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MTU Aero Engines is on track with the development of its fuel cell. The first 600 kW demonstrator is currently under construction.
The Munich-based engine manufacturer has been working on an aviation-compatible fuel cell drive for around five years. Last year, MTU Aero Engines successfully completed tests with the hydrogen fuel system. Recently, the "flying fuel cell" concept has reached further milestones. The design of the fully integrated, 600 kW powertrain has been finalized during the critical design review, the corresponding performance of the electric motor from MTU subsidiary eMoSys was recently verified, the first of two new test benches will soon go into operation - and production of the fuel cell stacks has started. A stack consists of several individual fuel cells. "All fundamental validations have taken place and we are now in the next evolutionary stage. Now the hardware for the overall integrated system is coming together," says Barnaby Law, Chief Engineer for the flying fuel cell at MTU Aero Engines.
MTU Aero Engines relies on low-temperature polymer electrolyte fuel cells (LT-PEM) developed in-house. There are several reasons for this in-house development: The stacks previously available on the market typically have their roots in the automotive sector. This means that they meet automotive requirements and not all aviation requirements. As a result, they are hardly certifiable for large aircraft. And, more importantly for Law: "Stack performance will always be the key to better, more fuel-efficient propulsion in the future. As a manufacturer of aircraft engines, we need to have a hand in this."
Two new test benches in Munich
"Our stacks are now going into the first pre-series, involving several thousand bipolar plates. That's around ten stacks that are being tested," says Law. Two new test benches have been set up in Munich specifically for this purpose: a fuel cell stack test cell, which will be used for the first time this year, and a test facility for the entire drive system, which, according to Law, is nearing structural completion and acceptance.
There is no shortage of challenges in the development of an aviation fuel cell drive. "We had to change suppliers in one or two places. And we have limitations in the system in one or two places due to limitations in the devices," explains Law. The design is also a technical balancing act. The key question is: "How far can I go in simplifying the system without reducing my end-of-life performance too much?" summarizes Law. It's about the balance of system effort and performance over the system's service life and the corresponding weight and costs. "It sounds simple, but it's actually very complicated. I have to understand all the degradation mechanisms, everything that happens during operation, really well." The ground tests on the test benches play an important role in this understanding. Law's goal is for the fuel cell stacks to remain under the wings for the entire life of the aircraft. The hydrogen fuel system should also not have to be replaced. "If there are components with a limited service life, we naturally make sure that we get into a letter check or engine overhaul cycle," says Law.
However, the MTU fuel cell engine will not be flying any time soon. The engine manufacturer has already withdrawn from the flight tests originally planned with a Dornier 228 from the German Aerospace Center (DLR) at the beginning of 2024. The financial and regulatory effort involved in equipping a twin-engine aircraft with a fuel cell drive on one side is too great. Instead, the Munich-based company wants to validate the innovative powertrain on a ground-based vehicle in 2026. Flight tests are still on the agenda. However, neither a new schedule nor a possible test aircraft have yet been named.
Even more powerful drives in the pipeline
In parallel to the 600 kW fuel cell drive, MTU is working with other partners, including MT Aerospace, Collins Aerospace and Lufthansa Technik, on a 1.2 MW ground demonstrator as part of the HEROPS (Hydrogen-Electric Zero Emission Propulsion System) clean aviation project. This power class would be required for use on regional aircraft. For short- and medium-haul aircraft, a hydrogen-electric propulsion system would even have to deliver two to four megawatts. MTU Aero Engines can envisage such an improved fuel cell drive for short and medium-haul flights from 2050.
Even though Airbus has postponed the introduction of a hydrogen regional aircraft from 2035 to the 2040s, MTU is not changing its strategy. "We are staying the course," says Law. "We need to make sure we fully understand the maturity, the metrics of the system and the risk. Once we have that, we'll talk about product development and the business case."
https://www.flugrevue.de/flugzeugbau/mtu-brennstoffzellenantrieb-nimmt-form-an/