Here’s how Aviation H2 plans to decarbonise the sector

Special Report: The aviation industry is a major contributor to global emissions and this Aussie company is looking to shake up the sector as the countdown to net-zero continues.

Decarbonising the aviation sector could well be one of the most challenging of all our emitting industries, and yet it is a challenge that has to be taken up given that it is responsible for anything between 2.5% to 3.5% of all emissions.

Speaking with Stockhead, Aviation H2 director Dr Helmut Mayer said even the contrails left by planes had a substantial effect on the climate that is right there with the effects of carbon being emitted into the atmosphere.

“While the carbon hangs around for hundreds of years, the contrails dissipate quickly but we keep generating them as our volume of flights goes up,” he explained.

“There’s a number of issues associated with aviation that contribute to climate change and we have a very limited time frame to get that cleaned up.

“2050 is when we are looking for net-zero and what that means is that by the time we get to 2035, we’ve got to have the solutions ready and cannot put any more aircraft using conventional fuels into service.

“That leaves us about 13 years, which is not a lot of time, so we must move as a matter of urgency.

Decarbonising aviation has some weighty challenges

While there is little doubt that decarbonising the aviation sector is important, achieving this objective has some significant challenges.

It all boils down to finding a suitable replacement for the usual Jet A-1 fuel – a grade of kerosene fuel suitable for most jet turbines while keeping the weight associated with its supporting infrastructure down to a minimum.

Dr Mayer added that conventional aircraft burning Jet A-1 also produce nitrous oxide – a harmful emission that is a by-product of oxidising fuels with air at high temperatures.

This means that besides eliminating carbon dioxide from being emitted, any alternative fuel would also need to either not produce nitrous oxide or have a catalyst that can break it down before it leaves the exhaust.

To achieve this objective Aviation H2 has weighed up all carbon-free fuels in terms of tank infrastructure, the amount of fuel that can or has to be carried as well as the reactant on board to break down the nitrous oxide.

One of the earliest casualties of this assessment was the use of fully battery-electric aircraft, which would otherwise have been perfect given the complete lack of emissions.
This was rejected due to two key reasons – weight and recharging.

Batteries are rather heavy – and that might be useful when positioned lower, like at the bottom of a car. However, Dr Mayer noted, that weight is anathema if you’re designing and flying an aircraft.

Recharging is also a major issue, as aircraft need just a tad more energy than a car.

“If you calculate how much energy is stored aboard an A380 for, say, a flight from Sydney to Dubai, it is an awful lot. If you want to charge a battery with that much energy in the two hours turnaround at the airport, you need to use between 500 megawatts to a gigawatt, that’s a small power station just for one aircraft,” Mayer added.

“While a 787 will only need half that much, when you’re trying to turn around one of those aircraft every five minutes, you just can’t do it. You couldn’t build enough power stations around Sydney airport to supply that kind of energy.”

Aviation H2 directors inspecting a Falcon 50

Why hydrogen – or rather ammonia – is the answer

Aviation H2’s studies quickly pointed to hydrogen as the answer towards replacing Jet A-1.

Not only can hydrogen be produced using carbon free methods, it also has sufficient energy density to be a viable replacement for Jet A-1.

While Jet A-1 has more than 43 megajoules of energy per kilogram (MJ/kg), hydrogen actually packs a bigger punch with about 120MJ/kg though its lower density means it needs a much larger volume – another important consideration for planes.

Reducing the amount of volume needed would require significant infrastructure, which would in turn result in higher weight.

This led the company to consider different ways to store hydrogen, some of which seem to come straight out of the pages of science fiction.

“There are about 120 ways to store hydrogen,” Mayer said.

“We looked at storing hydrogen as a film in a tube and the way we release it from the film is by heating it up by using a laser and spinning the film at high speed.

“The beautiful thing about that is you don’t have the high pressures, and you don’t have the toxicity of hydrogen or ammonia. We wanted it to work because it was just so appealing. But you have the extra burden of having to generate the heat.

“Another option was to sequester ammonia in a magnesium powder then you compact it and carry it. It’s actually incredibly efficient except that you have to heat it in a controlled way to get the hydrogen out.”

The process led Aviation H2 to select ammonia as its preferred energy source from a density and volume point of view.

Mayer explained that ammonia is a hydrogen carrier that has lower pressure requirements and much more manageable temperature requirements.

This is especially true given that ammonia actually has a higher fractional weight per cubic metre than pure hydrogen.

As an added benefit, ammonia can also be used to break down the nitrous oxides in the exhaust of the engine.

“It’s a bit like Adblue (urea) which is used to break down the nitrous oxide in the exhaust of diesel trucks,” Mayer added.

Aviation H2 also considered using liquid hydrogen but found that it was heavier than ammonia making it awkward to carry, refuel and defuel.

Business model

With ammonia the way forward, the company is now working on how to get it to work with its chosen business model, which is to take existing business jets and modify the engines and fuel systems for optimal ammonia integration.

“The reason why we’re doing this is simple – it is a quick solution to a problem that existing aircraft owners will have,” Mayer told Stockhead.

“They will be doing that for their larger aircraft while we are focusing on business jets and manufacturers of business jets can come to us to fit their aircraft with new fuel systems.

“Lear Jets, Dassault Falcons, those types of airplanes. We are not looking at big passenger liners, though that may come depending on what our results are.”

Forward plans

Aviation H2 will acquire one of the engines used in the Dassault Falcon 50 business jet – a long-ranged international business charter jet aircraft – and mount it in a test cell which is currently under wraps as Mayer’s team work on their own design.

This test cell will contain everything needed for testing within a shipping container, allowing the company to transport it to the various locations where it might want to test it.

The company will then run the engine on Jet A-1 fuel to get a good baseline of information about how the engine performs.

“We then modify the engine to run on ammonia and test it again and see how it performs compared to the Jet A-1 fuel,” Mayer added.

“And then if it works, we will purchase the Dassault Falcon 50 aircraft, modify it and get the prototype flying from the middle of 2023 to the end of the year and beyond.”

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