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As the aviation industry seeks to reduce its carbon footprint, hydrogen has emerged as a promising alternative to conventional jet fuel.

Despite setbacks (like Universal Hydrogen’s recent shutdown), companies think using this lightweight, energy-dense element has the potential to revolutionize air travel.

Hydrogen Propulsion Systems for Aircraft

Two primary methods of using hydrogen to power aircraft are fuel cells and direct combustion.

Fuel cells convert hydrogen into electricity through an electrochemical reaction with oxygen. This electricity then powers electric motors that drive the aircraft’s propellers or fans, with water vapor as the only byproduct.

In direct combustion, modified gas turbine engines burn hydrogen as the fuel source. While cleaner than conventional jet fuel, and with the capability to operate in existing engines, this propulsion options still produces some emissions. Chiefly, burning hydrogen directly creates NOX emissions, a pollutant which is the main ingredient in smog and acid rain and can cause respiratory issues.

There are benefits and disadvantages to both propulsion technologies. While fuel cells are more efficient and produce basically no emissions, current configurations are limited to smaller aircraft and shorter ranges. Their use of fuel cells also require completely redesigning aircraft to accomodate the new power source.

Direct combustion of hydrogen offers the advantage of a basically drop-in replacement fuel for existing engine configurations. Burning hydrogen without converting it to electricity also has a higher output, which makes it more sutiable for longer ranges and larger aircraft.

Companies Taking Off

Several aerospace companies and startups are investing heavily in hydrogen propulsion technology:

  1. ZeroAvia: This California-based startup is developing hydrogen-electric powertrains for commercial aviation. Their HyFlyer project aims to deliver a 19-seat aircraft with a 500-mile range using fuel cell technology. In 2020, ZeroAvia completed the world’s first hydrogen-electric passenger plane flight.
  2. Airbus: The aviation giant has unveiled its “ZEROe” concept aircraft, which includes three hydrogen-powered designs. Airbus is exploring both fuel cell and combustion technologies, with a goal to bring a zero-emission commercial aircraft to market by 2035.
  3. H2Fly: A German company that has successfully flown the HY4, a four-seat passenger aircraft powered by hydrogen fuel cells. They’re now working on scaling up their technology for larger aircraft.
  4. GKN Aerospace: This British company is leading the H2GEAR program, which aims to develop a liquid hydrogen propulsion system for sub-regional aircraft. Their goal is to have zero-emission aircraft entering service by 2026.

Investment in Hydrogen Propulsion

Both the European Union and the U.S. are spending billions on technologies to reduce pollution in the aviation industry. In the U.S., the Department of Energy (DOE), particularly through its Hydrogen and Fuel Cell Technologies Office (HFTO) and H2@Scale Initiative, allocates hundreds of millions annually. The Federal Aviation Administration (FAA) supports hydrogen research via the Continuous Lower Energy, Emissions, and Noise (CLEEN) Program and additional research grants. NASA’s Aeronautics Research Mission Directorate (ARMD) also contributes significant funds for sustainable aviation projects, which include hydrogen propulsion systems.

Moreover, the Infrastructure Investment and Jobs Act (IIJA) earmarks $8 billion for regional hydrogen hubs and $5 billion for alternative fuel corridors, part of which supports hydrogen infrastructure that benefits aviation. Additional funding comes from the Department of Defense (DoD), with programs like the Environmental Security Technology Certification Program (ESTCP) and DARPA projects. The Environmental Protection Agency (EPA) and state-level initiatives, such as California’s Hydrogen Initiative and New York’s Green Bank, further enhance available funds. In total, the funding available specifically for hydrogen technologies in the aerospace sector from the US government likely exceeds a billion dollars annually, encompassing direct investments, tax incentives, and infrastructure development.

Meanwhile, the European Union’s Clean Sky 2 program has allocated €4 billion to develop cleaner aircraft technologies, including hydrogen propulsion.

Despite some well-publicized shutdowns, investment into the hydrogen propulsion from the private sector is also growing. For instance, ZeroAvia has raised over $115 million in funding from investors including Amazon, Shell, and the UK government. While Airbus is inesting billions of euros in its ZEROe program.

In all, tens of billions of dollars are being spent by governments around the world to drive hydrogen adoption — including as a fuel for aviation.

Hydrogen Infrastructure at Airports and Airline Partnerships

Alongside the fledgling efforts of hydrogen aircraft to take off, airports are beginning to invest in the necessary infrastructure for a hydrogen-fueled future in air transportation.

Rotterdam The Hague Airport in the Netherlands announced in February 2023 that it’s working with a consortium including Airbus, refinery Rotterdam, and gas company Gasunie to develop a hydrogen fuel facility by 2026. And in Toulouse-Blagnac Airport in France, in partnership with Hyport, revealed plans in December 2022 to have a hydrogen production and distribution station operational by the end of 2023. Not to be left out, the British government alongside Highlands and Islands Airports Limited (HIAL) began collaborating with European Marine Energy Centre (EMEC) in July 2022 to develop a hydrogen hub at Kirkwall Airport in Orkney.

Outside of Europe, a number of major U.S. airports are also exploring the development of hydrogen infrastructure to support zero-emission flying. The list of airports exploring a hydrogen strategy include most of the nation’s largest flying hubs including: Los Angeles International (LAX), San Francisco International (SFO), Denver International (DEN), Dallas Fort Worth International (DFW), Seattle-Tacoma International (SEA), Orlando International (MCO), and Boston Logan International (BOS).

These initiatives are part of broader sustainability and emissions reduction programs, with projects focusing on hydrogen refueling stations for ground support vehicles and preparing for future hydrogen-powered aircraft. These airports are collaborating with airlines, technology partners, and leveraging funding opportunities to advance their hydrogen infrastructure projects.

Major Carriers are Stepping In

The big airlines are beginning to signal their willingness to place orders for new planes. In December 2021, United Airlines made a commitment to buy up to 100 hydrogen-electric engines for a new fleet of aircraft, and earlier this month, American Airlines placed a bet on ZeroAvia’s technology with an order of its own. Both carriers are also investors in the company.

Meanqhile, ASL Aviation Holdings, placed an order with the now-defunct Universal Hydrogen two years ago to buy up to 10 hydrogen-powered ATR 72 conversion kits. Icelandair was another carrier to make a bet on Universal Hydrogen’s ability to deliver hydrogen power systems for its regional aircraft.

With the announcement that Universal Hydrogen would wind down, it’s currently unclear who the two carriers might work with going forward. Despite the setbacks, the partnerships from major airlines show that, in principal, the market exists for these zero-emission and low-emission technologies… now they just need to scale.

Challenges and Setbacks

While the overall trend in hydrogen aviation is positive, the industry has faced some challenges. Universal Hydrogen hasn’t been the only company developing hydrogen technologies to shut its doors. Alaka’i Technologies, which was developing a hydrogen fuel cell-powered air taxi called Skai, appears to have ceased operations in 2022. And HyPoint, a company developing hydrogen fuel cell systems for aviation, announced in November 2023 that it was shutting down due to funding challenges.

Hydrogen in Aerospace vs. Total Hydrogen Market

Still, the total market for hydrogen is projected to grow significantly in the coming decades, driven by various applications including transportation, industrial processes, and energy storage. While exact figures vary, some projections suggest the global hydrogen market could reach $200 billion by 2030.

Currently, aerospace represents a small portion of this market. Most hydrogen is used in industrial processes like oil refining and ammonia production. However, as the aviation industry transitions to cleaner fuels, its share of the hydrogen market is expected to grow substantially.

Estimates vary, but some projections suggest that by 2050, aviation could account for 12-15% of the total hydrogen market. This figure is based on the assumption that a significant portion of the commercial aviation fleet will transition to hydrogen power in the coming decades.

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