Comment: material advances could help usher in a hydrogen revolution

Hydrogen has huge potential in delivering zero carbon energy. But hydrogen has very different qualities to natural gas, meaning the need for networks of storage and transportation that can cope with extreme variations in temperatures, its leachable nature, and all the related safety issues. We can't rely on standard materials to deliver a hydrogen economy — long term use will have an impact on structural integrity, leading to safety concerns.

Take our national network of around 7,600 km of pipelines supplying industry and commercial and domestic properties with natural gas. National Gas Transmission, the UK’s gas network operator, has made a commitment to upgrading the full network to allow for a switch to hydrogen, and has an objective of connecting up with continental Europe’s network of hydrogen-ready pipelines by early 2030s. Made up of tiny molecules, hydrogen is known for its diffusion into any type of material, causing different forms of structural damage to whatever material it might be. Using traditional metals for example, such as steel or aluminium, the hydrogen works its way into the lattice of the metal and causes it to become brittle over time, leading to cracking.

Cranfield, in partnership with Levidian Nanosystems, has developed a graphene-based paint which can be used to secure pipelines for safe hydrogen use. The simplicity of the structure means it’s easy to anticipate how it will behave — as well as being incredibly strong (estimated to be 200 times stronger than steel). The effectiveness of the new paint has been validated in the laboratory environment following National Gas standards. The next step is for large-scale production of the graphene paint, expected to begin this year, leading to general market availability for industry. The graphene itself comes from a new, scalable process developed by Levidian, making use of greenhouse gases such as methane as a feedstock, taken from sources such as organic wastes from agriculture and the venting and flaring release of natural gas.

The future viability of liquid hydrogen flight is dependent on safe storage on-board aircraft. Lightweight, cryogenic storage tanks need to be able to withstand extreme variations in temperature: between -253 degrees centigrade and room temperature. There is the need for a type VI cryogenic tank. This involves a new bill of materials and deployment of three levels of safety features: ensuring the hydrogen is kept at the right temperature; that the materials used will keep the liquid hydrogen at a safe temperature and pressure environment in the event of a failure; and so the tank can be disposed of safely — and the aircraft still has enough fuel to land — if there is an unforeseen event.

One type of material under development is a new form of self-healing polymers: particularly effective in repairing minor cracks and avoiding a worsening of the damage. The next critical material for the tank is a lightweight insulator, an aerogel: the synthetic porous ultralight materials derived from a gel which retain their form even when the liquid element is replaced with a gas. Finally, a two-dimensional graphene layer is being used to maximise the reduction of hydrogen leaks and to take the mechanical stability of the overall structure to another level.

Extensive work is ongoing at Cranfield around the material development and molecular tuning to achieve the levels of performance needed, as well as the use of different combinations in order to find the optimal mix of tank materials for performance and safety. The very first prototype of the type VI cryogenic hydrogen tank will be tested over the coming year, with flight testing (possibly from Cranfield airport) expected to start in 2026, and a system in use between 2030-35.

Other new materials are making alternative forms of transport possible in the form of zero-carbon balloon-power. A form of graphene-infused, impermeable rubber means hydrogen-filled balloons can be a practical alternative to carbon- intensive helium. Cranfield has developed and patented technology to make such structures. These kinds of balloons are able to float for very long periods of time without maintenance, and positioned below geo-orbit space will act as hubs for Internet access for remote populations previously cut off from communications networks. They are also a means of transporting hydrogen itself, moving supplies of fuel between balloon platforms, again supporting more inaccessible areas of the world. Plans are being made with partners in Malaysia to introduce balloon projects for its many islands, for example.

Big ideas for a new world of zero-carbon energy come loaded with design and materials problems. There’s no easy switch to new fuels. That means design engineers will be increasingly important when it comes to their work with new materials, assessing their potential, the scope for new combinations and configurations.

Krzysztof Kozioł, Professor of Composites Engineering and Head of Composites and Advanced Materials Centre, Cranfield University.