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Comment by iamthemonster | Hacker News Reader

2026 is still a very ambitious startup date for this. The International Maritime Organisation (IMO) has only just approved interim guidelines for the addition of ammonia to the IGF Code (use of gaseous fuels). There's a lot to it, but this is a good high level overview: https://www.linkedin.com/pulse/imo-interim-guidelines-safety...

A lot of commentators believe that since ammonia is less inherently safe it will inevitably be less safe in practice. I am not convinced by that argument, and in general if there's a strong enough business driver then anything can be made safe. But what really swung me against the idea of ammonia as a shipping fuel is that the expected cost is barely any better than methanol (which is much more inherently safe) and is more expensive than biodiesel.

The shipping companies have a real conundrum on their hands - do they go ammonia, methanol, stick with diesel, or try to get near-shore and inland shipping onto electric? Ammonia-fuelled ships have to be THOROUGHLY designed from the ground up specifically for ammonia use; you have to be 100% committed to go down that path. Whereas biodiesel can simply be dropped in (you can of course choose to fill up with a biodiesel blend today, but nobody does because you can put emissions into the atmosphere for free).

Unlike solar cells or battery cells, I don't really see much chance for 'learning rates' and technology improvement to drastically drive down the cost of green ammonia. Falling electrolyser costs are nice, but they're only a portion of the process plant CAPEX, and the cost of the green electricity dominates the economics over the process plant CAPEX anyway. You could get electrolysers for free and still be unable to make cheap green ammonia. So for green ammonia to get adopted, a strong 'carbon price' needs to be in place, and I think that same strong carbon price would make biodiesel competitive.

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I'm pretty sure the costs of producing a fuel based solely on making it with electricity is by far, of all the options you named, best done with Ammonia.

The reason the cost of ammonia is barely better, or even worse, than things like methanol, is because the electricity process is still expensive.

But that can (and soon would!) become waaaay cheaper. Electricity __NOT__ on demand is dirt cheap and can be halved and quartered some more: Solar panels are _idiotically cheap_ these days and that state of affairs is not temporary.

We need more not-on-demand needs. As in, 'hey, uh, if theres some power left over cuz it's windy and sunny.. no prob! Let me run these ammonia producing machines at full power for a bit. No need for ammonia right now? No problem - compared to electricity, ammonia is vastly simpler to store'.

Ammonia is a great not-on-demand consumer of electricty. That's why this is necessary.

As you said:

> the cost of the green electricity dominates the economics over the process plant CAPEX anyway.

That's exactly the factor that can become ridiculously cheap. It isn't today because there's not much point investing in solar/wind because they do not cover on-demand needs (when it's not particularly sunny/windy, then electricity prices are sky high and you want to build electricity production that can deliver then. And solar/windy by definition can't), and the primary issue is transport.

if the demand for ammonia skyrockets, you can solve it all. Ammonia does not need to be produced on-demand, and you don't need all that much transport (build the ammonia producing plant close to your solar/wind parks).

> Let me run these ammonia producing machines at full power for a bit.

The problem with this is the capex and running costs of that kind of machinery make it expensive to keep idle. It can be uneconomic even with free electricity.

Where are the costs. Many factories are only used 8 hours a day despite the high costs - it isn't worth the additional cost to have employees work overnight. Some really energy hungry factories traditionally run only overnight when energy is cheap, and they shutdown for yearly maintenance in December (thus freeing up their normal energy use when everyone is running Christmas lights) Now that wind and solar are coming online those are changing how they work.

Different factories have difference costs. When energy is significant they consider that. When energy is not significant they just run when it works out.

> Many factories are only used 8 hours a day despite the high cost

Is this true in chemicals?

Which chemical? Some yes, some no. Some processes work better in continue runs, some you are doing batches. Some batches take a few weeks, some are hours...

> Which chemical?

Any industrially-produced chemical where continuous production is possible. I haven’t heard of such systems being competitive if left idle so someone can sleep.

Continuous production implies at least a few people 24x7. Not all chemicals are continuous production. Often there is a choice of processes when you build a factory.

> Continuous production implies at least a few people 24x7. Not all chemicals are continuous production

Yes. I'm asking if there is a chemical-production process that can be run 24/7 but which isn't due to labour shortages somewhere that doesn't result in such production being shut down (or protected)?

Chemicals are globally-traded commodities. Some are perishable and/or difficult or even illegal to ship. So there is regional price variance. But ceteris paribus, if it can be run continuously, production will shift to where it is.

Normal operation of ammonia plants and methanol plants has been 24/7 for decades. Most other commodity chemicals too.

Loading & unloading ships & barges as well.

Some places only load railcars & trailers during days.

Also it's common for engineers to only work straight days and often their office is not on site, they actually only make visits. They do it as needed and can be very dedicated and effective, but of course they can't touch anything because that requires a unionized operator.

I've worked in two factories in my life. Dairy, and Printing. Dairy was 24/7/365. Printing was (averaging) 20/7/365 (product/layout change, maintenance, cleaning, etc.)

My father was a fireman. Knowing what I know from him, I would never go to work for a factory that they got THOSE massive energy demanding machines that run non-stop and the fuel is ammonia. It is a near-certain death sentence, especially in 'some countries' where safety is 'a bit more relaxed'.

> Many factories are only used 8 hours a day despite the high costs

I don't have a lot of direct experience but my dad worked in factories most of my childhood. Every single one ran nearly 24/7. Was that a chance occurrence of the types of factories we had near where I grew up?

Are you asking if all factories are like the ones that you grew up near?

My understanding is that manufacturing tends to be the way you describe. I'd be surprised if that held true for all sorts of factories, especially in chemical production. Just a guess but I think paying chemical engineers for overnight shifts might cut into profits somewhat

EDIT: another comment sparked a memory, I'm thinking specifically of batch operators.

Usually there will be only a single engineer or maybe two on staff for the night shift. But paying regular operating staff an additional 50% night shift bonus to keep the factory running is very often worth the price.

The night shift extra is usually much closer to 50 cents than 50 percent. A lot of places even give the night shift the same pay, especially when the labor market is favorable to employers.

That's crazy. In many countries (e.g. mine) night shift is an unwanted pay increase, and often on a week-on, week-off basis.

Stopping and restarting chemical plants is usually horribly expensive. Most of them run 24/7, non-stop, even if the companies have negative profit on some of the products.

The only confirmed example I know of is Harley-Davidson, roughly during the boom of cruiser motorcycles (1995-2010?): They only ran one shift, but the PR of waiting lists and extremely high instant resale prices made the choice appealing in the face of the capital costs.

Wouldn't this imply that the ammonia consumption would have to be near the solar plant?

No? For similar reasons that fossil fuel consumers don't need to be near an oil well.

You'd have to ship the ammonia to the point of use, which is going to be significantly more hazardous

It only needs to be easier to ship than hydrogen.

You “ship” electricity near a port via the electric grid, and then make ammonia near or in the port. Economies of scale might favor having a few ammonia factories and then shipping it around by boat.

Ammonia makes zero sense as a general use fuel, but ships need MW of power over several days and aren’t in populated areas.

Assuming, it’s actually viable which isn’t guaranteed.

OK, that sounds like a good plan. But that's the opposite of what was proposed further up this thread.

It depends on whether you prefer to transfer electricity or ammonia. You get to pick whatever is easier, which caps the difficulty at not high. The suggestion of shipping ammonia was for the sake of convenience, not a burden. It's optional.

the actual post I replied to originally said

"build the ammonia producing plant close to your solar/wind parks"

You can't pick that and then decide not to transfer the ammonia and decide not to transfer the electricity. Unless your solar plan is at the loading dock or something.

The suggestion of shipping ammonia was for the sake of convenience, not a burden. It's optional.

Yes you have to transfer electricity in that case. We already know transferring electricity is easy.

Don't get hung up on "picking" one as if the downsides get locked in at the pre-design phase. If it's difficult to transfer ammonia then nevermind go back to the existing easy option of wires.

In other words, if that specific detail doesn't work out, it is not an argument against ammonia. It was just a potential bonus, not core to the idea. And it doesn't fundamentally change things. It's not the "opposite" plan.

Someone makes a statement. I point out that statement has implications. Someone then suggests an idea that is counter to the original statement. I point out that is inconsistent. Your response is "Don't get hung up on".

Your argument at this point has just devolved into some variant of "don't confuse me with the facts"

You said the plan was the opposite, but it was only a tiny optional detail that's opposite.

The phrasing in that comment rejected the original plan as a whole, and that's not right.

Also the comment you called a "good plan" was still talking about shipping ammonia as a maybe! So even in that detail it's not the opposite of the original comment.

I think your first comment was fine, but it's not your first comment that I replied to.

I wouldn’t get that hung up on the specifics when we are using terms like ‘near’ which is why I said boats for economies of scale.

I was thinking of navigable waterways which are common near major wind farms and some solar, not just major ports which rarely have a lot of space available. The UK is already facing issues with moving offshore wind around the country, an Ammonia plant could theoretically make a lot of sense.

If ammonia cannot be shipped safely than the whole thing is moot. We're talking about "shipping" ammonia halfway around the world in the fuel tanks of these ammonia fueled ships. If storing it long term in fuel tanks can be done safely, than so can shipping it to port.

This also means ammonia may end up getting produced at the globally best places, the places where the solar resource is extremely good, like Chile, Namibia, parts of the middle East, then shipping elsewhere.

Sunny places with good ports and cheap land.

Shipping ammonia is commonly done already. For example, the first few search results for "ammonia tanker" has a story of Maersk ordering up to ten new tankers with 93000 cubic metre capacity each.

This is illogical - we ship a live nuclear reactor around the world in a nuclear carrier or icebreaker. But you cannot take it out and put it on a truck

That has more to do with the design of the vessel than anything.

> Ammonia is a great not-on-demand consumer of electricty.

This does not follow. The cost efficiency of ammonia production is highly dependent on the process being continuous and steady state. Every analysis that says ammonia is cost effective as a fuel is based on an efficient continuous process as a cost assumption.

If you are constantly starting and stopping based on electricity availability then your ammonia just became much more expensive. In which case, it is probably no longer cost effective as a fuel. Mixing "best possible price" and "worst possible process" and pretending these represent the same instance of reality is misleading to say the least.

> The cost efficiency of ammonia production is highly dependent on the process being continuous and steady state.

Hydrogen is the overwhelming energy input to ammonia production. Hydrogen is readily storable -- this is done even today, when the hydrogen comes from natural gas, to smooth things out to keep the ammonia plant running -- so intermittency of renewables will be almost entirely countered by doing the same thing and storing the green hydrogen.

What matters is cost of electrolysers, but they have been getting very cheap in China.

It is not just the cost of inputs.

Ammonia synthesis is a high-pressure high-temperature process. One of the reasons to use a continuous steady-state process is that cycling it up and down causes thermal and pressure fatigue in the reactor. The safe operating life of a reactor can be surprisingly short if it is not operated at a steady state. If you want this to scale, it needs to be low maintenance and have a long operating life.

You could in principle centralize ammonia production with sufficient reactant reserves to ensure continuous production from variable low-density energy sources like solar or wind. However, this would require hydrogen pipelines that largely don't exist and would take a long time to build. We can't repurpose existing natural gas infrastructure and similar because they weren't built with alloys resistant to hydrogen embrittlement. One of the big economic advantages of using methane for ammonia is that it takes advantage of the millions of kilometers of natural gas distribution pipeline that already exists.

I'm not averse to the idea but the enthusiastic proponents are pretending like the practical realities of industrial chemistry don't apply to them. We aren't going to get to a green future with rainbows and unicorns, we need to brutally realistic about the true requirements.

I wasn't talking about the cost of inputs, I was talking about their putative intermittency.

The argument that was being made seemed to be "renewables are intermittent, therefore ammonia synthesis based on renewable energy must be intermittent, or else use expensive storage". The counterargument is that hydrogen is the overwhelmingly most important input, and it is highly storable, so the intermittency of the inputs can be largely avoided at modest cost, allowing the ammonia plant to run 24/7.

You may not be aware, but we already have hydrogen pipelines coupled to ammonia plants. The US has ~1000 miles of hydrogen pipelines for this purpose. It's also not obvious to me why pipelines would necessarily be needed. After all, the ammonia plant could be built where the hydrogen is stored.

Can factories install local battery banks to cover a day’s utilization? Charge up the batteries on the cheap electricity during noon and run the plant off of those reserves. I assume other industries are already running these cost optimization analyses as the renewable electricity market continues to develop. There is a balancing point between the capex and opex, but unless it is insanely energy hungry (like aluminum), that seems possible.

> but unless it is insanely energy hungry (like aluminum)

Producing a ton of hydrogen by electrolysis requires ~3x the energy to produce a ton of aluminum. It is, in fact, "insanely energy hungry". This isn't necessarily a problem but it does create logistical challenges.

What comes back to the fact that you only need batteries for the ammonia production. Hydrogen production is a low-pressure process, and optionally even low-temperature.

It takes 11 MW of electricity to make 1 ton of ammonia, ammonia plants can make 1000 to 3000 tons a day. Providing battery storage for that production rate for 24 hours would probably cost more than the plant itself.

> It takes 11 MW of electricity to make 1 ton of ammonia

Do you mean MWh? Because the units given don't make sense.

But 11 MWh would be too low.

> You could in principle centralize ammonia production with sufficient reactant reserves to ensure continuous production from variable low-density energy sources like solar or wind.

I'm probably missing something here but why would you need to pipe hydrogen to the plant, rather than just generating it on site from power drawn from the grid?

Energy density mostly and being able to deliver that power where you need it. Aluminum plants are co-located with large-scale power plants, famously hydroelectric, for the same reason. Above certain power requirements, you essentially need the power generation to be onsite.

Hydrogen requires 3x the energy of aluminum per ton, so it is an even bigger problem for hydrogen. Unlike aluminum, it is feasible to have large numbers of small hydrogen production plants but then you need to transport all that hydrogen at an acceptable scale.

> Above certain power requirements, you essentially need the power generation to be onsite.

Is this due to transmission losses or just because you couldn't feasibly build enough capacity cables to transmit large amounts of power over long distances?

A single ton of hydrogen requires ~50 MWh of electricity. Small special-purpose ammonia plants, which are common for some industrial applications, typically require on the order of 50 tons of hydrogen per day. This would require ~2.5 GWh of electricity per day via electrolysis. To put that in context, that is in the same ballpark as the average output of the largest solar farms ever built in the US.

The largest ammonia plant in the US requires around 2,000 tons of hydrogen per day. That would require 100 GWh per day to produce by electrolysis, which would require the entire output of a large hydroelectric or nuclear power plant, much like large aluminum refineries. Otherwise, you need to move a lot of electricity or a lot of hydrogen to have good efficiency, and there is infrastructure for neither.

Converting natural gas into hydrogen is also energy intensive. One of the big advantages of natural gas is that your hydrogen source is also your energy source and there is vast infrastructure for moving natural gas around.

Building green hydrogen pipelines likely makes more sense than trying to backhaul electricity from diffuse sources. A single hydrogen pipeline can reify a lot of electricity production without the concomitant transmission and management infrastructure.

A ton of hydrogen seems to occupy a cube with a 23 meter side. Wonder if a bunch of those could be built to hold the excess gas for night time operation.

100GWh is not small, but it's not impossible. The largest solar farm in operation is 5GW, and that could get you theoretically halfway there operating 10 hours a day.

It feels like the challenges are a lot easier to solve than with fusion or nuclear.

The issue doesn't appear to be storage, but transmission. Hydrogen can leak through metal and lead to it becoming brittle, so you can't use conventional natural gas pipelines to transport it.

Exactly, these tanks can be giant balloons right next to the solar panels all feeding the in-situ ammonia plant.

That was my thinking, but I think what he is saying is that power plants won't generate enough electricity to make building an in-situ ammonia plant economical. You need to network power plants together to operate a centralized ammonia plant 24/7, and the network to move this energy (whether in the form of hydrogen or electricity) doesn't currently exist.

The land area of an all-in-one plant is maybe the biggest unknown for me with respect to just getting ownership and permits and such. But it's fun to imagine just picking a giant plot somewhere in the desert and plopping down 20 GW of solar panels, enough hydrogen storage to keep the less energy intensive steps operating throughout the night, and presumably batteries for whatever still requires electric power while panels are offline. Water and air in, sweet sweet ammonia out. :-)

Cloudy weather would be an interesting problem I guess.

It is doable in theory but would require the construction of large-scale supporting infrastructure that currently doesn't exist. I am not optimistic about our ability to undertake infrastructure projects of this magnitude without it taking several decades and incurring obscene cost overruns that make even the most pessimistic economic models look optimistic.

This will definitely be harder than nuclear. The expansive land use requirements means the legal battles pertaining to that would almost certainly span many decades. At least with nuclear there is a limited number of people that need to sign-off to have a viable project -- reforming that process probably would be simpler.

I can’t imagine it wouldn’t be stored either as liquid or at least pressurized.

Steam has something like 200x the volume of the water it’s boiled from.

One thing you can do there is have an onsite energy storage mechanism (battery, gravity, etc) and run the process 24/7, keeping the energy storage topped up whenever the cost of electricity falls below whatever threshold.

Worst comes to worse you run on grid for a few hours.

Liquid ammonia takes less energy and volume than liquifying hydrogen.

This has nothing to do with hydrogen as an input to the ammonia production process. This hydrogen is not liquefied, even if it is temporarily stored (as a compressed gas, for example underground in solution mined salt caverns.)

Do you have concrete capex and opex numbers for ammonia-from-electricity plants? I understand we should expect those to go down over time because of the learning curve, but I don't even know their order of magnitude right now. It would also be nice to have an idea of how much efficiency the electrolyzers lose when operated intermittently instead of continuously (so, for example, you can't keep them at their optimal temperature). But, since we're presupposing that intermittent electrical energy will be very cheap, efficiency is less important than capex per output and non-energy opex.

Supporting your point about solar panels continuing to be cheap, "mainstream" panels went up to 0.11€ per peak watt last month: https://www.solarserver.de/photovoltaik-preis-pv-modul-preis... which was a new historic low price in September and down 21% from 0.14€/Wp in February of last year, itself a historic record low price at the beginning of last year.

The last time something like this happened to the energy supply, it was James Watt's steam-engine.

What are the relative costs of producing methanol or ammonia from a kilowatt hour of electricity? I've always assumed methanol would be cheaper over all because it's less deadly.

We're already doing this with methanol in Sweeen though. So what's the point?

Note that biofuels aren't especially environmentally friendly, even just considering carbon emissions. See e.g. [1], which makes the most optimistic possible assumption by ignoring land use changes and still concludes "the reductions for most feedstocks are insufficient to meet the GHG savings required by the EU Renewable Energy Directive" (second generation biofuels may do better, but that isn't clear). Also ignoring land use changes is a very bad asssumption; if your plan is to run global shipping (or other industries) on biofuels it seems highly implausible that it's not going to end up with more land overall used for growing crops. If that's land that could otherwise be sequestering carbon (e.g. drained peat bogs, which have the advantage of being highly fertile), then it's clearly going to be a significant contribution to carbon emissions (not to mention the ecological impacts of converting yet more land to agriculture).

[1] https://royalsocietypublishing.org/doi/10.1098/rspa.2020.035...

> Unlike solar cells or battery cells, I don't really see much chance for 'learning rates' and technology improvement to drastically drive down the cost of green ammonia. Falling electrolyser costs are nice, but they're only a portion of the process plant CAPEX, and the cost of the green electricity dominates the economics over the process plant CAPEX anyway. (...) So for green ammonia to get adopted, a strong 'carbon price' needs to be in place, and I think that same strong carbon price would make biodiesel competitive.

You seem to be contradicting yourself here? If learning rates and technology improvement drastically drive down the cost of solar cells, as you say they might, and the cost of electricity dominates the cost of green ammonia, as you say it does, doesn't that mean that the learning rates and technology improvement in solar cells will drastically drive down the cost of green ammonia? Wouldn't that make ammonia much cheaper than biodiesel, keeping biodiesel from being competitive?

(I'm not sure ammonia is a competitive fuel for other reasons, such as the corrosion and safety issues discussed in the article, but it seems clear to me that if it's going to be uncompetitively expensive, it would have to be because one of the premises above is wrong, for example because the cost of green ammonia is dominated by capex or because solar cells stop dropping in cost. I don't see how you can sustain those premises and deny the conclusion.)

>Unlike solar cells or battery cells, I don't really see much chance for 'learning rates' and technology improvement to drastically drive down the cost of green ammonia. Falling electrolyser costs are nice, but they're only a portion of the process plant CAPEX, and the cost of the green electricity dominates the economics over the process plant CAPEX anyway. You could get electrolysers for free and still be unable to make cheap green ammonia. So for green ammonia to get adopted, a strong 'carbon price' needs to be in place, and I think that same strong carbon price would make biodiesel competitive.

There is a ton of research going into improving the efficiency of the H2 > NH3 conversion, and there are at least two startups (Tsubame in Japan and a new one I don't remember). There's no rule that says you can't beat Haber.

Compared to methanol, ammonia is currently more expensive but vastly more scalable in the long run; once you reach the biofuel "ceiling" (roughly corresponding to the availability of farming and forestry byproducts) you're stuck making it via carbon capture, which has its own efficiency problems.

By "efficiency" do you mean energy consumption or hydrogen consumption?

Energy consumption. I am pretty sure that the hydrogen utilization in most ammonia production is very high.

In theory the energy required to produce ammonia is negative (Hf < 0) but at standard pressure its formation is thermodynamically unfavorable (Gf = Hf + TdeltaS > 0). But the bigger issue is the very high activation energy barrier for ammonia synthesis, which results in a lot of energy being used to make ammonia at very high pressure and temperature.

Right now there are two competing approaches to reducing the cost of ammonia production. Tsubame is using a new ruthenium-based catalyst that lowers the reaction temperature (and therefore, also the pressure). The other method is by electrocatalysis. I don't know for sure that this is what NitroVolt is doing but their name certainly suggests it.

Thank you!

Presumably if you had some way of rapidly removing the ammonia produced from the reaction, like maybe a high-temperature highly polar solvent that reacted reversibly with the ammonia, but didn't dissolve much hydrogen or nitrogen, you could get by with a lower equilibrium amount of ammonia and thus much lower pressure. Anhydrous phosphoric acid seems like a potential candidate? But that's obvious enough that people probably tried it a century ago.

Short distance electric shipping seems the most feasible. Scotland is making steps in this direction. https://www.offshore-energy.biz/scotland-to-buy-seven-electr...

Long distance .. this is just a problem. As you say it won't be solved unless there's carbon pricing and ultimately restrictions on fossil fuels in general, forcing a replacement with more expensive synthetic and bio-fuels.

I think long distance might be solvable too with a little out of the box thinking. Imagine ships could swap out batteries every few hundred miles. Think simple container batteries and some off shore wind park with facilities for charging container batteries and a stash of charged batteries. Floating off shore wind is now possible as well.

Containers might be a bit tedious for this. So, why not use autonomous tug boats and barges. The tug boats simply pull the load between charging stations. When they are empty they head for a charger and a full one takes over. This could even work with existing ships, which are commonly maneuvered around harbors using tug boats already.

Probably more than a few engineering challenges lurking here but it gets us out of the mindset that ships must be able to go for thousands of nautical miles without stopping for charging. I could see that working for a lot of coastal shipping routes.

Container batteries already seem to be a thing: https://www.offshore-energy.biz/worlds-first-700-teu-pure-ba...

.. but again for relatively short distances. You do not want to have relatively unskilled personnel attempting swaps at sea, or in bad weather (which is also very dangerous for ships under tow).

The China-EU distance is about 24,000km. I don't think more than one or two charging/swap stops are feasible on that route, so you're going to need something with 10,000km range at the very least.

China-EU can follow the coast. It isn't unreasonable to just stop at a port every night. You can put the crew up in a hotel thus saving needing beds for everyone, and they can enjoy whatever meals they want. This will make the trip take 3x longer though, which is a very significant disadvantage, but if electric energy is enough cheaper they will go for it. Most things going via sea are not time sensitive, but the crew still needs to be paid along with the ship mortgage. China-US could do the same, but the trip is about 10x longer (I didn't bother to look this up) - even with free electric I'm not sure if it is worth it.

There are islands like Hawaii where the above is not possible though so we still need something else.

> It isn't unreasonable to just stop at a port every night

Is it? How many more deep water ports would be needed if every ship had to stop every night? What about if you're passing hostile or undeveloped countries? What about when you need to cross the Pacific or Atlantic? Cargo ships move at maybe 15mph - there's definitely huge parts of the world that don't have a well equipped deep water port every 360 miles. Even major western countries only have a handful of major ports.

I didn't say it was easy. Undeveloped countries would mostly welcome a chance for someone else to develop energy and port infrastructure. Hostile is a different issue, but you can bypass them as needed. (ships already pass by hostile countries)

> It isn't unreasonable to just stop at a port every night

You’re describing coaling stations [1]. They worked in the era of empires (one government controls the coaling network) and no other options. They’re uncompetitive today.

Any energy system requiring them will not be competitive against direct-sail systems. You’re paying for the crew and ship’s deterioration with every delay.

[1] https://www.britannica.com/topic/coaling-station

> So for green ammonia to get adopted, a strong 'carbon price' needs to be in place, and I think that same strong carbon price would make biodiesel competitive.

And next to ammonia, biodiesel is almost drinkable.

And there's the entire CO versus NO or NO2.

But well, the silver lining is that the combustion products literally burning your lungs means that you won't unknowingly lock yourself in a room with a running engine.

Also a very unlikely form of suicide - people generally opt for less painful ways to die.

Cost is indeed the core issue. It's an issue with most synthetic fuels and it's not an issue that is likely to go away. As long as that means you have to pay a steep premium to be green, it's not going to be popular. International agreement on carbon taxes is unlikely. And most ships operate in international waters under the flags of countries with favorable taxes and rules (e.g. Panama, Greece, etc.).

With shipping, shooting for perfect is really expensive. But we're starting with a status quo that is really bad that can be improved upon.

For example, most ships are made out of steel. Steel is relatively heavy. There's a ship yard in Tasmania working on a battery electric 300meter long ferry made out of aluminum. They've built dozens of aluminum ships already. Aluminum is much lighter than steel and that cuts the amount of energy needed to move it around by about half. That's nice because batteries are expensive and don't provide a lot of range. But making ferries out of aluminum is of course something that could work for any kind of ship.

Fuel is really expensive. 50% fuel savings are very attractive to ship operators. Most ships burn bunker fuel. That's properly nasty stuff. So using only half of that would be an improvement. It's toxic, causes lots of pollution and is nasty if it gets in the water. Some cruise ships run on LNG these days. Much cleaner but it takes up space. Those ships are mostly still made out of steel. If you make them out of aluminum, they'd be a lot lighter probably and use less fuel. So smaller LNG tanks, less CO2 emitted, and more space for the passengers. Win win.

There are also some interesting things happening with composites and carbon fiber. That stuff is even lighter and there are some companies focusing on marine applications as well. So, we could cut weight and fuel usage of ships by using modern/different materials.

There are some experiments happening with using sails on ships to cut fuel usage further. If you add all this up, we could be cutting fuel usage significantly (40-70%) and make the emissions problem a lot smaller. And unlike synthetic fuels, this also translates into financial savings. So that means it's more likely to happen.

And if we eventually put batteries in these ships, they'll go a bit further as well.

It's not perfect. But probably a lot better.

> Aluminum is much lighter than steel and that cuts the amount of energy needed to move it around by about half.

Hmm. I'm suspicious about this - might be true for cars, definitely true for planes, but ships sit at neutral buoyancy, most of the mass is cargo, and the main component of energy expenditure is actually drag. So there's significant benefits to low drag hull designs or "slow steaming", but the actual ship material isn't terribly high up on the priority list. And aluminium is way more expensive.

I think aluminum is mostly more expensive than steel because energy is expensive, but solar energy makes energy cheap.

If a ship's mass were mostly ship rather than mostly cargo, making it out of a heavier material would increase its water displacement, which would increase its drag. I don't know if that's a proportional effect; I think it's actually sublinear. But, since most of the mass is cargo, it won't make much of a difference.

If most of the mass weren't cargo, you could ship things more cheaply by sealing the cargo in giant plastic bags and towing it across the ocean behind a tugboat.

Both steel and aluminum production depend mostly on the cost of energy, so any improvements that would make aluminum cheaper would also make steel cheaper. Steel also has the benefit of being ferromagnetic so it’s a lot cheaper to pull scrap steel out of the garbage stream and recycle it, but that depends on having lots of scrap steel to begin with.

There’s really not a lot of room to make aluminum as cheap as steel, as all economies of scale have by now been mostly realized. The cost of energy is so dominant that it makes sense to run smelting plants idle most of the time with the crucible heated constantly just to take advantage of negative power prices (although there are other factors at play like subsidies and national security concerns).

Barring some sort of seismic scientific breakthrough in metallurgy, the current ratio of 2-3x the cost of steel is here to stay. There’s maybe a little room if we reach “peak aluminum” as the fraction of recycled scrap approaches 100%, but I don’t think that would make that much of a difference because we’re likely to hit “peak steel” before then (and again, its just easier to recycle from a logistics standpoint).

Hmm, really? I didn't realize that. Thank you!

aluminum has terrible metal fatigue issues. Ships that have been perfectly fine for years will suddenly just fall into pieces. Trucks where weight matter do often use aluminum trailers, but they keep careful track so they are scrapped before they fall apart. This fall about is not something an inspection will catch (not 100% true, ultrasound and other inspection methods will catch some of this, but for discussion it is close enough to say you just scrap aluminum before it fails instead of inspecting)

That isn't to say aluminum can't be used for ships. Only that it is tricky.

There are different alloys of aluminum with different properties. Just like steel. And of course it's been used in the aviation industry for a long time as well. Car manufacturers are using aluminum castings in cars these days. And there are engine blocks made out of aluminum as well.

Anyway, this is the ship yard I mentioned. They have a few decades experience making ships out of aluminum: https://en.wikipedia.org/wiki/Incat

As I understand it, the gotcha with aluminum is: there is no such thing as non-fatiguing stress — whereas, say, steels, have a range of elasticity where it can operate and not lose strength (or get cold-work hardened).

With aluminum, any flexion — no matter how little — marginally reduces the strength of the material. Ergo, even under ideal conditions it's saddled with a limited service life.

You just design it so the stress in the material gives a very long fatigue life (as in, how many zeros do you want?). It doesn't have a defined "fatigue limit", but it may as well have.

I don't understand how an aluminum structure can withstand the stresses in bulk-oriented ships without fatiguing to destruction in the first rough weather.

You make it thick enough so the material isn't stressed. This does require rigorous engineering processes, but it's pretty common.

At this risk envelope I don’t see why nuclear / battery hybrids are not a serious contender. We can for example have them work on purely electric mode when close to ports and then enable the reactor in the open sea.

We do something similar with bunker fuel of different grades. They are forced to use the good stuff near the ports and once in the open sea they start burning the muddy Godzilla.

That linkedin post seems AI generated, got a better source?

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