While the world may be focused on pure hydrogen as the most significant promise for clean-burning aviation fuel, Australian company Aviation H2 is looking to speed things up by utilizing the compound of nitrogen and hydrogen, commonly known as ammonia or NH3.

"Green" ammonia is often mentioned when it comes to decarbonizing the transport sector, but mostly in reference to trucking or long-haul shipping. Meanwhile, brothers Christof and Helmut Mayer, directors of Aviation H2, are planning to have a Falcon 50 business jet in the air and flying (partially) on ammonia by mid-2023 - in just a little over a year's time. They will then seek to certify and commercialize their engine retrofit product via a planned public listing towards the end of the year.

highres_AH2-142 (1)
One engine will run on ammonia and two on conventional jet fuel during test flights, scheduled to begin next year. Photo: Aviation H2

Simpler conversion compared to H2

Could using ammonia instead of pure hydrogen be a way of solving the onboard storage conundrum that the particularities of the gas entail? The Sydney-based brothers believe so and are focusing on converting existing airframes and engines to be powered by ammonia. Christof Mayer told New Atlas in an interview over the weekend,

"Hydrogen gas is very light for the energy it holds, and liquid hydrogen is even lighter. But the tanks are big and heavy. We certainly don't discount liquid hydrogen or any other form of hydrogen as an option. We're not shutting those down. We're just going with ammonia for now. It's the simplest conversion, and that intrinsically will make it the most reliable, and that in itself makes it intrinsically the safest."

highres_AH2-94
Aviation H2 has access to FalconAir's facilities and operating licenses. Photo: Aviation H2

Design of engine does not need to change significantly

The company is focusing on ammonia as a combustion fuel, which means regular jet engines can be modified to run on the colorless but somewhat distinctly pungent gas. For operators currently investing in new aircraft with lifespans in the decades, this may be a more welcome approach than retrofitting their new acquisitions with hydrogen fuel cell powertrains. Mayer added,

"We need to modify the fuel storage system into something that's basically similar to an LPG tank. So it's the fuel storage, the engine control, and the engine, those are the big-ticket items that we need to develop. But we're not really changing the design of the engine much at all physically."

Aviation H2 has partnered with FalconAir, a specialist aircraft charter operator serving Australia and the Asia-Pacific region. The collaboration will see FalconAir help acquire turbofan engines for ground-based testing. The company will also provide the aircraft itself, a nine-seater Dassault Falcon 50.

highres_AH2-48
The two brothers envision drop-in retrofit hangars across the world. Photo: H2 Aviation

The Falcon 50 has three engines, which means that two can run on conventional jet fuel while a third burns ammonia during the testing phase. Initial plans envision one-hour flights with the same capabilities currently provided by engines running on jet fuel. However, the startup endeavor believes it can bring ammonia-powered ranges close to current fossil-fuel distances.

Drop-in retrofit hangars

Ideally, Aviation H2 would run an operation where customers can fly in, leave their jets for a couple of weeks to have them retrofitted, and then off they pop, no longer spewing CO2 into the atmosphere. Business aviation accounts for a relatively small portion of aviation's total CO2 emissions (somewhere in the vicinity of 2%). Still, if the technology can gain regulatory approval and scale sufficiently, it could potentially become applicable to larger jets further down the line.

But what about emissions?

Meanwhile, burning ammonia for fuel in a combustion engine needs to be managed appropriately. Otherwise, it will release large amounts of nitrous oxide, another potent greenhouse gas. The process also produces water vapor - however, it does not release any CO2 when burned. That being said, current ammonia production is still a dirty business, with the preparatory steps causing methane gas leakage into the atmosphere. Green hydrogen production (currently accounting for less than 1% of global capacity) needs to pick up tremendously for either hydrogen or ammonia to become serious contenders for a zero-carbon future.

Source: New Atlas