Dutch brewery burns iron as a clean, recyclable fuel
newatlas.com
newatlas.com
You can do a lot of things with electricity: you can heat things, but also move them around and run your TV, all without any loss. With heat you can just... heat things. So you can't call this an "iron battery", because you don't get electricity out of it, just heat. Maybe call it a "heat battery" or "high performance heat pad".
Also note the efficiency numbers: "High-efficiency electrolysis of iron oxide can store as much as 80 percent of your input energy in the iron fuel" is the efficiency of the process itself. "Using this kind of cyclical process to generate electricity could approach a theoretical efficiency around 40 percent" is because you need to climb the ladder to low entropy again (probably by using the equivalent of a steam engine to run a generator).
Not sure how doable it would be from a chemistry point of view, though: you probably need at least one extra reagent or catalyst.
You can't use that heat to raise the temperature of something to 61C, for example.
What I've become interested in, is how easy it is to 'abuse' heat pumps like this. Could you take a heat-pump and this 60C water to heat a boiler to the point you can run a steam-turbine that produces more energy than it takes to run the heat-pump?
If not at 60C water, does this work at any temperature? There remains free energy in the temperature differential between an ambient 21C and the temperature of warmer water. It seems to me this should be harvest able. There are significant limits here from the Carnot theory, but they don't say this is impossible.
A heat pump is like a water pump: it's a lot easier to move water to a tank 61 feet off the ground from another tank 60 feet off the ground than from ground level, but you can't power the pump producing 1 foot of pressure head with a turbine being driven by 1 foot of pressure head.
Agreed, that's where spilling water comes into play:
┌───┐
┃ A ┊┃ │
┗━━━━━┛ │
│
│┃┈┈┈┈┈┈┈┈┃
└┨ B ┃
┗━━━━━┳━━┛
┇
┃ C ┇ ┃
┗━━━━━━┛
However, we're not bringing it down to B. We're bringing it down to C (ambient 21°C in their example). There will be losses, but shouldn't it be doable, depending on the B-C potential?
Wouldn't Peltier modules be 100% efficient in theory for rising B to A (as long as thermal losses go to the hot side, that is: tey keep a side cooler), for instance? If so, the generated energy is the one stored between A and C, minus conversion losses, minus A-B. That is, B-C minus conversions losses from A-C. Probably not very efficient at the end, though worth it if you have plenty of B (and a excellent "C" sink).
You most certainly can drain some of the water from B to C so as to move other water from B to A. But you will always do so at a net loss.
The unit of water moved from B=60 to A=61 gains A-B=1 unit of potential energy, in addition to the B-C=40 units of potential energy it already had for a total of A-C=41 units. However, without a 100% efficient (read impossible) pump and turbine combo, it takes more than 1 unit of energy to raise up that unit of mass. This means you need to spill more than 1/40 units of water from B to C to get that 1 unit from B to A. Now dropping that water from A to C would get you 41 units of energy, 1 more than if you had spilled it straight from B to C, but it cost you more than 1 unit of energy to get into this situation.
A is indeed a higher quality source than B, but you are using that low quality source of B to generate your energy, and the efficiency losses there will always be greater than the gains you make on the higher one. To break even the initial height/temperature differential would have to be infinitely high.
Now if for some reason you could not harvest energy directly from B-C, yes you could use water going from A to C to power the pump from B to A, it would just be less efficient. This would be the equivalent of a siphon.
> Now if for some reason you could not harvest energy directly from B-C, yes you could use water going from A to C to power the pump from B to A, it would just be less efficient.
I also think that was the initial point: some higher-efficiency generators ("steam turbine") are only available for high potential differentials. Whether raising the potential offsets the gains likely depends on the specific setup and energy source.
The heat pump requires power to run, the question is whether the power to run the heap pump is smaller than the power required to just generate the same heat differential directly.
You would always get more energy out of draining the whole 60 foot water tank directly to ground than you would by lifting the water to 61 feet and then draining it to ground.
Just let some of the water out of the 60 foot tank through a turbine. Put a shaft on that turbine, and put a pump on the other end. That pump should be able to pump water from the 60 foot tank up to the 61 foot tank. You would get less water in the 61 foot tank than in the 60 foot tank. Quite a bit less actually, but you could still harness the energy in the 60 ft tank to get some water to the 61 ft tank.
No one is saying it's impossible to lift water up 1 foot (that's incredibly easy), the problem is it always takes more energy to lift water 1 foot than you can ever get from lowering it 1 foot. Likewise a heat pump can easily and efficiently create a heat reservoir, but you need to drain some other, larger heat reservoir to do so.
Thing is, the free energy in 60C wastewater is hard to use, and the free energy in 200C steam is much easier to use (through steam-turbines). Hence, it might be worth it to sacrifice a large part of the free energy in the 60C wastewater to get it to a useable form.
What are the alternatives to use 60C wastewater to generate electricity? I can think of a sterling engine or a thermoelectric material. These would probably be more efficient, but they are new technologies, with practical limitations and development limitations. Hence, if my idea could generate any form of electricity, it might be more feasible than the other ideas.
From what I know about heat engines, I know it might not be possible to generate electricity this way.
There are other more complex processes like the sulfur-iodine cycle that was investigated for producing hydrogen from nuclear heat: https://en.wikipedia.org/wiki/Sulfur%E2%80%93iodine_cycle
As far as I can tell, these processes are probably less economical than generating electricity & then doing electrolysis.
Though, I would assume that iron-powered (steam?) vehicles would not be competitive due to the weight ? (Even despite the extra weight that hydrogen or electric batteries add.) Maybe iron-burning steam boats ? Steam rail ?
Nevertheless, fixed processes (far from hydropower), especially those requiring heat energy, seem to be a great niche for iron burning ! And I say niche, but this niche might be even bigger than transportation, which IIRC is only like 25-30% of total energy consumption ?
I don't imagine beer production requiring such high temperatures, but honestly I don't know anything about industrial beer production. Anyhow the tech presented in the article is very cool.
Another example for how electricity is a very valuable type of energy.
It's not the universal storage solution to end all search for other storage solutions because it's only really applicable in a niche (heat consumption), but that niche might not be as small as people think. I think that besides applications that require high temperatures it could also be a very good match where a particularly high maximum temperature isn't required (so heat pumps and the like could be applicable) but peak power demand is of a rarely occurring, intermittent nature. It might even be applicable to once-in-a-lifetime heat applications if they can be designed for easy oxide recovery.
What remains open is how cheap "charging" throughput can be built, as this is the weak spot of all other power-to-fuel concepts: the conversion facilities tend to be too expensive to remain idle outside of electricity oversupply times. And who knows, theoretically conversion throughput capacity might even turn out to be so exceptionally cheap (I certainly wouldn't expect that, but I'd be glad to be surprised) that even the inefficient electricity->fuel->heat->electricity might become competitive, once conversion outgrows direct heat applications. A market for inefficient but cheap long-term storage would definitely exist if there was any supply.
Seems like an engineering challenge to me not an actual limitation.
For example, a water-water heat pump can easily boost the temperature of your reactor to 80 deg C by using only 1 KWh of electricity for every 4KWh of heat delivered, the rest coming from a nearby large body of water and slowly recovered from the environment throughout the year. So we are looking at on order of magnitude more heat for the same electrical consumption 40% vs 400% efficiency. Instantanous renewable energy prices are low, but rarely that low.
The limit of efficiency is dictated by the boost in temperature needed, so you can't use heat pumps to get the 1000C generated by iron oxidation. There is certainly a niche for industrial processes requiring very high temperatures, but I can't imagine why on earth would a brewery need such temperatures.
The article takeaway is that iron powder is a surprising electricity—>heat battery.
This is why for example you see heat pumps installed all over the place in homes in the southern parts of the US where you also need little heating all around, while places up north where you do spend quite a bit on heating cannot really take advantage of heat pumps due to winters being too cold.
Amazingly (to me), there are now air source heat pumps that stay > 100% efficient down to -20C before regular electric heat takes over:
https://www.nordicghp.com/2017/01/heat-pump-effective-temper...
Though apparently you'd be better off with a ground source heat pump if your average temperature during heating season was below freezing or so.
[Edit: I mention this because I've heard that "you don't see heat pumps in the north" was true in the past but is now outdated -- they've made sense in warmer climates for a while but have only recently crossed over for colder climates, so it will take a while until they're common.]
Note: there are two popular "efficiency" measures, and its important to realize that they're incompatible.
Air conditioners are commonly "energy moved / energy used", which can reach greater than 100%. If you move 150W of heat using only 100W of electricity, you have 150% "efficiency".
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I don't know the term for the other kind of efficiency (I'm not a physicist), but lets call it "inverse engine efficiency". This is "energy out / energy in", which ends up being pretty close to "energy moved / (energy moved+electricity used)"
Under this measurement of efficiency, 150W moved with 100W of electricity is 60% efficient. This follows the more standard physics rule of thermodynamics (you can never go above 100% efficiency: it will always take some number of energy to move heat around).
Note: Car air-conditioners are funny systems. They use the heat from the combustion engine to move heat from inside the cabin to the outside world. So you are literally using heat to move other heat.
Car air-conditioners are not powered by heat from the combustion engine. They are powered mechanically by a belt ("serpentine belt") connected to the engine.
Or, in some cases such as battery electric vehicles, powered electrically with the compressor turned by an integrated electric motor. The extra heat produced is just a byproduct (thermal inefficiency) of producing and transmitting that mechanical/electrical energy.
But that belt is powered by the expansion of gas that takes place inside of a piston, due largely to the increase in heat from combusting gasoline. Ultimately, an ICE engine is a heat-engine (like a steam engine or sterling engine, but different).
Isn't that expansion of gas largely driven by the increase of heat?
https://en.wikipedia.org/wiki/Internal_combustion_engine
Wikipedia lists the ICE as a heat-engine.
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With that being said: the octane combustion formula has 25 O2 as input and 16 CO2 + 18 H2O as output (and I assume the H2O is mostly water vapor). So that's 25 molecules of gas input -> 34 molecules of gas output.
So it seems like more "CO2 + vapor" is created than the number of input O2 molecules. But that only accounts for 34% expansion of the volume of the stroke. (25 mols input -> 34 mols output).
The rest of the stroke's power comes from the ideal-gas law: higher temperature means higher pressure and larger volume. Literally the heat generated by the chemical reaction.
https://en.wikipedia.org/wiki/Seasonal_energy_efficiency_rat...
Heat pumps are designed so that their "efficiency" (performance) is never less than 100% (COP >= 1). In very cold conditions, they may not be more efficient than resistive electric heating, but they will never be worse.
> "places up north where you do spend quite a bit on heating cannot really take advantage of heat pumps due to winters being too cold."
You're talking about air-source heat pumps here. In colder regions, it's better to use ground source/geothermal heat pumps. Ground temperature is consistent year-round even in very cold climates.
So the price difference is not huge. In southern parts of the country, and for older houses with less expected life left in them, air-source pumps have proved more popular, whereas further up north and for newer buildings ground-source pumps are more often the choice.
The real challenge is reliability and cost of electricity. If your power goes out and you have heating oil you can still live for a week.
Brewing water temperatures peak at ~100C (pressurized steam is dangerous) and even with 20C water that’s an 80K difference so you’re down to 350% ideal, which probably puts you close to breakeven with pump losses. It’s the complexity that kills it.
At least over here, all oil boilers I've seen use mains electricity driven pumps, injectors etc.
For air source, in the north (at least in canada) they use ground source ones put below the frost line. So the ambient temperature down there is >0C .
And then after you've cooked it, you need to chill it down to around room temperature. Where you dump that heat could make a huge difference.
Remember this inherently allows them to load shift and thus get much lower electricity prices as well as reducing peak demand.
With iron burning you could theoretically create iron using solar power in Sahara and then ship that to the Netherlands for use in breweries.
Thus you can decouple where and when power is generated from usage.
There are still a small number of steam-turbine-powered merchant ships being built- specifically LNG carriers, where gas that boils off from the cargo can be used as fuel.
They are far more powerful than other kinds of spaceships
Wouldn't this imply that when heat is the goal we should always use these pumps? What is the limit of usefulness of these pumps? (eg, what if a whole city did it for all its heat needs?)
I remember looking at on-demand hot water heating. It's easier to do with natural gas.
But for electricity it would require something like a 100+amp electrical circuit and would have limits on flow rate and/or temperature increase.
for a heat pump, it just wouldn't work.
So for hot water the most common solution is to trickle charge a thermal battery - a hot water heater - and release it fairly quickly during a hot shower.
I can see the same sort of thing happening here.
Electricity <-> movement
↓
High quality heat (e.g. welding torch, tungsten lamp)
↓
Low quality heat (air conditioning)
Yet this has some huge advantages over batteries:
1. We already know how to create iron at massive scale. Various iron smelters are going green already.
2. This has much higher energy density than lithium-ion batteries. More similar to gasoline.
3. The cost of storage is very low. Capital expenses to build batteries is much higher.
4. You can save a lot more of money by using existing industrial infrastructure. We can convert existing coal plants and any industrial process needing heath such as concrete production to use this. This makes it possible to get a solution in quickly . Scaling up global battery production in contrast is an enormous undertaking and we must prioritize EVs over grid storage at least initially.
But add a fuel cell and the same reaction does give you an "iron-air battery":
https://en.wikipedia.org/wiki/Metal–air_electrochemical_cell...
Each kind of “energy storage application” can be broken down into different properties /requirements that can vary quite a bit.
Real time electricity response for 2-8hr periods so far seems well suited for Li-ion (LFP), given it is electrical energy, speed of response, and that it can be deployed virtually anywhere.
On the opposite end of the spectrum - you have seasonal energy storage (winter in colder climates, for example). When thinking about “energy containers” - Having iron powder doesn’t have the same requirements of alternatives I’ve heard, and seems like it could be the easiest to scale. Physically storing heat requires very large well insulated structures (rocks underground I’ve seen), hydrogen requires compressed gas cylinders, pumped hydro and compressed air needs specific geology (large valleys or large sealed underground caves).
Iron powder? An oxygen free warehouse Amazon sized. Helped that many winter applications ultimately only need heat, this seems like a good candidate that could be rapidly deployed given how on a relative basis - capital light and material accessible this is.
Fine steel wool will burn readily, yet it keeps underneath the sink and only rusts over a period of years.
There are many situations where it would be much less expensive and simpler to replace a coal- or oil-fired boiler with one that runs off of iron filings, while still maintaining all of the rest of the equipment as-is. These locations could be off the grid, or in locations where it's not feasible to get a connection capable of supplying the megawatts of electricity it might take to produce enough steam.
But it is a great idea to burn any fuel whose oxidized product is not a gas. The only reason why burning hydrocarbons is problematic is because carbon dioxide is a gas, otherwise it could be captured and recycled like this.
Burning hydrocarbons is problematic for a host of reasons besides CO2 release: fracking, oil spills, release of other pollutants, political issues with the supplier countries, pipelines, ...
Emphasis mine. Don't be a pedant.
70% vs 40% is a big difference, especially when you consider it from the losses column instead of the wins column. If I gave you a system that was losing 30% of a resource to replace a system that lost 60%, you've cut your losses in half.
If I told you a mechanical system could get that to 15%, you'd replace that again. Anyone who tells you they can get a heat engine down to 15% losses is a charlatan and should be reported for fraud.
If you wanted to convert that heat back to electricity, there would be losses, but nowhere near as much as some people are saying. 1800 degrees minus ambient is a very big delta T. You are not bound to a closed cycle, so Carnot does not apply. So it is likely 80+% would be achievable, maybe over 65% round trip.
From the article:
"High-efficiency electrolysis of iron oxide can store as much as 80 percent of your input energy in the iron fuel"
"Using this kind of cyclical process to generate electricity could approach a theoretical efficiency around 40 percent"
Moving fuel around is also a problem with coal and oil. We're basically burning fossil fuels to move fossil fuels around. In the case of oil, we than also have to run it through energy intensive processes to turn it into more palatable fuels than bunker oil, which is what is typically used for shipping things around.
A typical oil tanker consumes a couple of hundreds of tons of bunker fuel per day to move a couple of thousands of tons of fuel around. So, that's a sizable percentage of its load that is lost just to get the raw product from A to B. I'm sure the math is similar for producing and moving coal around.
It only makes sense if you get to pollute at will without financial consequences; which happens to be the case with shipping, which mostly takes place in international waters without any constraints or regulations on the amount of crap put in our atmosphere.
Ships actually switch to cleaner fuels when they get close to populated areas because otherwise they'd end up killing some of the locals with their fumes. Bunker fuel is nasty. Even more so than coal.
So, if we are debating efficiencies, we'd do well to apply the same scrutiny to existing solutions as well. The efficiency of coal should also include digging it up using diesel burning heavy duty equipment, moving it around, etc. I'd bet that knocks some percentage points of even the most efficient plants or ICE cars.
You could build the infrastructure to do the electrolysis immediately next to the coal plant to solve this problem. If this technology takes off that's most likely what will happen anyway.
We are not trying to transfer green energy to less windy/less sunny places, the grid can take care of that.
It also seems like it can make use of existing infrastructure and save money there.
At first glance it seems reasonably transportable, but I'm worried about how you prevent it rusting in the air. Maybe it would be useful to blend it with biodiesel for that purpose.
I imagine methane synthesis will beat some thinglike this out. Pipeline infrastructure exists, is convenient, etc.
Methane seems nice for the re-use of gas fired plants. I do think its gaseous nature has more downsides than upsides on the other two factors. There's also a gas-leak hazard with methane that doesn't exist here.
If the capital requirements are low enough, I could see a 40% efficient energy battery for smoothing out peaks being nicer than more complicated storage schemes.
For fuel that can be transported, methane is a winner. In addition to the distribution infrastructure, there's an awful lot of residential use, with lots of appliances that don't need replacement.
But secondly, wind power makes a lot more sence in northern latitudes.
Yes for short term batteries are better but for say seasonal storage or when power is generated far away from where it is used then metal is better.
This article suggests at top speed Panamax tankers carry 1.5-2mn gallons of fuel while burning 63,000 gallons per day (i.e. around 3-4% of capacity) at top speed.
That is considerably less than the 10% (200 tons to move 2,000 tons) that you suggest.
Also the article notes that reducing speed by 10% can reduce fuel use by a third. The tankers travel at 19mph, significantly less than their top speed of 23-28mph so fuel consumption is likely closer to 1%.
While it certainly makes sense to calculate for the entire journey, if you were talking about the "whole journey" why did you specify "per day"? It's hard to blame 'ximeng' for relying on your written comment rather than what you intended to say. :)
But second law of thermo dynamics applies. If this works at all it is because you are capturing a little more of the energy that was put in at the top and would otherwise be lost. You stil need to put in external energy to keep this system running.
If the process was 100% reversible, and friction free (probably a couple other loss factors I forgot about) it would be energy positive as the oxygen is making its way back up in the air is an external energy input. Of course in the real world both assumptions are wrong by more than enough that you can never get this to work.
Efficiency matters when you run out of space or resources. But you got vast areas like Sahara where solar power production could be combined with metal production. Wasting space in Sahara is a non-issue if it means you get the overall cost of system down.
What I haven't seen is many people doing both at the same time. I might have seen a desal unit powered by green energy, which tops up the water towers when power is cheap, but not much beyond that.
Now before one points out that burning lithium just makes this a battery; kinda but also no. If you burn lithium to turn a generator, I'd argue it's not much more a battery than burning oil to turn a generator. If you wanted a battery, you'd need a non-generator variant. That is where I'd differentiate.
Could also use Flourine and burn CO2, might be a viable carbon sink. Flouroalkanes from burning CO2 would be organically inert, don't deplete ozone if released and don't bioaccumulate. Only downside is they're very good greenhouse gases if you don't burn them down to the alkanes that are solid or liquid are normal temperatures. Those you could easily bury deep below the earth.
The only issue is obtaining a shitton of flourine to burn your carbon with and then not blowing yourself up in the process.
(Also yes, Flourine will burn CO2 and act as the oxidizer)
I think breweries are one of the types of business that could more easily use low density fuels. Right now a lot of the beer is moved by road, and the trucks that transport beer are often empty on their way to a brewery.
You have to transport the iron oxide back to where it can be recycled. That's the "advantage" of burning fossil fuels: most of the combustion products are volatile, so you can release them into the atmosphere.
drink less beer perhaps.
I can't remember if it was Fluorine or Chlorine Trifluoride referenced in the book "Ignition" as being capable of burning as fuels water, sand, and rocket test engineers.
Another bit of discussion on the stuff here[0], including the John Clarke "Ignition" quote you refer to.
[0]: https://blogs.sciencemag.org/pipeline/archives/2008/02/26/sa...
For asbestos you'll need some chlorine to make that flourine very excited about the idea of tearing apart some strong molecular bonds. Chlorinetriflouride is the candidate here, though Dioxygendiflouride also likes doing it, if in a more explosive fashion (it'll probably detonate in a hypergolic fashion with asbestos or sand).
Everything on the left side of the table gets lively with air and especially water; everything from sodium downwards explodes in water.
(I wonder if anyone is doing the 21st century version of Ignition!'s approach of setting random things on fire to see if they're good rocket fuels with potential electrolysis-cycle storable fuels?)
This version of the story mentions that NOx and particulates are something they will have to work on: https://www.deingenieur.nl/artikel/first-system-to-use-iron-...
At high temperatures.
Burning coal is clean in this sense, as I understand.
But higher temperatures seem to be much more dangerous. I've heard that from critiques of hydrogen burning, they said burning pure hydrogen is unacceptable due to high temperature leading to NOx emission.
Found this:
> It is believed that an increase in the maximum temperature in the combustion zone above 1850 K leads to unacceptably high NOx emissions , and one of the main ways to reduce emissions by the thermal mechanism is to prevent the formation of hot spots in the flame front.
https://translate.google.com/translate?hl=&sl=ru&tl=en&u=htt...
You can store the oxygen released when you produce iron from powdered rust, and use it to burn the iron later.
So having ships, planes or even cars powered by burning iron seems to be unfeasible (at least from energy production standpoint). Albeit iron has much higher density, so if weight is not a problem then it may work. Iron has energy density of about 40 MJ/liter which is comparable with coal, diesel, petrol, which have ~34-40 MJ/liter.
Most cars run on the Otto cycle, less efficiently. (It is named after the person, not the vehicle.:-)
aluminum of course. It is cheap too and has higher specific energy than iron. Using aluminum-air fuel cell instead of burning makes the efficiency about 2 times higher. The actual cars powered by aluminum have range up to 2000km per refueling.
Although we could have really fast nuclear powered container ships and the whole problem goes away
Edit: Made me day dream about Iceland exporting iron powder for burning, electrolysed with their geothermal energy.
This is just a way for the brewery to get cheap heat, with a level of indirection from the source coal so it can be advertised as green.
It's a shame the journalist that did this article didn't think to research how iron is typically made...
Then there would be NOx pollutants either.
It's a collaboration with a local university to test the technique on industrial scale. According to the researchers there the goal is to grow to grid-scale and convert coal-fired power plans in the coming decade.
In essence brewing process is a hell of a lot about moving heat around: You heat water to mash the grain to make wort, you boil the wort, then you remove the heat (via heat exchanger) as quickly as possible to get the wort down to where the yeast is happy. What are you going to do with all that energy you've pumped in to the fluid in the first place and have just pumped out again? If you're clever (energy conscious) you find a way to cycle that back into the process. There are lots of opportunities to optimise and conserve the energy that gets shunted back and forth in a brewery and it's a whole art/science in itself.
The brewery is like lots of other industrial processes. They need a lot of heath which typically coal produce today. Metal powder can replace coal in all these industrial settings.
And how do they get the 40% round-trip efficiency? Even if we assume the 80%, modern gas turbines have efficiency of up to 38%. In complicated combined cycle mode plants efficiency can be boosted up to 60%. And it is natural gas, a very convenient fuel to work with.
metal fires often burn at more than 5000 degrees F. That’s hot enough to disassemble water into its component parts, and one of those parts is hydrogen gas, which is not only flammable but explosive. any uncontrolled release of liquid into the fire would be catastrophic. Metal fires cannot generally be quickly extinguished in an emergency or uncontrolled accident.
metal fires also release toxic gasses and byproducts that often require more consideration than electric or gas.
as an update to a few questions: NEVER add water to a metal fire. it will cause an explosion.
depriving the fire of oxygen works, but only insofar as it remains deprived until the fuel source cools from 5000 degrees, or it risks spontaneous reignition. it generally has to be monitored similar to a crucible as it cools.
most accidental metal fires do not have a cogent or quick option to deprive the fuel source of air.
what happens if you spray a fire extinguisher into a metal fire?
In the case of a furnace, couldn't you simply cut off the oxygen supply?
[1] https://newatlas.com/energy/bavarian-brewery-carbon-free-ren...
[2] https://web.archive.org/web/20201104083956/https://newatlas....
It claims 'good' energy density and 40% roundtrip efficiency.
How does its energy density compare to existing liquid fuels?
Naturally, I'm wondering what an iron powder fueled internal combustion engine would look like!
Instead it works well I. Big open furnaces where you extract the energy via superheated steam.
Diesel engines have a thermodynamic efficiency of ~42% in optimal conditions - usually it's less.
Large marine units approach 50%, but the fuel they use is only technically liquid.
EDIT: I just noticed you were asking about density, not efficiency.
I suspect it's much less than liquid fuels, which derive most of their energy from burning the hydrogen in them.
The research is focused on the efficiency and CO2 footprint of all three stages.
Or the iron powder "wears out" somehow? less and less oxide can be converted back to iron powder? But then why
Making solar panels is not carbon free. Making batteries instead of emitting gases is not carbon free. We still have to recycle those panels and those batteries and take in account the impact of it.
I feel like we are changing the place where gases are emitted or residues stored instead of making less cars, consuming less in general, etc.
A whole new parallel infrastructure of low-quality electricity generation could be built without too much effort for electrolysis of iron oxide, powered by low-grade heat and motion sources that currently can't be effectively utilized.
Waste oxygen is a byproduct of ammonia production from water and air. You really want to use pure oxygen to burn your iron, to avoid producing NOx.
I've been saving 1lb propane containers because I thought I would experiment with low pressure (for safety) hydrogen storage as flame source. Then I see videos where people are putting on spark arrestors and using more involving methods to totally remove oxygen (electrically interactive element in a steel container - an amount as low as 4% mixed with hydrogens low ignition point could be hazardous). Combine this with all the hoses and couplings I'd have to put in and it could add up and get complicated (although Alex Lab is a neat channel for hydrogen experimentation).
Could I just put a grinder wheel to some pig iron and create a powder stock (high surface area)? Since the powder flows it could be delivered like a wood pellet stove with auto-feed and hopper storage, and maybe for cooking I could spoon feed powder into a bowl with air flow rate control for temperature adjustment? Then another batch would "charge" as a short between two electrodes of a voltage source. Would the constant voltage of a charge controller be necessary for this redox? Could it just be a container of oxidized iron that reacts as voltage is available?
> "the idea certainly seems to have some advantages over hydrogen, pumped hydro, batteries or kinetic energy storage"
What advantages though? If the process needs combustion then it's interesting but if the combustion is just used generate electricity then how is this better than the other methods?
This is where the brewery angle is interesting, since (as others have mentioned as well) what brewing needs is mostly heat for boiling. Combustion gives you heat directly.
https://en.wikipedia.org/wiki/Chemical_looping_combustion
e.g. the CO2 product stream might be clean enough to dispose of without putting it through an acid gas scrubber.
Can you expand on this?
Chemical looping can reduce the cost of these processing facilities (or eliminate them completely) by dramatically reducing the number of impurities in the CO2 that is produced from combustion, especially nitrogen. I.e. it makes a more pure CO2 product from the get-go, which means the total volume of gas to process is lower, and purification is even easier.
The obvious answer to this is
https://en.wikipedia.org/wiki/Amine_gas_treating
which is a well-understood process but it is not cheap. The other is to remove the N₂ before combustion. They do this
https://en.wikipedia.org/wiki/Rectisol
at what used to be the biggest carbon capture plant in the world
https://www.dakotagas.com/about-us/gasification/gasification...
but they have a liquid oxygen plant at the head end of the thing and they are separating acid gases from a stream of hydrogen and carbon monoxide about to be built up into methane.
There are other methods of combustion with oxygen but they are tricky: temperatures would be high (melt your turbine) if you really used pure oxygen, but if you recycle some of the output gas back into the turbine you might make it work.
Of course there is the cost of the oxygen separator so it is hard to be competitive. The hope with CLC is that you might be able to bolt it onto a fluidized bed combustion system and not raise the cost as much as the alternatives.
Personally I'm waiting for thunderf00t on this one. (But it's also cool to do strange stuff to brew beer, the story is an important part of the drinking, allegedly)
Looks promising for home heating during the winter; especially promising for areas of the world where the winter day is so short that using solar + battery for heating is impractical.
> Using this kind of cyclical process to generate electricity could approach a theoretical efficiency around 40 percent
My heat pump (air based) has a COE of 2.7. If the electricity was stored at 40% efficiency, that means I'm getting back 108% of the energy if combusting iron is used to store the energy!
Note: Where I live we have an old oil plant that only runs during cold snaps; and a newer gas plant next to it that runs when renewables are scarce.
Also , that electrolysis would surely leave behind some nasty acids and what not. What about their dumping ?
This process needs a lifecycle analysis, not just a round-trip analysis.
Electricity from renewables -> Hydrogen (electrolysis) -> (iron oxide to iron, in loop) -> heat -> iron oxide.
I would say this is a nice solution to the problem of storing hydrogen.
EDIT: Source, the publication: https://www.sciencedirect.com/science/article/pii/S036012851...
Presumably, this will be useful on a small scale to absorb certain types of scrap iron and steel that is contaminated with other elements that would make it unsuitable for normal recycling.
High quality iron would be better off being recycled, as the huge amount of energy originally expended in its reduction from oxide to iron doesn't have to be expended on the production of new iron.
These are the types of experiments that led to the discovery of oxygen.
Highly recommend this documentary funded by the NSF: https://youtu.be/z3Gt5IOjAu
Even my 4th grader liked it.
Seems like you could add water to the iron powder to get the exothermic rust reaction as well, if you don't need higher temperatures.
Wonder if this can be used for heating homes via small rechargeable cells that one recharges during summer with nothing more than a magnifying glass (well, or a concentrated solar plant).
I guess that's almost same as wood, except safer.
Where does the hydrogen come from when burning the iron powder since (presumably) water is not part of the burning process?
Critically, rust forms at much lower temperatures.
Edit - mistook oxides.
Honestly haven't been this excited by energy for years.
"Our ambition is to convert the first coal-fired power plants into sustainable iron fuel plants by 2030.”
They make it sound so clean with the ability to recover and reuse the iron. But if you replace coal with iron you'll need more than one coal fired plant to produce the energy to recover the burned iron. You can use wind or solar to power the electrolysis instead, but then theres no need to bother with the iron at all.
I bet they're hoping to just sequester the rust in a landfill or something.
Using iron as a big chemical battery seems at least plausible. More so if you get to reuse existing infrastructure to turn it back into energy.
Electrolysing rust into iron can be done when there is excess renewable energy available, and it can be burned when there is a deficit.
In other words, it's a chemical battery.
Iron needs to be mined, transported, ground and then the rust recycled somehow. Is the value of the energy released substantially more than the aggregate costs of releasing it?
sure hope he's not accidentally inhaling any of those fine particles bouncing off the funnel
https://toolsowner.com/blacksmith-forge-temperature
And we can use the Carnot formula to calculate efficiency:
https://en.wikipedia.org/wiki/Carnot%27s_theorem_(thermodyna...
efficiency = 1 - T_cold/T_hot = (T_hot - T_cold)/T_hot
First we must convert to Kelvin by adding 273.15 to the Celsius temperature. Here is a table with Carnot efficiencies calculated, assuming that the cool end of the cycle is something like a car radiator at just below the boiling point of water at 373 K (100 C or 212 F):
Material Temperature(Kelvin) Efficiency:
---
Coal 2250 83%
Iron 2073 82%
Propane 1533 76%
Wood 893 58%
Im having a hard time finding efficiencies for iron oxide electrolysis because all of the papers are behind paywalls. A big portion of the energy required is in heating the iron oxide in the first place, which could be done easily by solar collectors for free:
https://newenergyandfuel.com/http:/newenergyandfuel/com/2010...
This claims about 85-96% efficiency for aluminum oxide electrolysis:
https://www.tms.org/pubs/journals/JOM/9905/Welch-9905.html
I think a 95% efficiency might be reasonable for iron oxide if the temperature is raised by free solar thermal energy. So round trip efficiency is:
efficiency = 0.95 * 0.82 = 78%
This could be raised by a few percent by using a colder radiator (closer to room temperature at 300 K) and recapturing some of the waste heat with a Stirling engine. So I think that the article is accurate.
If someone has a table of electrolysis efficiencies for various compounds, that would be helpful.
Edit: after thinking about this for a moment, I realized that the Carnot efficiency should be calculated against room temperature if only the heat is being used and we aren't generating electricity. It only increases the efficiencies in the table above by about 3-8% from hottest to coldest, respectively.
Edit 2: for anyone curious, capturing heat and converting it to electricity is usually about 70% efficient at a turbine, and 95% efficient at a generator, for about 65% total. That's why a jet engine is limited to about 0.80 * 0.70 * 0.95 = 55% efficiency (40% in practice). Stirling engines are much closer to their ideal Carnot efficiency because their losses to turbulence (friction/entropy) are much lower. If my numbers are a little off here, please correct me.
Sounds pretty useless given that a) Elemental iron does not occur naturally on earth b) It requires a lot of energy, usually fossil fuels to make it.