3 ms·

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 passin

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

tgsovlerkhgsel 3y ago
My naive interpretation would be "almost 100% of the energy put into the process gets chemically stored in the ammonia".
- adrian_b 3y ago
  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.
cranky908canuck 3y ago
>> ... 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.
snewman 3y ago
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 3y ago
  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.
lambdatronics 3y ago
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.

tgsovlerkhgsel 3y ago

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

adrian_b 3y ago
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.

cranky908canuck 3y ago

>> ... 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.

snewman 3y ago

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 3y ago
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.

lambdatronics 3y ago

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.