“CooLTank”: CFRP tanks for cryogenic hydrogen for powering passenger aircraft

Hydrogen as an energy carrier is a key pillar for climate-neutral aviation – provided it is stored and transported safely and efficiently. The “CooLTank” (“Customizable, automated Research Platform for Machining, Assembly and Barrier Coating of Liquid Hydrogen Tanks”) project, funded by the German Federal Ministry of Transport (BMV) and initiated by Fraunhofer IFAM as part of the “H2AM” (“Hanseatic Hydrogen Center for Aviation and Maritime”), is establishing a globally unique research platform for the automated machining, assembly and barrier coating of large-scale, fiber-reinforced hydrogen tanks. This platform addresses not only the technological but also the economic challenges of future propulsion systems in aviation and the transfer to maritime applications.

CFRP hydrogen tanks: innovation potential and market relevance

The market does not yet offer any complete solutions for the economical and sustainable production of large hydrogen tanks made of carbon fiber reinforced plastic (CFRP) in passenger aircraft construction. “CooLTank” closes the gap by developing and integrating new technologies that go far beyond the current state of the art. This includes precise, automated machining and assembly as well as the development of highly efficient barrier coatings against hydrogen permeation.

The core objective of “CooLTank” is providing a flexibly configurable infrastructure for research and development relating to the automated production of XXL tank structures for cryogenic hydrogen. However, the resulting technologies can also be used to investigate storage solutions for the various hydrogen derivatives, for example for use in maritime applications. The primary focus is on type 5 hydrogen pressure vessels – meaning hydrogen tanks made almost entirely of carbon fiber-reinforced plastic, offering significant weight savings and excellent leak-tightness.
 

Structure of the “CoolTank” research platform

The new research platform to be established features a modular design and consists of various sub-plants, which will be constructed at the Fraunhofer IFAM sites in Bremen as well as Stade and cover different stages of tank production.

In Stade, a sub-plant will be specialized in the automated machining of large-dimensioned components made of carbon fiber-reinforced plastic. Using high-precision robot systems, a manufacturing tolerance of ± 0.2 mm will be achieved, ensuring the quality and dimensional accuracy of the tank structure. The objective is to produce components that meet the demanding specifications required for use in hydrogen storage tanks.

The subsequent process chain initially comprises the automated assembly of smaller modules as well as the integration of system components, such as valves and sensors, to ensure error-free and efficient operation of the tanks. This is followed by the precise and uniform application of thermal insulation materials to guarantee the functionality of the tank structures under realistic conditions. In addition, the process chain includes the automated assembly of large tank structures – the focus here is on the precise connection of the tank shells in order to achieve the required tightness and structural stability. The automation of the individual steps makes a significant contribution to increasing efficiency and quality assurance in production.

A further sub-plant is being built in Bremen, which will focus on the automated application of innovative barrier coatings to the inner surfaces of the tank structures. The specially developed coatings serve to significantly reduce hydrogen permeation and make a decisive contribution to maximizing tightness as well as increasing the service life of the storage structures. The automated application of the barrier coatings is a key contribution to the operational safety of the hydrogen tanks.

Each sub-plant features has a modular design, is equipped with innovative technologies, is engineered for the use of advanced robotic applications, incorporates adaptive component holding fixture systems and is prepared for end-to-end digitalization of the process chain. This flexibility enables the consideration of a wide range of geometries and requirements.

Technological highlights

• Modular design for easy reconfiguration of the plants
• Precise measurement and control technology for maximum quality assurance
• Integration of manual and automated process steps
• Innovative application technology for automated processes such as adhesive applications, barrier coatings and thermal insulation
• Integration of smart data analysis methods for process optimization and development of a digital twin
• Options for incorporating human-centered assistance robotics

The platform also clearly stands out from the state of the art due to its high degree of automation and consistent digital networking.
 

Research and cooperation

The research platform will not be operated purely as a production plant, but will serve as a flexible test and development environment for R&D projects once completed. In joint projects, partners from industry and science will be able to design the technologies for their own future applications and test them in practice without the need for large investments or resources for their own R&D facilities.

“CooLTank” is already closely linked to other research projects – such as the joint project “HYTANK” – and involves numerous partners from science and industry. The aim is to work with them to advance the development and production of new tank structures.

Fraunhofer IFAM also relies on a strong research landscape at its sites in Bremen and Stade. The German Aerospace Center (DLR) and the University Cooperation for High Performance Composite Production (HP CFK) are also represented in the “H2AM” network, enabling targeted coordination of technological development. Thus, DLR is responsible for testing processes manufacturing hydrogen tanks components using automated fiber placement as well as equipping a laboratory for permeation testing and microscopy of fiber composite laminates at room or liquid nitrogen temperatures. In conjunction with basic research on material technologies, structural design of hydrogen tanks and manufacturing simulation on the part of HP CFK, this offers a consistent value chain in research from the fundamentals through to industrialization.

Technology transfer for the use of hydrogen in the maritime industry

In addition to the focus on applications in aviation, these technologies can also be transferred to other sectors, such as the maritime industry. In particular, the high emissions of greenhouse gases, sulfur oxides and fine particulates produced by the heavy oil-powered propulsion systems used in shipping up until now are representing a significant environmental problem.

The flexible and modular plants make it possible to develop and investigate production processes specifically for tank structures in the shipping industry. The specific requirements of the maritime industry can be taken into account in order to test innovative solutions for the construction and equipping of tanks that, for example, enable the use of hydrogen or its derivatives as a clean energy carrier. In this way, the platform not only contributes to climate-neutral aviation, but also makes an important contribution to the development of technologies for greenhouse gas-neutral and more environmentally friendly shipping.

Funding

The “CooLTank” project is being funded by the German Federal Ministry of Transport (BMV) with a total of EUR 5,751,223. Funding for this measure is also provided as part of the German Recovery and Resilience Plan (GRRP) via the European Recovery and Resilience Facilities (RRF) in the NextGenerationEU program. The funding guideline is coordinated by NOW GmbH and implemented by Project Management Jülich (PtJ). The project duration is from December 2024 to February 2029.