Hydrogen Fuel Cells and Batteries for Electric-Vertical Takeoff and Landing Aircraft

Abstract

The primary drawbacks of battery-powered vertical takeoff and landing [electric vertical takeoff and landing (eVTOL)] aircraft are their poor range and endurance with practical payloads. The objective of this paper is to examine the potential of hydrogen fuel cells to overcome this drawback. The paper develops steady-state and transient models of fuel cells and batteries, and it validates the models experimentally. It demonstrates fuel cell and battery power sharing in a regulated parallel configuration to achieve a reduction in powerplant weight. Finally, the paper outlines the weight models of motors, batteries, and fuel cells needed for eVTOL sizing, and it carries out a sizing analysis for on-demand urban air-taxi missions. This revealed that, for ranges within 75 miles, a lightweight (5000–6000 lb gross weight) all-electric tilting proprotor configuration is feasible with current levels of battery specific energy () if high C-rate batteries are available (4–10 C for 2.5 min). For any mission beyond 50 miles, fuel cells appear to be a compelling candidate. Although fuel cells alone do not offer significant improvements to batteries, the two electric power sources can be combined for significant payload gains. In the combined powerplant, the fuel cell is sized to the low-power cruise mode and the battery supplements during higher power. For missions of less than 50 miles, the combination provides no advantage with current technology, and battery specific energy is the principal driver.