This week's Nova mentioned a battery I had never heard of, completely non-toxic and safe. I looked it up on Wikipedia but they are short on information this time. The best I can glean is a cell of this battery is fully rechargeable and is 1.3 volts. The materials are very very inexpensive and easily acquired. I would like more information on the structure of this battery if I can find it. I googled it and was swamped by people trying to sell solar power.
The best answer I have found at the moment is here
https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cplu.201402238

 

At last! Something useful to do with rust.

 

Who knew? I'm still trying to figure out the electrolyte (water?). I would love to find a schematic of a practical cell including the electrolytes. This would probably make a great science fair project for a kid.

https://www.google.com/search?clien...#fpstate=ive&vld=cid:45df7eef,vid:7Mh3P3G-EqQ

 

The electrolyte appears to be Potassium Hydroxide (KOH). In order to have OH radicals available there has to be a solvent, usually water that, allows the potassium and the OH radicals to exist as charged ions. This might be a moist paste as opposed to a solution. Thereafter the reactions proceed as determined by the standard oxidation reduction processes.

ETA: This is from the wiki on Potassium Hydroxide:

Aqueous potassium hydroxide is employed as the electrolyte in alkaline batteries based on nickel-cadmium, nickel-hydrogen, and manganese dioxide-zinc. Potassium hydroxide is preferred over sodium hydroxide because its solutions are more conductive.[18] The nickel–metal hydride batteries in the Toyota Prius use a mixture of potassium hydroxide and sodium hydroxide.[19] Nickel–iron batteries also use potassium hydroxide electrolyte.​

 

So one of the electrodes is iron, what would be a good material for the other electrode? Carbon?

 

So one of the electrodes is iron, what would be a good material for the other electrode? Carbon?

I get the impression that the other electrode is the air, which mostly consists of nitrogen, oxygen, and trace amounts of other gasses at standard temperature and pressure (273.15 °K, 100 kPa).

 

In order to understand the reactions in a battery the following article may be helpful:
https://www.thoughtco.com/oxidation...,need not be present in an oxidation reaction.

 

Couple of papers that might shed more light on it...

https://pubs.rsc.org/en/content/articlehtml/2012/ra/c2ra21992a

 

Thank you I studied that schematic quite carefully, but I cannot see a way around a liquid electrolyte. In some ways it is similar to a lead acid battery where do you start off with two blank plates of lead in the sulfuric acid. When electric charge is applied one of the plate takes on some sulfide ions and becomes a battery. In this you start off with two iron plates and when a charge is applied the O2 in the electrolyte plates one of the iron plates and it becomes a battery since air is not a conductor or transporter of ions I'm wondering if potassium chloride with oxygen in it would do the trick? Going back to the kids science fair project approach two steel plates in a conductive liquid solution potassium hydroxide and possibly a fish tank bowl bubbler hooked up to a power supply would charge the cell to the 1.3 volts amps unknown. Think this might work?

 

I agree, iron-air is a bit of a misnomer; air is an insulator & ions can't move through air - well not at 1.3V! So the O2 'air' needs a liquid transport. I think the idea is that somewhere along the line the O2 comes from the atmosphere. The 'solid' iron-air cell in that first link uses the Fe <-> FeO transition with a solid Zirconium Oxide (ZrO) 'electrolyte', but that phase transition, to achieve 1.3v, requires an 800degC environment. My chemical knowledge isn't good enough to assess your idea, other than Potassium is a metal, like Zirconium, but is it too reactive to release the O2 to allow the process to work at room temperature or near to it.

 

https://www.msn.com/en-us/news/tech...r&cvid=69b1c61611554c18a70a6c924f36ca0d&ei=14

 

That seems like a massive oversimplification. The reason that rust destroys iron is that the crystal lattice constant of the oxide is not the same as that of the metal. It can't form a coherent oxide film and so it breaks off. (Imagine trying to add a layer of lego bricks if the stud spacing on the new ones weren't the same as the existing ones)
So the major problem to solve is how to charge and discharge the battery without a layer of iron falling off with every charge/discharge cycle.

 

Steel is cheap, when they are recycled It is both cheap and 100% recoverable.. I would still like to see a science fair type project.

 

https://www.msn.com/en-us/news/tech...r&cvid=69b1c61611554c18a70a6c924f36ca0d&ei=14

The numbers seem a bit suspect, but I don't really know what is realistic.

They say that the number of modules needed for supplying 1 MW is half an acre. But then they talked previously about having a capacity of 300 mW. That would require 150 acres to be complete covered with their battery modules.

Separately, they talk about this same 300 MW installation being able to supply power for 100 hours, compared to just 4 hours for a Li-Ion battery. But that's apples and oranges. If you through enough land and money at an Li-Ion battery bank, you could make it last just as long. The question is how many acres would be required for an Li-Ion battery bank of comparable power and capacity?

And then there's the whole issue that this battery is NOT powering the data center, regardless of what the headline claims. It is storing electrical energy produced by some other means, including the inevitable losses do to converting from electrical to chemical potential energy and back to electrical. The article conveniently ignores the point that Li-Ion technologies have round-trip efficiencies in the 95% range while iron-air batteries can barely break 70%.

One place where their numbers may hold up is the energy density. They say that their modules are roughly shipping-container sized, which would make them about 9 ft tall. If 150 acres were completely covered, with no gaps, with these modules, that would result in an energy density of about 18 Wh/liter. This seems to be in the ballpark of what commercial-scale systems can currently achieve.

It will be interesting to see what the impact of such poor volume efficiency has. A comparable battery bank of lead-acid batteries would only require about 50 acres and Li-Ion batteries would only take up about 3 to 4 acres. One of the big costs for electric utilities is the cost of the land for their power line right-of-ways. So much so that they are willing to eat the inefficiencies associated with rectification and inversion of DC monolines in exchange for the smaller land footprint.

 

Don't forget every one of those modules are excellent platforms for solar cells or wind farms. giving the cells something to charge from other than the grid.

 

Don't forget every one of those modules are excellent platforms for solar cells or wind farms. giving the cells something to charge from other than the grid.

A complete non-factor. Solar fields in typical large-scale projects need about 1.5 acres of land for every 1 MWh/day of electricity they produce. That means that if the entire 150 acres were covered, it would produce about 100 MWh/day. That's not a very significant fraction of the 7200 MWh/day that might be needed (barely over 1%). To produce that much energy, the solar field would need to cover a million acres, which would be a square plot of land about 40 miles on a side. Wind is far worse, needing five to ten times the land for the same production, so now you are talking about a wind farm that is over 100 miles on a side. That's the kind of ridiculous energy demands these data centers have.

 

No-one should be allowed to be a science journalist unless they can prove that they know the difference between power and energy.
Some electric cars have 1000hp motors, so their batteries are getting damn close to producing 1MW.

 

No-one should be allowed to be a science journalist unless they can prove that they know the difference between power and energy.
Some electric cars have 1000hp motors, so their batteries are getting damn close to producing 1MW.

In fairness, this article didn't seem to conflate the two (though certainly lots of articles do). It just completely failed to establish what the Li-Ion battery bank that it was making the comparison to was and why it was a meaningful comparison. Was it being compared to an Li-Ion bank that cost the same as this iron-air bank? That would be a reasonable comparison, but we have idea whether that was the case or not.

 

Still, it would be interesting to see a comparison between lithium and steel air batteries. Is there anywhere close this make a nice alternate for cars? Time will tell,and I don't have the IQ to figure out what is which. I'm pretty sure that the fire risk between the two is pretty significant.

 

Still, it would be interesting to see a comparison between lithium and steel air batteries. Is there anywhere close this make a nice alternate for cars? Time will tell,and I don't have the IQ to figure out what is which.

I'd be surprised if it does.
i) 3.6V per cell instead of 1.3V per cell. Almost needs three times as many cells:
ii) iron is 16 times as dense as lithium
iii) Iron batteries are a surface chemistry effect, so only the surface of the electrode takes part in the reaction. Lithium is an intercalation, so the lithium ions go inside the electrodes. That's effectively a lot more active material.