Could hydrogen fuel-cell tech replace aircraft jet engines?

Airbus recently announced its plans to design, build and demonstrate a “megawatt-class propulsion system” aimed at large-scale passenger aircraft, featuring hydrogen fuel cell technology with cryogenic hydrogen storage, in less than four years.

This doesn’t mean that hydrogen fuel cell jumbo airplanes are on the way in that timeframe, or that the company sees fuel cell technology as a complete replacement for jet engines. But it may replace some jet engines on a smaller scale long before internal combustion engines are completely removed from cars.

The company says it “could be tested in flight by the middle of the decade — around 2026,” and called hydrogen a “very attractive option” in the company’s quest to bring zero-emission aircraft to market by 2035.

As the company outlines, it has three effective options with hydrogen. It can burn hydrogen in a modified gas turbine engine; it can use hydrogen fuel cells to generate electric power; or you can use a combination of both.

For either of these paths, it could (as explained in the video section below) generate hydrogen from renewables like wind and solar, but going the fuel cell-EV route means such an aircraft would effectively be zero emissions.

If holding cars to higher standards, why not planes?

It would help to dispel an inconvenient truth—that cars, trucks, and buses are not the only transportation emissions problem. Commercial air travel accounts for about 2% of global greenhouse gas emissions or, in the US, more than 3% of GHG emissions and about 10% of total transport emissions. If auto emissions can make such leaps and bounds with electrification, why can’t airplane makers step up their game?

That’s partly because the other inconvenient part is this: today’s automotive battery technology isn’t yet as energy-intensive as that needed to fly long commercial routes or larger planes. Even hydrogen storage will require new kinds of solutions to take advantage of the energy densities required of airplanes.

Airbus, in a recent announcement, said that the aircraft will use cryogenic hydrogen storage tanks, which operate at -253 degrees Celsius. Storing hydrogen at the ultra-high pressure of 700 bar wouldn’t be enough, he said, but at colder temperatures it becomes a more energy-dense liquid. Even so, four liters of liquid hydrogen is equivalent to just one liter of standard jet fuel, Airbus said. So don’t expect a range to rival the Boeing 777 or Airbus A350.

Airbus liquid H2 tank

Safety and endurance requirements are tougher than possible for space launchers, Airbus said, because commercial aircraft not only need to survive 20,000 takeoffs and landings but also need to withstand liquid hydrogen much longer. For that solution, we are working on a composite materials approach.

The fuel cell demonstrator has many steps to go into development and testing. It will be built on the Airbus A380 MSN001 “multi-modal test platform” and will be externally modified to carry a fuel cell engine pod. Airbus is partnering with automotive supplier Elring Klinger and in a joint venture with a company called Aerostack for fuel cell stacks, which generate electricity (plus some water and heat) from hydrogen through carefully managed electrochemical reactions.

The Airbus ZeroE platform

It seems likely that, as in a fuel cell car like the Toyota Mirai, the lithium-ion battery pack will play a role in helping buffer energy—or in this case, providing emergency lowering if the stack goes out.

The role of fuel cells in ground transportation is not over

Such a solution might fit into a future where big picture research suggests fuel cells could have a big future in aviation, shipping, and heavy industry — while the window of opportunity for fuel cells may be fading fast for many truck and bus formats. .

Meanwhile, both Airbus and Boeing are reportedly continuing to work on a next-generation hybrid engine that can electrify turboprops. And smaller companies have completed short flights of electric commercial airplanes.

In the US, airplanes are not subject to any greenhouse gas standards until 2020, when the US EPA adds them for new commercial airplanes and large passenger jets after years of industry rejection. It is entirely possible to see a time when regulatory frameworks will serve stricter goals, so until things like high-speed teleportation or tunneling become a reality, innovation in jumbo jets may be the way to save their existence.