A new to study of the International Council on Clean Transportation (ICCT) found that although liquid hydrogen (LH2)-Combustion aircraft are not as capable as their jet-fueled counterparts, but they can still play an important role in meeting aviation’s 2050 climate goals.
The study explores the potential performance characteristics, fuel-related costs and emissions, and LH replaceable fossil fuel market2motorized aircraft entering service in 2035. Only evolutionary advances in design parameters achievable by 2035 were considered.
CO2e emissions from passenger aviation under various LH adoption scenarios2– powered aircraft, 2020 to 2050. Mukhopadhaya and Rutherford (2022)
The study explores two LH2 burning designs:
- a smaller turboprop aircraft targeting the regional market; and
- a narrow-body turbofan aircraft suitable for short- and medium-haul flights.
These designs are compared to the ATR 72 and the Airbus A320neo respectively. Both designs require an extended fuselage to accommodate LH2 storage behind the passenger cabin.
Representation of the tank and passenger cabin layout for the LH2 powered narrow body. Mukhopadhaya and Rutherford (2022)
The study found that, compared to fossil fuel aircraft, LH2– powered aircraft will be heavier, with an increased maximum take-off weight (MTOM), and less efficient, with a higher energy requirement per revenue passenger kilometer (MJ/RPK). They will also have a shorter range than fossil fuel aircraft. Nevertheless, the authors considered that the evolutionary LH2-motorized narrow-body aircraft could carry 165 passengers up to 3,400 km and LH2-turboprop planes could carry 70 passengers up to 1,400 km. Together, they could serve about a third (31-38%) of all air passenger traffic, as measured by revenue passenger kilometers (RPK).
LH supply2 designs with green hydrogen are expected to cost more than fossil jet fuel, but less than using blue hydrogen and e-kerosene. While the LH market2 the plane could be wide, fueling it with green LH2 will increase fuel costs compared to conventional Jet A aircraft. Carbon pricing would be needed to make LH green2 cost competitive, according to the authors, with a break-even point against Jet A expected between $102 and $277/tonne CO2e in 2050, depending on geography.
However, given the industry-wide push towards non-biomass SAFs, synthetic fuels like e-kerosene would likely be a better cost comparison for hydrogen than Jet A, especially from of 2035.
ICCT results suggest that green LH2 will be cheaper than electronic kerosene on routes up to 3,400 kilometers.
Under the most optimistic fuel and fleet rotation assumptions, scalable LH2-powered aircraft could cap, but not absolutely reduce, aviation CO2 compared to 2035 levels, the authors found. This would require all replaceable missions in 2050 to be serviced by LH2-propelled aircraft using green hydrogen and would result in 628 Mt-CO mitigation2e in 2050, representing 31% of CO emissions from passenger aviation2and emissions.
ICCT modeling suggests that an adoption rate of 20% to 40% is realistically achievable and would mitigate 126 to 251 Mt-CO2e in 2050, representing 6% to 12% of CO2e emissions from passenger aviation. Other technologies, including more fuel-efficient aircraft and sustainable aviation fuels, as well as measures to moderate traffic growth, will be needed to meet the airlines’ aggressive climate goals of net zero emissions by 2050.
Even after accounting for performance penalties for carrying LH2 as a fuel source, the aircraft modeled in this work can capture a large portion of the aviation market. They can provide significant carbon emissions reductions from the captured market, but can, at most, cap global passenger aviation emissions at 2035 levels. The aircraft can fit into existing flight operations, but will require significant investments in infrastructure to make them viable.
—Mukhopadhaya and Rutherford (2022)