[hn_throwaway_99]

This would be a gigantic breakthrough if true and scalable, correct? Most ammonia production for fertilizer currently uses natural gas, and of clean sources of electricity with such a high yield of ammonia production would have a huge worldwide impact. So is there something I'm missing?

[credit_guy]

The scalable part is going to be difficult though.

This is not all that different from the production of hydrogen. Hydrogen is most economically produced from natural gas nowadays. You can produce it from water, with (just like here) an almost 100% current-to-hydrogen efficiency. But it's still twice as expensive, if not more.

[Superfluidity]

Electrolysis of water is 70–80% efficient (a 20–30% conversion loss) while steam reforming of natural gas has a thermal efficiency between 70 and 85%. https://en.m.wikipedia.org/wiki/Hydrogen_production#:~:text=....

[ororroro]

Current/Faraday efficiency is an entirely different thing. 100% current efficiency means you won't get a buildup of side products or erosion of your electrodes due to stray electrons. In isolation it is not a measure of power efficiency.

[pfdietz]

Not if the energy efficiency were poor, compared to electrolytic hydrogen into a conventional Haber-Bosch process. And remember hydrogen is very storable, so that process could buffer renewable intermittency and keep the H-B plant running continuously. Electrolyzers are getting cheap.

[jillesvangurp]

Actually storing and transporting hydrogen are technical challenges. It takes up a lot of space and hydrogen molecules are so small they leak through a lot of materials. Not impossible but you need a lot of expensive infrastructure to handle it.

Most hydrogen produced today is consumed very close to where it is produced. Also energy storage and fuel type use cases rank very low on Michael Liebreich's hydrogen ladder. That's a nice tool that ranks different uses of hydrogen by their economic feasibility and overhead. Chemically binding it to something else to store it works of course. Ammonia (NH3) is common for this; and in fact the biggest use case for hydrogen. People have speculated about using that as a fuel. It's much easier to store and transport. And of course these chemical transformations also have an energy cost.

[pfdietz]

Actually, storage and transportation are positives for hydrogen. It's easier to transport and store hydrogen than it is to transport and store electricity. Hydrogen can be stored underground in caverns very cheaply (this is a demonstrated technology already in use for buffering hydrogen produced from fossil fuels), compared to the cost of equipment for storing electrical energy. Hydrogen is a viable for seasonal storage of renewable energy, unlike batteries.

The negative for hydrogen is poor round trip efficiency of electricity -> hydrogen -> electricity. But for sufficiently long storage times the lower cost of storage capacity vs. batteries overwhelms that, and hydrogen becomes cheaper for grid storage.

[hiddencost]

If you can start/stop the process easily, it could be a great sink for excess solar capacity.

[lambdatronics]

Probably not just yet. I calculated downthread that the productivity is something like 16x less per unit area than a hydrogen electrolyzer, so that would need to be improved to make it cost-effective probably. Also they don't mention the energy efficiency, only the "current efficiency" so I would assume the energy efficiency is also poor. Sounds like there's much to be done still.