Hydrogen has been identified as a key priority to achieve the European Green Deal for a sustainable economy. By converting the construction of the hydrogen tank from existing metallic solutions to composites, the liquid hydrogen (LH2) composite tank will achieve weight savings that enable the advancement of liquid hydrogen as a sustainable fuel source for civil aviation. This will lower the carbon footprint of air travel and extend the flight range of aircraft by reducing construction weight and cost.
The challenge
For single-aisle commercial aircraft, the energy density of compressed hydrogen gas is not sufficient to provide the necessary range; this can only be reached with liquid hydrogen, stored at 20 Kelvin/-253 °C. The project aims to develop a linerless long-life lightweight composite tank that can withstand the low temperature of liquid hydrogen and related thermal stress.
The solution
The project will focus on the application of microcrack-resistant composite materials with sufficiently low permeability for hydrogen. In order to comply with boil-off and dormancy requirements without adding significant weight and/or volume, a vacuum/MLI insulated tank has been developed with contributions of all consortium members. The tank is equipped with fluid level sensors and sensors for safety systems. During the design phase, digital design strategies were used to minimise thermal stress and optimise utilisation of automated manufacturing technologies.
What we did
NLR has developed additional facilities for testing composite materials at 20 Kelvin. Several thermoset and semi-crystalline thermoplastic composites (Toray) have been screened regarding
their properties at this very low temperature. The materials were also characterised regarding their permeability properties and resistance against thermal cycling down to 20 Kelvin. Together with project partners, a suitable thermoplastic composite material was selected for the inner tank and characterised regarding engineering properties at 20 Kelvin.
For the outer tank a thermoset composite material was elected. With these materials a composite tank has been designed and manufactured. The tank will be tested with liquid hydrogen in 2026. The health and safety of the tank will be monitored with various fibre optic sensors. Because of their minimal heat ingress, these sensors are also used to monitor the temperature, pressure, LH2 fuel level and leak detection.
Project partners:
Toray (project lead), Royal NLR, SAMXL, ADSE, Airborne, Bold Findings, Cryoworld, Fokker Aerostructures, IT’S Engineering, KVE, PhotonFirst, Somni Solutions, TANIQ, TU Delft
Project timeline:
2022-2026
This project is partially funded by the Dutch Government (RVO/Netherlands Enterprise Agency) through “Subsidieregeling R&D Mobiliteitssectoren” (RDM).
