Spanish technology center Aimen has 3D printed a cryogenic tank meant to store liquid hydrogen for use as aviation fuel. This test tank was made as a part of OVERLEAF, an EU-funded project aiming to make lightweight liquid hydrogen fuel storage safe for aviation. The ambitious project wants to use recycled materials to make a tank that works on an aircraft, The project partners consisted of aerostructures engineering firm Aciturri, French researcher Canoe, Italian innovation firm Icons, specialty materials firm Arkema, plastics researcher Aimplas, Romanian cryogenics lab ICSI and the universities of Delft, NTNU & Girona. TU Delft did the leak detection and sensors, Girona was in charge of coupons and mechanical tests, Aciturri designed the tank, ICSI completed the CFD work, and Arkema made the insulator material.
Hydrogen and aviation go back a long way, but the marriage of the two has not always been a happy one. From the Hindenburg disaster in 1937 to present day, there have been many accidents. But, vehicle-involved incidents amount to only 0.5% of all hydrogen accidents, with many more stemming from storage, transport, and processing. The EU seems to think hydrogen is a suitable fuel, but it’s kind of like standardizing on one battery technology and investing billions to process it. Perhaps many new battery technologies could be much safer and more efficient in the long run. But, with large deposits of hydrogen being found in France, for example, and another $95 trillion deposit in another part of France, the new energy revolution could come much closer to home. With hydrogen replacing oil and coming from allied nations, the EU is understandably tempted to invest in it.
Pablo Romero, Team Leader of the Additive Manufacturing of Composites R&D group at AIMEN, said,
“This is a technological solution that will mark a before and after in the manufacturing of components for sustainable aviation. We have applied all our knowledge in robotics, additive manufacturing, and process design to address a highly technical challenge.”
Meanwhile, researcher Xabier Pérez stated,
“This project demonstrates how technology can respond to the major challenges of decarbonization. Investing in hydrogen as an energy vector also means transforming the systems that make it viable, and AIMEN has a lot to contribute to this¨
Through the OVERLEAF project, a tank that functions at -250°C was made of an inner thermoplastic component and an outer shell of CFRP, with a diameter of 1.5 meters. The inner tank was made by AIMEN using a robot cell production system and was 3D printed in 100 hours. The material used to fabricate the tank was bio-based, with natural fibers that will make it easy to recycle.
Using a sustainable carbon fiber alternative is a really smart move here because a lot of the aviation industry wants to move to easier to use, safer, and easier to recycle CFRP materials. A cell-based manufacturing solution is also a very inexpensive way to make such a large structure. The combination between thermoplastics, different walls, and a foam could end up making a very strong structure. Sadly, of course when we think of carbon fiber pressure vessels many of us will be reminded of the Titan submersible explosion, which showcased how catastrophic a cavalier attitude to risk can be. The Titan is a bit of a marketing problem for the folks at OVERLEAF and beyond. Consumer acceptance and money from larger corporations and governments will be in shorter supply for such initiatives. At the same time, the use of a Hydrogen cell Toyota Mirai as a donor vehicle for a bomb by Ukraine could not have helped matters. Hydrogen has always had a bit of a marketing problem from a safety perspective.
I also find myself being quite skeptical of polymer and thermoplastic pressure vessels as well. We know that the market for DED metal pressure vessels is growing quickly. These vessels are easy to test, usually expensive, and work well in DED. Now, polymer-based materials may be used as alternatives. We do not know yet if this will work, but even if it does not find acceptance, I think that this kind of a structure may be used in less critical applications in the years to come.