How is it that rust is turned back to unoxidized Iron? They say this as if it's some sort of commonplace happening, but as far as I can tell it's not at all. You could always melt the rust particles down into iron again, but that's gong to take a lot of energy and there would be substantial material loss?

It's been done for over 2000 years with iron oxide ores.

Using, amongst other things, charcoal. The carbon combines with the oxygen ...

Right but heat required, requiring energy, requiring the burning of something....

My ellipses was in place of " producing CO2"

The link in the OP refers to an 'electrical process'. Maybe something in here: https://onlinelibrary.wiley.com/doi/10.1002/srin.201900108

Iron. A closed system: You burn iron to get iron to burn iron to get iron to burn iron to get iron. That's its potential, anyway.

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"Time is the wisest counselor of all." - Pericles

"I remain not entirely convinced of it." - Nano

Right I understand, I'm just wondering about efficiencies here

Well, I'm no expert, but my first guess is that the only way to know is to try it and see how the numbers pan out long-term.

What I keep coming back to is that someone has actually gone there. I'd be surprised if a putatively carbon-conscious brewery is only in it for the novelty and nothing more.

_________________
"Time is the wisest counselor of all." - Pericles

"I remain not entirely convinced of it." - Nano

It's not closed. You get energy out when you burn the iron so you have to put at least as much energy in to unburn it. It's a storage system with no CO2 generated in the output phase. The article is describing the easy to understand part but the story is incomplete without telling us about turning rust back into iron (as PB+J says).

No disagreements there. If it's a strictly chemical process, then the system's not closed. But if power is required, then the burning of iron to power the "unburning' of iron sounds like a distinct possibility. Wouldn't that be a closed system?

_________________
"Time is the wisest counselor of all." - Pericles

"I remain not entirely convinced of it." - Nano

Firstly, there is no such thing as a closed system, unless you mean the universe itself. Secondly, this particular one is not closed. From reading about this elsewhere, when the iron powder is first subject to combustion, the product of that combustion is light, heat and rust particles. In order to re-use those rust particles, you need to extract the oxygen. This is done by adding hydrogen and power, to produce, by electrolysis, iron and water. So, in total, you're putting in oxygen and hot gases at the start in order to sustain the combustion process, and you're putting in hydrogen and more power* to recycle the iron. No power is produced in the second phase, although it is in the first phase in the form of light and heat.

Sorry for my slapdash use of various quasi-scientific terms there ...


* I see that they're saying that solar or wind power could be used for this phase but, if that's the case, it rather begs the question as to why they don't just use solar or wind power in the first place. As I understand it, it's because, "due to location or other factors," it is not always possible to use solar or wind power. That leads to the presumption that, in order to recycle the rust particles in an environmentally friendly way, you might have to transport them. Hmmm ...

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I think the idea is along the lines of 'unburning' iron when the wind blows or the sun shines and burning it when needed. The iron being easier to store and handle that hydrogen.

I think Law of Conservation of Energy means you have to burn at least as much iron as you would get back from unburning the rust. No such thing as free beer (or whatever the brewery produces).

If I understamd it right Nano'a proposition is a fiery version of this:

The original linked article mentioned this specifically as an energy-storage option. Remove oxygen from the rust with solar power when the sun is shining, burn the iron back into rust when the sun isn't shining. I've been reading about various methods to do this for at least 30 years. One of the more interesting ones that evidently didn't pan out was pumping water up into high water towers during the day to store mechanical energy, drop the water at night to generate electricity.

_________________
Charlie
Whorfin Woods
One cat short of crazy.

Maybe it's a matter of scale https://en.wikipedia.org/wiki/Dinorwig_Power_Station

A perpetual motion machine? That would be nice, but I'm not so naive as that; I figure no system's going to be perfect. What I am suggesting, on no basis of any expertise, is that my fiery proposition must surely be able to come notably closer to paying for itself than the usual methods.

But this is speculation. I'm happy to be proven wrong, because I value knowledge and facts. But if nobody's tried it yet, somebody ought to ask: Okay, then - why not? Omelettes and eggs, and all that.

_________________
"Time is the wisest counselor of all." - Pericles

"I remain not entirely convinced of it." - Nano

Cool! I'd only heard of it in the context of solar/wind power, but it appears quite widely used.

_________________
Charlie
Whorfin Woods
One cat short of crazy.