10 ms·

Just to spell out something that's been implicit in other comments: the entropy level of your energy matters a lot. Electricity > movement > heat. To go down th

Just to spell out something that's been implicit in other comments: the entropy level of your energy matters a lot. Electricity > movement > heat. To go down the chain is almost free, to go up the chain you have to spend quite a lot. 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).

ReptileMan 6y ago
Still an option for the mix if you have to capture a huge surplus of renewables. And there are no metallurgy smelting plants nearby.
MayeulC 6y ago
You are right, of course, but I wonder if you couldn't use "waste heat" as the energy input of this "heat battery"? This would make the economics much better: instead of going, say, nuclear -> steam engine -> electricity -> iron -> heat (-> electricity), you could skip the first conversion losses. Not sure how doable it would be from a chemistry point of view, though: you probably need at least one extra reagent or catalyst.
- abdusco 6y ago
  Source temperature of waste heat is an important factor. Heat radiating from a 2000C source is a lot more valuable & useful than that from some warm water at 60C. You can't use that heat to raise the temperature of something to 61C, for example.
  - rocqua 6y ago
    But you could use a heat pump and 60C water to raise the temperature of something to 61C. And would take a lot less energy to run that heat-pump than to actually heat that something to 61C. 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.
    - jjk166 6y ago
      No that explicitly violates the second law of thermodynamics. 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.
      - JoeAltmaier 6y ago
        Well, not without losing some water in the process. If you spill 10 gallons of water through the pump to pump 1 upward, sure that works.
        MayeulC 6y ago
        And this is the exact idea behind ram pumps: https://en.wikipedia.org/wiki/Hydraulic_ram https://en.wikipedia.org/wiki/Hydraulic_ram
        jjk166 6y ago
        Well in this case you need to pump 10 gallons up to get those 10 gallons to spill down. At some point in the chain, you need to consume energy from the environment to drive the system.
- lambdatronics 6y ago
  For short-term storage at a nuclear plant, you could use molten salt thermal storage. In terms of a 'battery,' decomposing ammonia to H2+N2 is one way to directly convert heat to chemical stored energy: https://eeme.anu.edu.au/research/research-projects/ammonia-based-energy-storage https://eeme.anu.edu.au/research/research-projects/ammonia-b... 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 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.
BlueTemplar 6y ago
You have to compare the efficiency to other similar options. For instance, (hydrogen-based) fuel cells also only have around 40-60% efficiency… 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 ?
- jmvoodoo 6y ago
  My immediate thought was production of quicklime for concrete.
  - BlueTemplar 6y ago
    Yeah, and concrete making releases a lot of concentrated CO2, so there's already a lot of potential for algae-growing to make liquid hydrocarbon fuels there !
sergiosgc 6y ago
Some industrial processes require very high temperatures, for which electrical generation is ill suited. Glass furnaces are one such case. Having an efficient local energy delivery mechanism that may be "recharged" with electricity is quite interesting. 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.
- ahartmetz 6y ago
  On the other hand, electricity can create almost "infinite temperature" with relative ease. Temperature is, roughly speaking, the average kinetic energy of a material's molecules, and you can accelerate particles to extremely kigh kinetic energy with electromagnetic fields. So if you need that kind of "temperature", electricity is very suitable, even though it's expensive per unit of energy. Another example for how electricity is a very valuable type of energy.
- usrusr 6y ago
  An asynchronous high intensity heat source, asynchronous in that it can be "charged" from electricity ahead of utilization time, whenever intermittent energy sources are high. According to the article at 80% efficiency, that's pretty good for a storage method that is cheap in capacity (think seasonal storage or beyond). 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.
yholio 6y ago
The most important take away from this is that electrical energy can be easily "multiplied" into thermal energy by using it to move around the almost unlimited thermal energy contained in the environment around us. 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.
- harperlee 6y ago
  But this is not a takeaway that’s specific to this process, that’s how ubiquitous heat pumps work in residential HVAC. The article takeaway is that iron powder is a surprising electricity—>heat battery.
- IgorPartola 6y ago
  The other way to put it is that your efficiency is proportional to 1/(delta T). In other words if your heat pump is working between two environments with very close temperatures then the heat transfer is very efficient (for example 19 degrees C outside, 21 inside). But if you are trying to heat your house to a livable temperature while it’s -20 outside, your efficiency is terrible. 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.
  - Reason077 6y ago
    > "But if you are trying to heat your house to a livable temperature while it’s -20 outside, your efficiency is terrible." 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.
mihaaly 6y ago
Yes, it is not battery for electricity. As here the point was to get heat where heat is required, it is still very spot on.
hamilyon2 6y ago
I always thought about it as Electricity <-> movement ↓ High quality heat (e.g. welding torch, tungsten lamp) ↓ Low quality heat (air conditioning)
jacquesm 6y ago
Electricity is steak, heat is hamburger.
socialdemocrat 6y ago
It is true that it is a less efficient way of storing electric power than a battery as you need to created steam to drive turbines. 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.
Reason077 6y ago
> "So you can't call this an "iron battery", because you don't get electricity out of it, just heat." 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#Iron–air https://en.wikipedia.org/wiki/Metal–air_electrochemical_cell...
clomond 6y ago
A really interesting application of this came to mind that seems like an optimal use of this “iron heat battery” from a pure physics perspective. 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.
- jseutter 6y ago
  An oxygen free warehouse is overkill. Iron needs both oxygen and water to rust, so you can store it in a warehouse with just some climate control to manage the humidity. You could treat it like any other flammable powder, where you keep dust down as much as possible, and keep flame sources away. Fine steel wool will burn readily, yet it keeps underneath the sink and only rusts over a period of years.
URSpider94 6y ago
My counterpoint would be that efficiency isn't always the most important variable in an energy supply chain, especially when your energy supply is renewable, and thus non-polluting, and as the marginal cost for generation of renewable energy continues to drop. 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.
commonturtle 6y ago
Thanks for pointing this out. I was wondering if there was a catch. So this might be a good way to heat things but not to generate electricity.
patall 6y ago
With large amounts of heat in your home, you can do cogeneration (combined heat and power). Heat some water via oxidation, produce electricity with the steam, collect the excess heat to keep the house warm. And you can do that all winter long as long as your basement is full of iron powder. And in the summer, you reduce the iron oxide again with excess solar power. (That's not what they want to do here but that would be the idea)

ReptileMan 6y ago

Still an option for the mix if you have to capture a huge surplus of renewables. And there are no metallurgy smelting plants nearby.

MayeulC 6y ago

You are right, of course, but I wonder if you couldn't use "waste heat" as the energy input of this "heat battery"? This would make the economics much better: instead of going, say, nuclear -> steam engine -> electricity -> iron -> heat (-> electricity), you could skip the first conversion losses. Not sure how doable it would be from a chemistry point of view, though: you probably need at least one extra reagent or catalyst.

abdusco 6y ago
Source temperature of waste heat is an important factor. Heat radiating from a 2000C source is a lot more valuable & useful than that from some warm water at 60C. You can't use that heat to raise the temperature of something to 61C, for example.
- rocqua 6y ago
  But you could use a heat pump and 60C water to raise the temperature of something to 61C. And would take a lot less energy to run that heat-pump than to actually heat that something to 61C. 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.
  - jjk166 6y ago
    No that explicitly violates the second law of thermodynamics. 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.
    - JoeAltmaier 6y ago
      Well, not without losing some water in the process. If you spill 10 gallons of water through the pump to pump 1 upward, sure that works.
      - MayeulC 6y ago
        And this is the exact idea behind ram pumps: https://en.wikipedia.org/wiki/Hydraulic_ram https://en.wikipedia.org/wiki/Hydraulic_ram
      - jjk166 6y ago
        Well in this case you need to pump 10 gallons up to get those 10 gallons to spill down. At some point in the chain, you need to consume energy from the environment to drive the system.
lambdatronics 6y ago
For short-term storage at a nuclear plant, you could use molten salt thermal storage. In terms of a 'battery,' decomposing ammonia to H2+N2 is one way to directly convert heat to chemical stored energy: https://eeme.anu.edu.au/research/research-projects/ammonia-based-energy-storage https://eeme.anu.edu.au/research/research-projects/ammonia-b... 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 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.

BlueTemplar 6y ago

You have to compare the efficiency to other similar options. For instance, (hydrogen-based) fuel cells also only have around 40-60% efficiency… 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 ?

jmvoodoo 6y ago
My immediate thought was production of quicklime for concrete.
- BlueTemplar 6y ago
  Yeah, and concrete making releases a lot of concentrated CO2, so there's already a lot of potential for algae-growing to make liquid hydrocarbon fuels there !

sergiosgc 6y ago

Some industrial processes require very high temperatures, for which electrical generation is ill suited. Glass furnaces are one such case. Having an efficient local energy delivery mechanism that may be "recharged" with electricity is quite interesting. 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.

ahartmetz 6y ago
On the other hand, electricity can create almost "infinite temperature" with relative ease. Temperature is, roughly speaking, the average kinetic energy of a material's molecules, and you can accelerate particles to extremely kigh kinetic energy with electromagnetic fields. So if you need that kind of "temperature", electricity is very suitable, even though it's expensive per unit of energy. Another example for how electricity is a very valuable type of energy.
usrusr 6y ago
An asynchronous high intensity heat source, asynchronous in that it can be "charged" from electricity ahead of utilization time, whenever intermittent energy sources are high. According to the article at 80% efficiency, that's pretty good for a storage method that is cheap in capacity (think seasonal storage or beyond). 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.

yholio 6y ago

The most important take away from this is that electrical energy can be easily "multiplied" into thermal energy by using it to move around the almost unlimited thermal energy contained in the environment around us. 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.

harperlee 6y ago
But this is not a takeaway that’s specific to this process, that’s how ubiquitous heat pumps work in residential HVAC. The article takeaway is that iron powder is a surprising electricity—>heat battery.
IgorPartola 6y ago
The other way to put it is that your efficiency is proportional to 1/(delta T). In other words if your heat pump is working between two environments with very close temperatures then the heat transfer is very efficient (for example 19 degrees C outside, 21 inside). But if you are trying to heat your house to a livable temperature while it’s -20 outside, your efficiency is terrible. 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.
- Reason077 6y ago
  > "But if you are trying to heat your house to a livable temperature while it’s -20 outside, your efficiency is terrible." 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.

mihaaly 6y ago

Yes, it is not battery for electricity. As here the point was to get heat where heat is required, it is still very spot on.

hamilyon2 6y ago

I always thought about it as Electricity <-> movement ↓ High quality heat (e.g. welding torch, tungsten lamp) ↓ Low quality heat (air conditioning)

jacquesm 6y ago

Electricity is steak, heat is hamburger.

socialdemocrat 6y ago

It is true that it is a less efficient way of storing electric power than a battery as you need to created steam to drive turbines. 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.

Reason077 6y ago

> "So you can't call this an "iron battery", because you don't get electricity out of it, just heat." 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#Iron–air https://en.wikipedia.org/wiki/Metal–air_electrochemical_cell...

clomond 6y ago

A really interesting application of this came to mind that seems like an optimal use of this “iron heat battery” from a pure physics perspective. 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.

jseutter 6y ago
An oxygen free warehouse is overkill. Iron needs both oxygen and water to rust, so you can store it in a warehouse with just some climate control to manage the humidity. You could treat it like any other flammable powder, where you keep dust down as much as possible, and keep flame sources away. Fine steel wool will burn readily, yet it keeps underneath the sink and only rusts over a period of years.

URSpider94 6y ago

My counterpoint would be that efficiency isn't always the most important variable in an energy supply chain, especially when your energy supply is renewable, and thus non-polluting, and as the marginal cost for generation of renewable energy continues to drop. 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.

commonturtle 6y ago

Thanks for pointing this out. I was wondering if there was a catch. So this might be a good way to heat things but not to generate electricity.

patall 6y ago

With large amounts of heat in your home, you can do cogeneration (combined heat and power). Heat some water via oxidation, produce electricity with the steam, collect the excess heat to keep the house warm. And you can do that all winter long as long as your basement is full of iron powder. And in the summer, you reduce the iron oxide again with excess solar power. (That's not what they want to do here but that would be the idea)