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Assertion: Around 4.06 liters (volume) of hydrogen is needed to replace one liter of jet fuel; and 0.36 kilograms (weight) of hydrogen is needed to replace one kilogram of jet fuel

Establishing how much hydrogen would be required to replace jet fuel is an important step in determining the technical requirements of the hydrogen aviation industry. To make a rough comparison, we can look at the energy densities of both fuels. Hydrogen has a higher energy content by mass, but a much lower energy content by volume. This means that while you would need less hydrogen by weight, you would need significantly more space to store it.

For this estimate, we will focus on volumetric energy density, measured in megajoules per liter (MJ/L). There are two reasons for using this metric: first, jet fuel is primarily measured by volume, so maintaining this standard makes it easier to compare current fuel needs with future hydrogen requirements. Second, a major engineering challenge for hydrogen-powered aircraft is storing the fuel, given that hydrogen takes up much more space than jet fuel. Comparing the volume requirements for both fuels will better demonstrate this challenge.

The difference in volumetric energy density between the two fuels is significant. Jet fuel provides about 34.52 MJ/L, while liquid hydrogen delivers just 8.50 MJ/L.1 Therefore, it can be roughly estimated that about 4.06 liters of liquid hydrogen would be required to replace 1 liter of jet fuel.

This estimate is only a rough estimate and may change as hydrogen aviation technology develops. Hydrogen engines might have different efficiency characteristics due to variations in combustion temperatures and hydrogen's unique properties. If these efficiency differences are significant, they could drastically impact the fuel requirements for hydrogen-powered aircraft.

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Footnotes​

  1. Wang, Z. Hollebone, B.P., Fingas, M. Fieldhouse, B. Sigouin, L. Landriault, M. Smith, P. Noonan, J. Thouin, G. (2003, July). Characteristics of Spilled Oils, Fuels, and Petroleum Products: 1. Composition and Properties of Selected Oils. National Exposure Research Laboratory Office of Research and Development United States Environmental Protection Agency https://cfpub.epa.gov/si/si_public_file_download.cfm?p_download_id=525041&Lab=NERL ↩