From article:

" Currently, ammonia is synthesized through the Haber–Bosch process by converting hydrogen and nitrogen into ammonia. In this process, hydrogen is mainly produced via steam methane reforming. This fact makes the process of fossil-fuel-based ammonia synthesis very carbon dioxide intensive, accounting for ≈1% of the global carbon dioxide emissions.[11, 16] Yet more sustainable ammonia synthesis pathways are under development to mitigate carbon dioxide emissions in the ammonia industry.[11, 16] For instance, the electrically driven hybrid Haber–Bosch process (via replacing the steam methane reforming by water electrolysis to obtain green hydrogen and coupling with an ammonia synthesis reactor in the Haber–Bosch process) or direct electrosynthesis using renewable energy (via nitrogen reduction reaction) enables the production of green ammonia.[11, 16] "

Not sure how that is kicking the can.

I work at a company that is creating better electrolyzers for this process. Ammonia producers are clamoring for this technology. It works, and it is happening!

Could ammonia be used for stable seasonal storage of energy?

The abstract suggests that ammonia is much nicer to transport and store than hydrogen. If we can use it to store summer solar to run winter heat-pumps with a low roundtrip efficiency but even lower costs per kWH of capacity it could really help.

It could work theoretically. The only question is if it is economical to do so. And the answer to that is probably not. It ranks pretty low on the list of possible solutions in terms of cost and efficiencies.

Hydrogen and ammonia (you typically generate one to generate the other) are interesting as a fuel in some use cases (anywhere the weight of lithium ion batteries is a problem basically). Main use cases seem to be shipping, and maybe long haul aviation. Probably not for road transport (battery electric seems adequate there for most vehicle categories).

But as a battery/energy storage solution it makes less sense. The round trip from solar/wind energy to hydrogen to ammonia and back to electricity loses most of the energy in the process. It's doable but there are probably more efficient and cheaper ways to store the energy. You lose about half (at least, that's a super optimistic percentage) of the energy creating the hydrogen. Then some more creating the ammonia. And then some more converting that back to electricity. It's pretty easy to waste less energy than that.

For heat, simple thermal mass is very efficient, low tech, and has already been demonstrated to work for seasonal storage. Throwing away half the energy to create ammonia simply makes no sense. All you need for thermal mass is some basalt, sand, etc. with a lot of mass, a container to put it in, and some cheap way to insulate it (wool would do the job). Heat it up in the summer, extract heat in the winter. It scales. The raw materials are dirt cheap (because they are literally dirt), the complexity is low (pipes, plumbing, insulators, sand/rock).

That's not quite correct.

Long term storage solutions are dominated by capital cost. You can use batteries to store electricity from day to night because you recoup part of your capital investment every day for ten years or so. But if you can only sell electricity once a year, then whatever profit you make it better be good, because you only get that 10 times in 10 years. The alternative is to have dirt cheap capital cost.

Pumped storage works where the lake and dam already exist, because the capital storage is essentially zero.

Everywhere else, nothing works. Batteries don't work, chemical storage (like ammonia or hydrogen) doesn't, compressed air, or molten salt, nothing works.

What will work is a way to "cheat". If you can mimic the day-night cycle of batteries and make a profit every day, you win. The way to do that is by long-distance transportation: you make ammonia in Australia, or Morocco, or Saudi Arabia and sell it in Japan, China or Europe. You may incur round trip losses of 80% or more, but if the price you pay for one kwh is one cent, and you sell for 10 cents, you can still make a profit.

Ammonia can indeed be used as a longish term energy storage. It's not as great as methane (that can be pumped into underground caverns), but it liquefies at room temperature at just around 9 atmospheres or at -33C at atmospheric pressure.

Though it's pretty poisonous if it leaks.

It's corrosive to humans, toxic to aquatic life, but once you dilute it, humans survive easily.

The dangers are in confined spaces.

it's caustic if it leaks, but in the environment it quickly reacts to produce nontoxic products

same :-)

This is not just for green steel, it's largely used for fertilizer and some other industrial purposes. Making it green is going to be big business!

Haber-Bosch seems to be only feasible at large scale. It would be great to make this scale down and be more efficient.

It's the secret to a whole lot of ways to combat rising carbon.

What's interesting is that H2 + N2 -> NH3 reaction is thermodynamically favorable, so in theory with a good enough catalyst it can be driven at mild conditions.

And this has actually been achieved back in early 2000-s! But the catalysts are very finicky and they get poisoned too quickly for industrial use. Additionally, it'd be nice to be able to use water instead of hydrogen directly.

There are some interesting developments in this area, like this one: https://www.nature.com/articles/s41467-022-34984-1 - they synthesized ammonia using visible light as an energy source.

And yet the creation of hydrogen through electrolysis of water is both well understood and potentially green if solar and wind electricity is used for electrolysis. This would also bypass either the capital intensive requirement to moderate solar and wind electricity with battery energy storage and/or the losses in transmitting solar and wind electricity over the grid.