Authors: Maria Chiara Massaro, Roberta Biga, Artem Kolisnichenko, Paolo Marocco, Alessandro Hugo Antonio Monteverde, Massimo Santarelli
Publication Date: January 2023
Category: Hydrogen
DOI: 10.1016/j.jpowsour.2022.232397
Abstract (Official): Electric aircrafts are being developed to reduce greenhouse gas emissions in the aviation sector. The use of hydrogen in combination with fuel cells is likely to be a suitable solution to power electric motors with almost zero emissions, but its technical feasibility still needs to be investigated. Hydrogen is characterised by a very low density at room temperature, requiring very large storage volumes and heavy tanks. This could be a limitation in the aviation sector, where compactness and low overall weight are needed due to limited space and the need not to increase the required propulsion power. Moreover, hydrogen-based mobility concepts directly depend on the availability of storage options that meet the requirements of safety, quick hydrogen release, technical maturity, economic viability, efficiency and environmental sustainability. In this work, the main hydrogen storage technologies are investigated and compared on the basis of key performance parameters identified as crucial for the aviation sector. The aim is to identify the most promising solutions for on-board hydrogen storage. Then, the sizing of a propulsion system is carried out based on a real mission profile, and the weight increment is compared to that of a conventional aircraft powered by kerosene. A regional passenger aircraft, ATR72-600, is selected for this work. The potential reduction in the overall weight of the aircraft is also explored, considering both future improvements in storage technologies and fuel cell systems.
GAT Editor’s Comments: This article discusses potential challenges with hydrogen (H2) storage for electric aircraft.
1) Storing H2 at low pressure and temperature eliminates need for high-strength material pressure vessels, reducing costs (including for a thermal management system) and increasing gravimetric density (wt%). In this investigation, wt% was considered as the weight of H2 in relation to total mass of the storage system. However, H2 has low density at low pressures, so large storage volumes would be needed. So, eight performance indicators were used to compare existing physical and material-based storage methods. Storage methods include: compressed H2, liquified H2, cyro-compressed H2, metal organic frameworks, carbon nanostructures, metal hydrides, metal borohydrades, liquid organic hydrogen carriers, and ammonia.
2) The article’s case study involving a “weight change” comparison of an all-electric and conventional kerosene-fueled ATR72-600 aircraft concludes all-electric technology aircraft are currently unfeasible. An all-electric aircraft is 25-50% heavier than kerosene aircraft. Instead, a hybrid propulsion configuration using both H2 and kerosene is suggested as it still reduces CO2 emissions and is lighter than the all-electric configuration. To note, this study’s prediction is lower than the 40% heavier conclusion in Massaro et al.’s article “Optimal design of a hydrogen-powered fuel cell system for aircraft applications”; an Editorial Summary for this paper was released on 3 December 2024.
Liquid and cryo-compressed hydrogen were determined as the most promising solutions for on-board storage due to
1) the higher gravimetric density, and
2) more compact and easier hydrogen release system. Sustainable Aviation Fuels (SAFs) are recommended as a short term solution to start reducing CO2 emissions. Interestingly, a literature review of papers on electric-related aircraft solution over the last 20 years was conducted – there was significant interest in proton-exchange membrane fuel cells (PEMFCs).
