat utilization, clean power grid, low hover share and an effective reduction in travel distance. We further conclude that, with a combination of the most optimistic assumptions, Urban Air Mobility concepts may environmentally compete with battery-powered cars.

Modeling CO2 Emissions from Trips using Urban Air Mobility and Emerging Automobile Technologies

“…The WTS emissions ( normalE normalI normalWTS ) is an analysis of UAM trip emissions from the generation and consumption of electricity from the grid during operations ( E I grid ) since the batteries of eVTOL aircraft or electric automobiles require charging after each flight or drive. The WTS emissions index is calculated using a modified Equation 5 taken from Andre and Hajek ( 11 ), which originally included CO 2 emissions from battery production. We omitted battery production emissions in this study because of uncertainties in their production processes.…”

“…However, they have a carbon footprint on the ecosystem just as gasoline vehicles do. A cradle-to-grave emissions analysis ( 11 ) of processes that happen from the mining of materials to the discarding of materials shows how production phases, operational phases, and disposal phases of an eVTOL aircraft release CO 2 gases into the atmosphere. This paper focuses on the operational phase known as well-to-shaft (WTS) emissions analysis.…”

“…The production of batteries (e.g., lithium-ion batteries) also release CO 2 emissions ( 13 ). Current estimates for battery production in the United States range from 120 to 173 grams of CO 2 per kWh ( 11 ). However, because of the evolutionary nature of battery technology and uncertainties in the production methods and operations (e.g., supply chain, location of country they are made in, energy densities, number of cycles, inefficiencies, etc.…”

Rotorcraft systems for urban air mobility: A reality check

“…On the contrary, battery charging requires energy from somewhere else, which is likely to be supplied via source that may or may not be renewable. The production, servicing and disposal of batteries requires the use of energy and high-value materials and chemical compounds, which may or may not be sustainable (55) . Most often there is no proper accounting of the environmental credentials of these new systems.…”

Configuration Study of Electric Helicopters for Urban Air Mobility

“…Several additional configuration studies [9][10][11][12][13][14] omitted consideration of a single-mainrotor electric helicopter entirely, with the closest typically considered configuration being a side-by-side helicopter.…”