Introduction

The long-cherished dream of hydrogen-fueled aviation edged a bit closer to reality with Airbus recently restating that it plans to launch its first zero-emission hydrogen commercial flight by 2035. The appeal of this technology is obvious: it represents a real opportunity to decarbonize the industry at a time of increasingly acute public concern about climate change.

However, any large-scale shift from fossil fuels to hydrogen will require an extraordinary level of commitment and coordination if the sector is to address the numerous technical and economic challenges inherent in such a transition. Airports will be the crucial cornerstone of this possible future, but four challenges will prove particularly significant (see figure 1).

Production of green hydrogen at sufficient scale

The first challenge is to produce enough hydrogen to meet the prodigious energy needs of the aviation industry. To reduce CO₂ emissions by any meaningful amount, the electricity used for hydrogen electrolysis and liquefaction must be generated from renewable energy sources (while today more than 95 percent of the hydrogen is produced from natural gas), which raises a practical problem.

Hydrogen production is currently a low-efficiency proposition; the energy value of hydrogen is 60 to 70 percent of the total electricity used to produce it. This means the amount of renewable power required to produce liquid hydrogen is immense—a factor often overlooked by the most optimistic assessments.

The production of hydrogen at scale will remain the main challenge to be addressed. For example, filling up 30 percent of flights with hydrogen at Paris Orly Airport would require producing approximately 270 tons of liquid hydrogen per day, assuming a consumption of 1.5 tons for a 1,500-kilometer flight for short-range, turboprop airplanes.

Since hydrogen is produced through electrolysis, this translates to 18 gigawatt-hours every day, equivalent to the full production of one typical nuclear plant of 900 MW. If, to ensure that hydrogen production actually reduces carbon emissions, the electricity is produced through solar power, 44 square kilometers of solar panels would be needed—a footprint representing three times the entire surface area of the Orly airport itself. Covering the entirety of an airport such as Orly would only produce enough fuel for two to three aircraft a day.

In addition, even the largest hydrogen-electrolysis plants currently in existence hardly exceed 20 megawatts of capacity, delivering a maximum production of just 0.5 gigawatt-hours a day—and even this modest amount assumes the plants are functioning at 100 percent. But even this fanciful amount of electrolysis capacity would have to be multiplied by a factor of at least 50, an unrealistic attainment with today’s current technologies.

Given these forbidding limitations, hydrogen could only remain a niche aviation fuel in the midterm, with alternative technologies such as hybridized engines and sustainable biofuels perhaps representing more viable pathways to low-carbon aviation for now.

Reshaped infrastructures and logistics

In addition to the production challenge, a shift to hydrogen will require airports to adapt their infrastructure and logistical systems. Take storage, for example. The levels of daily production hypothetically sketched out above would require more than 70 tanks of hydrogen with a capacity of around 10 cubic meters—meaning that each tank is roughly equivalent in size to the amount of concrete carried in a single mixer truck at full capacity.

That may not sound too daunting, but consider also that hydrogen is highly explosive at ambient temperature, meaning that each of these tanks will need a certain circumference of space in order to reduce the chances of chain-reaction explosions, significantly increasing the overall space needed for storage. Then there’s this additional storage factor: the best way to keep hydrogen is in liquid form, but this requires cryogenic units capable of keeping the hydrogen at -253° Celsius, generating a new level of safety-management and logistical complexity.

Additionally, this hydrogen will somehow need to be routed to planes, but transportation via trucks brings some formidable logistical limitations. Hydrogen requires four times more volume than conventional jet fuel to supply the same amount of energy, which means four times the truck traffic, which would greatly exacerbate the burden on the already congested internal roadways of an airport such as Orly, which currently sees 12,000 vehicle trips per day.

An alternative means of delivery would be to use pipelines, but this too presents some obstacles, notably the fact that hydrogen can’t be blended with kerosene and would have to be extracted from the end of the pipes using a specialized mechanism (to keep it “cold”). So, part of the existing in-ground networks would have to be dedicated to hydrogen, creating a need for separate terminals and runways for hydrogen aircraft. Under such a scenario, airports would need to manage two energetic chains at a time until a full shift to hydrogen is completed.

At the supply stage, additional challenges would be encountered. Indeed, the loading of hydrogen in the aircraft remains an unsolved question: how will the hydrogen be pumped into the aircraft and what safety measures would be put in place during refueling? But innovative logistical models are emerging that reimagine the way planes store and refill hydrogen on board, such as by loading prefilled hydrogen tanks directly onto the aircraft.

Depending on the answers to such questions, the grounding time of airplanes could be impacted. Since regulatory limitations in Europe state that aircraft can’t be refueled with passengers inside, the daily flight tempo could be significantly reduced. A likely redesign of hydrogen aircraft due to specific requirements (mainly related to energy density, fuel handling, and turbines) may impose additional constraints on airports. Aircraft design might also evolve, with larger wingspans or longer fuselages, leading to reconfigured terminals and parking areas.

Impact on ticket price and consumer demand

The future of a more sustainable form of aviation will also depend on customers’ response to the technology: will they be willing to pay a premium for greener flights? In addition, customers may be reluctant to fly on such new aircraft due to their perception of heightened safety risks.

It’s possible that ticket-price increases might not be such a deterrent. The combined effects of a decreased cost of green hydrogen production and the imposition of new carbon taxes would likely limit the premium to about 13 percent (see figure 2). This remains within customers’ willingness to pay for greener flights, estimated at about 15 percent according to a February 2020 Technology in Society study. As a comparison, the “use of 10 percent biofuel for a round trip from Paris to New York would increase ticket price by ~10 percent ($50),” explains Paul Mannes, director of aviation at TotalEnergies.

Global industry collaboration

To take up all these challenges, a strong collaborative system needs to be built among energy suppliers, original equipment manufacturers (OEMs), airports, and airlines worldwide. Building a global and cooperative ecosystem with all players in the value chain seems to be the key to achieve a truly competitive and sustainable hydrogen aviation industry.

Because of future competition across industries for sourcing green hydrogen, airports will certainly want to build their own hydrogen-production capacity and generate economies of scale for other applications. However, since self-sufficiency appears out of reach, a partnership with energy suppliers may be considered. The vast quantities of hydrogen needed for aviation would need to be routed to the airport through pipelines and be liquified on site. A whole ecosystem will then have to be put in place between airports and energy producers.

Furthermore, infrastructure systems would need to be implemented in more than one airport to facilitate the refueling of planes traveling in each direction. Regulations and technical standards also need to be set up accordingly between countries, governing both air traffic and the use of hydrogen on the ground.

For now, only a few such initiatives have been launched globally, mostly concentrated in Europe. On September 21, Aéroport de Lyon, Air Liquide, and Airbus announced a hydrogen-aviation partnership, following the one on June 21 among Aéroport de Paris, Air Liquide, and Airbus; both projects have the long-term goal of decarbonizing air transportation. A similar project was announced on July 6 among Hamburg Airport, Lufthansa Technik, the German Aerospace Center (DLR), and the Center for Applied Aeronautical Research (ZAL).

Conclusion

Hydrogen aircraft still has a long way to become a sustainable reality. A strong collaboration among all players throughout the value chain and across geographic locations is required. In the meantime, alternatives (such as the hybridization of engines) can be explored to reduce carbon emissions. In any case, 2035 is not a long way off by the standards of aviation-sector planning—so the time for action to meet this deadline is now.

Source: Kearney