Fliegen war bisher nicht ohne Abgase möglich

03.11.20 Hydrogen aircraft The long haul to more sustainable aviation Hans-Joachim Ziegler • 10 min.

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Summary

The corona pandemic, which all but grounded the airline industry, will hopefully soon pass. But another issue will challenge jet travel for decades to come: climate change. That’s why aircraft manufacturers are exploring sustainable hydrogen propulsion systems. Debate.Energy looks at how far has this technology has progressed and what hurdles it faces.

Although aviation is responsible for less than 3% of global carbon emissions, it exemplifies the tradeoff between lifestyle and climate protection: would be people willing to forgo the convenience of jet travel in order to protect the planet? Yet it may also be an exciting example of how advanced technologies can render such tradeoffs superfluous: can an aircraft be developed that makes flying convenient, affordable, and climate-neutral?

Alternative fuels

Which energy source will power tomorrow’s clean aircraft is still unclear. Some developers place their faith in electric-powered planes, others in aviation biofuels, and still others in synthetic kerosene made from captured carbon and renewable hydrogen. Hydrogen itself can also serve as a fuel for modified jet engines or used in fuel cells that run electric propeller engines. The latter variant is more sophisticated technologically but climate-friendlier, since it releases no nitrogen oxides, only water vapor. The potential adverse climate impact of water vapor can be minimized by flying such aircraft at certain altitudes.

Ready for takeoff?

In September 2020 Britain-based ZeroAvia conducted a successful test flight of a commercial-scale hydrogen fuel cell aircraft. The converted six-seater Piper Malibu was only aloft for eight minutes. But the test proved that hydrogen fuel cells, which are already used in road transport, have potential for aviation as well.

One of ZeroAvia’s competitors is industry giant Airbus, which intends to launch its own hydrogen aircraft by 2035. In September the company unveiled three ZEROe hydrogen-powered concepts. The smallest ZEROe is a turboprop aircraft that could transport up to 100 passengers about 1,850 kilometers. It would be powered by burning hydrogen in modified turbines.

The second ZEROe is a larger turbofan plane that would use hydrogen to power modified jet engines. It could take roughly twice as many travelers twice as far as the turboprop concept. Airbus CEO Guillaume Faury says the advantage of these two designs is that they “wouldn’t require investment in completely new technologies.” The third ZEROe is much more futuristic. It features a blended wing-body design whose wide fuselage creates more options for accommodating bulky hydrogen fuel tanks.

Turbulence ahead?

Although Airbus is ultimately unlikely to choose it, the futuristic wide-body design underscores one of the challenges to be overcome before hydrogen aircraft can enter production: how to store enough fuel onboard. Even in its liquid form hydrogen takes up much more space than kerosene. A McKinsey study published in May 2020 estimates that tank size would have to be halved for the technology to be viable. In addition, airports would need hydrogen refueling and maintenance infrastructure. Moreover, using hydrogen only makes sense if the hydrogen is green; that is, produced in electrolysis plants powered by renewable electricity. This would necessitate a massive buildout of wind and solar farms. The same McKinsey study estimates that converting the aviation industry to hydrogen would require up to 1,500 gigawatts of additional renewables capacity—more than half of the world’s current renewables capacity.

The right climate Hydrogen aircraft won’t get off the ground without the right policy and regulatory environment. Björn Nagel, Founding Director of the German Aerospace Center’s Institute of System Architectures in Aeronautics, has pointed out that “green hydrogen ... will likely remain more expensive than kerosene is today.” He says the technology will therefore require taxes and subsidies to make it economically as well as ecologically sustainable.

In short, hydrogen-powered aviation faces both large technological and policy hurdles. Before passengers can board a hydrogen aircraft like ZEROe, they’ll have many opportunities to decide whether a (fossil-fuel-powered) airplane trip is really justified. Still, the Hydrogen Strategy the EU adopted in mid-2020 and aircraft manufacturers’ ambitious designs serve as beacons of hope for a new era of zero-carbon aviation. And for an end to flight shame.

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