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

Abstract

Urban air mobility (UAM) operations provide the potential for more, or more attractive, trips in a metropolitan area relative to wholly surface-based transportation. But the emissions produced by a UAM mode must be studied in relation to these benefits. In this paper, an emissions model for the UAM context using electric vertical takeoff and landing (eVTOL) aircraft is developed that incorporates CO2 gases emitted from the electricity production required to charge the vehicle batteries. The model quantifies trip emissions using UAM for part or all of the trip and compares these with automobile-based trips. The estimations consider using gasoline and electric automobiles, with the impact of autonomy and average ground speeds in traffic. Trip case studies in the Chicago and Dallas metropolitan areas showcase the regional differences when using UAM and different automobile technology scenarios. In particular, differences stemming from how electricity generation from power grids (i.e., grid emission index) contributes to CO2 emissions of eVTOL trips and electric automobile trips in the Chicago and Dallas metropolitan areas are computed. This paper introduces trip properties called the surface-to-air distance ratio and the detour ratio to understand how they influence the CO2 emissions of a trip. Results from the simulation on identified trip cases in Chicago and Dallas illustrate the significant impact of the grid emission index of a region’s power plant on the emissions of electric vehicles.

A Methodology for the Comparative Analysis of Hybrid Electric and All-Electric Power Systems for Urban Air Mobility

“…The present work differs from [12,16] in the following aspects that constitute its novel contribution to the scientific literature on UAM:…”

“…A similar but more detailed analysis is performed in [16], in which the authors developed a model to quantify trip emissions using UAM and compared them with automotivebased trips. The authors of this study consider gasoline and electric vehicles as automotive technology and calculate the emissions associated with electricity production using the emission factor of the metropolitan area of Chicago and Dallas.…”

“…A more complete analysis of the environmental impact of road and air vehicles should be performed at the cradle-to-grave emissions level [16], i.e., taking into account all processes from the extraction to the discarding of materials (thus including production, operation, and disposal phases). However, this is beyond the scope of this investigation.…”

“…The iteration is terminated when the convergence on the empty mass is reached. The take-off power is calculated as suggested in the literature [12,16] for VTOL vehicles by using the formula for the power request in hover:…”

“…where δ is the disk loading and ρ a is the sea-level air density (1.22 kg/m 3 ), g is the gravity acceleration. For all the powertrains, a value of 0.85 was assumed for the propulsive efficiency [16] and the disk loading was set to 380 Nm −2 [16,27]. The results of the procedure are shown in Figure 1, Tables 2 and 3 in terms of final take-off mass and powertrain specifications.…”