All-electric commercial aviation with solid oxide fuel cell-gas turbine-battery hybrids

All-electric aircraft have the potential to eliminate greenhouse gas emissions produced by air travel, but the energy storage density of batteries, 0.35 kWh∙kg−1, severely limits payload and range. This study introduces a fuel cell-gas turbine hybrid arrangement that utilizes liquid hydrogen fuel and superconducting motors to achieve energy storage densities in excess of 7 kWh∙kg−1, more than 20× state-of-the-art battery technology. The analysis considers off-design performance of the pressurized hybrid system meeting the flight profiles of four commercial aircraft. The estimated power density of 0.9 kW∙kg−1 is twice that of prior studies considering fuel cells in aviation, which results in a payload capacity similar to existing commercial jet aircraft powered by gas turbines achieving 10 kW∙kg−1. Prior studies considered advanced, high efficiency distributed propulsion systems to compensate for mass added by electric power systems. This study foregoes such aerodynamic enhancements and transformational aircraft designs to consider only the side-by-side performance of fuel cells against existing turbofan engines. The results show that fuel cells can power much larger aircraft than were previously considered feasible, although novel fuel cell designs are necessary to compete with next generation gas turbine technology.