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Reaction Engines assembles partners for its ammonia aviation project

Reaction Engines assembles par...
The new ammonia propulsion system uses heat exchanger technology originally developed for Reaction Engines' Skylon spaceplane
The new ammonia propulsion system uses heat exchanger technology originally developed for Reaction Engines' Skylon spaceplane
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The new ammonia propulsion system uses heat exchanger technology originally developed for Reaction Engines' Skylon spaceplane
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The new ammonia propulsion system uses heat exchanger technology originally developed for Reaction Engines' Skylon spaceplane
A compact, lightweight cracking reactor for green ammonia, for use in aviation, shipping and off-grid power generation
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A compact, lightweight cracking reactor for green ammonia, for use in aviation, shipping and off-grid power generation
The ammonia-cracking tech will produce an ammonia-hydrogen blend suitable for use in combustion engines
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The ammonia-cracking tech will produce an ammonia-hydrogen blend suitable for use in combustion engines
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The UK's Reaction Engines has announced a joint venture to create compact, lightweight ammonia reactors it says can be used to decarbonize difficult sectors like shipping and off-grid energy generation – and surprisingly, also aviation.

We've written before about ammonia's potential in the clean transport sector; check out our ammonia clean fuel primer piece from September. Compared against hydrogen, ammonia's much easier and cheaper to store and transport, and although it only carries about 20 percent as much energy as hydrogen by weight, it carries about 70 percent more energy than liquid H2 by volume.

The weight issue generally rules ammonia out of aviation discussions; at less than half the specific energy of jet fuel it looks less attractive than hydrogen. But hydrogen's volume issues must also be taken into account. Today's airliners are built for jet fuel so retro-fitting large-volume long-range hydrogen tanks can mean you lose seats. And anyone who's flown economy can attest, airlines really like fitting in as many seats as they can.

With that in mind, maybe ammonia becomes another option to put back on the table. And that's one of the things Reaction Engines has proposed in its new joint venture with IP Group and the UK-Government-funded Science and Technology Facilities Council (STFC).

The partnership would use heat exchanger technology Reaction developed for its Synergetic Air-Breathing Rocket Engine (SABRE), designed for hypersonic and space travel applications – and combine it with STFC's work in ammonia catalysts.

A compact, lightweight cracking reactor for green ammonia, for use in aviation, shipping and off-grid power generation
A compact, lightweight cracking reactor for green ammonia, for use in aviation, shipping and off-grid power generation

As we explained when Reaction first brought the idea to light a few months ago, here's the rough idea: the heat exchanger would capture heat from a jet engine's exhaust and use it to power a cracking reactor. The reactor would catalytically convert pure ammonia into an ammonia-hydrogen blend that'll work as an easily combustible fuel that's more or less a drop-in replacement for jet fuel.

So an airline operator can now choose between weight and volume, with the added benefit that this system wouldn't require an entirely new electric powertrain. In a shipping setting, this ammonia-hydrogen fuel would be used as a pilot fuel, and it would also be suitable for use in generators for off-grid power production.

How green will it be? Well, the combustion products will be nitrogen and water. But both ammonia and hydrogen tend to produce nitrous oxides, or NOx emissions, when burned. Carbon emissions may contribute to climate change, but NOx emissions are harmful to humans, animals and entire ecosystems, creating smoggy air and contributing to the formation of acid rain. So we certainly hope this consortium takes care of that side of things.

It's an interesting idea, and we're fascinated to learn how it pans out economically. Ammonia and recyclable aluminum-air batteries offer interesting alternatives to hydrogen in the nascent clean commercial aviation space, and with cost being such a powerful driver we'd love to know how they stack up. Not to mention, how they'll stack up with regards to efficiency, considering that all three of these fuel alternatives will be created from green energy that the world can't afford to throw away.

That's another issue with ammonia, too; green ammonia is rare and expensive at this point, and green hydrogen is one of the required inputs. Clean combustion engines won't be so clean if they're fueled by ammonia produced using methane gas, like the vast majority of what's available today.

Still, we're fascinated to see how this all pans out. Stay tuned.

Source: Reaction Engines

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8 comments
8 comments
David
It will be interesting to see how Reaction Engines keep the hydrogen and nitrogen separate to avoid production of nitrogen oxides. Perhaps their different liquefying temperature or pressure can be used. In addition, though, is it possible to easily extract oxygen from the atmosphere to avoid (or minimise) ambient nitrogen being burned.
paul314
Let's not forget that ammonia is also intensely corrosive and toxic. Handling it in kiloton volumes right next to large assemblies of people will be interesting.
Bob809
A question from a layman. Where will the amonia come from, and how easy is it to get, to transport it to user, and transfer it to aircraft/boats/power stations. Like safety issues, are there any. Will it corrode any piping, engines and so on. I know this is only a short article and does not go deep enough into the guts of it, but I'm just asking. I know how the systems work that currently use fossil fuels, how they are transported etc., but this is something new isn't it, on this proposed scale?
DaveWesely
Interesting application of anhydrous ammonia. @Bob, ammonia is NH3. The Hydrogen comes from water or fossil fuels. Nitrogen comes from the atmosphere. Its primary use is as nitrogen fertilizer on farms and is a significant safety risk for farmers. Compared to hydrogen, storage is easy with most tanks lasting at least 50 years. Small leaks are readily apparent, just like the diluted cleaner we use at home. The concentrated, or pure form as anhydrous ammonia is quickly lethal until dissipated. I doubt it would be a good fit for airports. Ocean shipping would be a better alternative.
FB36
Using ammonia for land/sea/air transportation would require MASSIVE infrastructure & redesigning & replacing ALL land/sea/air vehicles!!!
What if there is actually no need at all?
All light/small vehicles are already becoming fully electric & all heavy/big land/sea/air vehicles just need us to start producing biodiesel/biofuel at large scales!
(From all possible industrial/agricultural/forestry waste/biomass & trash & sewage!)
jerryd
Ammonia will last until the first mass deaths of a most painful way to die, your lung being chemically burned. And ammonia flows downhill killing everything in it's path a recent accident did cutting us off from town for 3 days from just a 1/4" leak.
I didn't realize how much space it took up.
paleochocolate
@FB36 Biofuel is never a solution. Biofuel needs more energy to create it than it has energy to give.

Large commercial applications need hydrogen to be an improvement over current methods.
EH
For all the reasons the other commenters have given, this is an unbelievably terrible idea. If it helps R.E. stay afloat, then good, but if takes resources away from better ideas -- and there aren't many worse -- then let's hope this dies more quickly than a man with a lung-full of ammonia.