Diamond Aircraft is coordinating a pioneering project, funded by the Austrian Research Promotion Agency (FFG), to deepen our understanding of the potential of gaseous hydrogen as a fuel for hybrid propulsion systems in general aviation. The “H2EDT” (Hydrogen-Based Twin-Engine Electrification and Digitalization Testbed) project consortium, which brings together researchers from FH JOANNEUM (Institute of Aeronautical and Electronic Engineering), the Technical University of Graz (ITnA), HyCentA, and IESTA, is designing an experimental hybrid testbed to explore the challenges posed by hydrogen as an aviation fuel. Research will continue at Diamond Aircraft’s Wiener Neustadt facility until the end of 2025, including manufacturing and testing.

Hydrogen is a carbon-neutral fuel that could play a decisive role in the future of sustainable aviation. It can be used both in fuel cells, where electrochemical reactions produce energy from hydrogen and oxygen with water as a byproduct only, and in internal combustion engines. In both methods, hydrogen does not produce carbon dioxide. Only in high-temperature reactions, such as hydrogen combustion, can nitrogen oxide emissions occur, in some cases.

The zero-emission profile of low-temperature fuel cells and their quieter operation are some of the reasons why this technology is gaining ground, not only in the automotive and marine sectors, but also in aeronautical applications. Furthermore, hydrogen propulsion systems offer higher system-level energy density compared to purely electric systems, enabling greater range and endurance for zero-emission aircraft.

However, relying solely on hydrogen for aircraft propulsion poses significant challenges. These include the low power-to-weight ratio of hydrogen fuel cells, which would make them too heavy to cover peak power demand, and hydrogen storage, which requires considerable volume due to its low density, within the confines of an aircraft’s fuselage. Another challenge is safety and certification due to hydrogen’s propensity to leak and its low ignition energy, as well as the safety issues posed by cryogenic or high-pressure hydrogen storage systems.

For these reasons, the research team is implementing a hybrid hydrogen-electric architecture. They believe this is key to leveraging both the high power density of the batteries and the high energy density of the hydrogen fuel cell propulsion system. This architecture also offers greater redundancy as an added benefit.

The testbed will be a scaled-down general aviation platform and will include an fuselage, independent battery arrays, a hydrogen fuel cell and hydrogen storage system, and up to 10 electric motors and propellers. The research team initially planned to develop a testbed that simulates the propulsion systems typically used in a twin-engine general aviation aircraft. However, given the growing interest in advanced air mobility, the team has adapted its design to allow for testing of a VTOL (vertical takeoff and landing) platform with up to 10 engines.

With the H2EDT testbed, the project aims to test a holistic approach to energy management and heat recovery, while also investigating the performance and reliability of hydrogen fuel cells and storage and distribution systems for aviation applications.

What sets the H2EDT apart is its digital power management system, implemented using a power distribution board developed by FH JOANNEUM, as well as its parallel hybrid architecture, where batteries and hydrogen fuel cells can directly power any engine in the system. The innovative H2EDT system leverages digital sensors and multiple power sources to automatically combine electric and hydrogen power as needed, significantly improving efficiency and safety.

Press Release by Diamond Aircraft 

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