Ammonia combustion engines: latest research (2021) | Hacker News Reader

Ammonia combustion engines: latest research (2021)

ammoniaenergy.org

63 pointscolinprince65 comments

I am the cofounder at Airthium (YC S17), we make a seasonal energy storage system based on green ammonia and thermal storage (molten salts or sand). We are currently developing a low NOx ammonia burner in partnership with UC Louvain in Belgium

Check us out! https://airthium.com

Checking.

It seems more likely that most users will prefer to import ammonia from tropical solar farms, and keep local tankage of just a couple of weeks' worth. It is hard to imagine where seasonal storage would be needed.

Global energy supply chain brittleness has come in the foreground recently due to war. I can imagine interest in seasonal storage.

Practically everyone imports what they need, at need, today. Only pipelines have lately been considered a problem. "Strategic National Reserves" are a thing, but thus far only used for economic leverage, to my knowledge. Underground storage of NG is pretty common, but again used mainly for price stability.

But this is not the only place where I see people honestly believing that seasonal storage would be desirable and important. I hope they are not, in the end, disappointed by slack demand.

The long term goal is to replace NG. What we are building is the functional equivalent to a natural gas fired powerplant, without the CO2 emissions.

Yes.

People using NG plants depend on reliably regular deliveries of NG. They should be equally willing to depend on regular deliveries of NH3.

Could u share some of your bizdev journey?

Are potential (commercial) partners willing to engage or is it just PR ?

Are they mostly concerned with projected cost/performance/response?

Is everyone waiting for someone else to build the FOAK?

(FWIW, my own interest is in green heavy transport)

thanks

We are targeting the industrial heat market first.

Our proprietary electric heat engine (=a heat pump) can generate heat up to 1000℉, and we will use it to replace industrial gas boilers and dryers with a CO2 free solution. We are in discussions with multiple potential customers for this product.

The development of the ammonia burner is done in parallel as it will be useful in a few years, when we will be ready to deploy the seasonal energy storage system.

A few companies like Form Energy are starting to deploy their first pilots at scale, let's hope they succeed!

There was a Hackaday post about this recently. Here are a couple links that go into more detail about using Ammonia in engines. https://spectrum.ieee.org/why-the-shipping-industry-is-betti...

https://hackaday.com/2022/09/27/japan-wants-to-decarbonize-w...

On a related note, the renowned North American X-15[1] was one of the very few rocket/plane powered by a rocket engine[2] that consumed ammonia as fuel.

[1] https://en.wikipedia.org/wiki/North_American_X-15

[2] https://en.wikipedia.org/wiki/Reaction_Motors_XLR99

Is this really better than producing something like synthetic methane (ie, natural gas?) We have vast experience using this as a fuel already.

It does contain carbon (methane is CH4) so you’d need to produce it using carbon from the atmosphere in order to achieve neutrality.

The atmosphere is approximately 78% nitrogen and 0.04% carbon dioxide. That means that separating pure nitrogen from the atmosphere is relatively simple while separating pure CO2 is more complex and energy intensive. The additional complexity and energy requirements are such that it may be worthwhile developing ways to use ammonia as a fuel, as in this work, even though methane is more well established.

> separating pure CO2 [from the atmosphere] is more complex and energy intensive

Maybe we could find some kind of existing organism with the right chemistry to do this? Seems like such a beast would be very successful if that trick could be accomplished.

No, seriously, this is what plants do. Just ask them for help; we've done it before, we have their number in the rolodex.

You can use the NaOH/CaO cycle to scrub carbon dioxide at atmospheric conditions and even regenerate the calcium carbonate with a (fairly cheap) methane + pure oxygen lime kiln (electric lime kilns are currently in testing).

I'm fact, as long as we still use mined limestone to feed kilns, one can just switch them over to burn with pure oxygen (possibly diluted with it's own exhaust to reduce flame temperatures) and get a pure CO₂/H₂O exhaust. Usage in construction partially reacts back to limestone using atmospheric CO₂.

The issue with plants is just that they are really inefficient compared to solar panels, to the point where scientists have some success feeding solar-industrial synthetic acetate to plants [0] and ending up substantially more efficient per solar-capturing area than outdoor plants.

[0]: https://news.ycombinator.com/item?id=31957068

Have you heard about the (possible) Azolla Event? https://en.wikipedia.org/wiki/Azolla_event

I bought some to grow in an unused tub in my yard until I figure out what to do with it. Not exactly a major CO2 vacuum, but I like the idea. I've wondered if there's something to using such plants as a way to reduce CO2 emissions from various plants. What to do with the plants is not clear since sequestration is the important part.

Here is a lab working on something like what you described. https://www.azollahs.com/research

Grow plants > feed to goats > collect menure > anerobic decay (aka methane digester) > natural gas (pretty close anyway) + good fertilizer.

That's the system I'm interested in. The only real issue is needing to filter out a sulfer based gas (forgetting the exact thing off the top of my head, but it's corrosive to metal)

Hydrogen sulfide (H2S) is pretty easy to clean from biogas.

Did this person lie or something? Why the downvotes? HN is bizarre sometimes.

It only talks about separating gas from the atmosphere. You then have to split up the molecules to do useful things with the atoms, and nitrogen in the air is triple bonded diatomic N2.

N2 gas takes 945 kilojoules per mole to split, while CO2 takes 393 kJ/mol. Since the thermodynamics aren't as favorable, the difference in concentration cost needs to be pretty good. Which it probably would be, (LN2 has been produced at scale for a century via cryogenic air separation and costs about a buck a liter) but green NH4 v green CH4 synthesis is not a slam dunk and it's not clear yet which one will be cheaper at the "replacing all transport oil consumption worldwide" megascale.

You don't even need to purify N₂ that much, as you can just add air to H₂ and feed that to the reactor, wasting some H₂ on O₂ but AFAIK it's quite cheap to enrich air to low-purity N₂ via pressure-swing adsorption, and it's just O₂ that's cheaper to get high concentration of via cryogenic distillation. [Upon further reading, iron-based catalysts in Haber-Bosch synthesis are fairly sensitive to water as it promotes recrystallization of the high-surface-area needle geometry into more clumpy structures with less surface area and thus less catalytic activity; apparently it's thus preferable to cryogenically distill the oxygen out of the air to get by without a water-condenser-trap between the nitrogen feed and the catalytic reactor (ammonia condensing happens between reactor outlet and re-compressing to reactor inlet pressure).]

The bigger issue is that NH₃ (there is the ammonium cation NH₄⁺, but it's charged and thus needs an anion nearby to cancel the charge as coulomb repulsion would otherwise strongly limit the density of your (bulk) substance) is fairly toxic to inhalation when spilled, due to absorbing into water on the surfaces of your mucous membranes, eyes, and lungs.

It is technically also slightly toxic once in your bloodstream, but it's hard to experience that toxicity if you follow "GTFO once you smell" as most non-fish (mammals, sharks, amphibians, birds, reptiles, and terrestrial (i.e., non-aquatic) snails) have fairly capable metabolic excretion pathways due to protein "burning" (breaking down protein from old cells and food for energy) having ammonia as a waste product.

NH₃ is fairly toxic to fish because most assume they can just dump their own ammonia waste into the surrounding water and therefore rely on the surrounding water having concentrations far enough below what would be toxic inside the fish, as there needs to be some gradient to support the waste production/excretion rate.

I have a very naive assumption that the amount of energy needed to break apart molecules for fuel, is roughly the energy we get back when burning them.

Is there any truth to that?

Approximately. Burning H2, you have to separate the H2 to cram an oxygen in between.

thanks

There's that "HN Egg Cup" picture someone shows, if the person hits their site from HN.

I have a couple of downvote stalkers. It's really cute. One of them even went and wrote a pretty much embarrassingly childish one-star review on one of my Apple App Store apps. It was so bad that Apple hid it.

Sometimes, we deal better with machines, than with other people.

I'm sure some people would consider me a troll, while I think I'm just writing honestly when I see things I don't agree with. Yet reading what you just wrote makes me want to quit this site forever. On most sites we know not to reveal enough to get doxxed. Here we reveal a lot thinking we're dealing with serious people. Stupid mistake. Thanks for the warning about the stalkers.

I’m not too concerned about it. I’m a fairly tough old coot (I’m a reformed troll, myself). I’ve dealt with much worse. As you can tell, more folks seem to value what I have to say, than have issues with it. I make a sincere effort not to bring negativity (and boy, oh boy, is that something I can do).

I’m pretty sure that the ones that have problems with me, consider me to be an arrogant old “OK boomer.” Maybe they’re right. I don’t think so, but, as they say, if your feet are wet, and you see pyramids, you’re in de Nile (or a fountain in Vegas). I don’t attack folks, or try to intimidate them. My worst crime is to be annoying.

This is a professional venue. It may not always seem like it, but people can get and lose careers, by their behavior, hereabouts. I’m done with mine. I don’t really need to impress anyone, but if I fight with someone, it could have severe consequences for them. I know how to draw the worst out in people, and make them show their ass. They may “win” their fight, here, and lose everything else. A pyrric victory.

Even if I don’t like someone, I don’t actually want to cause them damage. I would sincerely like to be a positive influence, if at all possible. As I said, I used to be a rather nasty troll, and one of the reasons I participate here, is as recompense. I believe amends need to be made.

This site is Disneyland. Maybe it can’t last, but it has, so far. I like it here. Most folks here have some truly great stuff to share, and I learn something every day. I am truly humbled by some of the participants, here. I make a point of hanging out with people smarter than I am. I’ve done that, all my life. I participate, because I want to be a good citizen, and it’s actually kind of an honor to be here.

If it gets bad, I can always hightail it outta here. I have done that many times, in the past.

Please don't criticize the downvoting system, you will get in trouble.

The primary advantage is that ammonia is much easier to liquefy than methane.

Ammonia also plays better with alkaline fuel cells, as there is no CO2 to precipitate carbonates (as there would be with methane as the hydrogen source). You still would have to filter CO2 from the air being fed into the fuel cell, though.

I'm not sure about how bad/dangerous the failure modes are (relative to the anhydrous NH₃), but cryogenic O₂ stores quite easily and the purified O₂ should come out of the (solar-powered) production of NH₃, some even already as a liquid.

I am trying to get a good overview of how NH3 would work at scale as an energy carrier versus H2 or CH4. Any reason to speculate that one of them will dominate? Have you read any good overview?

NH3 and CH4 both get produced with H2. H2 is difficult to transport in a lot of situations, so the idea is to transform it into NH3. For CH4 you need carbon capture which is energy intensive and only makes sense when you need the carbon like in chemical processes.

Thank you for your comment. I'm really looking for a more extensive overview, an extensively motivated educated guess.

For example, catching CO2 might be done much more cheaply when burning CH4 at a power station. This might change the equation or not. There also seems to be quite a bit of evolution in reducing the price of carbon capture. [0][1] I seem goals of $30/ton for carbon capture and wonder what factors will change the equation...

[0] https://www.pnnl.gov/news-media/cheaper-carbon-capture-way

[1] https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10....

> For example, catching CO2 might be done much more cheaply when burning CH4 at a power station

There's something quite absurd about catching CO₂ at a power station.

A more sensible source is at cement factories.

I see a certain elegance rather than absurdity in closed cycle green energy storage. Whether H2, NH3, CH4 or something else, chances are that will require high quality CO2 sources. Both CO2 based electric power plants and cement factories look like excellent candidates.

I find the simplicity of compressed CO2 energy storage [0] ten times more elegant, but I'll be happy with any progress towards scalable distributed abundant cheap energy storage.

I guess he is trying to say: use existent gas stations and/or we might be able to capture all the CO2 therein. But I am not gp, obviously.

I just read an estimate that said carbon adds 30% to the cost of producing the hydrogen alone (by electrolysis). If you can use smaller, simpler storage, transport, and consumption structures (for CH4 over H2), that have lower safety demands, then it may be a wash.

And those caverns, pipes and gas turbines are already there. Admittedly they depreciate at 4% - 14%, so not there for all that long in the scheme of things, but they're there now. And the manufacturing and regulatory infrastructures and engineering knowledge are there now too. At global scale.

But NH3 is deadly. Household NH3 is 99% water and then you dilute it 16:1 to use, and still need windows open.

CH4 is environmentally unfriendly, but you don't need nearly as much safety gear to work with it.

The world produces and transports anhydrous ammonia in the millions of tons annually. There is plenty of experience with it. Its hazards are well known and well compensated for.

The world also uses a lot more natural gas and despite uses less precautions.

I work at John Deere, there are a lot of product ideas that never made it to the drawing board because someone came up with an accident scenario involving NH3. The stuff is not to be taken lightly. People who refuse to wear seat belts or motorcycle helmets wear full protective gear when around it.

NH3 is easier to make into liquid. CH4 requires cryogenic temperature and high pressures to liquify. For that reason I think that NH3 will dominate in the long run. But, CH4 can be made passively from organic waste so it might eek out an edge. It would be interesting to see the energy cost breakdown for production, storage and transport of both.

Methane already has a place in our energy economy. I speculate it will lead over NH3 for quite awhile.

I haven't seen any good summary, but there's one new contender that needs to be mentioned: hydrogen peroxide.

It doesn't burn, but oxidizes heavily whatever it touches, releasing energy in the process. Can also be used in fuel cells.

In pure form it's even nastier than ammonia, but contrary to that chemical it's liquid at room temperature. Also it mixes well with water producing a less nasty solution.

Energy density is low, but that is not a constraint for grid storage.

From reading Ignition, a book about the development of liquid rocket fuels, there was quite a lot of research into using peroxide as an oxidizer. But turns out it's really hard to make it behave during storage.

At above 50% it likes to become water, exothermically. It is routinely shipped in bottles at 30%.

From a CO2 emissions reduction perspective, it seems far better to use green ammonia as a direct replacement for fossil-derived ammonia used in fertilizers.

Exactly. Ammonia gets produced from (mostly) grey hydrogen. And the most common application for ammonia is producing fertilizers. Making that process green, would cut down on a lot of carbon emissions (several percent of global emissions) and should be the first priority before considering inefficient ways to use hydrogen and ammonia like this.

Ammonia as a fuel is quite inefficient due to all the energy conversions. You use renewable electricity to generate hydrogen. You use that to create ammonia. And you then burn that to produce mechanical energy. Each of those steps has poor efficiencies and they multiply. It is way less efficient than using renewable energy to charge a battery that powers an electrical motor. If you start with 10kwh of renewable electricity, you'd be struggling to get more than 1-2kwh delivered in the form of mechanical energy with ammonia. With battery electric it's more like 8kwh. Charging and discharging the battery loses some energy and electrical motors are of course also not 100% efficient.

And when I say inefficient, I mean costly. You waste most of the energy that you put in. It's much more cost effective to use the energy in a more efficient way. By about a factor of 4-5. If you operate any business where energy cost is significant the value proposition of paying 4-5x more is not great.

It's why ammonia as a fuel really barely makes any sense. And hydrogen as a fuel is pretty bad for the same reason. It's a really hard sell when battery electric is a feasible alternative. The economics are flawed. And the second law of thermodynamics means there is no technical fix for this either. There are some hard theoretical limits here.

Efficiency is very important when your energy is costly. But other attributes like reliability, safety, environmental benignity, "fit" in the overall energy system, and aesthetics start to take precedence over energy efficiency at some point.

The way things are trending with PV, efficiency may recede in importance in a couple of decades. Currently electricity costs tens of dollars per MWh. With developments in manufacturing and install protocols, and tech emerging from the lab, and using DC directly from PV panels, that cost may fall to $0.1 per MWh. Using that to manufacture your ammonia means you won't worry so much about pure efficiency

I still prefer methane over ammonia. Much less toxic when things go wrong.

Electrical motors are about as reliable and safe as it gets.

I agree energy will eventually get very cheap and plentiful, which would enable more frivolous uses of excess energy. But still, that won't happen any time soon and the value proposition of paying several times more for energy is very limited. And while there is a shortage of green energy, using it for the creation of fuels seems like it is costly and wasteful.

>Electrical motors are about as reliable and safe as it gets.

Electricity isn't free. If you're already wasting sufficient amounts of the requisite elements as waste products of some other thing you're already doing then finding a way to bond those elements and then burn the resultant compound for rotary power may be more economically efficient.

> If you're already wasting sufficient amounts of the requisite elements as waste products of some other thing you're already doing then finding a way to bond those elements and then burn the resultant compound for rotary power may be more economically efficient.

Your sentence is a bit vague, but "some other thing you're already doing" sounds like petroleum refining, which is precisely what we need to do less for use as a fuel. Also, ammonia created from petroleum isn't being wasted today. It's used for making fertilizer, and the whole process has a high cost in CO2 emissions.

When the time comes that we have so much carbon-free energy that we can afford to use the excess to generate ammonia, we ought to use it to displace petroleum based ammonia for fertilizer. There may be a few niches (ocean shipping) that require a liquid fuel like ammonia, but it makes little sense to use it for ground transportation. If a liquid fuel is required, things like sustainable biodiesel make more sense.

Ammonia is fine for big industrial use: we process it in the many millions of tons, already. I would not like to see it pumped at gas stations.

I work at an industrial place that had a big ammonia leak in the last few years. I don't think it's fine.

Can you enlarge? How many tons, how many casualties/deaths?

The advantage of ammonia is in the transportation and refueling. If you can refuel a car in the same amount of time that it would take to refuel it with gasoline, then it is a huge plus as it would allow a single fuel station to fuel many more vehicles in the same amount of time.. for instance, in the time it would take to fuel a EV to even 20% charge, you could conceivably fuel dozens of vehicles with ammonia.

That apart, for fast charging or even standard charging you need a reasonably heavily power load from the grid - if you have even 4-5 vehicles charging simultaneously. This would require big changes in the electricity distribution infrastructure.. something which is not required if you continue to use the existing infrastructure used to take fuel to the fuel stations.

Consider that you could easily fully refuel an 18-wheeler in a few minutes time with just a low powered pump.. which is not really possible if the 18-wheeler was a pure EV.

But then consider that you need about 8x the electricity to pull that off; which you pay for at the pump and suddenly that 30-40 minute charging break sounds pretty sweet. Especially when considering your drivers are required to take such long breaks every 4-5 hours. Private drivers get irrational and emotional about this stuff. But most commercial transport is cost driven. 8x is a great argument. Ammonia doesn't stand a chance.

As for the grid, a lot of charging infrastructure relies on batteries and some local production via renewables. That evens out the load on the grid and helps balance things.

Certainly, however Europe won’t be able to fulfill all of its energy needs by local production. Hydrogen is too difficult to ship, so probably ammonia will get shipped instead.

Also you have the issue of ships that can’t get electrified yet. Green ammonia might be one way to replace fossil fuels.

> Europe won’t be able to fulfill all of its energy needs by local production

In the long run, why not? Between overbuilding renewable capacity (needed for green ammonia anyway), using nuclear when it's cost effective and renewable energy is limited, and multi-day storage, Europe should get pretty close. The last couple percent can be bridged with fossil fuels.

I think using an integrated nuclear reactor would be a better solution than using ammonia fuel. Better energy efficiency, increased speeds, reduced fuel handling costs, and greater operational flexibility are clear advantages. I would also argue the environmental risks are reduced.

So designing a ship from scratch with a reactor that doesn't exist that would cost at minimum well over double what existing entire ships cost which uses high enriched fuel that almost as much in raw natural Uranium as existing (filthy) bunker fuel and then sending that high enriched Uranium (which will have a high percentage of chemically separable plutonium unless you refuel yearly at enormous expense and downtime) all over the world, without security or oversight, managed by an industry that cuts costs and breaks laws constantly is a better plan than...

Changing some emissions control equipment, enlarging the fuel tank a little and giving them ammonia when they dock?

I am confused. Why do you think a nuclear cargo ship would use highly enriched uranium?

Low enrichment, compact, long fuel cycle. Choose two.

Natural gas pipelines can be upgraded to transport hydrogen instead.

Not that easy. Hydrogen is very hard to contain.

Given gas leaks and gas explosions are already a regular thing, pushing hydrogen through the same leaky pipes is not going to improve things.

There's this hydrogen fantasy where people think it's a drop in replacement for methane. The reality is that most hydrogen that is currently produced (from vast amounts of methane typically), is used on site. Transporting it around is just very hard. Even in compressed form, it still takes up a lot of space. Diesel has much better energy density by volume than hydrogen compressed at 300 bar. About 18x for the same volume.

I know, this information is coming from a private conversation with an expert who has done an analysis on this and says it's actually both plausible and much cheaper to do than shipping hydrogen.

There are already definite plans in play to transition shipping to green ammonia.

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