Sustainability has been a hot topic among aviation professionals for quite some time.
Although several businesses in the aviation industry concentrate on efficiency and environmental programs, a larger issue has been on people’s minds: sustainable aircraft. Aviation fuel is one of the major sources of emissions in the industry, so it’s past time for the industry to change its attention to greener fuel choices. The new fuel must be globally available, as well as clean, environmentally friendly, and cost-effective. Hydrogen has the potential to revolutionize the aviation industry by replacing existing aviation fuel.
Hydrogen has a number of advantages as an energy carrier for aircraft, including low emissions, global availability, and protection, making it an ideal aviation fuel. Hydrogen has a higher energy density than Lithium-ion batteries, both in terms of gravimetric and volumetric steps. Furthermore, hydrogen is projected to gain prominence and traction in a variety of industries, accelerating the production of fuel cells and storage systems as well as the development of required infrastructure. These factors, along with the use of hydrogen as an aviation fuel, are expected to propel the global hydrogen aircraft market to a projected value of $27.68 billion in 2030 and $174.02 billion in 2040.
Professionals have been thinking about hydrogen-powered aircraft for decades. The US Air Force used hydrogen fuel in B-57 aircraft in the 1950s, and Tupolev converted a Tu-155 aircraft to a hydrogen gas turbine in the 1980s. Although the emphasis has shifted to hydrogen due to environmental issues, Tupolev’s argument was more cost-effective at the time – the comparatively low cost of fuel production using nuclear power made hydrogen an appealing option.
The use of hydrogen fuel, on the other hand, presented some difficulties. Hydrogen takes far more space than fossil fuels due to its lower energy density, and it must be cooled to a daunting temperature of minus 253 degrees Celsius to remain liquid in order to conserve space. The Tu-155 aircraft had a huge hydrogen tank in the back part of the passenger cabin to store the fuel, which took up around a third of the space there. The aircraft received a total of 30 additional systems to allow it to operate on hydrogen. On board were three engines: two traditional turbojets and one NK-88, an experimental turbojet that ran on hydrogen or natural gas.
The aircraft has completed over 100 journeys, some of which used hydrogen and others which used natural gas. International flights were also conducted: Moscow – Hanover and Moscow – Bratislava – Nice. For years, the Tu-156 project, which used a revised version of the natural gas engine (NK-89), had been in the works. The software was finally shut down, most likely as a result of the Soviet Union’s demise.
The use of hydrogen in aviation is still in its infancy. In 2008, Boeing flew the world’s first hydrogen-powered plane, and in 2020, ZeroAvia will fly the world’s first hydrogen-powered commercial plane. The biggest industry player, however, is Airbus, which is already working on bringing hydrogen-powered aircraft to market.
Hydrogen can be used in two ways for hydrogen-powered aircraft: as a fuel source for fuel cells, where hydrogen reacts with oxygen to create electricity that drives the engine, or directly as a fuel source in a modified engine. Both of these approaches are being considered by Airbus for aircraft. The company has also committed to having the first hydrogen-powered aircraft in operation by 2035, after presenting three versions of updated aircraft.
However, there are several drawbacks to using hydrogen. The most significant drawback of using hydrogen as a fuel is storage. Since liquid hydrogen has a quarter the energy density of jet fuel, it requires a storage tank four times the size to store the same amount of energy. As a result, aircraft will need to be upgraded to accommodate more fuel storage.
Furthermore, a completely new system for transporting and storing hydrogen at airports will be needed. However, since hydrogen can be extracted from water, airports may produce their own hydrogen fuel, reducing the need for fuel transportation, removing associated pollution, and potentially reducing transportation safety risks.
Although hydrogen has yet to be widely adopted in aircraft, it has already demonstrated its benefits in automobiles. Toyota Mirai’s, hydrogen-powered vehicle’s, tank weighs 87,5 kg and holds 5 kg of hydrogen, so the total of 92,5 kg weight allows you to drive 500 km according to the WLTP standard. Meanwhile, the Tesla Model 3, with a 321 kg battery, can drive only 430 km according to the WLTP standard, meaning that 1 kg of hydrogen allows a vehicle to travel 5,4 km while 1 kg of batteries – only 1,33 km. Perhaps the aviation industry will be the next to demonstrate hydrogen’s efficacy?
While hydrogen’s potential as an aviation fuel is undeniable, there is still a long way to go. But the constantly growing attention to aviation sustainability will act as a catalyst in making a hydrogen-powered aircraft a reality.