European aircraft manufacturer Airbus Industries has unveiled plans to develop hydrogen powered zero emission airliners in an effort to reduce the industry’s impact on climate change. It’s an interesting announcement, but the company will face challenges handling and storing the new fuel, as well as with public perceptions over the dangers of hydrogen.
According to industry figures, emissions from airplanes worldwide amounted to more than 900 million tons of carbon dioxide in 2019, which is about 2 per cent of total human produced carbon dioxide. While that seems to be a small percentage, the industry has been steadily growing (until this year) so emissions have continued to rise. And decarbonizing aviation is a big challenge.
Advances in engine design and improved aerodynamics have made today’s jets far more efficient than they were in the 1950s, just as cars are. But like cars, there are many more of them than there used to be. So to avoid increased emissions, and to cut current emissions, the industry will need to find another way to fly.
Airbus aims for a hydrogen-powered future of flight
Airbus’s solution is to burn hydrogen in the engines instead of kerosene-based jet fuel. When hydrogen combines with oxygen during combustion, the product is H2O, or water. That’s it. Carbon is not part of the equation, although the engine exhaust will contain a lot of hot water vapour which could produce extra long contrails.
Airbus’ new ZERO E concept is a plan for three aircraft types: a turboprop commuter, a mid-range turbofan jet and a futuristic blended- wing airliner. All will use engines that have been designed to run on hydrogen. The company calls the planes “hydrogen-hybrid” aircraft as an electric powered boost will also be provided by hydrogen fuel cells.
In a press conference, Airbus engineers identified some of the strengths and challenges in the new concept.
Liquid hydrogen can deliver similar energy to jet fuel, at one-third the weight, which is a big advantage in aircraft. Unfortunately, while it’s light, it’s not very dense. So even supercooled liquid hydrogen takes up four times more space for the energy than jet fuel. That means reimagining how to store fuel on the plane.
New fuel, new aircraft
The plan anticipates large tanks within the fuselage at the rear of the plane. In other words, within the same body that carries the passengers. This might make some people nervous knowing there is explosive fuel behind their seats. Shades of the Hindenburg disaster.
But pre-world war two zeppelin catastrophes aside, hydrogen is no more inherently risky than any other fuel. Airbus’s new concepts include a venting system that runs up through the tail to disperse any fuel leakage away from the plane.
Hydrogen is, of course, lighter than air, so if there is a leak, it rises up and dissipates very quickly. A leak of jet fuel or gasoline, on the other hand, pools under the aircraft and burns from there. There have been many cases where passengers have survived an air crash, only to die in the fire that breaks out after the plane hits the ground.
One big difficulty is that hydrogen is difficult to handle compared to ordinary jet fuel. To keep it liquid, it has to be chilled to –253 degrees. This means the fuel tanks must be well insulated, and equipment such as pumps and pipes must be designed so they don’t freeze up when handling such cold liquids. This will require a huge transition at airports, with new fuelling procedures and storage systems for cryogenic fuels.
Producing hydrogen without greenhouse gases
And then there’s the emissions question. Hydrogen can be, but isn’t necessarily, a “green” fuel. This has been called the “green” versus “black” hydrogen issue. And it comes down to the fact that hydrogen is not an energy source that can be dug out of the ground like oil. It must be made.
Traditionally most industrial hydrogen has been produced from fossil fuels — in fact from “reforming” natural gas (by removing the carbon from its carbon-hydrogen bonds). This produces greenhouse gases.
You can also produce hydrogen by breaking down water into hydrogen and oxygen through electrolysis. Airbus says the electricity to make its hydrogen from water will come from clean alternatives such as wind or solar. But we already face a challenge scaling those up.
Hydrogen has been around for decades, driving the early space program, running fuel cell cars and buses. But it has remained somewhat on the sidelines because of a lack of storage and distribution networks, plus the fact that batteries have become so much more efficient and inexpensive.
But batteries are still too heavy for larger aircraft, so hydrogen offers a clean alternative to fossil fuels, and if the airline industry can prove that it is practical and safe, it may work its way more fully into other areas of transportation to keep wheels turning without compromising the climate.