Honeywell Explores Future of Hydrogen-Powered Aircraft

Hydrogen fuel cells already power thousands of cars, SUVs, transit buses and unmanned aircraft. Can conventional airplanes be far behind? Honeywell says “No.”

“We anticipate the use of conventional jet aviation fuel will go away in the next 20-30 years,” said Phil Robinson, Senior Director of Zero-Emission Aviation at Honeywell. “The aviation industry is already moving to sustainable aviation fuel (SAF) made from renewable feedstocks, which is much cleaner, but still doesn’t get us to our ultimate goal of zero carbon emissions. Hydrogen can be used to generate power for all-electric and hybrid-electric propulsion systems and auxiliary power units, with water as the only byproduct.”

That makes hydrogen much cleaner than the fossil fuels aircraft have burned throughout the history of flight. Utilizing hydrogen, either through combustion or via a fuel cell, can eliminate most pollutants associated with Jet-A, which include carbon monoxide, carbon dioxide, particulates, nitrogen oxide (NOx) and unburned hydrocarbons. In addition, the only sound from hydrogen fuel cell aircraft is from the rotors, a real benefit to those living near a busy airfield.

Of course, not all hydrogen is created equal, noted Taylor Alberstadt, Honeywell’s Senior Director of Business Development, Electric/Hybrid-Electric Propulsion. “When you talk about hydrogen’s environmental footprint, you also need to consider how the hydrogen is manufactured,” he said. “Ideally, aircraft should use ‘green’ or ‘clean’ hydrogen, which is produced using energy from renewable sources like solar or wind power through a process called electrolysis.  Understanding the full life cycle of the fuel is a key element in achieving overall sustainability.”

Traditionally, industrial hydrogen has been produced from petroleum sources – most recently natural gas. Dubbed “gray hydrogen,” this hydrogen doesn’t really carry a reduced carbon footprint – it just moves the emissions from the vehicle to the production plant.

“Blue hydrogen” is a big step in the right direction. It is also produced from natural gas, however the carbon produced during the conversion to hydrogen (called reformation) is captured rather than released into the air. This sequestered carbon dioxide is pumped underground, where it cannot affect the atmosphere. “Green Hydrogen” is the end game, but it will take a while before we have enough solar and wind capacity to make a meaningful amount of it – so in the meantime blue hydrogen is critical.

With all of hydrogen’s potential, it’s no surprise that government agencies, airlines and aerospace companies are coming onboard, said Robinson. “Through the Clean Aviation Joint Undertaking, the European Union is investing heavily in hydrogen-powered aircraft,” he noted. “In the U.S., the FAA and Department of Energy are advocating for both hydrogen and electro-fuels (man-made SAF) as cleaner alternatives to fossil fuels in aviation and other applications, though public sector funding still remains tiny compared to the EU.”

IATA – the International Air Transport Association – views hydrogen as a key element of the airline industry’s goal of achieving net-zero carbon emissions by 2050. IATA sees hydrogen-powered aircraft flying short-haul routes of up to 120 minutes within the next 20 years.

Aircraft manufacturers continue to study hydrogen’s potential. As a leader in hydrogen-propulsion evolution, Airbus is working on a ZEROe project, which aims to develop a zero-emission aircraft by 2035. It has announced plans to use an A380 as a test bed for propulsion systems that use liquid hydrogen. Deutsch Aircraft plans to fly a Dornier 328 hydrogen fuel cell demonstrator in 2025 and other airframe manufacturers continue to investigate the possibilities of hydrogen flight.

The green evolution from jet aviation fuel to SAF and ultimately to battery and hydrogen comes with a unique set of challenges according to Alberstadt. “Jet fuel has about four times the volumetric energy density of hydrogen,” he said. “That means you need four times as large a fuel tank to fly the same distance.”

“This and other factors make production, transportation and storage more complex, largely because efficient hydrogen infrastructure is in its infancy,” Robinson added. “Then there’s the price. Hydrogen currently costs about four times as much as jet fuel on a flight-mile basis. The price will drop once production is scaled-up, but hydrogen will remain more costly than conventional jet fuel for a considerable time, unless increasing carbon taxes cause jet fuel prices to rise while hydrogen costs are falling.”

“The move to hydrogen fuel cells is entirely motivated by sustainability and an industry-wide commitment to shrinking aviation’s environmental footprint,” he said. “Hydrogen power is certainly part of the answer and companies like Honeywell are working hard on innovations that will help the industry accelerate the pace of change and reach our net-zero emissions milestones.”

Building on decades of experience, Honeywell established itself as a leader in hydrogen fuel cells for unmanned aerial vehicles with the 2020 acquisition of Ballard Unmanned Systems, which integrated more small fuel cells into more drones than all other companies combined. Meanwhile, through its UOP business, Honeywell is a key player in blue hydrogen production, recovery and storage processes. And, at Engines & Power Systems, Honeywell engineers are inventing new electric and hybrid-electric powerplants that will run on hydrogen.

“Protecting the environment for future generations is of utmost importance to all of us,” Alberstadt said. “Honeywell’s broad technology portfolio supports sustainability efforts across all aspects of the aviation industry. This has created a powerful catalyst for us to support customers and partners in delivering the benefits of clean hydrogen to the aviation world.”

Robinson agrees. “We’ve designed and built more small turbine engines and auxiliary power units than anyone, and it’s extremely exciting to be able to bring this rich history and experience to enable sustainable aviation for a greener planet.”