[Barraketh]

Ammonia has been mentioned a few times in this thread, but I will expand a bit, because I believe it is the most promising hydrogen-based approach. Essentially, the idea is to use ammonia directly as fuel. There is an ARPA-E funded project (that I'm currently failing to find) that cracks ammonia into hydrogen and nitrogen using heat. They claim that they can create a mixture of H2 and ammonia that will burn at any required flame temperature (H2 burns too fast / hot for existing turbines, ammonia too slow, so a mixture is the right way to go). Theoretically, with this process, you could use ammonia as a drop-in replacement for LNG. The LNG infrastructure can also be converted to carry ammonia instead.

Now, there are still obvious energy losses from creating and then burning ammonia. One thing that this technology could be very helpful with is overcoming the NIMBY-ism around nuclear power - that is, build nuclear reactors to produce ammonia, then ship the ammonia to where it will be used. It would obviously be more efficient to just run power lines from nuclear power plants, but given the wide-spread opposition, it could be politically easier to build the nuclear plants in the middle of nowhere.

[perihelions]

The downside is that ammonia is a heavier-than-air poison, like chemical weapons from WW1. Its hazards are significant.

- "Anhydrous ammonia is lighter than air and will therefore rise (will not settle in low-lying areas); however, vapors from liquefied gas are initially heavier than air and may spread along the ground."

https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=7&toxid=2

[ncmncm]

We already synthesize and handle industrially millions of tons of it annually, and have done for going on a century. If there were a worrying problem with ammonia, you would already be hearing about it.

[pixl97]

Heh, this is how I know you didn't grow up on a farm. You ever see a leaking anhydrous tank and you run for your life.

[ncmncm]

My father reports feeding raw ammonia directly into furrows being cut.

Yes, a leaky ammonia tank would be a problem, but it is not exactly odorless.

[jacquesm]

By the time you can smell it from a leaking tank depending on the speed of the spill you may already be inviting lung damage, if it overwhelms you you're as good as dead. With some regularity farmers here are overcome by ammonia that has pooled in manure storage pools.

This article starts up with 'three dead per year through fertilizer vapors, one breath and you are gone'.

https://www.rtlnieuws.nl/nieuws/nederland/artikel/5022231/no...

[ncmncm]

Three from a population of how many? Compared to how many in some other possible world?

As long as people are being killed in numbers many orders of magnitude greater, just so sugar sellers will have good quarterly profits, it will be hard to count those.

[perihelions]

- "If there were a worrying problem with ammonia, you would already be hearing about it."

We hear about it pretty regularly,

https://www.google.com/search?q=ammonia+spill+site%3Areddit....

Fortunately the main use of anhydrous ammonia (agriculture) is in sparsely populated places, so its impact is limited. I think it's a questionable idea to put it in urban vehicles though.

[ncmncm]

Ammonia will not be used in urban vehicles.

It will be used in farm equipment, and in place of bunker oil in ships, and burned in combined-cycle turbines in times when wind and sun are not providing, and other, cheaper storage has been used up.

[Jistern]

Ammonia seems too dangerous. With cheap electricity from solar and wind, cheap hydrogen seems like a better answer. Sure, it's not a perfect answer, but it seems better because it seems much safer.

As recently as approximately 200 years ago steel was very expensive, as was aluminum. Now both of those materials are cheap and used in a plethora of applications.

Cheap electricity will similarly enable us to cost-effectively do many things that heretofore were prohibitively expensive.

The whole, "Hydrogen is bulky and difficult to store" canard of an argument doesn't sway me... at all. Hydrogen storage could certainly be improved, but even if it never were, for long distance shipping and air travel it's good enough as it is.

"But, but, but... you'd need to build ships and planes 50% larger!!!" Sure. Ok. Yes. The world is not running out of steel.

And, of course, if ships and planes were running on hydrogen instead of gasoline and diesel, a huge amount of research would go into improving hydrogen storage.

The Ford Nucleon (a nuclear-powered concept car) never made it into production, yet we do have nuclear submarines. Choosing the correct fuel for a given application is important.

[ncmncm]

You will see a very great deal of anhydrous ammonia stored, transported, and used, but will not be asked to handle it yourself. Shipmakers are already gearing up to retrofit ships with ammonia tanks, to burn in existing engines. Probably important ports will start to forbid docking of bunker-oil craft.

You probably will not have much contact with hydrogen, either.

[ncmncm]

A safety argument does not favor consumer-level use of hydrogen. Nor, of ammonia.

But synthetic liquified hydrogen, produced at airports from power delivered on transmission lines at times when power is cheapest, and banked, will certainly come to drive aircraft where cost matters.

[beanjuice]

To add on to this comment for anyone curious about ammonia: Green ammonia production is among the top 10 emerging technologies in chemistry in 2021 [1,2]. The Haber-Bosch process consumes 1% of the worlds global energy, and generates 1.4% of the worlds carbon dioxide [3].

That being said there is a lot of research both to generate ammonia from green energy, and the work to harvest ammonia for use as a fuel cell would benefit as a secondary emergent technology.

[1] https://iupac.org/what-we-do/top-ten/ [2] https://www.degruyter.com/document/doi/10.1515/ci-2021-0404/... [3] https://www.nature.com/articles/s41929-019-0414-4

[japanuspus]

Just wanted to add some basic chemistry information as background

Hydrogen (H) can be split from water (H2O) with a by-product of Oxygen (O). Hydrogen is hard to handle logistically (as discussed elsewhere in the thread), and the real idea in "Power to X" is to include Hydrogen in another molecule with better logistics. Main contenders are Ethanol (C2H5OH, alcohol), Methane (CH4, ~natural gas), and Ammonia (NH3).

Ethanol and Methane are by far the nicest products: already used as energy carriers, easy to handle, relatively non-toxic, but they have one problem: They require Carbon (C) to manufacture in addition to Hydrogen. Even with increased atmospheric CO2 levels, CO2 concentration in the atmosphere is only on the order of 400 ppm and extraction is expensive.

Ammonia (NH3) is synthesized directly from Hydrogen and Nitrogen (N) which is makes up 70% of the atmosphere. The Haber-Bosch process used for this synthesis is a cornerpiece of industrial chemistry.

[p_l]

Interestingly enough, at least in USA the proposed automotive hydrogen solution is one that reduces logistical problems by placing electrolysis equipment at filling stations - then you have reduced transport to just on-site piping and storage tank, and it makes sense to colocate charging of electric cars with hydrogen ones, as well as use demand-response for the stations (providing extra load balancing for the energy grid, which benefits renewables and nuclear alike)

[scythe]

The problem with any fuel containing H2 in any existing engine is hydrogen embrittlement. Hydrogen is a reactive gas that attacks steel.

Ammonia fuel cells have a comparable weight proposition to hydrogen at small sizes because the tank is so much lighter. I think that has legs (or wheels?). For stationary storage, the ammonia-CO2 adduct is a solid, which is nice.

[ncmncm]

Hydrogen embrittlement is always hyped to the sky.

It is not a serious problem unless you are trying to keep warm, gaseous hydrogen under high pressure. So, don't. Furthermore, aluminum is quite resistant to embrittlement.

Of possibly greater moment is that it leaks, and has ~200x GHG over CO2 (including secondary effects). Leaks are not dangerous in the open, or in confined places with positive airflow, but punishment for neglect is visited on all bystanders. LN2 storage is better, where you can afford the insulation and refrigeration.

[shawndrost]

I think this is incorrect; I have seen GWP20 numbers like 38, eg here[1], or lower numbers for GWP100. Do you have a citation?

[1] https://www.greenbiz.com/article/inside-misconception-hydrog...

[tuatoru]

> Of possibly greater moment is that it leaks

It leaks very readily, it ignites very readily, it burns with a wide range of air:fuel proportions, it burns with a high flame speed, and it burns hot.

Hydrogen is ... not a good choice for something to reticulate widely around the world.

Edit: That's leaving aside its low energy density. You need three times the volume of hydrogen as natural gas for the same quantity of heat, so existing pipe networks are unlikely to be useful.

Global warming potential is off to the side of all this.

[ncmncm]

Yet, millions of tons of hydrogen are today produced, transported and used.

There is nothing special about the volumetric energy density of NG. H2 has to move faster, if carried in the same pipe for the same use. Its lower viscosity means it can.

Municipal gas networks used to carry "lamp gas", a mix of CO and H2, in cast-iron pipes.

[katmannthree]

> trying to keep warm, gaseous hydrogen under high pressure

Which of course nobody would do? Unfortunately, those are the circumstances in which H2 is made from fossil fuels and likewise the circumstances under which it is combusted in turbines. You can't just handwave materials compatibility away.

[ncmncm]

Keyword is "keep". Hydrogen will not be penetrating and weakening turbine blades.

[katmannthree]

The turbine blades are downstream of the combustion chamber so they handle combustion products not hydrogen-rich gas. The turbine combustion chambers, fuel handling system, and high pressure H2 compressors[0] _do_ have to function in a high pressure high temperature H2-rich environment.

0: Take a guess as to what those look like inside.

[ClumsyPilot]

From what I read, the efficiency of ammonia production is like 16%, which is well below hydrogen at like 40% or whatever. Even with cheap renewables that is terrible amount of losses even before you get to use the fuel.

[avmich]

Let me quote Clark, from Ignition! https://library.sciencemadness.org/library/books/ignition.pd...

> the nature of the chemical industry being what it was, and is, one could be confident that it would come down to a reasonable figure when anybody wanted it in quantity.

[xyzzyz]

We do want and produce ammonia in immense quantities already, so no, it’s not reasonable to bet on cost going down significantly.

[ZeroGravitas]

We produce it in immense quantity from fossil fuels and vent the fossil CO2 into the atmosphere.

The price of which is forecast to go up.

Green Ammonia is made from renewable energy, which is forecast to become cheaper.

It also requires electrolysers which are ramping up production and are also predicted to fall in price as they get made at scale from cheaper components.

So it's a fairly safe bet even if you don't believe all the published academic papers that go through the working in great detail, or the business cases that predict a multi-Billion dollar market for it.

[ClumsyPilot]

Ammonia production is already in billions of dollars, we produce 191 million tonnes

What is the basis in physics for your belief that ammonia can be produced more efficieblntly, and why was it not done already?

[ZeroGravitas]

Because it piggybacks on the political might of fossil fuel producers who are subsidized by taxpayers and don't have to pay for their externalities.

It's not "cheaper" for a mob connected waste disposal firm to dump waste into a river. If they were prosecuted for the damage they did to other people's property and had to pay for the damage they did then they'd need to raise their prices to the point that just dealing with it properly would be cheaper.

In physics terms:

Dig up hydrogen connected to carbon. Separate the hydrogen from the carbon. Release the fossil carbon into the atmosphere as CO2. Capture the same amount of CO2 from the atmosphere. Seperate it from oxygen, store the carbon. Use hydrogen to make Ammonia.

Versus

Use electricity to split water into hydrogen and oxygen. Use hydrogen to make Ammonia.

[rstuart4133]

Are you referring to this: https://www.csiro.au/en/research/environmental-impacts/fuels... ?

[ncmncm]

Diverting money from building out renewables to building nukes, for whatever purpose, brings climate catastrophe nearer.

If ever there was a process forgiving of intermittently available energy, it is chemical synthesis. The same money spent on wind and solar would produce a lot more ammonia.

Conversion losses don't matter much when marginal cost of generation is near zero, as we get with renewables, but very much not, with nukes. You just build out more panels.

[rini17]

Technically it may be forgiving, but not economically. Imagine electrolyzer or ammonia plant that uses only 20% of full capacity on average because of using only peak electricity surplus. The rest 80% is basically wasted. Classical plant with higher capacity factor might still be more profitable even if it uses more expensive electricity.

[ZeroGravitas]

Any electricity demand that can be modulated is good for renewables.

Big plants have been doing this for decades, even before renewables were a thing. The new thing is computers making it cheaply automatable and networked so that e.g. a fleet of cars can organise their charging schedule via the internet.

But rising electricity demand isn't a problem for renewables and climate change, it is in fact a required and desirable part of a virtuous cycle.

So build the Green Ammonia plant and build the renewables to power it 100% of the time but have the option to turn your electrolysers down and sell a small percentage of that to the grid when market prices let you profit from that. It's a win-win-win, less gas peakers, more green electricity and green hydrogen.

[ncmncm]

There is nowhere that you would operate at only 20% utilization.

Demand for ammonia will be so strong that, after enough renewable overcapacity is built out, you would run electrolysers off your other storage, 24/7.

A nuke would, of course, produce exactly zero grams of ammonia for ten years. It would also require burning coal for those ten years. Ten years of coal is part of the cost never accounted for, like the public indemnification subsidy, and cost of decommissioning.

Starting after the ten years, the nuke would produce a fraction of the ammonia, per dollar, that the renewables would have, because operating cost of nukes is quite high, against zero for renewables.

[rini17]

(*) storage cost neglected