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The Shadow

Hydrogen May Be Coming to the Friendly Skies Sooner Than You Think

Image credit: Pixabay.com

The coming revolution in aviation propulsion has mainly focused on electrical aircraft, even though battery technologies have not quite evolved to be practical quite yet for most planes.

There are several smaller aircraft, UAV/air taxis, and VTOL aircraft, which are being developed to work off of batteries for use in electric or hybrid-electric implementations. While electric aircraft powered by batteries may one day enter commercial service, it will take further innovation to develop high-capacity power storage capabilities to provide enough power to do so. With all of the investment around the world in dozens of companies and research labs, that day may come sooner than initially envisioned. But there is a competing set of efforts to power aircraft in a sustainable manner, and that is the use of hydrogen fuel cells.

Too-Brief Background on Hydrogen and Fuel Cells

Skipping over volumes of details and facts, currently, hydrogen has two potential use cases, with the first being that it can be burned in a jet engine (or any type of internal combustion engine), or secondly it be used in a fuel cell to generate electricity to power a propeller engine. Some experts argue that a synthetic fuel mixture approach is considered a third option.

Another critical technical characteristic of hydrogen aircraft is that the fuel should only be stored in tanks in a fuselage, not the wings, due to the need to store gas in non-irregular-shaped fuel tanks and instead use a cylinder or spherical tanks. Leaks are a concern and are one of the primary design considerations for this type of aircraft. With current aircraft design limitations and economic impacts (hydrogen is rather expensive today, but this is changing as the price drops), this drives the use of hydrogen in aircraft towards using fuel cells in propeller-driven aircraft for the time being. The power density of fuel cells for aviation use will need to be scaled up for larger and heavier aircraft.

The automotive sector is launching more vehicles with fuel cells, especially in medium- and heavy-duty trucks. The US Department of Energy (DOE) announced earlier this year that it would set aside $100 million to construct an industry-ready Class 8 fuel cell truck and funding to improve and increase hydrogen production through electrolysis. This action will bring the prices down for the fuel for other industries such as aviation.

Innovation around this area is taking place across various industries, and several governments are supporting this with increased funding. This may positively impact current economic assumptions on not only the fuel but may drive down costs on crucial technology components used in product designs due to an expanded market for such items. To provide some perspective on how predictions are quickly obsolete, Figure 1 shows how IATA (International Air Transport Association) forecasted in 2019 the progression of electrical and fuel cell aircraft to enter commercial use. It seems that we will have retrofitted regional aircraft much sooner than 2035, as the article identifies further down.

Figure 1: Step-by-step approach in the penetration of the electrically-powered aircraft into the market (Source: IATA)

Electric taxis are being flight-tested in 2020 but have not entered commercial service yet, but many seem to be prepared to provide such a service in 2021. Hybrid-electric aircraft are also being tested now, with projected entry dates later this decade. Figure 2 is an intriguing synopsis of the capabilities of various fuels and technologies which will drive adoption by various types of aircraft.

But the quicker-than-forecast announcements regarding fuel cell technology in aircraft is an unexpected development. We see several industry teams working on hydrogen fuel cell solutions for smaller and regional aircraft, and Airbus is moving beyond this. Let’s touch on some of the more notable projects.

Figure 2: Comparison of Common Fuel and Technologies (source: “Hydrogen-Powered Aviation” report released by Europe’s Clean Sky and Fuel Cell and Hydrogen research program)

ZeroAvia Completes The World First Hydrogen-Electric Passenger Plane Flight

On September 24, 2020, this company accomplished the world’s first hydrogen fuel cell-powered flight of a commercial-grade aircraft. This event took place at ZeroAvia’s research facility in Cranfield, England, using a Piper M-class six-seat airplane and consisted of a taxi, takeoff, a full pattern circuit, and landing.

“While some experimental aircraft have flown using hydrogen fuel cells as a power source, the size of this commercially available aircraft shows that paying passengers could be boarding a truly zero-emission flight very soon,” Val Miftakhov, the CEO of ZeroAvia, said in a released statement.

ZeroAvia is a company dedicated to enabling zero-emission aviation using hydrogen-electric technology. The company states it targets aircraft with flights in the 500-mile range, with a seating capability of 10–20 seats (or cargo space). They are based in London and California and have already secured experimental certificates for their two prototype aircraft, having passed key flight test milestones, and expect to be ready for commercial operations in 2023. The company’s expanding UK operations are partially funded by a grant from the UK’s Aerospace Technology Institute and Innovate UK. Zeroavia is also part of the UK Governments Jet Zero Council (a public-private partnership to enable the delivery of new technologies and innovative ways to cut aviation emissions).

According to their press release, this zero-emission commercial flight is part of the UK Governments HyFlyer research project and follows the UK’s first-ever commercial-scale battery-electric flight in June 2020. ZeroAvia plans on doing a 250-mile zero-emission flight out of an airfield in Orkney (UK) later in 2020 as the final stage of its six-seat development program, before they scale up to larger aircraft. This will demonstrate the viability of their test aircraft for a similar range of heavily trafficked routes for instance Los Angeles to San Francisco and London to Edinburgh.

According to statements by ZeroAvia, their technology will scale to larger aircraft, and they are projecting that 10–20 seat aircraft will be in service in three years, as well as 50–100 seat aircraft by 2030 and a 200-seat aircraft with a range of over 3,000 nm by 2040.

One of the key partners that ZeroAvia is working with Intelligent Energy, which has over 30 years experience in fuel cell engineering capabilities from various industries. Intelligent Energy will optimize its high-power fuel cell technology for use in aviation applications. They have their headquarters in the UK, with additional operations in the US, Japan, Korea, and China.

Another is the European Marine Energy Centre (EMEC), which will supply green hydrogen from an onshore hydrogen production plant using surplus tidal and wind energy for flight tests and develop a mobile refueling platform compatible with ZeroAvia’s plane.

Universal Hydrogen and MagniX + Plug Power

Universal Hydrogen is a recent startup company based in the Los Angeles area and is an end-to-end fuel logistics company planning to make hydrogen-powered commercial flight a near-term reality. It began operating earlier this year and was co-founded by former Airbus chief technology officer Paul Eremenko, with its initial plans being to convert regional airliners to hydrogen power. The company states its business model will encourage early adoption of the carbon-free fuel by the air transport industry before manufacturers begin developing new-design aircraft with hydrogen propulsion as standard equipment.

Universal Hydrogen plans to offer a cost-effective approach to the logistics of using hydrogen by transporting it in modular capsules via intermodal freight containers from green production sites to airports around the world (refer to Figure 3). These can be stacked in racks of 54 modules and fit inside a standard freight shipping container, eliminating the need for airports to build new pipelines or dedicated storage tanks. This business strategy is expected to hasten market adoption. In a statement, the company identified that these Kevlar-coated modules will measure about seven feet long and three feet in diameter and contain the hydrogen in liquid or compressed gas form, which will be loaded into an aircraft using standard cargo loading equipment or a forklift. The company is creating a conversion kit to retrofit existing regional airplanes with a hydrogen-electric powertrain and modular capsule capability.

Figure 3 (source: Universal Hydrogen)

The last two rows of seats in an aircraft will be removed to make room for the compartment housing a hydrogen module, which will reduce the seating capacity from ~50 to ~40 passengers (for the initial Dash 8 aircraft), but the expected cost-per-seat will not change.

According to another article, Universal Hydrogen states that the plumbing lines will be installed to connect the modules via an aircraft’s dorsal fins into each of the two nacelles. This is where the hydrogen fuel cells and electric motors will be located, which in turn will provide power to the existing propellers in order to minimize the scope of the upgrade. Thus hydrogen technology can compete economically and logistically with battery-driven electric propulsion systems.

Universal Hydrogen is initially targeting aircraft such as ATR 42 and the Dash 8. Its kit will support a 400 nm usable range (with reserve range) with compressed gas hydrogen or 550 nm when using liquid hydrogen. Such capabilities will allow operators to serve most of the routes now flown by these two targeted aircraft models. The goal is to retrofit the powertrain into the first aircraft and perform flight test completion and regulatory approval under a supplemental type certificate (STC) by 2024.

Universal Hydrogen has teamed with several other technology providers, one being Redmond, Wash.-based MagniX, which makes electric propulsion systems including motors, inverters, and motor controllers for commercial aviation. They will supply the electric motors for the Universal Hydrogen offering. This company had previously flight-tested an all-electric version of the de Havilland Beaver (in conjunction with Vancouver, B.C.-based Harbour Air in 2019) and a Cessna Grand Caravan this year.

According to a press release from Harbour Air, this was the successful flight of the ePlane, a six-passenger DHC-2 de Havilland Beaver powered by a MagniX’s 750-horsepower (560 kW) magni500 high-power-density electric propulsion system. Harbour Air is partnering magniX to develop and build the world’s first entirely electric commercial seaplane fleet. This aircraft is proceeding through the certification and approval process for the propulsion system and aircraft retrofitting. Harbour Air expects to use such electric aircraft to transport passengers around British Columbia and the Pacific Northwest.

Plug Power has also partnered with Universal Hydrogen, and it is using its 20 years of fuel cell experience from other industries (freight/delivery, forklifts, stationary fuel cells to run data centers). It will now provide a fuel cell generating 1.5–2 megawatts for each aircraft propeller.

Airbus Plans to have the world’s first emission-free passenger aircraft to market by 2035

In September 2020, Airbus publicized three concepts for the world’s first zero-emission commercial aircraft slated to enter service by 2035. Each of the three takes a differing approach to reach their goal, using various technology pathways to move the company away from fossil-fueled aircraft.

The one thing that they have in common is the use of hydrogen as the primary power source.

“This is a historic moment for the commercial aviation sector as a whole, and we intend to play a leading role in the most important transition this industry has ever seen. The concepts we unveil today offer the world a glimpse of our ambition to drive a bold vision for the future of zero-emission flight,” said Guillaume Faury, Airbus CEO, in a recent press release. “I strongly believe that the use of hydrogen — both in synthetic fuels and as a primary power source for commercial aircraft — has the potential to significantly reduce aviation’s climate impact.”

These three concepts, all codenamed “ZEROe”, are as follows:

1) A turbofan configuration, which will have two hybrid hydrogen turbofan engines. The liquid hydrogen storage and distribution system are located behind the rear pressure bulkhead (very similar to the approach taken by Universal Hydrogen’s proposed configuration). This aircraft design would hold 120–200 passengers and have a range of 2,000+ nautical miles, capable of operating trans-continentally and powered by a hydrogen-powered modified gas-turbine engine, rather than jet fuel, through combustion.

2) This is a turboprop configuration, having two hybrid hydrogen turboprop engines. The liquid hydrogen storage and distribution system are located behind the rear pressure bulkhead — projected passenger capacity of up to 100, with a range of 1,000 nautical miles. The turboprops will use hydrogen combustion in modified gas-turbine engines. Figure 5 shows the conceptual drawing from Airbus.

3) Blended-wing body configuration with two hybrid hydrogen turbofan engines, with a passenger capacity of up to 200 (no range provided). The blended wing design has a wider fuselage in which to provide liquid hydrogen storage tanks with ample room.

Further details were not provided at the time of writing. But with this announcement, it is quite clear that Airbus has committed to experimenting with hydrogen as a primary fuel source for future aircraft, no matter which design approach wins out of these three.

Boeing has also released statements in the past year or so on the potential longer-term advantages of moving to a hydrogen power source but has indicated it believes the timeline to incorporate this needs more time.

Conclusion

There are many other examples of aviation moving towards hydrogen, especially with smaller aircraft, as well as some airports. Many challenges still need to be overcome, with the price of hydrogen being one. However, governments are already tackling this due to the need to support cars and trucks entering commercial use right now (along with busses, ferries/ships, freight/logistics/warehouse-type-operations, and for use on the micropower grids in certain use cases).

Figure 5: A computer simulation of Airbus’s Turboprop Conceptual Aircraft (source: Airbus)

There are still many challenges for the industry to overcome, primarily since hydrogen is not incorporate into the aviation ecosystem. Real estate on any aircraft is at a large premium, and hydrogen needs a more significant amount of storage space in non-irregular shaped containers. But as a positive, it has three times the energy density of kerosene, which provides a substantial advantage over current-technology batteries while weighing substantially less. There is much more to cover on the technical aspects from a pros and cons standpoint. Still, it seems plausible to retrofit small and regional aircraft with existing technology approaches already.

The first such attempt was back in 1988 by Soviet engineers doing so to a Tupolev Tu-154 airliner so that the right engine was powered by hydrogen. They called the test aircraft the Tu-155. So current attempts are not altogether all that novel.

It is apparent that hydrogen-power fuel cell technology may be superior to pure battery-driven aircraft, at least for larger commercial transports (smaller air taxis and similarly sized aircraft are an exception to this apparently). This emerging solution may be one of the speedier ways to reduce greenhouse gas emissions from aircraft (and other modes of transportation) and provide competition to biofuels.

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OPM Research

OPM Research

Am a technologist who focuses on aerospace/aviation, communications, and new technologies in general. My main website is OPMResearch.com.