[HN Gopher] Iron as an inexpensive storage medium for hydrogen
___________________________________________________________________
Iron as an inexpensive storage medium for hydrogen
Author : bornelsewhere
Score : 134 points
Date : 2024-08-31 05:03 UTC (17 hours ago)
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| teruakohatu wrote:
| At scale, what I don't get is this requires a lot of energy to
| kickstart the reaction (heating the iron ore to 400 degrees).
| Where is that energy coming from when energy production is
| constrained in winter.
|
| Or would the plan be to slowly heat over fall?
| jl6 wrote:
| They mention using waste heat from the reaction to minimize the
| energy cost of discharge. As long as they still get some power
| out of it, it could be a win even if it's quite inefficient.
| When the input hydrogen is "free" in the summer (due to excess
| production), inefficiency can be tolerable.
|
| I do wonder if "free" will actually pan out, or whether someone
| will find a way to demand-shift from winter to summer and use
| it all up.
| zdragnar wrote:
| They're storing the hydrogen as water, though. The only
| reason to produce it in the summer from excess production via
| electrolysis is to be able to reduce iron oxide to pure iron
| rather than just buying the pure iron to start with.
| londons_explore wrote:
| I suspect in the next 50 years electricity will end up
| globally transportable via undersea cables, like the internet
| does for data today.
|
| At that point, it's always summertime somewhere and it's
| always daylight somewhere, and if prices were to fall to zero
| there is always someone who would like more heat for
| something.
|
| Therefore I suspect zero-priced energy will stop existing.
| outop wrote:
| 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 value
| computation for free'?
| londons_explore wrote:
| 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 more water when
| prices are cheap.
|
| Or heaters which switch between natural gas and heat pump
| based on price.
|
| Or electric car chargers which charge during the cheapest
| hours.
|
| (all of these already exist, but none are yet common).
|
| Over the long term there is also plenty of elasticity. If
| electric heating is expensive, people will install
| gas/oil heaters when they renovate. If electricity is
| cheap, more people buy electric cars. With cheap
| electricity, maybe fewer people decide to add more
| insulation to their houses. Businesses don't upgrade
| energy inefficient equipment to be more energy efficient,
| etc.
|
| Plenty of demand elasticity in both the short and long
| term. End result: As long as the market is unconstrained,
| prices won't hit zero more than say ~5% of the time.
| outop wrote:
| 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.
| brazzy wrote:
| Energy production _from solar_ is lower in winter, but it 's
| not zero. And other forms (notably wind) are not reduced.
|
| It's a non-problem, really. Especially at scale.
| zdragnar wrote:
| The article says they're currently powered from a grid
| connection but hope to be fully solar powered soon.
|
| What I'm not getting is how this process produces more energy
| than the solar input to power the process.
|
| Unless they're getting solar collectors to try to generate 400
| degree temperatures rather than PV solar to electricity, but
| that seems like a sketchy proposition at best in winter.
| MadDemon wrote:
| It does not, but they are storing the energy for winter.
| Solar produces a lot more energy in summer, which is
| especially true in Switzerland or Europe in general.
| mark-r wrote:
| The difference depends on your latitude. On the equator the
| seasons won't make a difference, above the arctic circle
| you'll get diddly-squat from your panels in the winter
| during the endless night. Switzerland is at 47 degrees, not
| quite arctic circle but far enough north to see a huge
| difference.
| adrian_b wrote:
| Even most internal-combustion engines require energy stored in
| a battery to kickstart them, so this is not different.
|
| Obviously the energy efficiency of this process based on iron
| is modest. It is likely that the energy efficiency is even
| lower than for the process of storing energy by making
| synthetic hydrocarbons (e.g. synthetic gasoline), which are
| much easier to use once energy is stored in them.
|
| The only advantage is the very low cost even for very large
| storage capacities.
| moffkalast wrote:
| My immediate thought is, why not store it as peroxide? It
| takes more energy to make too, but at least it's liquid
| rocket fuel instead of gaseous rocket fuel.
| DrNosferatu wrote:
| I hear peroxide conversion efficiency can be as low as 30%,
| and concentrated peroxide is quite dangerous.
| moffkalast wrote:
| > Efficiency Admittedly, the current, non-optimized,
| technical trial-level efficiency of the here-built system
| was very low, with an overall storage efficiency of
| 11.4%,
|
| So far their is even lower, though they claim a
| theoretical max of 79%. Storing large amounts of energy
| that's ready to be used is rarely not dangerous in any
| case. Except maybe potential energy of a tank of water on
| a mountain.
| mark-r wrote:
| There's an advantage to pure hydrogen vs. synthetic
| hydrocarbons, the lack of carbon means no greenhouse gas
| production when you use it.
| johndough wrote:
| Heat losses at the surface of a sphere scale with the square of
| the radius, while the energy density scales with the cube of
| the radius, so you can just scale it up until the heat loss is
| relatively small.
|
| In the paper, the authors mention 11.4% efficiency for this
| system and a theoretical maximum efficiency of 79% if scaled
| up, so it might take a lot of scale.
| jillesvangurp wrote:
| The right question is what the efficiency of this process is.
| End to end, not just the charging/discharging.
|
| Both charging and discharging seems to require a lot of heat.
| Waste heat is essentially lost energy that is released in the
| form of heat. I assume the discharge reaction is exothermic.
| That would be the energy stored in the summer months. Heating
| up a lot of tons of iron during charging is also not going to
| be free. It doesn't matter whether you do it slowly or quickly.
|
| Creating the hydrogen is also not a loss free process. Nor is
| doing something useful with it like using it in a fuel cell
| (0.85), burning it (0.45), etc. These inefficiencies multiply.
|
| All that lost energy comes out of the original budget of energy
| that came out of the solar panels.
|
| Even if you use some wildly optimistic numbers, they multiply
| to something well below 0.5 pretty quickly even before you
| consider charging & discharging.
|
| But lets do something silly and unrealistic and just do the
| math for an average step efficiency at 0.7, 0.8, and 0.9. We're
| talking four conversions here so that's 0.7^4 =0.24 vs. 0.41
| and 0.66. And forget about getting anywhere near average 0.9
| efficiencies with all of those steps. I'm assuming 0.7 would
| already be on the high side. Add more steps to the process and
| it only gets worse. Pipes aren't perfect. If you need to
| pressurize the hydrogen before you use it (like in a car), that
| isn't free either.
|
| Basically, this takes a system that was already quite
| inefficient end to end and adds two more steps that sound like
| they involve some pretty significant energy losses to it (i.e.
| probably well below 0.5 when combined), thus making the system
| as a whole a lot more inefficient. Hydrogen as a battery
| already sucked with normal storage. This doesn't improve
| things.
|
| There's a good reason that most hydrogen produced is used at or
| close to its site of production: it minimizes the energy losses
| and producing hydrogen is really expensive so it's not really
| desirable to lose 80-90% of the energy unless you really need
| to.
| DoctorOetker wrote:
| would you mind explicitly listing the 4 conversions?
|
| I see:
|
| 1) generation 2) storage efficiency (energy while storing
| divided by energy upon release)
|
| what are the other 2 you had in mind?
| jillesvangurp wrote:
| 1) generate hydrogen 2) store hydrogen in iron oxide 3)
| discharge hydrogen again 4) convert it into something
| useful (electricity, heat, movement, etc.).
|
| All those steps lose energy. And there's stuff that happens
| in between involving pipes, leaky valves, tanks,
| compression, etc.
| toast0 wrote:
| If this is intended to support a grid, rather than be grid
| forming or isolated, then you'd sequence that somehow.
|
| Somewhere with lots of solar on the grid probably has excess
| energy, even during winter, during the day, so you'd plan to
| put in the input energy to start the reaction during the
| afternoon peak, and if you miss that for some reason, some sort
| of coordinated startup procedure would likely be used.
| jval43 wrote:
| Actual publication linked is very readable:
| https://pubs.rsc.org/en/content/articlelanding/2024/se/d3se0...
| johndough wrote:
| I'd like to point out row 3 of the excellent Fig. 6 where the
| authors evaluate the risk of fine iron powder being exposed to
| air, which heats up to about 600degC due to oxidation.
| https://pubs.rsc.org/image/article/2024/se/d3se01228j/d3se01...
| erickj wrote:
| I believe most Swiss scientific investigations are legally
| required to involve Cervelat
| HeatrayEnjoyer wrote:
| What is it?
| micwag wrote:
| The national sausage of Switzerland:
|
| https://en.wikipedia.org/wiki/Cervelat
| lta wrote:
| This is one of the most absurd comment I've read in a
| while. I love it, thank you.
|
| Fwiw, cervelat is also very common in France, I grew up
| eating that stuff. Maybe that's why I liked the article so
| much. There's something to dig up there
| pfdietz wrote:
| Fires are one of the risks of so-called Direct Reduced Iron.
| The product has high surface area which leads to fast
| oxidation.
|
| https://www.metallics.org/dri.html
|
| > Being a highly reduced material, DRI has a tendency to re-
| oxidise, an exothermic reaction. Thus, without appropriate
| precautions being taken in its handling, transport and
| storage, there is a risk of self-heating and fires. The
| International Maritime Organisation's International Maritime
| Solid Bulk Cargoes Code classifies DRI - Direct Reduced Iron
| (B) - as Group B (cargo with chemical hazard) and class MHB
| (material hazardous only in bulk) and requires that DRI be
| shipped under an inert atmosphere, usually nitrogen.
|
| It would be nice if the iron could be in an alloy that, in
| addition to being oxidized/reduced, could further absorb
| hydrogen when in the reduced state. FeTi absorbs hydrogen,
| but I don't think the titanium would withstand repeated
| oxidation/reduction cycles. The Ti would go to the +4
| oxidation state and stay there.
| ttflee wrote:
| Looks like a variant of iron-air battery project to me.
| w-m wrote:
| This seems to be the most important problem to be solved for a
| green, future grid. So I'm happy there's a new solution shown
| every other month.
|
| It's annoying that they always seem to contain some hand-wavy
| efficiency calculations. I think this one didn't even consider
| the losses from hydrogen production? Is there a benchmark out
| there, of these long-term electricity storage solutions? Like:
| you get 1 MWh at 25 deg C, and 6 months later, it's measured how
| much your system restores. Everything taken from the grid during
| storage for upkeep or kickstarting the process is subtracted as
| well.
| 7952 wrote:
| The focus on efficiency can be short sighted though. The whole
| point of storage is that the energy you sell is more expensive
| than the energy you buy. If the profit margin is high enough
| then you can afford to waste energy through inefficiency. And
| grids with lots of renewables will naturally have times where
| energy is cheap and times when it is expensive.
|
| Also, I doubt this will exist in isolation. It will probably be
| built in places that already have demand for hydrogen,
| available land, have accessible energy, a good grid connection,
| and existing iron-ore infrastructure. It will be built in such
| a way to minimise costs and maximise available customers.
| rini17 wrote:
| If it has 33% net efficiency that sets it back 3 times
| compared to batteries right from the outset. With stainless
| steel pressure vessels needed here and hydrogen precautions,
| not holding my breath.
| micwag wrote:
| This is for seasonal energy storage with only 1 charge and
| discharge per year. It competes with water reservoirs not
| with batteries.
| rini17 wrote:
| That means it has only 1 chance per year to recoup the
| investment. And that requires exorbitant energy spot
| selling price, which too rarely happens to rely on. The
| economics just isn't there.
| 7952 wrote:
| But there comes a point where battery storage has all been
| used and prices go even higher. You sell at a x6 profit
| margin. And are able to sell at x3 profit margin for longer
| than the battery operators. And that assumes that 100% of
| the fuel would need to come from storage.
| rini17 wrote:
| You are betting against batteries? That's becoming risky,
| Na-ion has the potential to be literally as cheap as
| dirt. And they are not flammable.
| miohtama wrote:
| Is this same as rust batteries earlier?
|
| https://www.scientificamerican.com/article/rusty-batteries-c...
| aDyslecticCrow wrote:
| I thought the same thing, but no, the chemical process is
| different. Iron-air batteries are traditional flowcell
| batteries (with some extra complications).
|
| This paper uses hydrogen as an intermediary, which has
| advantages but also adds some questionable margins in
| efficiency. But I don't know the efficiency of the suggested
| iron-air batteries either.
|
| This may be nicer if you want hydrogen rather than an electric
| battery. But if you turn that hydrogen into a fuel cell... the
| efficiencies of producing and consuming that hydrogen add up.
| dest wrote:
| The energy density of the system is surprisingly high (in my
| modest perspective). It looks like 800kWh per ton of iron. Isn't
| it ~five times as much as the batteries we have in cars?
| ben_w wrote:
| I've seen claims up to 300 Wh/kg for batteries, but yes this is
| still more than that.
| AtlasBarfed wrote:
| Is that lithium iron or for sulfur chemistries?
|
| And for good batteries their density doesn't really matter.
|
| Sodium ion batteries will be fantastic grid storage simply
| because they're just going to be dirt cheap
| Temporary_31337 wrote:
| production and conversion are inefficient compared to other
| sources of energy, as up to 60 percent of its energy is lost in
| the process.
| nomercy400 wrote:
| Lost, as in turned into heat?
|
| Is it possible to capture that heat during production and
| conversion, and use it to run a turbine?
| tonfa wrote:
| In winter I think the plan is to use the heat for district
| heating.
|
| (which is also kinda interesting since in parts of
| Switzerland district heating through waste management
| facilities starts to be a problem due to a reduction of the
| amount of waste available)
| kitd wrote:
| 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.
| AtlasBarfed wrote:
| How do all of those factors compare with say the sodium ion
| or sodium sulfur battery?
| DrNosferatu wrote:
| Efficiency is quite low: 40%-60%.
|
| I would say it's only worth it if the marginal cost of producing
| the hydrogen is close to 0.
| goodpoint wrote:
| This not a problem at all when using PV. Plus, the generated
| heat can be used.
| rini17 wrote:
| It is, water electrolysis is surprisingly fickle process.
| crote wrote:
| The issue is that it's a self-defeating mechanism. PV doesn't
| produce _zero_ energy during wintertime, they just produce
| _less_. You 're going to be building additional PV to charge
| the Season Battery, but those additional panels will also be
| providing power during the winter.
|
| If your battery's efficiency gets bad enough the added winter
| power from those extra panels is going to be enough to cover
| the winter shortage - so you don't even need the battery at
| all. You'd essentially just be turning a huge amount of power
| into heat for nothing.
| derriz wrote:
| A good point.
|
| Depending on the latitude/weather/etc, the difference
| between winter PV production can see a reduction of between
| 40% and 85% compared to summer output (sampling from [0]).
|
| Panel prices have dropped so much, it's far more likely
| that, at least with places where summer output is double
| that of winter or less, that simply doubling the number of
| panels solves the problem.
|
| Batteries and PV are cheap and getting cheaper all the
| time, are proven and are absolutely trivial to install,
| operate and maintain compared to ANY conceivable process
| that involves hydrogen.
|
| I don't get the apparently insatiable drive/impulse that
| drives people to put so much effort into shoehorning
| hydrogen into the energy sector. It's expensive,
| inefficient, dangerous, leaky and is a potent greenhouse
| gas[1].
|
| The hydrogen idea has been around for over 100 years, has
| never worked at scale, despite many efforts and large
| investments. It's time to walk away and concentrate effort
| into technologies that have actually delivered and have
| already reduced carbon emissions at scale.
|
| [0] https://pvwatts.nrel.gov/pvwatts.php
|
| [1] https://www.dnv.com/article/is-hydrogen-a-greenhouse-
| gas--24...
| thargor90 wrote:
| The biggest problem is heating in winter, which requires
| way more energy than cooling in summer. So for colder
| areas doubling Panels will not be enough.
| 7e wrote:
| There will always a use for surplus energy. Are you really
| going to curtail surplus solar in the summer when you could
| just build storage for it? That's the profit maximizing
| solution, even if the efficiency isn't high. It just needs
| to be cheap.
| crote wrote:
| Of course there will always be a use for surplus energy.
| It's basically free, so we'll probably see whole new
| industries pop up to make use of it.
|
| For example, an aluminium smelter might use free summer
| energy to turn alumina into aluminium, and turn the plant
| off in the winter - at which time the labor force can do
| extended maintenance and do post-processing on the
| aluminium produced during the summer.
|
| Although finding an industry where such seasonal
| turnovers are viable isn't trivial, _if_ you find one it
| 's going to be far more profitable than very lossy
| storage.
| aDyslecticCrow wrote:
| Cut down for another 60%-80% efficiency for producing the
| hydrogen.
| https://www.sciencedirect.com/science/article/pii/S136403212...
|
| Unless you also have a nuclear reactor to perform the high-
| temperature electrolysis process.
| https://en.wikipedia.org/wiki/High-temperature_electrolysis
|
| Which only Japan seems to be working on building at the moment.
| https://www.hydrogeninsight.com/production/japan-plans-hydro...
|
| It's cool tech, and I like that it's researched. But I think
| it's not a breakthrough that could realistically help the grid
| at the moment.
| samatman wrote:
| 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 whimsical and absurd
| epicycles, which make no sense at all unless you're playing that
| game.
|
| Seasonal storage of 2GWh? Please. A 2GW plant produces 2GWh every
| hour, with 90% uptime. And it doesn't involve losing more than
| 90% of the photovoltaic energy, I will eat my whole hat if the
| ray-to-electricity pipeline for this boondoggle exceeds 10%
| efficiency.
|
| Can we please stop wasting time and effort, and invest in the
| buildout of a substantial nuclear fleet to provide baseline
| power?
| ComputerGuru wrote:
| China seems to be working towards that goal. Everyone else, not
| so much.
| AtlasBarfed wrote:
| 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).
| fredgrott wrote:
| This solution is better and no toxicity
|
| https://www.pnnl.gov/news-media/baking-soda-solution-clean-h...
| kimmk wrote:
| 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.
| msandford wrote:
| 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.
| credit_guy wrote:
| 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 are probably bigger energy losses
| bringing the reactant mass at the required temperature (400
| degrees C).
|
| Unfortunately, I don't see this making any sense for large scale
| energy storage. Storage tanks for compressed hydrogen enjoy the
| square-cube law. The larger they are the less expensive they are
| proportional to the mass of hydrogen they hold.
|
| With this iron oxide method, you need 27 tons of iron oxide for
| one ton of hydrogen. You can procure right now tanks that can
| hold 2.7 tons of hydrogen and weigh 77 tons empty [1], the ratio
| is 28 to 1. But the round-trip efficiency of the tank is
| virtually 100%. The efficiency of the iron-based storage is only
| 50%. The tanks are not very expensive.
|
| I can't see the niche that this idea can apply to.
|
| [1] https://www.iberdrola.com/press-room/news/detail/storage-
| tan...
| paulsutter wrote:
| Hydrogen is difficult to store and transport, you really want
| natural gas or jet fuel
| kilotaras wrote:
| 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?
| kilotaras wrote:
| 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/d3
| se0...
| A4ET8a8uTh0 wrote:
| << I can't see the niche that this idea can apply to.
|
| 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.
| mppm wrote:
| > Storage tanks for compressed hydrogen enjoy the square-cube
| law.
|
| Not really. Wall thickness is roughly proportional to diameter,
| and surface area to the square, so you don't gain anything in
| terms of storage mass ratio by building bigger tanks.
|
| > But the round-trip efficiency of the tank is virtually 100%
|
| This is oversimplifying quite a bit. Compressing hydrogen, the
| lightest gas, is very energy intensive per unit of mass, and
| this energy is not fully recoverable upon decompression (due to
| general pump efficiency and thermal losses in the intercooler).
| MobiusHorizons wrote:
| Also hydrogen loves to leak through tank walls, and can make
| metals brittle (this was covered in the article)
| kortex wrote:
| Iron oxide is completely inert. You can store it in piles,
| under the elements. Iron powder less so, you need to keep it
| dry, but again you can just pile it up. The only tricky part is
| moving dense dry solids around at the huge scales required.
|
| Edit: wait I forgot that direct reduced iron powder
| exothermically reacts with oxygen and water in the air, that's
| how single-use instant hand warmers work. So yeah you gotta
| isolate the iron powder a bit more than stick it under a tarp.
|
| I've been playing too much Factorio lately so of course my mind
| goes towards rail systems (could repurpose coal plants) in
| combination with pneumatics.
| paulsutter wrote:
| You really want to store excess energy as natural gas or jet fuel
| because of all the existing infrastructure. Especially since
| excess power is available at so many solar sites, we're so good
| at transporting these fuels, and the cost of photovoltaic will
| keep going down
|
| The vast, cheap power that photovoltaic will provide is a giant
| opportunity. Please review the links below
|
| https://terraformindustries.com/
|
| Terraform industries converting sun and air into natural gas:
|
| https://techcrunch.com/2024/04/01/terraform-industries-conve...
|
| The solar industrial revolution is the biggest investment
| opportunity in history:
|
| https://caseyhandmer.wordpress.com/2024/05/22/the-solar-indu...
| shikon7 wrote:
| Why would you use hydrogen to extract the energy of the iron?
| Wouldn't it be more efficient to burn the iron directly?
| Likewise, is there no better way to reduce iron oxide to iron
| than by creating hydrogen first?
| dredmorbius wrote:
| 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)
| mglz wrote:
| How much incoming solar power ends up in the methane? And how
| do you get the energy back out?
| wffurr wrote:
| >> How much incoming solar power ends up in the methane?
|
| As in how many power to gas plants are operating currently? I
| would guess not many due to the price vs fossil methane, but
| as the GP notes this is a major market failure due pricing
| the externalities of fossil methane.
|
| >> And how do you get the energy back out?
|
| Easy, burn it. For heat, or with a turbine, electricity. Zero
| carbon impact because it started out as atmospheric CO2.
| User23 wrote:
| The usual way--boiling water.
| zahlman wrote:
| 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?
| usrusr wrote:
| > "So why not just, well, burn (i.e. rust) the iron directly?
| What exactly is the dissociation and re-combination of the
| steam accomplishing?"
|
| Direct use of reduced iron as an energy carrier has been
| discussed here:
|
| https://news.ycombinator.com/item?id=24996153
|
| Oxodizing iron gives rather low intensity heat, comparable,
| iirc, to burning lignite. That might be good for some combined
| cycle applications (but still a logistics nightmare?), but it's
| not a drop-in replacement for anything. Hydrogen on the other
| hand is good for an extremely wide range of applications, from
| fuel cells to e-fuel production (and all kinds of other
| chemical processes) to flying Neil Armstrong to the moon.
|
| To succeed in decarbonization we will need an entire "cache
| hierarchy" to solve the intermittency problem, a single storage
| solution will never be enough. Batteries to make hydrolyzers
| able to run around the clock during high availability seasons,
| hydrogen storage to make converters further down the pipeline
| run continuously during surplus seasons and not only on the
| best days.
|
| What will definitely not get us to decarbonization is any of
| the following three approaches:
|
| (a) building enough production capacity that we don't need
| storage (most production would be idle most of the time for
| lack of a buyer)
|
| (b) focusing on one kind of storage (same problem again, now
| with conversion capacity)
| kortex wrote:
| > Rather, it's using the energy to deoxidize rust.
|
| Exactly, really what they are storing is electrons.
|
| Rusting the iron directly releases heat, which limits your
| efficiency to the delta-T of the process. Reducing steam to
| hydrogen and then converting the hydrogen in a fuel cell allows
| higher efficiency to produce electricity.
| czierleyn wrote:
| Is this the same idea as?
|
| https://teamsolid.org/
| ano-ther wrote:
| Despite the cycle losses, this seems like a good idea for easy to
| maintain storage. And they plan to use the heat as well, so that
| will step up efficiency.
|
| Will be interesting to see how their campus power project works
| out in the next years.
|
| Also, innovative "sausage safety test" for the Fe powder reacting
| with air (figure 6: https://doi.org/10.1039/D3SE01228J ).
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