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Iron as an inexpensive storage medium for hydrogen

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Re: Iron as an inexpensive storage medium for hydrogen

#61

Post by msandford »

kimmk wrote: post #53

For seasonal grid-level storage, I wonder if simple compressed hydrogen storage (around 350 bar) is the most reasonable solution. AFAIK doesnt require any high-tech materials, avoids most embrittlement caused by LH2 and boil-off rates are reasonable.

The most efficient seasonal battery is probably synthetic hydrocarbons. By the time you get to propane (3 carbons) the pressures for liquid are super super reasonable (400psi including a giant safety factor) and there's zero embrittlement.

Further is that vehicles can use propane so you don't even have to idle the plants during the winter so long as there's some PV from the southern states. They might be running at 100% capacity in summer and 40% capacity in winter but that's way better than 0%. It's a lot easier to keep people employed to operate the plants if they're needed year round.

Re: Iron as an inexpensive storage medium for hydrogen

#62

Post by kilotaras »

credit_guy wrote: post #56

This is a pretty elegant idea. It takes 826 kJ to split a mole of iron oxide (Fe2O3) and it takes 855 kJ to split 3 moles of water (H2O). So if you take H2 and blow over one mole of Fe2O3 you can strip the O3 for the cost of 826 kJ but then by burning the hydrogen in oxygen you get 855 kJ, for a net exothermic effect of 29 kJ, which is a rounding error. The opposite reaction requires 29 kJ, again negligible, there ar…

27 tons of iron oxide have a volume of 5m^3 and can be stored in pretty much a hole in the ground.

2.7 tons of hydrogen have a volume of almost exactly 30000 m^3, requiring storing it under high pressure in specialized containers. Hydrogen is famous for being hard to store without losses.

For long-term storage storage and losses are a problem.

> But the round-trip efficiency of the tank is virtually 100%. The efficiency of the iron-based storage is only 50%

Maybe I'm missing something, but why? As you mentioned it takes 29kj to restore 3 moles of H2 out of (3 moles of H20 + 1 mole of Fe2O3). Where does 50% comes from?

Re: Iron as an inexpensive storage medium for hydrogen

#63

Post by kilotaras »

kilotaras wrote: post #62
credit_guy wrote: post #56

This is a pretty elegant idea. It takes 826 kJ to split a mole of iron oxide (Fe2O3) and it takes 855 kJ to split 3 moles of water (H2O). So if you take H2 and blow over one mole of Fe2O3 you can strip the O3 for the cost of 826 kJ but then by burning the hydrogen in oxygen you get 855 kJ, for a net exothermic effect of 29 kJ, which is a rounding error. The opposite reaction requires 29 kJ, again negligible, there ar…

27 tons of iron oxide have a volume of 5m^3 and can be stored in pretty much a hole in the ground. 2.7 tons of hydrogen have a volume of almost exactly 30000 m^3, requiring storing it under high pressure in specialized containers. Hydrogen is famous for being hard to store without losses. For long-term storage storage and losses are a problem. > But the round-trip efficiency of the tank is virtually 100%. The efficie…

i.e. the paper[0] states that first "discharging" produced 7.09kg of H2 out of 8.71 theoretically possible

the efficiency is super low, but again, according to the paper, "most of the energy input was due to thermal losses at the reactor surface (83.9%)", which also benefits from square/cube law.

[0] https://pubs.rsc.org/en/content/articlelanding/2024/se/d3se0...

Re: Iron as an inexpensive storage medium for hydrogen

#64

Post by dredmorbius »

We have a cheap, stable, infrastructure-friendly, high-density storage formula for hydrogen. Or better, since the application here isn't hydrogen-specific but is simply looking to find a fuel-storage solution: energy storage.

It's hydrocarbons.

In this case, synfuel hydrocarbons as direct analogues of fossil-fuel based compounds of chain-lengths 1 (methane) to around a dozen or so (kerosene / aviation fuel, at a stretch, diesel fuel).

It stores forever (proved to 300 million years), it is drop-in compatible with extant infrastructure and equipment, it's infinitely miscable with present fuels, it doesn't leak out of storage, it doesn't embrittle metals (and in fact generally lubricates and protects them).

Yes, the round-trip storage efficiencies are low (as low as ~15--20% recovery based on thermal electrical generation, roughly the same as the solution named here), but that's in exchange for something that can readily provide weeks to months of storage capacity in a stable, low-risk form. Where you need storage that's long-term stable, dense, safe, and instantly dispatchable, your options are few.

The technology has been demonstrated in numerous experimental trials, and is similar to processes run at national scale for decades in Germany and South Africa. US-based research has been conducted at Brookhaven National Laboratory, M.I.T., and the US Naval Research Lab, amongst others. The stumbling block to date has been that fossil fuel prices are sufficiently low[1] that synfuels simply are not competitive presuming market-based mechanisms which fail to account for externalities and other market failures.

I've be aware of this for about a decade and have written about the technology, Fischer-Tropsch fuel synthesis, multiple times on HN:

https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...>

________________________________

Notes:

1. A market failure of staggering proportions, as the under-pricing is on the order of a million-fold. See: Jeffrey S. Dukes, "Burning Buried Sunshine", https://core.ac.uk/download/pdf/5212176.pdf> (PDF)

Re: Iron as an inexpensive storage medium for hydrogen

#65

Post by zahlman »

I don't think I understand the idea here properly.

When storing energy, the idea is to split water into hydrogen and oxygen, and then let the hydrogen recombine with the oxygen from iron oxide... to make water again. Meanwhile the oxygen from the original water is just released (since it's everywhere anyway)? That doesn't really seem to me like "storing hydrogen", since you just get the water back that you already had. Rather, it's using the energy to deoxidize rust.

Then on the recovery side, why use this steam process? Apparently (because the thermodynamics work out so that this whole thing has efficiency > 0) you get energy out of the process of putting the oxygen back into the iron. So why not just, well, burn (i.e. rust) the iron directly? What exactly is the dissociation and re-combination of the steam accomplishing?

Re: Iron as an inexpensive storage medium for hydrogen

#66

Post by mglz »

dredmorbius wrote: post #64

We have a cheap, stable, infrastructure-friendly, high-density storage formula for hydrogen. Or better, since the application here isn't hydrogen-specific but is simply looking to find a fuel-storage solution: energy storage. It's hydrocarbons. In this case, synfuel hydrocarbons as direct analogues of fossil-fuel based compounds of chain-lengths 1 (methane) to around a dozen or so (kerosene / aviation fuel, at a stre…

How much incoming solar power ends up in the methane? And how do you get the energy back out?

Re: Iron as an inexpensive storage medium for hydrogen

#67

Post by AtlasBarfed »

kitd wrote: post #22
Temporary_31337 wrote: post #19

production and conversion are inefficient compared to other sources of energy, as up to 60 percent of its energy is lost in the process.

Energy efficiency is only one part of the equation. There are economic and social efficiencies in using simple, eco-friendly components that are easy to build/transport/store/run/scale up. Those can easily offset any energy losses over the lifetime of the technology.

How do all of those factors compare with say the sodium ion or sodium sulfur battery?

Re: Iron as an inexpensive storage medium for hydrogen

#68

Post by A4ET8a8uTh0 »

credit_guy wrote: post #56

This is a pretty elegant idea. It takes 826 kJ to split a mole of iron oxide (Fe2O3) and it takes 855 kJ to split 3 moles of water (H2O). So if you take H2 and blow over one mole of Fe2O3 you can strip the O3 for the cost of 826 kJ but then by burning the hydrogen in oxygen you get 855 kJ, for a net exothermic effect of 29 kJ, which is a rounding error. The opposite reaction requires 29 kJ, again negligible, there ar…

Tbh, I am not sure either. I think the main benefit of this is FeO is inert under temps/conditions humans consider normal so maybe it long term storage is not that far fetched. I like the idea. I am just unsure about its practical applications.

Re: Iron as an inexpensive storage medium for hydrogen

#69

Post by outop »

londons_explore wrote: post #52
outop wrote: post #45

Earlier quoted context omitted.

Isn't it possible that such a system will over-produce 99% of the year and that therefore, the marginal cost will almost always be $0? 'Take my energy and allow me to stop accelerating my flywheels which regulate production' seems more plausible than 'someone would always like more heat for something' (what?) Or possibly 'take my energy and I'll cut off some of the people using spare energy to do low priority, low va…

I think electricity use is far more elastic than you're imagining. Plenty of big users can turn up/down production and already do so based on prices. If wide price swings got more frequent, more stuff would get dynamic. You can imagine home appliances having an 'eco' setting which runs the appliance like the washing or the dishwasher at the cheapest time in the next 12 hours. Or the water heating systems which heat m…

I disagree that this argument makes it less likely to have very low prices much of the time. I think it makes it more likely.

If peak to trough is a large gap, say 60% of peak, this tends to make it less likely that peak will be met by overproduction, since that would involve very large capital costs.

The picture you paint above would suggest a very small gap between peak and trough, say 2% of peak. This means that almost certainly there would be enough over capacity to more than meet peak demand. Therefore the total daily demand would be more than met by capacity, leading to some energy being thrown away. So at all times except the peak, the marginal cost would be zero.

You have given an accurate argument for why demand would be elastic at trough. But you haven't given any reason why overall demand would be very elastic.

Re: Iron as an inexpensive storage medium for hydrogen

#70

Post by AtlasBarfed »

samatman wrote: post #42

When I was a child, we would play a game called "the floor is lava". It's a simple game: you have to get around, but not touch the floor. Jumping on the furniture and such. Fine for a pastime, when you're small, but to get places, you use the floor. A certain faction of the project to decarbonize the electrical grid likes to play a similar childish game: "nuclear power is lava". It causes them to come up with whimsic…

Are you totally ignorant of how much nuclear costs?

Go ahead and look at the lazard lcoe numbers, and this year was an odd increase for solar wind that will basically be the best that nuclear can hope for.

If nuclear could provide a cheap scalable easily approved rapidly deployed safe and low waste reactor that could be price competitive with solar and wind, then they be in the game.

That is not happening without probably 10 to 20 years of research and development with billions of dollars of funding.

Old nuclear was solid rods and gigantic domes and all of that stuff simply is not price competitive, and even if you dropped everything and started attempting to get approvals and construction for hundreds of nuclear plants, they won't come online for 10 to 20 years themselves.

When's going to get cheaper solar? Certainly going to get cheaper with perovskites. Stores will get cheaper with lfp and sodium ion improvements, solid state and hopefully someday sulfur chemistries.

The nuclear industry needed to get its act together decades ago. In my opinion, it made a huge error in abandoning msr in the 70s (which has all the features of a competitive nuclear plant if they could figure out the materials science) and other breeder reactors.

A solid fuel rods reactor is simply not reliably safe in all disaster scenarios (Fukushima).

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