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The problem is not flying the problem is the dirty fuel. There are currently two alternatives: Sustainable Aviation Fuels (SAF) and Hydrogen. Hydrogen is extremely light and contains three times more energy per kilogram than jet fuel, which is why it’s traditionally used to power rockets. Hydrogen can be burnt in an engine or used in a fuel cell which combines hydrogen and oxygen to produce electricity, heat, and water or to make drop-in synthetic sustainable aviation fuels (synfuels). Synfuels are drop-in replacements for fossil-based kerosene and require no significant aircraft or engine changes. The development of all three alternatives requires very considerable investment and kerosene remains very much cheaper. It is obviously important that only green hydrogen is used, created using only renewable energy. Most hydrogen is still produced from fossil fuel methane which is mixed with steam at high pressures. This process releases significant CO2 emissions.
Europe’s Clean Sky and Fuel Cell and Hydrogen research programmes published on Hydrogen -powered aviation in May 2020. They concluded that fuel cells could reduce the climate impact of aircraft by 75-90%, direct combustion by 50-75% and synfuels by 30-60%. Contrails may be an issue. So might the supply of green hydrogen which needs clean water and green electricity. Aviation will be competing with other sectors fo hydrogen.
Hydrogen offers an alternative fuel at least for flights up to 2,000km (1,200miles), New York is 5,600 km, Palermo in Sicily is 1,819km. SAFs have the advantaged that they are drop-in fuels, they can be added to kerosene reducing greenhouse gas pollution per passenger-km. Hydrogen has the advantage of zero greenhouse gas emissions.
Short and medium-range flights generate two-thirds of current aircraft emissions.
As Hydrogen is lighter than kerosene, storage will require more space on aircraft or the space needed can be reduced by storing the gas under pressure. This raises the weight of the fuel tank.
However, the announcement in September 2020 by Airbus that it plans to develop a new zero-emission aircraft
Airbus revealed three concepts for the world’s first zero-emission commercial aircraft which could enter service by 2035. These concepts each represent a different approach to achieving zero-emission flight, exploring various technology pathways and aerodynamic configurations in order to support the company’s ambition of leading the way in the decarbonisation of the entire aviation industry.
All of these concepts rely on hydrogen as a primary power source – an option which Airbus believes holds exceptional promise as a clean aviation fuel and is likely to be a solution for aerospace and many other industries to meet their climate-neutral targets.
The three concepts – all codenamed “ZEROe” – for a first climate-neutral zero-emission commercial aircraft include:
1. A turbofan design (120-200 passengers) with a range of 2,000+ nautical miles, capable of operating transcontinentally and powered by a modified gas-turbine engine running on hydrogen, rather than jet fuel, through combustion. The liquid hydrogen will be stored and distributed via tanks located behind the rear pressure bulkhead.
2. A turboprop design (up to 100 passengers) using a turboprop engine instead of a turbofan and also powered by hydrogen combustion in modified gas-turbine engines, which would be capable of travelling more than 1,000 nautical miles, making it a perfect option for short-haul trips.
3. A “blended-wing body” design (up to 200 passengers) concept in which the wings merge with the main body of the aircraft with a range similar to that of the turbofan concept. The exceptionally wide fuselage opens up multiple options for hydrogen storage and distribution, and for cabin layout.
Challenges
1. Hydrogen tanks would have to be more sturdy and high-pressure than those that hold traditional jet fuel. Such tanks would be too heavy to fit in a plane’s wings, where jet fuel is currently stored. The Bristol Composites Institute (ACCIS) is looking at nanoporous materials that behave like molecular sponges, spontaneously absorbing and storing hydrogen at high densities for onboard hydrogen storage in future aircraft designs.
2.Infrastructure to deliver Hysrigen fuel at airports. Universal Hydrogen is developing a type of capsule technology that would enable either liquefied or gaseous hydrogen to be shipped using the existing freight shipping system and delivered to airports to fuel up planes.
3. Hydrogen is the most abundant chemical substance in the universe but it needs to be isolated and produced emission-free. Most current production is not emission-free. As of 2020, 
the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas, partial oxidation of methane, and coal gasification
PlugPower produces green hydrogen at an industrial scale. Universal Hydrogen and Plug Power are working together to retrofit a regional aeroplane with hydrogen fuel cells to power its two propellers. They aim to have a plane ready and government-certified to fly by 2024. more More detail in Aviation Today
Boeing is considering a new narrow-body single-aisle plane but it appears not to be looking at hydrogen. more
September 2021
"The need for large airliners optimised for flights of less than 4,000km was identified by the DLR (German Aerospace Centre) when it upgraded its air traffic model to include airport capacity constraints, etc. The chart below summarises the results, with the scope of ‘<4,000km’ overlaid. Note that the chart shows the percentages of CO2 produced if all flights still used kerosene. The bottom line is that almost 60% of the CO2 produced by aviation will be removed if the ‘<4,000km’ type of large airliner is powered by hydrogen." Chris Ellis FBCS, Prof. John Coplin more
13 Jan 2021 Opinion: Leave Hydrogen For Dirigibles Alan H. Epstein is the R.C. Maclaurin professor emeritus at the Massachusetts Institute of Technology.
Hydrogen "is a less-than-compelling response to aviation’s challenges. Almost all of today’s hydrogen is made from natural gas or coal, so it is not in any way green. Much of the enthusiasm for H2 presupposes that it will be made with green electricity, much of it excess. The energy in the jet fuel consumed in 2019 was equivalent to about 14% of the world’s electricity, so a considerable added capacity would be needed."
"Airliners will require liquid hydrogen (LH2). With current technology, producing and liquefying hydrogen with electricity costs about 50% of the input energy. The vast infrastructure needed to generate the power and then produce, liquefy and distribute the hydrogen to airports and aircraft at the scale needed will cost several trillion dollars, so this will not be cheap fuel. Also, the existing fleet will need to be replaced with airliners that can fly on hydrogen."
"Liquid hydrogen requires fuel tanks that are about three times larger than those for jet fuel. Since the LH2 must be kept at -240°C (-400°F), heat leakage is very important, so highly insulated spherical or compact cylindrical tanks are needed, significantly increasing airplane volume and drag."
Epstein concludes "Overall, the vision of hydrogen-fueled aviation is inconsistent with the reality of the looming 2050 need. An aviation-size, worldwide hydrogen supply and airliners capable of using it are decades and trillions of dollars away. In terms of a timely green return on investment, the money would be much better spent on SAJF, both for capital investments in capacity and for technologies that improve yields and reduce costs." Full article
06 Jan 2021 Sale of four CityHawk's to Hatxolah Air announced. CityHawk is a twin engine Fancraft™ designed to existing FAA standards including “Category A” takeoffs. It accommodates up to six occupants (including a pilot). Fancraft™️ technology is a groundbreaking suite of aerodynamic innovations that make it possible to design a vehicle that is actually the size of a car and can carry the same number of passengers but can fly with no exposed rotor powered by fuel cells. It can literally take-off and land anywhere, any time, in any weather. More
04 Jan 2021 The renewed interest in hydrogen by the private sector is illustrated through the recent strong growth in Venture Capital funding (EUR 591m during 2014-2019). The Venture Capital funding rounds are primarily in the later investment stages, which means investments are flowing to more established ventures in the market. more
16 Dec 2020 ZeroAvia secures £12.3m UK Government grant to bring 19-seat hydrogen-electric aviation powertrain to market
£12.3m ($16.3m) in UK government funding through the Aerospace Technology Institute (ATI) to deliver a breakthrough 19-seat hydrogen-electric powered aircraft that is market-ready by 2023. ZeroAvia will collaborate with two partners, the European Marine Energy Centre and Aeristech. The HyFlyer II project will conclude with another world's first hydrogen-electric flight by ZeroAvia in a 19-seat aircraft, with a 350-mile flight in early 2023. Typically, up to 19-seat aircraft such as the Cessna 208 Caravan and the Viking Air DHC-6 Twin Otter are used in regional aviation and cargo transport worldwide. ZeroAvia's 600kW hydrogen-electric powertrain is platform-agnostic and will begin to make zero-carbon flight over meaningful distances a reality for passengers. more
Reuters reports that British Airways, Shell and Amazon have joined the venture. more
Zeroavia describes the problem well.
14 Dec 2020 HY4 Test Flight - Hydrogen Fuel Cell
"The Hy4 has now been presented with its sixth drive generation. “The system includes redundancy concepts for the hydrogen tank, fuel cell, energy distribution and the electric drive,” says the director of the Ulm-based institute. The resulting increased efficiency and improved safety architecture would make hydrogen-powered aircraft for up to 40 passengers and with ranges of 2,000 kilometres possible in the next ten years. more
12 December 2020 British Airways has teamed up with ZeroAvia
The collaboration, which reflects the importance of sustainability at British Airways, will see ZeroAvia embedded in the heart of the airline. The team will work remotely alongside mentors and experts to explore the transformational possibilities of moving from fossil fuels to zero-emission hydrogen to power the airline’s future fleet. The partnership forms part of IAG’s industry-leading Hangar 51 accelerator programme, which works with start-ups and scale-ups from around the world, providing them with an opportunity to develop and test their products on real-world business challenges on a global scale. At the end of the programme, research and learnings from the process will be shared and the ZeroAvia and Hangar 51 teams will consider how the partnership will progress longer term. more
16 Nov 2020 Hybrid Air Vehicles
Airlander developing fuel cell technology to offer 90+ passengers to ranges of 750km using the hybrid-electric variant of Airlander 10 (expected to be in service from 2025). They are working with Collins Aerospace and the University of Nottingham to develop electric engines via our E-HAV1 programme. more
08 October Aviation Week
Boeing sees the longer-term advantages of switching to a hydrogen ecosystem but believes the process will take longer than the schedules suggested by Airbus. “We do see promise in a transition to more hydrogen-based fuels over time. However, I don’t believe it’s something that’s right around the corner. There’s a lot of infrastructure and regulatory framework that has to evolve with the technology, and that is not a fast process,” says Mike Sinnett, Boeing Commercial Airplanes vice president of product development and future airplane development.
" Whether it is consumed in a fuel cell, burned in a turbine or converted to synfuel, production and distribution of enough green hydrogen to meet the expected demand for decarbonization coming from all sectors of industry and society could prove one of the biggest challenges facing aviation.
“In 2019, around 90% of the hydrogen produced in the planet was from fossil sources. In 2019, the commercial fleet burned just shy of 100 billion gal. of fuel,” says Michael Winter, Pratt & Whitney senior fellow for advanced technology. “If you were to replace 10% of that enthalpy with hydrogen, you’ve used 90% of the world’s hydrogen production in 2019. So the question is, if we’re going to put money into infrastructure, where would we rather put it as a society: synthetic aviation fuel or hydrogen?”
Hydrogen may hold out hope for decarbonizing aviation, but a sustainable way to scale up production is essential. “That will need investment, and it will need the appropriate incentives because we’re going to need hydrogen to decarbonize the whole world, not just aviation,” Newby says. “One of the particular challenges we face as an industry is how that adoption will be prioritized among various sectors.”more
07 Oct 2020 The Road to Hydrogen
In Washington, a coalition of major oil & gas, power, automotive, fuel cell, and hydrogen companies have come together to develop a Road Map to a US Hydrogen Economy. In the most ambitious scenario, the authors concluded that hydrogen demand potential across all these applications could reach 17 million metric tons by 2030 and 63 million metric tons by 2050.
01 Oct 2020 Will Contrails Be Hydrogen Fuel’s Achilles' Heel?
04 Sept 2020 Universal Hydrogen is working to get a supplemental type certificate (STC) to convert a De Havilland Aircraft of Canada Dash 8-300 aircraft to hydrogen-electric. “The aircraft will have a fuel-cell that converts hydrogen gas into electricity, which will then power two electric motors. The hydrogen gas will be stored in large capsules and pressurized at 850 bar. The Dash 8-300 is an out-of-production 50-seat commuter aircraft. Universal Hydrogen has said it plans to make space for the hydrogen-filled capsules by taking out 10 of the aircraft’s passenger seats, making it a 40-seater. Universal Hydrogen is designing the hydrogen-filled storage capsules and will be developing the ground infrastructure to distribute hydrogen gas and liquid hydrogen to airlines. more
20 July 2020 Faradair will develop its BEHA (Bio Electric Hybrid Aircraft) Short Take-Off and Landing (STOL) aircraft at Duxford Airfield
With a triple box wing, STOL for 18 passengers, hybrid-electric, "whisper quiet" and a carbon-neutral footprint, carbon composite frame to deliver a 1,150 mile range. Faradair
07 July 2020 ZeroAvia Completes First Phase of Test Flights On Path to Hydrogen-Electric Turboprop
"Over the course of two weeks, the ZeroAvia team completed multiple test flights, while capturing data about the temperatures, power flows and torque characteristics of the aircraft at takeoff, cruise and landing. Miftakhov said that the biggest overall challenges in preparing for and operating the flights were the thermal management of the electric motors, inverters and heat exchangers. .....ZeroAvia and its partners for Project HyFlyer are now preparing for the next round of flight-testing using the hydrogen-electric powertrain that they ultimately want to use for zero-emissions passenger-carrying aircraft. In that system, the power inverters and electric motors still drive the propeller, however, the electricity is provided by the hydrogen fuel cell system in place of the battery. Instead of getting electricity from the battery we get it from the hydrogen fuel cell system, which takes hydrogen from the tanks, combines it with oxygen from the air, and produces electricity,” Mifthakhov said, adding that the biggest cost savings for their preference of hydrogen to battery power is the limited lifespan of batteries compared to the life of the aircraft." more
22 June 2020 An independent study, commissioned by Clean Sky 2 and Fuel Cells & Hydrogen 2 Joint Undertakings on hydrogen’s potential for use in aviation, found that hydrogen – as a primary energy source for propulsion, either for fuel cells, direct burn in thermal (gas turbine) engines or as a building block for synthetic liquid fuels – could feasibly power aircraft with entry into service by 2035 for short-range aircraft. Costing less than €18 [$20] extra per person on a short-range flight, and reducing climate impact by 50 to 90%, hydrogen could play a central role in the future mix of aircraft and propulsion technologies. more
12 June 2020 Jet Zero Council to drive forward the decarbonisation of aviation.
UK Transport Secretary Grant Shapps "we’re bringing together leaders from aviation, environmental groups and government to form the Jet Zero Council. This group will be charged with making net zero emissions possible for future flights." "Our goal – within a generation – will be to demonstrate flight across the Atlantic, without harming the environment.” more
FlyZero was announced by Business Secretary Alok Sharma MP on 20th July 2020. Created and led by the ATI, FlyZero will kick start exploration into a zero-carbon emission commercial aircraft and determine the strategic options for the UK to secure a global lead.
May 2020 Report published by the EU's CleanSky programme on Hydrogen-powered Aviation
Novel and disruptive aircraft, aero-engine and systems innovations in combination with hydrogen technologies can help to reduce the global warming effect of flying by 50 to 90%
The study found that hydrogen – as a primary energy source for propulsion, either for fuel cells, direct burn in thermal (gas turbine) engines or as a building block for synthetic liquid fuels – could feasibly power aircraft with entry into service by 2035 for short-range aircraft. Costing less than €18 [$20] extra per person on a short-range flight, and reducing climate impact by 50 to 90%, hydrogen could play a central role in the future mix of aircraft and propulsion technologies.
The technical challenges and unique characteristics of hydrogen as an on-board energy source make it best suited to commuter, regional, short-range and medium-range aircraft. For the next decades, long-haul air travel is likely to be based on liquid hydrocarbon fuels; but increasingly these too will need to be sustainable and these ‘drop-in’ fuels will also rely on hydrogen for their production. Read the full study here.
6 May 2020 A prototype jet engine that's able to propel itself forward only by using electricity.
Researchers from the Institute of Technological Sciences at Wuhan University in China, compresses air and ionizes it using microwaves. This then generates plasma that thrusts the engine forward. The prototype plasma jet device was able to lift a one-kilogram steel ball over a 24-millimeter diameter quartz cube, which is where the high-pressure air is transformed into a plasma jet thanks to passing through a microwave ionization chamber. To keep things in scale, this corresponds to the thrusting pressure comparable to a commercial plane jet engine. more
11 March 2020 The German Consultancy, Roland Berger forecast that if other industries de-carbonize in line with some projections, aviation could account for up to 24% of global emissions by 2050 unless there is a significant technological shift. Their study concluded that "Relative to conventional fuels and SAFs, hydrogen is superior because it removes carbon dioxide emissions entirely, but also has the potential to reduce other GHG emissions. Relative to batteries, hydrogen has a superior energy density, both in gravimetric and volumetric measures. Additionally, hydrogen is likely to penetrate into other industries, which could speed up the development of fuel cells and storage systems, promote downstream infrastructure and push down supply chain costs."
In hydrogen combustion aircraft, thrust is generated through the combustion of hydrogen in a modified jet engine, which eliminates most but not all GHG emissions. Overall, the transition would require less aircraft and engine redesign than hydrogen fuel cell propulsion, making it somewhat less disruptive to the current setup of the aerospace industry.
Berger identified five key barriers to hydrogen technology:
January 2020 National Centre for Propulsion and Power
Whittle Laboratory, which is due to open in 2023, will bring together researchers from across UK universities with industry partners such as Rolls-Royce, Mitsubishi Heavy Industries, Siemens and Dyson to accelerate the development of low-carbon technologies for the propulsion and power sectors. more
20th March 2019 The Commercial Aircraft Corp of China (COMAC) said its new-energy plane Lingque H (LQ-H2), powered by hydrogen fuel through a fuel-cellsystem, has completed another test flight in Zhengzhou, Henan Province, with sound performance. more
Way back in 1988
Source: Prof. Dr.-Ing. Dieter Scholz, MSME, HAW Hamburg
Design of Hydrogen Passenger Aircraft - How much "Zero-Emission" is Possible?
More resources
Green Air Online
Hydrogen Fuel The Conversation
H2 View was established in July 2019, with the aim to be the must-read service for the ever-growing hydrogen economy globally.
