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    Flight Testing

    Truly Clean Aviation

    Hydrogen-electric engines for zero-emission flight

    Truly Clean Aviation

    Hydrogen-electric engines for zero-emission flight

    The Problem

    Aviation is the fastest-growing source of greenhouse gas emissions

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    % of total Human Climate Impact

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    Its share of climate impact is expected to be 25-50% by 2050. Regulators worldwide are pushing for green aviation and net-zero carbon emissions by 2050.

    Today’s aircraft engines emit substances in addition to CO2 that double or even triple aviation’s climate impact

    NOx, contrails, and particulates have a specific warming effect of their own. Non-carbon emissions are thought to account for around two-thirds of climate impact.

    • OZONE
    • SOOT

    The Solution

    A hydrogen-electric engine in every aircraft; delivering a world of truly clean flight

    With up to 60 times greater specific energy and lower cycling costs than lithium-ion batteries and numerous advantages over all other decarbonisation solutions, hydrogen-electric powertrains are the only viable, scalable solution for zero-emission aviation.


    Hydrogen-electric is the best option for long-term transition to clean aviation

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    Reduction in climate impact


    Net Impact

    Key challenges

    Direct CO2


    Water vapour & contrails

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    Weight of the powertrain; Higher volume fuel tanks required

    H2 combustion
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    Higher non-CO2 climate impact than fossil fuels; Even higher volume fuel tanks required

    Sustainable aviation fuels
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    Bio feedstock sustainability; High cost of synthetic fuels Same in-flight emissions

    Battery electric
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    Weight of battery precludes large aircraft; Frequent replacement

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    Small incremental impact (10-20% max) on both economics and climate

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    Hydrogen-electric engines are a superior propulsion system, offering lower fuel and maintenance cost, zero emissions and commercial ranges even when retro-fitted

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    90% lower

    life cycle emissions compared to turbines

    40% lower

    fuel and maintenance costs compared to turbines

    75% lower

    hourly maintenance costs

    250 – 1000nm

    Retrofits up to 300NM <19 seat missions from 2025 and up to 1000NM 50-90 seat from 2027. Ranges cover 95%+ of missions flown today, including reserves

    Delivering Future Zero-Emission Aviation Fuel

    Green hydrogen produced through electrolysis with clean power – assured hydrogen delivery is part of ZeroAvia’s propulsion offering

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    H2 Compression & Storage

    H2 Compression & Storage:

    Hydrogen from the primary low pressure storage vessel is pushed to a compressor and compressed 15-20 times the source pressure (20-30 bar → 400 bar) and stored in high pressure vessels.

    Some airports already use hydrogen to produce electricity and to power ground vehicles and other systems.

    Energy Conversion Electrolysis

    Energy Conversion – Electrolysis:

    Producing hydrogen takes energy because hydrogen atoms don’t exist on their own — they are almost always stuck to another atom, often another element (on earth, hydrogen is abundant in the form of water – H2O). Creating pure hydrogen requires breaking those molecular bonds.

    Electrolysers split water into hydrogen and oxygen. The oxygen is released into the atmosphere through a vent. The hydrogen is directed towards a storage vessel at low pressures (20-30 bar).

    Energy Source

    Energy Source

    Zero-emission aviation starts with green hydrogen.

    Green hydrogen is produced by taking renewable electricity – from wind, solar or hydro-power – to power electrolyzers.

    Many airports already use solar and wind power to decarbonize their operations

    Fuel Tanks

    Fuel tanks

    If it’s Dornier 228 on the infrastructure scheme, then we have 2 fuel tanks under each wing (4 fuel tanks in total)

    Fuel tanks are high pressure tanks (at up to 350BAR), where hydrogen received from a truck or from the pipeline, is stored.
    Transferring gas from one storage tank to another without a compressor will always result in less pressure in the destination tank. This is why primary storage should always be at a higher pressure (hence, 400BAR for primary storage, and 350BAR for aircraft storage).

    Hydrogen has much higher energy density (about 3 times) than normal kerosene. Hydrogen storage still needs more volume than typical kerosene storage, because of the much lower density of hydrogen. This is why, for retrofitting small aircraft for hydrogen, externally carried hydrogen storage tanks are required.

    H2 Transportation and Fuelling

    H2 Transportation and Fuelling:

    When required, the high pressure hydrogen is then fed from the storage vessels through a pipeline to an airside refueler to refuels the aircraft. Alternatively, a refueling truck can be used to move the hydrogen to airside and refuel the aircraft.

    Refueling Truck

    The refueling truck can take low pressure hydrogen or high pressure hydrogen and drive to the parked airplane on the airfield.

    The Refuler consists of high pressure vessels if H2 was compressed on the storage site.
    The Refueler truck may also have a compressor on board to compress low pressure hydrogen from 20-30 bar to 400 bar, Then it pushes compressed H2 into the high pressure vessels (which are also inside the truck).

    The truck regulates the flow into the aircraft from its high pressure tanks to the aircraft fuel tanks..


    From the storage high-pressured hydrogen enters the pipeline through the fixed point start and goes to the fixed point airside.

    A refueling trolley then connects the fixed airside of the pipeline and the aircraft, and regulates flow of the hydrogen into aircraft fuel tanks.



    ZeroAvia’s powertrain repowers existing airframe models

    We work with certified fixed-wing airframe models to retrofit and linefit with our hydrogen electric powerplant, simplifying regulatory issues and reducing time to market.

    The typical airframes will be:

    For ZA600 model:

    • DHC-6 Twin Otter
    • Dornier 228
    • Cessna 208B Grand Caravan

    For ZA2000 model

    • DHC Dash 8 Family
    • ATR 42/72

    For ZA2000RJ model

    • CRJ100/200

    Hydrogen-Electric Propulsion System

    Hydrogen-Electric Propulsion System:

    Includes: fuel cell, engine, propeller

    How does the hydrogen-electric powertrain work?

    ZeroAvia’s hydrogen-electric powertrain brings state-of-the-art fuel cell and electric motor technology together to create an unparalleled aircraft engine that will deliver improved operating economics without harming the planet.

    The powertrain uses hydrogen:

    • for ZA600 propulsion system – gaseous H2 stored onboard in lightweight tanks
    • for ZA2000 and ZA 2000RJ propulsion systems – liquid hydrogen stored onboard in lightweight cryogenic tanks
    • Hydrogen and oxygen (from the air) are fed into the fuel cells and are converted into electricity by the electrochemical reaction in the fuel cells.
    • The only by-products of the fuel cells are water and heat.

    Electricity generated by the fuel cells is used to:

    • power electric motors, which drive propulsors or propellers to generate thrust
    • power ancillaries
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    Powertrain Timeline

    A plane

    9-19 seats

    300 NM range

    First commercial offering

    A plane

    40-80 seats

    1,000 NM range

    A plane

    100-200 seats

    2,000 NM range

    A plane

    200 seats

    3,000 NM range

    A plane

    200+ seats

    5,000 NM range

    The Markets

    We are working with aircraft operators, owners and manufacturers to supply the world’s breakthrough zero-emission engines and the infrastructure and fuel to power a revolution in green flight.



    Switching to hydrogen-electric propulsion can deliver 40 percent operational cost savings and zero-emission flights



    The only alternative propulsion system that can deliver the range, payload and emissions elimination required by the market



    Dramatically cut operating costs, deliver zero-emission flight and significantly lengthen the lifespan of existing aircraft in service



    Cut emissions from flights operated and wider footprint, reduce noise and air quality impact, and secure new revenue streams

    News on ZeroAvia Flight Testing Program

    We have retrofit our prototype ZA600 engine to power the left side propeller of our Dornier 228. We’ll use this page to share the latest updates from the flight test program, including photos and videos from flights, as well as behind the scenes content.