How iron-air batteries could fill gaps in renewable energy

[Ivan Seeking]

Yes, regular-old iron and air. Humans have known for millennia that when water, oxygen, and iron mix, they create rust. We’ve learned more recently that that reaction also releases energy. Iron-air batteries capture that energy and turn it into electrical current—then recharge by reversing the reaction, “unrusting” the iron and returning it to its metallic form. NASA experimented with rust-based batteries in the 1960s, but the resulting units were considered too heavy, slow, and clunky to be good for much. Today, Form Energy hopes they might be exactly what we need to move away from fossil fuels, revitalizing post-industrial communities like Weirton along the way.

How iron-air batteries could fill gaps in renewable energy

Rust Belt cities could be the perfect place to develop this renewable energy solution.

www.pbs.org

This only came to my attention recently and I haven't had time to look at the economics, but that is where I would expect problems - things like energy density vs the cost of land and the taxes.

 

[billvon]

This only came to my attention recently and I haven't had time to look at the economics, but that is where I would expect problems - things like energy density vs the cost of land and the taxes.

The biggest competition for this are LFP batteries - they are becoming dirt cheap. $81 per kwhr last time I checked. That means a battery that could run an average house for a day would cost under $2000.

 

[geordief]

The biggest competition for this are LFP batteries - they are becoming dirt cheap. $81 per kwhr last time I checked. That means a battery that could run an average house for a day would cost under $2000.

That is the same stuff as I use in the garden to kill slugs? (ferric-phosphate pellets)

Any other uses?

 

[billvon]

That is the same stuff as I use in the garden to kill slugs? (ferric-phosphate pellets)

Plus lithium, yes.

 

[TheVat]

I find adding lithium helps keep the slugs from wild mood swings.

 

[exchemist]

How iron-air batteries could fill gaps in renewable energy

Rust Belt cities could be the perfect place to develop this renewable energy solution.

www.pbs.org

This only came to my attention recently and I haven't had time to look at the economics, but that is where I would expect problems - things like energy density vs the cost of land and the taxes.

Just in case anyone is wondering how this works chemically, the two half reactions seem to be:-

At the iron anode (-ve terminal of the battery, releasing electrons into the circuit during discharge): Fe -> Fe²⁺ + 2e⁻

At the air cathode (+ve terminal of the battery, collecting electrons from the circuit during discharge): 1/2O₂ + H₂O + 2e⁻ -> 2 OH⁻

the net effect thus being to produce iron(II) hydroxide, Fe(OH)₂ during discharge. (The reverse, reforming metallic iron and releasing oxygen during charging.)

From what I read there are various challenges. One is that the hydroxide is alkaline. Alkaline solutions tend to absorb CO2 from the air and convert it to carbonate: 2OH⁻ +CO₂ -> CO₃²⁻ +H₂O. (You may remember at school bubbling your breath into limewater, whereupon it goes milky as carbonate is formed.) These carbonates tend to be insoluble and gum up the air electrode. Another problem is that the oxygen <-> hydroxide reactions at the air electrode tend have fairly slow kinetics. It is a challenge to find catalysts to accelerate the reaction.

There are high temperature iron/air batteries that get round these issues by use of molten salts but these present other challenges related to their operating temperature. There is also research into solid state iron air batteries, enabling, in theory, operation at ambient temperatures while avoiding the problems of an aqueous electrolyte.

So there is a lot going on but evidently a number of problems to be overcome.

More here: https://pubs.rsc.org/en/content/articlehtml/2024/se/d4se01224k

 

[Ken Fabian]

How iron-air batteries could fill gaps in renewable energy

Rust Belt cities could be the perfect place to develop this renewable energy solution.

www.pbs.org

This only came to my attention recently and I haven't had time to look at the economics, but that is where I would expect problems - things like energy density vs the cost of land and the taxes.

Lots of different battery chemistries and variations are being researched - up to 70 different types by one list I saw and new ones and variations keep being added. Lots of that R&D is being led by China now. Cutting back on science is what other nations (like mine, Australia) are doing. Sigh.

Right now LFP is surging ahead and may become (if not already) top of the list - our household batteries are LFP, as is our ride on mower. Going by the claimed 3,000 cycles and expected use the mower battery it will outlast the mower, probably several mowers (60 years to get to 3,000... and 3,000 isn't necessarily end of life, just reduced capacity). I won't last long enough to find out, even optimistically. Which gives is cause for optimism for future generations amidst the pessimism.

Sodium types are heading into large scale production and others are coming out of the labs, including a 'tofu water' saltwater battery with exceptional life - 120,000 cycles. As always the reality may not come up to the early press releases but very long life is a valuable property, if harder to monetise (but may suit 'socialising', as national infrastructure). Yet even falling short on such a big advance in durability can get us ahead.

Good inventions have been held back by upfront costs. Isn't it that thinking that is starving R&D? And held back decarbonisation across the board?

Ivan, I am not convinced cost of land is a major problem for batteries (nor for solar and wind) and for types with low fire risks they can probably be installed more compactly than the battery farms being built now, despite higher energy density, with less or no spacing, possibly stacked.

Taxes and or subsidies can go either way.

 

[exchemist]

Lots of different battery chemistries and variations are being researched - up to 70 different types by one list I saw and new ones and variations keep being added. Lots of that R&D is being led by China now. Cutting back on science is what other nations (like mine, Australia) are doing. Sigh.

Right now LFP is surging ahead and may become (if not already) top of the list - our household batteries are LFP, as is our ride on mower. Going by the claimed 3,000 cycles and expected use the mower battery it will outlast the mower, probably several mowers (60 years to get to 3,000... and 3,000 isn't necessarily end of life, just reduced capacity). I won't last long enough to find out, even optimistically. Which gives is cause for optimism for future generations amidst the pessimism.

Sodium types are heading into large scale production and others are coming out of the labs, including a 'tofu water' saltwater battery with exceptional life - 120,000 cycles. As always the reality may not come up to the early press releases but very long life is a valuable property, if harder to monetise (but may suit 'socialising', as national infrastructure). Yet even falling short on such a big advance in durability can get us ahead.

Good inventions have been held back by upfront costs. Isn't it that thinking that is starving R&D? And held back decarbonisation across the board?

Ivan, I am not convinced cost of land is a major problem for batteries (nor for solar and wind) and for types with low fire risks they can probably be installed more compactly than the battery farms being built now, despite higher energy density, with less or no spacing, possibly stacked.

Taxes and or subsidies can go either way.

It feels to me as if safety (fire risk) may become a big determinant of battery technologies. The fire brigades seem to have quite a bit of trouble putting battery fires with the Ni/Co system.

 

[billvon]

It feels to me as if safety (fire risk) may become a big determinant of battery technologies. The fire brigades seem to have quite a bit of trouble putting battery fires with the Ni/Co system.

Yep. NCA and NMC chemistries are somewhat fire prone, and are going away for stationary storage. Even in cars, LFPs are replacing NMC. Most Teslas built are LFP now, for example.

NMC will still have a home for a while for the ultra long range (400-600 mile) cars, but as LFP improves, it will take more and more of the market.

 

[Ken Fabian]

It feels to me as if safety (fire risk) may become a big determinant of battery technologies. The fire brigades seem to have quite a bit of trouble putting battery fires with the Ni/Co system.

Less flammable types will help but the high power applications relying on NMC are probably going to rely on battery management systems and safety standards rather than change battery type. Unless better options emerge - which is very possible too.

It seems the largest - or most prevalent - fire problem is with small batteries, their chargers and their incorrect disposal. A large part of that is how common their use; our relatively frugal 2 person household has a score or more devices and tools with batteries, often with inbuilt chargers. (Lots of USB powered). A few more seem to find their way into our home or garage. Especially problematic when they come from dodgy suppliers who aren't abiding by industry standards.

Small batteries are starting fires in household waste trucks, recycling centres and landfill, whereas large batteries have siting and safety requirements that are harder to circumvent.

Most larger batteries come from reputable manufacturers who intend staying around and don't want the legal liabilities. Their installation is regulated, eg our home solar battery has rules about placement, battery management systems, disposal. And wiring. (And wiring is a significant source of fire risk).

Grid batteries are even more regulated; the spacing we see seems primarily about preventing fires spreading between the containers. The toxicity from battery container fires appears similar to house fires. Only very foolish car dismantlers would put EV's into crushers - and the batteries are going to be worth money. Any battery dismantlers/reusers will need regulating. Whilst nations with entrenched corruption may get high levels of improper disposal it isn't so easy around here. But corruption, like absence of industry standards and regulation, has so, so many downsides, making every problem harder and the consequences worse.

I note that a recent Australian government scheme to subsidise home batteries saw more takeup than expected; fire risk may put some off but most people seem confident in installing them. Those susceptible to alarmist fear of renewable energy and batteries are going to miss real opportunities.

 

[billvon]

It seems the largest - or most prevalent - fire problem is with small batteries, their chargers and their incorrect disposal.

Definitely. The #1 source of fires around here is bike batteries, and they are almost always Chinese knockoffs of mainstream batteries. Locally knockoffs of Rad power bike batteries are a particular problem. They just went bankrupt due to tariffs, so replacement batteries aren't really available from Rad any more.

the batteries are going to be worth money.

Definitely. Around here a used Tesla battery goes from $2000-$5000, definitely worth their time to separate out and store.

 

[TheVat]

We got fed up with the shoddy NiMH battery in our electric mower and went back to a corded mower with a 75' extension cord. Wrangling the cord while mowing is a nuisance but less nuisance (and far less expense) than batteries. And most cordless mowers still lack the power of corded ones, which is starkly demonstrated when the grass gets long and is a bit damp. If I ever go back to cordless, it will be LIP (or LFP, the abbrev seems to depend on the brand). I suspect they just stopped selling the NiMH machines, due to their driving away customers. (they also can't handle any deep cycling - and on lower-end mowers the warning light that was supposed to warn you to swap out your battery would often fail so you would keep running it to zero and ruin it fast)

 

[geordief]

We got fed up with the shoddy NiMH battery in our electric mower and went back to a corded mower with a 75' extension cord. Wrangling the cord while mowing is a nuisance but less nuisance (and far less expense) than batteries. And most cordless mowers still lack the power of corded ones, which is starkly demonstrated when the grass gets long and is a bit damp. If I ever go back to cordless, it will be LIP (or LFP, the abbrev seems to depend on the brand). I suspect they just stopped selling the NiMH machines, due to their driving away customers. (they also can't handle any deep cycling - and on lower-end mowers the warning light that was supposed to warn you to swap out your battery would often fail so you would keep running it to zero and ruin it fast)

Corded mowers can be dangerous.Someone once I met had been mowing in barefoot in wet grass when the plug pulled out of the mower (I always assumed from his story that the plug was at the mower end but maybe the cord just frayed and snapped)

Anyway ,it landed live into his open hand which involuntarily closed tight on it so that he had to pull it away from his fist using his other hand( the effort last a long ,presumably excruciating time)

That was around 50 years ago...

 

[TheVat]

Corded mowers can be dangerous.Someone once I met had been mowing in barefoot in wet grass when the plug pulled out of the mower (I always assumed from his story that the plug was at the mower end but maybe the cord just frayed and snapped)

Anyway ,it landed live into his open hand which involuntarily closed tight on it so that he had to pull it away from his fist using his other hand( the effort last a long ,presumably excruciating time)

That was around 50 years ago...

Ours has a cord clamper so that detachment is unlikely, probably a safety feature added due to incidents like that. And my ext cord has a GFCI. I wouldn't mow barefoot with any sort of mower - that part sounds a little crazy. Some of my caution with mowers is from when I was a youth, there was a news story of a local fellow who was mowing and the mower propelled a 16d nail through his eye and into his brain (I don't recall how the blade cowling didn't stop the nail - possibly he had the grass catcher off and was stooping down beside the mower to pick something up). Amazingly, to me, was that some eminent neurosurgeon was able to extract the nail, leave the eye partly functional, and his brain fairly intact.

 

[Sarkus]

On a similar vein (please do get it moved if not appropriate here):

Anyone keeping track of the Donut Labs solid-state battery tests that have been going on for a while? They've been drip-feeding the results of testing after making some quite bullish specifications, the most notable being that it didn't contain Lithium, and that it had a density of 400 wh/kg... which would put it c.30-40% better than those typically used in the EV market at the moment. It's also supposed to have much faster charging than normal, and 100,000 cycle life.

A (supposedly independent) company has done a number of tests on 3 cells, and the results are promising. One cell showed fast charging capability, another was heated to 100-C and, while this was higher than the vacuum pack seals, the battery later could be charged reliably to c.40-50% - which isn't itself great, but the fact that it still operated at all after going well beyond normal safety tests was a big plus. No news on energy density, though. Battery chemistry is also just a matter of abduction rather than any confirmations, as noone has yet been allowed to take one apart to test. Initially, despite saying that there was no lithium it was thought to resemble lithium in (iirc) it's voltage profile, but consensus in on some form of sodium-ion.

However, as with all things that look too good to be true, we're coming up to 1st April, so this may all just be a deliberate marketing ploy for funds, and ultimately a scam.
But, well, it's quite an elaborate scam if it is one. And if it is as good, or even relatively close, to what they've stated, it will be a significant improvement on current EV tech, at least for the likes of vehicles.

 

[geordief]

Ours has a cord clamper so that detachment is unlikely, probably a safety feature added due to incidents like that. And my ext cord has a GFCI. I wouldn't mow barefoot with any sort of mower - that part sounds a little crazy. Some of my caution with mowers is from when I was a youth, there was a news story of a local fellow who was mowing and the mower propelled a 16d nail through his eye and into his brain (I don't recall how the blade cowling didn't stop the nail - possibly he had the grass catcher off and was stooping down beside the mower to pick something up). Amazingly, to me, was that some eminent neurosurgeon was able to extract the nail, leave the eye partly functional, and his brain fairly intact.

Just recently I was working on the mower (the carb, basically) and with the engine running and the blades spinning I got down on all fours to see which cable was which.

My hand was level with the cowling but obviously too close as I felt something strike my finger and numbing it.

Just the very lightest "ear of the emperor " contact but it did lift one side of the nail off its bed with a little bleeding.

It is the confidence that is a killer(not in this case .I was just really lucky.)

As per your story I will be sure to clear the lawn of any metallic-or hard debris before working now.

 

[billvon]

the most notable being that it didn't contain Lithium, and that it had a density of 400 wh/kg.

I have at this point tested four such wonder batteries (to evaluate them for mobile device work) and none of them panned out. The most promising was lithium sulfur. They worked, but lasted only 20 cycles before they became unsafe. We talked to the company that provided them and they said "huh, they shoud have lasted at least 50." (They were touting up to 500 cycles, which is marginally useful for a cellphone.)

A battery that is amazing in 12 ways but has a minor problem with that 13th is generally useless. I am at the "I'll believe it when I see it" phase now.

 

[billvon]

We got fed up with the shoddy NiMH battery in our electric mower and went back to a corded mower with a 75' extension cord.

I've been converting various things (like older tools and ebikes) to use cordless tool batteries. I use the DeWalt line and they work well. It's likely you could retrofit your mower a similar way.

 

[exchemist]

On a similar vein (please do get it moved if not appropriate here):

Anyone keeping track of the Donut Labs solid-state battery tests that have been going on for a while? They've been drip-feeding the results of testing after making some quite bullish specifications, the most notable being that it didn't contain Lithium, and that it had a density of 400 wh/kg... which would put it c.30-40% better than those typically used in the EV market at the moment. It's also supposed to have much faster charging than normal, and 100,000 cycle life.

A (supposedly independent) company has done a number of tests on 3 cells, and the results are promising. One cell showed fast charging capability, another was heated to 100-C and, while this was higher than the vacuum pack seals, the battery later could be charged reliably to c.40-50% - which isn't itself great, but the fact that it still operated at all after going well beyond normal safety tests was a big plus. No news on energy density, though. Battery chemistry is also just a matter of abduction rather than any confirmations, as noone has yet been allowed to take one apart to test. Initially, despite saying that there was no lithium it was thought to resemble lithium in (iirc) it's voltage profile, but consensus in on some form of sodium-ion.

However, as with all things that look too good to be true, we're coming up to 1st April, so this may all just be a deliberate marketing ploy for funds, and ultimately a scam.
But, well, it's quite an elaborate scam if it is one. And if it is as good, or even relatively close, to what they've stated, it will be a significant improvement on current EV tech, at least for the likes of vehicles.

Drip-feeding results sounds scammy to me. If the technology is genuinely new, I’d have thought they would have patented it and then they could say what the technology was. In any case, once it is commercially released people can dismantle one and find out.

I read about a sodium battery using Prussian White, with a large ferrocyanide anion that formed an open structure big enough to accept Na ions reversibly. That was a couple of years ago. Avoiding dependence on lithium deposits and refining would be geopolitically very helpful. I don’t know about its inflammability.

 

[TheVat]

Cycle life is a

I've been converting various things (like older tools and ebikes) to use cordless tool batteries. I use the DeWalt line and they work well. It's likely you could retrofit your mower a similar way.

Sounds tricky. Bypass the bridge rectifier, then put some tool batts in series until I get 40-odd VDC? A couple nominal 18 V batteries might do it.