German HY4 project successfully tests a four-person aircraft with a zero-emission engine
Late last month, a four-seat passenger plane, powered only by a hydrogen fuel cell, recorded an 11-minute test flight at Germany’s Stuttgart Airport. The craft – dubbed ‘HY4’ by researchers from the German Aerospace Centre (DLR) – is reportedly the first of its kind.
The aircraft is the culmination of a joint project between DLR, aircraft construction company Pipistrel and a number of researchers from the University of Ulm.
In the same manner as terrestrial FCVs, the hydrogen fuel cell uses electrolysis to separate electrons from the hydrogen fuel to generate electricity. The leftover hydrogen ions then simply combine with oxygen from the air to create water which, in theory, is the fuel cell’s only waste product.
The cell is fuelled by two high-pressure carbon fibre hydrogen tanks, and in addition to the cell, the HY4 is equipped with a backup lithium-ion battery for cruising in case of failure. The 170 kg fuel tanks can hold up to 9 kg of hydrogen at 437 bar.
The power output of the engine is around 80kW, and with a maximum take-off weight of 1500kg and a predicted range of 1500km, it is theoretically not too different from a comparable 4-seat avgas-powered plane such as the Cessna 182T (which offers a maximum take-off weight and range of 1400kg and 1800km respectively).
However, the devil is in the detail. In the case of the HY4, the 400kg engine is almost half of the weight of the entire aircraft when empty, and whilst the range can technically stretch to 1500km, this is only if the engine is developed to run on liquid hydrogen. Using the gaseous form, as the aircraft currently does, it can only stretch to 750km, and even that was far from demonstrated at last month’s test.
The future of aviation?
Nevertheless, this success represents an exciting breakthrough, and one which adds to the buzz currently surrounding EV aircraft following technology giant Siemens’ successful test of a lithium-ion battery powered plane engine in July. That test, conducted at Schwarze Heide Airport near Dinslaken, demonstrated a far more powerful motor with a continuous power output of 240 kW which weighed just 50kg.
Siemens already have short term plans to market their motor to developers of hybrid planes, which would use standard avgas for the processes of take-off and landing, but could curb overall emissions by running solely on the battery in-flight.
The HY4 team have even more ambitious plans for the near future. Josef Kallo, a professor from the University of Ulm who was working on the project, said that: “With the HY4, we now have an optimal platform to continue developing the use of fuel cells on aircraft”. He believes that soon, with steady improvement of fuel cell technology, aircraft such as the HY4 will be operating as regional “air taxis” all over Europe and beyond, eventually looking to ferry as many 20 people per trip.
If the maths check out, this early model should already be able to transport four passengers the distance between London and Aberdeen with power to spare, and Kallo thinks that the idea will catch on quickly as it will be less hassle and more cost-effective than driving, and should have the added bonus easing up congestion on busy motorways
Whether such a plan could actually prove commercially viable, or whether it is just enthusiasm on the part of the researchers remains to be seen. The longer-term goal of transitioning traditional air travel to all-electric crafts seems more plausible for now, but either way the progress is important. Victoria Bluc, EU Transport Commissioner, said, “Such forward-looking activities embody the future of zero-emission flying”, adding that renewable, cost-effective aircraft were key to helping bring people and businesses together in the future.
The fully-electric aircraft is still only a nascent project, and commercial applications are still quite some way away, but with all sorts of milestones in hydrogen and battery-powered planes being reached this year, I would say watch this space.