Hydrogen-powered aviation - techno-economics of flying with green liquid hydrogen

a holistic evaluation of the pathway to climate-friendlier air travel

authored by

Julian Hölzen

supervised by

Richard Hanke-Rauschenbach

Abstract

The aviation sector set itself the target of net-zero CO2 emissions by 2050. However, there is no silver bullet such as a single technology to achieve this ambitious goal. New technologies like hydrogen (H2) propulsion do not only change future aircraft design but also fuel supply chains and operations of aircraft. In comparison to that, new fuels like drop-in synthetic kerosene imply mostly changes to the fuel production and supply infrastructure only, but might cause higher costs and lower resource efficiencies. The time for technology decisions is now. The sector’s main “workhorse” with the most take-offs and causing around 50% of all commercial aircraft emissions is the single-aisle aircraft segment. In this category, the next product launches are expected in the 2030s with final investment decisions by aircraft manufacturers already in less than 5 years. These new aircraft will shape the development of the sector’s climate impact in the following 20-30 years and will determine if the 2050 net-zero target can be reached. Consequently, a holistic techno-economic investigation is undertaken for this aircraft segment to evaluate the economic competitiveness of H2 propulsion concepts compared to other decarbonization options. It is derived that H2-powered single-aisle aircraft technology alone would lead to an average 5%-increase in total direct operating costs for airlines. Therefore, major technology developments are required targeting inter alia the onboard liquid H2 (LH2) tank, high-performing H2 combustion engines, and safe H2 fuel system integration. Moreover, the analysis shows that the main economic uncertainty arises from the supply costs for green LH2. Demand scenarios for 2050 indicate that larger-scale supply chains for aviation use might be needed. With annual demands of 100 ktLH2 or more, major national and intercontinental hub airports could take a H2 hub role dominating regional H2 consumption. Regarding the supply pathways for green LH2 to airports, three main options are identified: on-site, LH2 off-site, or gaseous H2 off-site production. In a first optimization task, it is derived that costs could reach 2.04 USD/kgLH2 in a 2050 base case scenario for locations with strong renewable energy source (RES) conditions and greater LH2 demands. This could lead to cost-competitive flying with H2 compared to fossil kerosene in combination with emission taxes. While the main costs are caused by the RES, water electrolysis, and H2 liquefaction, the costs for the LH2 refueling system only mark 3–5% of the total supply costs. If techno-economic uncertainties are reflected, the LH2 cost span ranges between 1.37–3.48 USD/kgLH2 at different airports with good and weaker RES conditions. For the latter, H2 imports from larger H2 markets/exporting countries are of special importance to achieve these costs – not only due to less performing RES locally, but also due to limited space availability. A European-centered case study is performed to combine the optimization of green LH2 supply and aircraft designs with the investigation of operational strategies in one specific air traffic network. In a 2050 scenario, it is calculated that LH2 could cost around 2–3 USD/kgLH2 at main European airports. Then, average total operating costs would be 3% less expensive than flying with synthetic kerosene in the considered network. Tankering, an operational strategy to save fuel costs, might only enable reduced operating costs for H2-powered aircraft in the early adoption phase when no larger-scale H2 import would be available. Finally, it is found that using LH2 for aircraft propulsion might lead to lower installation requirements for RES capacity when compared to the synthetic kerosene option. This resource efficiency aspect is another important criterion for choosing the future decarbonization technology in air travel since green electricity will most likely be a constraint resource in the next decades.

Organisation(s)

Section Electrical Energy Storage Systems

Type

Doctoral thesis

No. of pages

152

Publication date

29.02.2024

Publication status

Published

Sustainable Development Goals

SDG 7 - Affordable and Clean Energy, SDG 8 - Decent Work and Economic Growth, SDG 12 - Responsible Consumption and Production, SDG 13 - Climate Action

Electronic version(s)

https://doi.org/10.15488/16391 (Access: Open)