Hydrogen Planes Show Promise—and Their Limitations

Hydrogen hype is at a high. While producing the gas cleanly by electrolyzing water is still expensive, the war in Ukraine has emphasized the need for the West to gain energy independence and raised the cost of conventional fuels.

Last year,

Airbus

unveiled three hydrogen-aircraft concepts, one or more of which it hopes to realize by 2035. It has a regional plane project, and two that would cover most routes flown by its narrow-body A320, the world’s most popular jet. In a recent report, the International Council on Clean Transportation estimated that hydrogen jets would make up half of regional and narrow-body sales in a scenario in which aviation stops using fossil fuels by 2050.

Yet the term “hydrogen plane” is ambiguous, referring to different technologies that each come with their own challenges. ZeroAvia’s propulsion system works like a hydrogen car, with fuel cells that turn hydrogen into electricity to move the propellers, whereas pure hydrogen planes are those that burn the gas in a conventional engine, as tested in the 1950s.

Generating enough power with fuel cells alone has been hard. Following the crash of a smaller prototype last year, ZeroAvia has decided to test its new 600-kilowatt powertrain—scheduled for certification in 2024—on two 19-seat Dornier 228 planes, one of which will supplement the fuel cells with a battery and the other with a conventional engine, at least initially.

And these aircraft will only serve niche players. Mainstream regional operators need turboprops with at least 50 seats and a 400-mile range. This means waiting for ZeroAvia’s next powertrain, which should produce between 2,000 and 5,000 kilowatts. The company hopes to deliver it by 2026.

Beyond regional distances, the weight of fuel cells becomes a big problem. Mr. Miftakhov believes the technology will improve fast enough to power A320-style planes sometime in the 2030s, but experts tend to see burning liquid hydrogen as a more feasible option at those ranges. Airbus remains open to using cells, but this is only likely if it settles for its first, regional design—in which case its 2035 delivery target seems unambitious. Also, working against the interests of turbine-engine makers such as GE Aviation and Pratt & Whitney, which each have around $20 billion in annual sales, could be challenging.

Hydrogen combustion has different problems. It is less efficient than fuel cells and generates large emissions of non-carbon gases such as water vapor and nitrogen oxides. Their environmental impact is unclear, which is why Airbus announced last month it will use hydrogen test gliders to study the line-shaped clouds they generate. This is a wise move, but underscores the unknowns that could sink the technology as a green alternative. It is revealing how much wiggle room the European plane maker has given itself to decide which type of hydrogen jet to develop.

Whether used in a turbine engine or fuel cell, hydrogen occupies much more space than kerosene and can’t be stored in the wings. This makes airframes increasingly hard to redesign as the range increases, even though only 7% of passenger carbon emissions come from regional planes.

While ZeroAvia’s time line appears optimistic, the current buzz could well spell a period of hydrogen-electric upheaval for regional jets in the 2030s. Promises to fly further than a few hundred miles with hydrogen, however, still look vaporous.

Write to Jon Sindreu at [email protected]