8 ms·

Researchers make a supercapacitor from water, cement, and carbon black

164 points by ranit 2y ago

jakelsaunders94 2y ago
I’m not sure if I’ve misread the article but it seemed unclear as to whether the concrete needed to remain soaked in potassium chloride? Surely keeping a whole foundation soaked indefinitely would be impractical?
- rini17 2y ago
  Some electrolyte is certainly required for a supercapacitor. Hopefully battery research(solid electrolytes) carries over so that there will be no need for soaking concrete in corrosive solution.
amarant 2y ago
I don't want to be a naysayer, but I do have to wonder, are there any risks associated with making the walls themselves store large quantities of energy? I'm thinking fire hazards or shorts associated with, say, hanging a framed picture on the wall (or anything else that would involve drilling in the concrete)
- teraflop 2y ago
  I mean, one way to look at it is that the energy density of this concrete supercapacitor, when fully charged, is about 4 orders of magnitude smaller than the chemical energy density of wood. So depending on the design, electrical shorts might be something to worry about, but I have a hard time worrying about it as a significant fire hazard when compared to all of the other flammable things you might find in a house.
- killingtime74 2y ago
  300 watt-hours per cubic meter is not large by any means. You can get 300wh portable batteries and they are the size of a loaf of bread, this is at least 1 magnitude bigger/less dense
  - Earw0rm 2y ago
    Not even. I've a 500wh ebike battery which is about 3 litres in volume. We're talking 1/500th the density. Which is a good thing, as EV battery fires are nasty. A lot of stored energy there!
- kwhitefoot 2y ago
  It's only half the energy associated with raising the temperature of the same mass of concrete by one kelvin.
kallistisoft 2y ago
I'm happy this invention is still in the news cycle after the initial announcement 10 months ago... [0] https://news.ycombinator.com/item?id=36958531 https://news.ycombinator.com/item?id=36958531 [1] https://news.ycombinator.com/item?id=36993411 https://news.ycombinator.com/item?id=36993411 [2] https://news.ycombinator.com/item?id=36951089 https://news.ycombinator.com/item?id=36951089 While I'm fairly dubious about the proposed dual-purpose structural implementation of this material -- if this works at scale it would be a boon for low cost DIY local energy storage in the developing world and remote areas in other places. The idea that someone with minimal education/training can construct a durable electrical storage solution using commonly available materials and techniques is an absolute game changer!!
- westurner 2y ago
  - "Low-cost additive turns concrete slabs into super-fast energy storage" (2023) https://news.ycombinator.com/item?id=36964735 https://news.ycombinator.com/item?id=36964735
imtringued 2y ago
Why not use this for a way more obvious application such as corrosion protection? You can then mix in the sacrificial anode as a powder instead of having discrete anodes.
- contingencies 2y ago
  At least in a nautical context, sacrificial anodes wear out every few years and have to be swapped out for new material. That will be impossible if the anode is embodied within the material. But yeah, it probably has applications somewhere.
abdullahkhalids 2y ago
> larger versions, including one up to 45 cubic metres (1,590 cubic feet) in size that would be able store around 10kWh of energy needed to power to power a house for a day. 45 cubic meter is a cube with side 3.56 meter. That is not large at all. Especially, if it can be sunk into the ground. I assume septic tanks are also about the same size. Paper, if anyone interested: https://www.pnas.org/doi/full/10.1073/pnas.2304318120?doi=10.1073%2Fpnas.2304318120 https://www.pnas.org/doi/full/10.1073/pnas.2304318120?doi=10...
- kwhitefoot 2y ago
  A septic tank is usually only a few thousand litre. In the UK a house with a maximum occupancy of six would have a septic tank capacity of about 3 000 litre, that is, 3 cubic metre. A cube of just under 1.5 m on a side. See https://www.ukseptictanks.co.uk/size-septic-tanks https://www.ukseptictanks.co.uk/size-septic-tanks
- idiotsecant 2y ago
  That is quite an expensive battery if you're just sinking it into the ground as a cube, though. Concrete is pretty expensive and I'm sure carbon black makes concrete look cheap. I imagine the benefit would be if you can use it to build your foundation and get energy storage for 'free' in which case that's quite a lot of foundation.
  - abdullahkhalids 2y ago
    You are actually right [1]. Using the quoted figures of 30'x30'x4'' = 8 meter cube costing 7.5k USD, we get 41k USD. Which is crazy expensive even for foundation. [1] https://homeguide.com/costs/concrete-slab-cost https://homeguide.com/costs/concrete-slab-cost
    - dyauspitr 2y ago
      But you just need 45 cubic meters of concrete. That’s about $5k.
abeppu 2y ago
> For now, the concrete supercapacitor can store a little under 300 watt-hours per cubic metre – enough to power a 10-watt LED lightbulb for 30 hours. > The power output "may seem low compared to conventional batteries, [but] a foundation with 30-40 cubic metres (1,060-1,410 cubic feet) of concrete could be sufficient to meet the daily energy needs of a residential house", says Stefaniuk. This made me suspicious, because it sounded too low. But it turns out it's true ... for an average British home that's heavily dependent on gas. 40 m^3 * 300 watt-hours/m^3 = 12 kwh. I.e. 500 watts for a whole day. Apparently the average American residential electricity use is 10,791 kwh/year, which is ~1,231 watts, whereas the average British home is only 2,700 kwh/year which is ~308 watts. I had no idea that the difference was so large. https://www.eia.gov/tools/faqs/faq.php?id=97&t=3 https://www.eia.gov/tools/faqs/faq.php?id=97&t=3 https://www.britishgas.co.uk/energy/guides/average-bill.html https://www.britishgas.co.uk/energy/guides/average-bill.html
- tombert 2y ago
  I'm saying this with no data, but could it be because energy is just cheaper in the States? I have been using considerably less electricity since moving to NYC, since the price-per-KWh is about double what my costs were when I lived in Texas. Also, I'd be curious how much of this could be due to electric car usage increasing? This of course is anecdata, but I think a large percentage of it might come down to the fact that UK houses don't seem to run AC nearly as much. I spent two weeks in York a few years ago, during an extremely hot summer, and I was missing my AC very very much.
  - dgacmu 2y ago
    Some quick checking: Average (well, median) US house size: 2000 ft^2 Average UK house size: 68 m^2 = 740 ft^2 That makes for a very, very different HVAC bill. Numbers vary a lot by source but the relationship (2x+ larger in the US) holds. For example: https://www.zigguratrealestate.ph/post/how-big-is-a-house-average-house-size-by-country-2023 https://www.zigguratrealestate.ph/post/how-big-is-a-house-av...
    - tombert 2y ago
kwhitefoot 2y ago
That's a very poor article. It doesn't explain what the potassium chloride is for. It's interesting but you can store a lot of thermal energy in concrete. The heat capacity is 1050 J/(kg.K). One cubic meter of concrete is about 2 400 kg and the heat capacity is roughly 1 x 10^3 J/(kg.K) so raising the temperature by just 1 degree C would store 2.4 x 10^6 J. That's 666 Wh. Twice the energy storage for only one kelvin temperature rise with no technological breakthroughs needed. Granted it's not electricity but in temperate and colder climates a lot of the energy needed in a home is heat. Still a very interesting idea and if it can be made to work cheaply enough even at the storage capacity they quote it would add a lot of flexibility to the energy system.
ranit 2y ago
This is the research paper linked in the article. https://www.pnas.org/doi/10.1073/pnas.2304318120 https://www.pnas.org/doi/10.1073/pnas.2304318120
swores 2y ago
> "Supercapacitors are not perfect. Existing iterations discharge power quickly, and are not ideal for steady output, which would be needed to power a house throughout the day." Could someone kindly explain to me how this works? For example, if you had an empty lithium battery which can store X amount of power, and a fully charged supercapacitor which holds 10X, can you charge the lithium battery to full and leave 9X in the supercapacitor? If no, why not and how do you (both safely and usefully) get energy out of a supercapacitor? Or if yes, could a relatively small battery between the SC and a house act as a buffer to stop it mattering that the SC discharges "too quickly and unsteadily"?
- IX-103 2y ago
  The issue with a super-capacitor is that it leaks. If you put X Joules in there and wait a while then you will only have X/2 Joules. Wait a little longer and you'll only have X/4. So on the other hand, super-capacitors are great at charging and discharging rapidly with low loss. So if you want to fire a high powered laser for a few femtoseconds then they work great. You can't get power into and out of a battery that quickly because chemical reactions take time, so super-capacitors have their applications. It's just that holding power for more than a few minutes is probably not it.
  - swores 2y ago
    Thanks!
- EricE 2y ago
  You just have to put regulation in for supercapacitors that batteries don't need. Batteries have natural internal resistance, so they "meter" the power out, whereas capacitors are perfectly happy releasing all of their energy at once (also known as a bomb). If accounted for I don't see it as a big deal, but it is a potentially explosive risk.
  - swores 2y ago
    Thanks!
restalis 2y ago
The most relevant (practical) questions to me are, how does this capacitor behave long-term? How does it fare over a large number of charge/discharge cycles? I'd like to assume that, since it's not a battery, thus not based on chemical process for energy storage, it will retain its initial performance for a long time, but the question is - how long? A human generation (i.e. 25-30 years)? Or maybe longer, as for at least ten generations? That would directly affect the demand for long term investments in the construction sector. And if things may sound rosy from its storage capacity capability, if it will get used for combined structural and energy storage use, what long term impact on structural properties may render this dual use?
nanomonkey 2y ago
When looking at the diagrams for an ideal wall [1], I am reminded of diagrams of capacitors from Physics classes. This got me to thinking that two conductive vapor barrier with a dialectic/insulator sandwiched between them, such as aerogel, would work well as a wall element, and a capacitor storage device for a house. [1][https://buildingscience.com/documents/insights/bsi-001-the-perfect-wall https://buildingscience.com/documents/insights/bsi-001-the-p...]
- deleted 2y ago
  [deleted]
- Anarch157a 2y ago
  Until someone drills the wall, shorts the capacitor and causes a fire, while at the same time electrocuting whoever was doing the job. Capacitors need to be kept away from damage, so putting them on the foundation and sealed in concrete is a much safer approach.
- gravescale 2y ago
  Normal capacitors have to have absurdly thin dielectrics to get any appreciable charge storage. An aluminium electrolytic capacitor (the can shaped ones) use just thickness of an aluminium oxide layer. Any sandwich thickness that would be practical for thermal insulation will have essentially zero capacitance. And even if you could have a super thin, delicate layer in the walls, and the builders don't break it putting it in, why not just roll it up tightly and put it safely in a can along with any electrolyte it needs in the first place? The key feature of supercapacitors is that they exploit 3D effects (or rather a 2D effect around very tiny features in a 3D volume) that allow them to use the volume of the material, combined with a very tiny effective charge separation.
deleted 2y ago
[deleted]
Log_out_ 2y ago
So what happens if your house capacitor blows?
seu 2y ago
I see these things as a waste of time and resources. We already have all sorts of ways of storing energy, from chemical to mechanical to biological, which are known to work. There are myriad open questions regarding the practicalities of incorporating a battery as the frame of your house, and given the "technological inertia" of the building sector and its regulations, it would take several decades before we even start experimenting with this in real houses. Meanwhile, the world burns and we increase our energy consumption. Again, a waste of time and resources.

164 points by ranit 2y ago

I’m not sure if I’ve misread the article but it seemed unclear as to whether the concrete needed to remain soaked in potassium chloride? Surely keeping a whole foundation soaked indefinitely would be impractical?

rini17 2y ago
Some electrolyte is certainly required for a supercapacitor. Hopefully battery research(solid electrolytes) carries over so that there will be no need for soaking concrete in corrosive solution.

amarant 2y ago

I don't want to be a naysayer, but I do have to wonder, are there any risks associated with making the walls themselves store large quantities of energy? I'm thinking fire hazards or shorts associated with, say, hanging a framed picture on the wall (or anything else that would involve drilling in the concrete)

teraflop 2y ago
I mean, one way to look at it is that the energy density of this concrete supercapacitor, when fully charged, is about 4 orders of magnitude smaller than the chemical energy density of wood. So depending on the design, electrical shorts might be something to worry about, but I have a hard time worrying about it as a significant fire hazard when compared to all of the other flammable things you might find in a house.
killingtime74 2y ago
300 watt-hours per cubic meter is not large by any means. You can get 300wh portable batteries and they are the size of a loaf of bread, this is at least 1 magnitude bigger/less dense
- Earw0rm 2y ago
  Not even. I've a 500wh ebike battery which is about 3 litres in volume. We're talking 1/500th the density. Which is a good thing, as EV battery fires are nasty. A lot of stored energy there!
kwhitefoot 2y ago
It's only half the energy associated with raising the temperature of the same mass of concrete by one kelvin.

kallistisoft 2y ago

I'm happy this invention is still in the news cycle after the initial announcement 10 months ago... [0] https://news.ycombinator.com/item?id=36958531 https://news.ycombinator.com/item?id=36958531 [1] https://news.ycombinator.com/item?id=36993411 https://news.ycombinator.com/item?id=36993411 [2] https://news.ycombinator.com/item?id=36951089 https://news.ycombinator.com/item?id=36951089 While I'm fairly dubious about the proposed dual-purpose structural implementation of this material -- if this works at scale it would be a boon for low cost DIY local energy storage in the developing world and remote areas in other places. The idea that someone with minimal education/training can construct a durable electrical storage solution using commonly available materials and techniques is an absolute game changer!!

westurner 2y ago
- "Low-cost additive turns concrete slabs into super-fast energy storage" (2023) https://news.ycombinator.com/item?id=36964735 https://news.ycombinator.com/item?id=36964735

imtringued 2y ago

Why not use this for a way more obvious application such as corrosion protection? You can then mix in the sacrificial anode as a powder instead of having discrete anodes.

contingencies 2y ago
At least in a nautical context, sacrificial anodes wear out every few years and have to be swapped out for new material. That will be impossible if the anode is embodied within the material. But yeah, it probably has applications somewhere.

abdullahkhalids 2y ago

> larger versions, including one up to 45 cubic metres (1,590 cubic feet) in size that would be able store around 10kWh of energy needed to power to power a house for a day. 45 cubic meter is a cube with side 3.56 meter. That is not large at all. Especially, if it can be sunk into the ground. I assume septic tanks are also about the same size. Paper, if anyone interested: https://www.pnas.org/doi/full/10.1073/pnas.2304318120?doi=10.1073%2Fpnas.2304318120 https://www.pnas.org/doi/full/10.1073/pnas.2304318120?doi=10...

kwhitefoot 2y ago
A septic tank is usually only a few thousand litre. In the UK a house with a maximum occupancy of six would have a septic tank capacity of about 3 000 litre, that is, 3 cubic metre. A cube of just under 1.5 m on a side. See https://www.ukseptictanks.co.uk/size-septic-tanks https://www.ukseptictanks.co.uk/size-septic-tanks
idiotsecant 2y ago
That is quite an expensive battery if you're just sinking it into the ground as a cube, though. Concrete is pretty expensive and I'm sure carbon black makes concrete look cheap. I imagine the benefit would be if you can use it to build your foundation and get energy storage for 'free' in which case that's quite a lot of foundation.
- abdullahkhalids 2y ago
  You are actually right [1]. Using the quoted figures of 30'x30'x4'' = 8 meter cube costing 7.5k USD, we get 41k USD. Which is crazy expensive even for foundation. [1] https://homeguide.com/costs/concrete-slab-cost https://homeguide.com/costs/concrete-slab-cost
  - dyauspitr 2y ago
    But you just need 45 cubic meters of concrete. That’s about $5k.

abeppu 2y ago

> For now, the concrete supercapacitor can store a little under 300 watt-hours per cubic metre – enough to power a 10-watt LED lightbulb for 30 hours. > The power output "may seem low compared to conventional batteries, [but] a foundation with 30-40 cubic metres (1,060-1,410 cubic feet) of concrete could be sufficient to meet the daily energy needs of a residential house", says Stefaniuk. This made me suspicious, because it sounded too low. But it turns out it's true ... for an average British home that's heavily dependent on gas. 40 m^3 * 300 watt-hours/m^3 = 12 kwh. I.e. 500 watts for a whole day. Apparently the average American residential electricity use is 10,791 kwh/year, which is ~1,231 watts, whereas the average British home is only 2,700 kwh/year which is ~308 watts. I had no idea that the difference was so large. https://www.eia.gov/tools/faqs/faq.php?id=97&t=3 https://www.eia.gov/tools/faqs/faq.php?id=97&t=3 https://www.britishgas.co.uk/energy/guides/average-bill.html https://www.britishgas.co.uk/energy/guides/average-bill.html

tombert 2y ago
I'm saying this with no data, but could it be because energy is just cheaper in the States? I have been using considerably less electricity since moving to NYC, since the price-per-KWh is about double what my costs were when I lived in Texas. Also, I'd be curious how much of this could be due to electric car usage increasing? This of course is anecdata, but I think a large percentage of it might come down to the fact that UK houses don't seem to run AC nearly as much. I spent two weeks in York a few years ago, during an extremely hot summer, and I was missing my AC very very much.
- dgacmu 2y ago
  Some quick checking: Average (well, median) US house size: 2000 ft^2 Average UK house size: 68 m^2 = 740 ft^2 That makes for a very, very different HVAC bill. Numbers vary a lot by source but the relationship (2x+ larger in the US) holds. For example: https://www.zigguratrealestate.ph/post/how-big-is-a-house-average-house-size-by-country-2023 https://www.zigguratrealestate.ph/post/how-big-is-a-house-av...
  - tombert 2y ago

kwhitefoot 2y ago

That's a very poor article. It doesn't explain what the potassium chloride is for. It's interesting but you can store a lot of thermal energy in concrete. The heat capacity is 1050 J/(kg.K). One cubic meter of concrete is about 2 400 kg and the heat capacity is roughly 1 x 10^3 J/(kg.K) so raising the temperature by just 1 degree C would store 2.4 x 10^6 J. That's 666 Wh. Twice the energy storage for only one kelvin temperature rise with no technological breakthroughs needed. Granted it's not electricity but in temperate and colder climates a lot of the energy needed in a home is heat. Still a very interesting idea and if it can be made to work cheaply enough even at the storage capacity they quote it would add a lot of flexibility to the energy system.

ranit 2y ago

This is the research paper linked in the article. https://www.pnas.org/doi/10.1073/pnas.2304318120 https://www.pnas.org/doi/10.1073/pnas.2304318120

swores 2y ago

> "Supercapacitors are not perfect. Existing iterations discharge power quickly, and are not ideal for steady output, which would be needed to power a house throughout the day." Could someone kindly explain to me how this works? For example, if you had an empty lithium battery which can store X amount of power, and a fully charged supercapacitor which holds 10X, can you charge the lithium battery to full and leave 9X in the supercapacitor? If no, why not and how do you (both safely and usefully) get energy out of a supercapacitor? Or if yes, could a relatively small battery between the SC and a house act as a buffer to stop it mattering that the SC discharges "too quickly and unsteadily"?

IX-103 2y ago
The issue with a super-capacitor is that it leaks. If you put X Joules in there and wait a while then you will only have X/2 Joules. Wait a little longer and you'll only have X/4. So on the other hand, super-capacitors are great at charging and discharging rapidly with low loss. So if you want to fire a high powered laser for a few femtoseconds then they work great. You can't get power into and out of a battery that quickly because chemical reactions take time, so super-capacitors have their applications. It's just that holding power for more than a few minutes is probably not it.
- swores 2y ago
  Thanks!
EricE 2y ago
You just have to put regulation in for supercapacitors that batteries don't need. Batteries have natural internal resistance, so they "meter" the power out, whereas capacitors are perfectly happy releasing all of their energy at once (also known as a bomb). If accounted for I don't see it as a big deal, but it is a potentially explosive risk.
- swores 2y ago
  Thanks!

restalis 2y ago

The most relevant (practical) questions to me are, how does this capacitor behave long-term? How does it fare over a large number of charge/discharge cycles? I'd like to assume that, since it's not a battery, thus not based on chemical process for energy storage, it will retain its initial performance for a long time, but the question is - how long? A human generation (i.e. 25-30 years)? Or maybe longer, as for at least ten generations? That would directly affect the demand for long term investments in the construction sector. And if things may sound rosy from its storage capacity capability, if it will get used for combined structural and energy storage use, what long term impact on structural properties may render this dual use?

nanomonkey 2y ago

When looking at the diagrams for an ideal wall [1], I am reminded of diagrams of capacitors from Physics classes. This got me to thinking that two conductive vapor barrier with a dialectic/insulator sandwiched between them, such as aerogel, would work well as a wall element, and a capacitor storage device for a house. [1][https://buildingscience.com/documents/insights/bsi-001-the-perfect-wall https://buildingscience.com/documents/insights/bsi-001-the-p...]

deleted 2y ago
[deleted]
Anarch157a 2y ago
Until someone drills the wall, shorts the capacitor and causes a fire, while at the same time electrocuting whoever was doing the job. Capacitors need to be kept away from damage, so putting them on the foundation and sealed in concrete is a much safer approach.
gravescale 2y ago
Normal capacitors have to have absurdly thin dielectrics to get any appreciable charge storage. An aluminium electrolytic capacitor (the can shaped ones) use just thickness of an aluminium oxide layer. Any sandwich thickness that would be practical for thermal insulation will have essentially zero capacitance. And even if you could have a super thin, delicate layer in the walls, and the builders don't break it putting it in, why not just roll it up tightly and put it safely in a can along with any electrolyte it needs in the first place? The key feature of supercapacitors is that they exploit 3D effects (or rather a 2D effect around very tiny features in a 3D volume) that allow them to use the volume of the material, combined with a very tiny effective charge separation.

deleted 2y ago

[deleted]

Log_out_ 2y ago

So what happens if your house capacitor blows?

seu 2y ago

I see these things as a waste of time and resources. We already have all sorts of ways of storing energy, from chemical to mechanical to biological, which are known to work. There are myriad open questions regarding the practicalities of incorporating a battery as the frame of your house, and given the "technological inertia" of the building sector and its regulations, it would take several decades before we even start experimenting with this in real houses. Meanwhile, the world burns and we increase our energy consumption. Again, a waste of time and resources.