From Past to Future: Chasing Zero Emission

Zero Emission is not a new concept, and hydrogen is an obvious candidate propellant. It produces only water vapor in its exhaust and packs the highest energy density of any fuel. Therefore, it has been viewed as the ideal fuel for the future of aviation.

Engineers have been experimenting with the idea of flying on Hydrogen dating back to 1957. However, the advancement of combustion engines has outpaced the production of hydrogen. Therefore, while gas-powered engines saw performance leaps, few vehicles rely on hydrogen today. 

In the last decade or so, many startups have shown renewed interest in hydrogen-powered flight. Even aviation giants like Airbus promise to bring hydrogen-powered aircraft to the market by 2035. Will that change soon?

We’ll look at all the active demonstrator projects and find out.

H2FLY HY4 and Deutsche Aircraft D328 Alpha 

H2Fly is using the HY4 aircraft to demonstrate the potential for flights powered by liquid hydrogen. (Photo: H2Fly)

H2FLY is a spinoff from the German Aerospace Center(DLR). It was one of the earliest developers of fuel-cell-powered flight technologies. The German company worked with DLR and modified two Taurus G4 gliders into the HY4, which it uses to test its fuel-cell technologies. The demonstrator made its maiden flight in 2016 and has created many firsts since then.

Its latest achievement was to complete the first piloted flight of a liquid hydrogen-powered aircraft in September 2023. Liquid Hydrogen has a much higher energy density by volume but requires more stringent storing conditions than its gaseous form. It’ll enable airframers to build larger planes with longer ranges.

The Deutsche 328 ALPHA has completed wind tunnel test. (Photo: Deutsche Aircraft)

The Stuttgart, Geramny-based developer is also collaborating with Deutsche Aircraft to bring new life into the Dornier 328 platform. The latter is reviving production for the regional aircraft that already has turboprop and turbojet versions. The two are working on a demonstrator called D328 Alpha, which will utilize liquid hydrogen fuel cells to achieve zero-emission flight. The airplane manufacturer has completed the wind tunnel test of the Alpha demonstrator and plans to have the first flight in 2025 or 2026.

ZeroAvia HyFlyers and HyperCore

ZeroAvia’s HyFlyer I which later crashed during flight test. (Photo: ZeroAvia)

ZeroAvia is another early entrant to Hydrogen-based propulsion. The California-based developer flew its first demonstrator, a Piper Malibu, in early 2019. Not much information about its configuration is available online, only that the aircraft was flying zero-emission without any fossil fuel support. The purpose of the demonstrator was mainly to validate the integration of a complete powertrain system.

The company later claimed to have completed its first hydrogen-electric powered flight in September 2020, using a Piper Mirage named HyFlyer I. However, the HyFlyer I was lost due to a crash landing due to power loss induced by propeller windmilling.

ZeroAvia’s Dornier 228 departure for the first flight. (Photo: ZeroAvia)

The propulsion developer has since built HyFlyer II from a Dornier 228 plane. The HyFlyer II performed its maiden flight in January 2023 and has conducted several more test flights since then. 

ZeroAvia will convert this DHC Dash 8 Q400 to fly on hydrogen. (Photo: ZeroAvia)

While both HyFlyers were testing the company’s 600kW engine, it also set sights on larger regional aircraft. In May 2023, the engine maker made a joint announcement with Alaska Airlines that it will retrofit a former Alaska De Havilland Canada Dash 8 Q400 with 1.8MW motors. The company has been testing its latest technology using a truck at its Hollister location in California. It also received the Q400 from the Seattle-based airline and plans to conduct the first flight of the retrofitted plane sometime in 2024.

Britten-Norman Project Fresson

The U.K. is positioned to become a center for hydrogen aircraft development. In addition to ZeroAvia, Britten-Norman is also working on retrofitting its iconic Islander aircraft with hydrogen-powerplants. The planemaker is working with Cranfield Aerospace on Project Fresson, named after the Scottish pioneer aviator Ted Fresson, which aims to convert the nine-seat Britten-Norman 2 Islander to a hydrogen fuel cell-powered plane.

Cranfield Aerospace Solutions (CAeS) welcomes Evolito, a ground-breaking UK technology innovator onboard as the motor; inverter supplier for its hydrogen-powered aircraft demonstrator – Project Fresson. (Photo: Cranfield Aerospace)

The consortium has announced several major announcements regarding supplier selections and plans to conduct the first flight in 2024. What made the Islander different from the rest of the demonstrators is that “The CAeS propulsion system design does not include batteries for transient power needs such as a go-around due to the fact that we have sized the hydrogen fuel-cell system so no battery energy storage is required and the HFCS power output is controlled directly to achieve the necessary responsiveness and stability without a buffer energy store.”

Universal Hydrogen Lightning McClean

The demonstration on the ATR-72 showed the loading and unloading of Universal Hydrogen’s modular hydrogen capsules into the aircraft. (Photo: Universal Hydrogen)

Like ZeroAvia, Universal Hydrogen is another company with locations in Europe and the United States. Its primary business is to deliver a modular hydrogen power delivery system. However, the company is working with several suppliers to develop its propulsion system ecosystem to promote its product. It has two technology demonstrators in progress. The first one is an ATR 72, which demonstrated the company’s liquid hydrogen loading and unloading of its liquid hydrogen modules at Toulouse Blagnac Airport in November.

Lightning McClean cruising the skies of Mojave. (Photo: Universal Hydrogen)

The second airframe, nicknamed Lightning McClean, is a DeHavilland Canada Dash 8-300. It’s conducting flight tests with gaseous hydrogen powering the fuel-cell batteries in Mojave, Calif. The batteries power a Magnix650 electric motor. The plane flew from Moses Lake International Airport in Washington in March 2023 for 15 minutes. It is the largest fuel-cell-battery-powered aircraft to date. It’ll receive upgrades to utilize the company’s liquid hydrogen tank in 2024.

Airbus ZEROe and upNext HyPower

Last but not least, Airbus also has its ambition set on hydrogen. It’s the first established airframer to commit to using hydrogen as a power source in its future planes. It has unveiled several concept airplanes in the ZEROe family that would fly on hydrogen, and it’s working on several demonstrators to make that ambition a reality. 

Airbus’s A380 MSN1 will serve as test platform for both hydrogen fuel cell and combustion propulsion technologies. (Photo: Airbus)

Airbus will add a fifth engine mount to its A380 MSN1 test platform to help advance hydrogen propulsion. It had plans to outfit the aircraft with an Airbus-developed fuel-cell-powered engine with flight tests scheduled for 2026. The airframer also had planes to install a hydrogen combustion engine that’s undergoing development by GE with funding from the HYdrogen Demonstrator for Aviation(HYDEA) project. The engine maker expects to install the modified engine on the A380 in the 2027-2028 time frame, which deviated from its original plan to flight test the engine in 2025.

Airbus will test HyPower, a hydrogen fuel cell battery on the A330 technological demonstrator.(Photo: Airbus)

In addition to using Hydrogen for propulsion, the European company is also exploring opportunities to use hydrogen-powered auxiliary power units (APUs). Airbus UpNext will replace the actual APU of an A330 with a hydrogen fuel cell system that will generate electricity. Known as HyPower, the hydrogen fuel cell demonstrator also aims to reduce the emissions of CO2, nitrogen oxides (NOx), and noise levels associated with a traditional APU. The company expects the demonstrator to start flying in 2025.

Most companies developing hydrogen propulsion technologies are working with fuel-cell batteries and are moving toward using liquid hydrogen. The engine makers are experimenting with engine modifications to reach higher outputs with hydrogen combustion technologies. While none of the developers are conducting flight tests as frequently as the hybrid-electric technology demonstrators, the hydrogen ones still outperformed the battery-electric planes. It’s likely that Mr. Steven Udvar-Hazy, Air Lease Corporation executive chairman, is right again. There is a future for clean, hydrogen-powered aircraft, but it will take several decades before the technology is fully commercially viable and ready to replace modern jets.

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Fangzhong Guo

Fangzhong grew up near an OEM airport in northeastern China, where he developed his enthusiasm for aviation. Taking upon his passion, he's now working as an aircraft interior design engineer. Besides working in the aerospace industry, Fangzhong enjoys trying out different types of airplanes and seeing how airplane interiors have evolved. So far, he's flown on over 80 types of aircraft. He also planespots in his spare time. His rarest catches included the 747 Shuttle Carrier Aircraft and AN-225.

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