Sure you could use renewables to make iron. But that thought process also extends to other methods too. You could use renewables to make other non renewable fuels.
I think this is likely more of an energy storage project, rather than an energy production one (which seems to be the stance the article takes).
At grid-level, battery tech is challenging, requiring technologies like pumped storage that require particular environments (e.g. damming a river) and can't really be transported.
If this works out you could use excess solar during the day to deoxidize the rust produced, and then run the iron reactor overnight, or on cloudy, windless days.
Well, if you can burn it to produce energy + spent fuel
and then put back energy in the spent fuel to make new fuel again
then you have really a battery. That's how li-ion batteries work. The issue is the efficiency: how much of the energy you used to recharge the "battery" (iron) is going to be available when you discharge (burn) it
Non-rechargeable batteries are also consuming a fuel. The products just stay in the same enclosed container. Same with rechargable batteries, just that there the process is easily reversible.
It is a bit of a fuzzy distinction. Batteries are typically simple chemical reactions that cause electrons to move around. But viewed from the outside a hydrogen fuel cell behaves the same; so why not call this one a battery too (especially since the process is reversible).
A useful distinction seems to be that batteries are solid state and don't use high process heat, else something would be seriously wrong. Of course, the underlying reactions are probably very similar if you look at them with a chemist's eye.
Well, it ties into the storage issue that we see with renewable. We still need energy when there is no wind at night. Burning iron at night and regenerating during the day could be a solution.
It needs to prove that it can be competitive with the other methods (compressed air, li-ion batteries, flow batteries, molten salts, flywheels...).
> It needs to prove that it can be competitive with the other methods.
I think the one thing is that iron storage would be a potential long term form of storage, while all those other methods that you mentioned are really short term, designed primarily just to deal with the daily peaks and troughs of renewable production, but not as much the "it's been completely overcast for 3 weeks" problem. The only other form of storage I'm aware of that is also long term like that is pumped water storage, and that is obviously very geographically limited.
If using Fe why not iron batteries? Keep the redox, remove the energy from the system via eletrical current instead of low efficiency heat, boiler and steam engine combo.
Great point. Fe batteries are very new so I'm not aware of the cost/benefit or if Fe batteries still slowly discharge over time, but yeah in both cases you're just oxidizing iron, so why not take the more direct route to generate electrical current directly.
Here’s an out of the box thought. Can we wrap the globe in undersea cables or does transmission losses kill the idea? Reason being that time zones and hemispheres make the “renewable is not always on” problem go away. It’s always on somewhere, so if there was a global grid you don’t really need storage?
They mention that with hydrogen. It's cheaper to produce hydrogen but much harder to transport it. Fortunately, hydrogen can reduce iron oxide, which turns out to be a great complement. Their analysis is that the system cost of burning iron and renewing it at electrolysis plants is lower cost (and safer) than using hydrogen directly.
Because renewables are intermittent and unevenly located. This could potentially solve those problems.
There could be a space for it. Or maybe batteries will just always be better. Depends on the full costs of each and the use case. Burning fuel to make electricity is pretty inefficient, but burning fuel for heat compares better.
At grid-level, battery tech is challenging, requiring technologies like pumped storage that require particular environments (e.g. damming a river) and can't really be transported.
If this works out you could use excess solar during the day to deoxidize the rust produced, and then run the iron reactor overnight, or on cloudy, windless days.