[HPsquared]

What does the term "current-to-ammonia efficiency" mean here? I imagine it would refer to the specificity of the reaction, i.e. that 99% of the electrons passing through the system are used in the main reaction, and <1% on side reactions.

The abstract doesn't go into detail on energy efficiency and a comparison to the old method using gas. For instance, would this method result in less CO2 emissions using regular grid electricity, or would it need to be 100% low-carbon electricity? If, say, the electricity came from a CCGT plant, how would that compare? Etc etc

[cranky908canuck]

>> ... would this method result in less CO2 emissions using regular grid >> electricity, or would it need to be 100% low-carbon electricity? ...

Who cares? This is about electricity to ammonia.

Given: a very efficient way to make ammonia (as an energy store) using electricity, this becomes a storage mechanism. So then, make ammonia and money whenever the grid is in a 'pay to take power' state, and (up to a point) even if you have to pay. End source is irrelevant.

Alternate process: run a solar farm, produce ammonia whenever that's cheaper than paying someone to take the power (or curtail), then sell the stored power when prices are high. Or, sell the ammonia directly.

[tgsovlerkhgsel]

My naive interpretation would be "almost 100% of the energy put into the process gets chemically stored in the ammonia".

[adrian_b]

Not 100% of the energy, because even if no current is wasted, the voltage applied to the electrolysis cell is higher than the minimum value that corresponds to 100% energy efficiency.

To know the energy efficiency, besides the current efficiency, which is close to 100%, we need to know how big is the overvoltage needed for electrolysis.

[lambdatronics]

Probably refers to "Coulombic efficiency." Ie, it takes 4 electron transfers to turn 2 H2 + N -> NH4, so that gives you a conversion factor between Coulombs of electrons (1 Amp of current is 1 Coulomb per second) and number of NH4 molecules produced.

Yeah, someone would have to get access to the paper to see if they state the energy efficiency. I assume that b/c they don't mention it, it is abysmal. There's pressure to put good results into the abstract.

[snewman]

Bear in mind that grid electricity is getting cleaner over time. We need to skate to where the puck is going, which is 100% clean electricity. Now is an excellent time to be developing and preparing to scale technologies that work well with clean electricity.

[HPsquared]

Yes - in theory, it's probably pretty efficient. Just would be interesting to see how it compares. We know it has good Coulombic efficiency, but that's only half the picture - at least for energy storage / synfuel applications.