7 ms·

This is absolutely fascinating. Interestingly, the cement industry produces ~5% of global c02 emissions [0]. (Cement is an important binding element in concret

This is absolutely fascinating. Interestingly, the cement industry produces ~5% of global c02 emissions [0]. (Cement is an important binding element in concrete [1].) As this technology is presumably most useful for storing surplus energy from unpredictable renewable sources (e.g. wind, solar) I wonder if there is a conflict of interest? I'd love to know more about the carbon economics involved, perhaps they could use reclaimed (i.e. recycled) cement. [0] https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-cement-industry/ https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-... [1] https://www.thespruce.com/difference-between-cement-concrete-and-mortar-2130884 https://www.thespruce.com/difference-between-cement-concrete...

JudasGoat 8y ago
Would it matter if it was containers filled with water, soil, trash instead?
- monochromatic 8y ago
  Way less dense than concrete. So less energy stored.
  - yummybear 8y ago
    Sand and water?
    - LeifCarrotson 8y ago
      Rock.
- MauranKilom 8y ago
  Aside from mass density, the problem here would be structural integrity. How high can you stack buckets of water before the tower collapses? Probably not 120 meters. It comes as no surprise to me that this would use the same kind of material as a 120 m tall "normal" building.
  - CamperBob2 8y ago
    Considering that water isn't compressible, I'd think you could stack them even higher. Just use cylindrical containers with high strength in the radial direction. Also, how about compressing plain old air in an array of individual columns? It might be reasonable to improve the efficiency with some sort of heat exchanger.
    - MauranKilom 8y ago
      That would be a lot of steel. 100 meters of water is submarine territory. You need some thick walls to stem the radial pressure alone, probably at least 5 inches or 13 cm of steel (consider [0] and [1], this value also agrees with my intuition from engineering education). Assuming a barrel of 2 m radius and 3 m height (volume ~36 m³), that's 5 cubic meters (or 8 tons) of steel you'd need for the cylindrical hull alone, costing around 8000 USD in material [2] (varies wildly of course, but you're probably not using submarine grade steel). Per ~40 ton barrel. Would make about 40 million in steel costs alone for the number of barrels shown. I have no idea what your air compression idea entails, but it doesn't sound more realistic. Concrete is pretty good at being stacked (source: look around you). [0] http://www.madehow.com/Volume-5/Nuclear-Submarine.html http://www.madehow.com/Volume-5/Nuclear-Submarine.html [1] https://en.wikipedia.org/wiki/Submarine_hull#Dive_depth https://en.wikipedia.org/wiki/Submarine_hull#Dive_depth [2] https://www.wolframalpha.com/input/?i=steel+cost https://www.wolframalpha.com/input/?i=steel+cost
    - camtarn 8y ago
      Compressed air energy storage is also being investigated in a variety of forms: https://en.wikipedia.org/wiki/Compressed_air_energy_storage https://en.wikipedia.org/wiki/Compressed_air_energy_storage
- CydeWeys 8y ago
  They're not containers, they're structural. They need to be stackable dozens tall. You're basically limited to the kinds of materials you can build tall buildings out of -- concrete or steel. And concrete is much cheaper.
deleted 8y ago
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seanmcdirmid 8y ago
It’s not like they have to make concrete all the time, you would amatorize the concrete capital and environmental costs over the lifetime of the tower.
- deleted 8y ago
  [deleted]
MauranKilom 8y ago
Let's investigate this! For reference, a common electricity mix currently generates about 0.5 tons of CO2 per MWh [0][1]. Now, for the device in question: Creating 1 ton of cement releases about 1 ton of CO2 [2]. A common ratio of cement per mass of concrete is maybe 1/5 [4]. The article says they found a way to reduce that to a sixth, so we are at about 1/30 of the concrete mass in cement. From the article, each block weighs 35 tons. So we'll just assume 1 ton of cement (and CO2) per block. The graphic in the article shows ~40 layers of no more than 20x6 concrete blocks can be stacked around the tower, each weighing 35 tons. Therefore, each such installation would cost about 5000 tons of cement or CO2. So its building cost in cement alone is the equivalent of 10000 MWh. Fully "charged", it stores 20 MWh. It would therefore have to complete 500 full cycles of taking energy available for free (and otherwise lost) and feed it back. Roughly assuming it can do that every week (no idea, really depends), that would be ten years to become CO2 neutral, just in terms of cement. So there's your reference value. However, I haven't seen this kind of calculation for other energy sources. That would be interesting. Edit: Here is a review of CO2 from lithium-ion batteries: https://www.ivl.se/download/18.5922281715bdaebede9559/1496046218976/C243+The+life+cycle+energy+consumption+and+CO2+emissions+from+lithium+ion+batteries+.pdf https://www.ivl.se/download/18.5922281715bdaebede9559/149604... They say 150-200 tons of CO2-equivalent (!) per MWh stored, which is very close to the device in the article (in the above estimate it would be 250 tons of CO2 per MWh, although I did not check whether that is pure or CO2 equivalent). [0] https://www.eia.gov/electricity/state/ https://www.eia.gov/electricity/state/ (randomly sampled some states) [1] https://www.umweltbundesamt.de/sites/default/files/medien/376/bilder/entwicklung_der_spezifischen_kohlendioxid-emissionen_des_deutschen_strommix_1990-2016.png https://www.umweltbundesamt.de/sites/default/files/medien/37... (German statistics) [2] https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-cement-industry/ https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-... [3] https://sans10400.co.za/concrete-mixes-by-weight/ https://sans10400.co.za/concrete-mixes-by-weight/
- h4b4n3r0 8y ago
  I’ve also read that concrete absorbs CO2, in significant enough quantities that an isolated ecosystem experiment had to be aborted because plants weren’t getting enough of it.
abalone 8y ago
So it uses concrete which is VERY BAD and also needs a lot of it, but at maybe 1/6th the impact of regular concrete.[1] It's unclear how this works out in the end. Exactly how much cement do they need to scale this up? What's the CO2 impact per MW of storage, for example? I would say anything that involves significant CO2 emissions is not an ideal candidate for renewable energy storage. [1] From the article: "Energy Vault would need a lot of concrete to build hundreds of 35-metric-ton blocks... [but they've] developed a machine that can mix substances that cities often pay to get rid off, such as gravel or building waste, along with cement to create low-cost concrete blocks. The cost saving comes from having to use only a sixth of the amount of cement that would otherwise have been needed if the concrete were used for building construction."
- montalbano 8y ago
  I missed that bit in the article, thanks for pointing it out. So they are already developing ways to reduce c02 output of concrete production, nice. This would change c02 balancing estimates greatly.
  - azernik 8y ago
    You may have meant this, but just to clarify - they're developing methods of lowering the CO2 output (and financial cost) of their concrete weights, not concrete in general; they do this by not having to meet the structural strength requirements of regular concrete.
- Fjolsvith 8y ago
  So, how does the CO2 emissions of concrete production compare to that of Lithium ion battery production? Wouldn't it be mitigated by only being created once and then have a very long lifetime of utilization (vs the battery form of storage)?
  - pinko 8y ago
    Depends on how much the inferiority of the concrete vs. that used for construction affects its durability and longevity. It needs to be able to withstand weight from blocks above, impact whenever it or an adjacent block is moved, and corrosion from any metallic material within. I could almost imagine these blocks needing to be tougher over time than something made from cement used in construction, to avoid crumbling under those conditions.
baron816 8y ago
Couldn't they just use recycled concrete (from broken up roads and buildings) or just rocks instead?
- deleted 8y ago
  [deleted]
- VectorLock 8y ago
  Presumably they would need to build a vessel to hold the concrete rubble in, as opposed to casting their concrete directly in the shape they desire.
- CydeWeys 8y ago
  No, the whole point is that they need to stack these blocks up very high. You need uniformly shaped blocks for this, so no rock, and recycling concrete doesn't let you reuse the cement as binding agent -- it's already inactivated. You just get to use reuse the aggregate, which isn't the environmentally expensive component to manufacture.
  - dagss 8y ago
    People have turned rocks into uniformly shaped objects for thousands of years...
    - onetimemanytime 8y ago
      at a huge cost.... https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQlz2Q6AHm2JjaXwIxXEgUXVtEgCCT8XH3DuQGOBryDDAXEQUEaxA https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQlz2Q6...
pas 8y ago
They could make the concrete (the cement) in plants with CO2 capture. Sure, costs a lot more, but then it'd CO2 negative (as curing concrete binds CO2 from the air).

JudasGoat 8y ago

Would it matter if it was containers filled with water, soil, trash instead?

monochromatic 8y ago
Way less dense than concrete. So less energy stored.
- yummybear 8y ago
  Sand and water?
  - LeifCarrotson 8y ago
    Rock.
MauranKilom 8y ago
Aside from mass density, the problem here would be structural integrity. How high can you stack buckets of water before the tower collapses? Probably not 120 meters. It comes as no surprise to me that this would use the same kind of material as a 120 m tall "normal" building.
- CamperBob2 8y ago
  Considering that water isn't compressible, I'd think you could stack them even higher. Just use cylindrical containers with high strength in the radial direction. Also, how about compressing plain old air in an array of individual columns? It might be reasonable to improve the efficiency with some sort of heat exchanger.
  - MauranKilom 8y ago
    That would be a lot of steel. 100 meters of water is submarine territory. You need some thick walls to stem the radial pressure alone, probably at least 5 inches or 13 cm of steel (consider [0] and [1], this value also agrees with my intuition from engineering education). Assuming a barrel of 2 m radius and 3 m height (volume ~36 m³), that's 5 cubic meters (or 8 tons) of steel you'd need for the cylindrical hull alone, costing around 8000 USD in material [2] (varies wildly of course, but you're probably not using submarine grade steel). Per ~40 ton barrel. Would make about 40 million in steel costs alone for the number of barrels shown. I have no idea what your air compression idea entails, but it doesn't sound more realistic. Concrete is pretty good at being stacked (source: look around you). [0] http://www.madehow.com/Volume-5/Nuclear-Submarine.html http://www.madehow.com/Volume-5/Nuclear-Submarine.html [1] https://en.wikipedia.org/wiki/Submarine_hull#Dive_depth https://en.wikipedia.org/wiki/Submarine_hull#Dive_depth [2] https://www.wolframalpha.com/input/?i=steel+cost https://www.wolframalpha.com/input/?i=steel+cost
  - camtarn 8y ago
    Compressed air energy storage is also being investigated in a variety of forms: https://en.wikipedia.org/wiki/Compressed_air_energy_storage https://en.wikipedia.org/wiki/Compressed_air_energy_storage
CydeWeys 8y ago
They're not containers, they're structural. They need to be stackable dozens tall. You're basically limited to the kinds of materials you can build tall buildings out of -- concrete or steel. And concrete is much cheaper.

deleted 8y ago

[deleted]

seanmcdirmid 8y ago

It’s not like they have to make concrete all the time, you would amatorize the concrete capital and environmental costs over the lifetime of the tower.

deleted 8y ago
[deleted]

MauranKilom 8y ago

Let's investigate this! For reference, a common electricity mix currently generates about 0.5 tons of CO2 per MWh [0][1]. Now, for the device in question: Creating 1 ton of cement releases about 1 ton of CO2 [2]. A common ratio of cement per mass of concrete is maybe 1/5 [4]. The article says they found a way to reduce that to a sixth, so we are at about 1/30 of the concrete mass in cement. From the article, each block weighs 35 tons. So we'll just assume 1 ton of cement (and CO2) per block. The graphic in the article shows ~40 layers of no more than 20x6 concrete blocks can be stacked around the tower, each weighing 35 tons. Therefore, each such installation would cost about 5000 tons of cement or CO2. So its building cost in cement alone is the equivalent of 10000 MWh. Fully "charged", it stores 20 MWh. It would therefore have to complete 500 full cycles of taking energy available for free (and otherwise lost) and feed it back. Roughly assuming it can do that every week (no idea, really depends), that would be ten years to become CO2 neutral, just in terms of cement. So there's your reference value. However, I haven't seen this kind of calculation for other energy sources. That would be interesting. Edit: Here is a review of CO2 from lithium-ion batteries: https://www.ivl.se/download/18.5922281715bdaebede9559/1496046218976/C243+The+life+cycle+energy+consumption+and+CO2+emissions+from+lithium+ion+batteries+.pdf https://www.ivl.se/download/18.5922281715bdaebede9559/149604... They say 150-200 tons of CO2-equivalent (!) per MWh stored, which is very close to the device in the article (in the above estimate it would be 250 tons of CO2 per MWh, although I did not check whether that is pure or CO2 equivalent). [0] https://www.eia.gov/electricity/state/ https://www.eia.gov/electricity/state/ (randomly sampled some states) [1] https://www.umweltbundesamt.de/sites/default/files/medien/376/bilder/entwicklung_der_spezifischen_kohlendioxid-emissionen_des_deutschen_strommix_1990-2016.png https://www.umweltbundesamt.de/sites/default/files/medien/37... (German statistics) [2] https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-cement-industry/ https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-... [3] https://sans10400.co.za/concrete-mixes-by-weight/ https://sans10400.co.za/concrete-mixes-by-weight/

h4b4n3r0 8y ago
I’ve also read that concrete absorbs CO2, in significant enough quantities that an isolated ecosystem experiment had to be aborted because plants weren’t getting enough of it.

abalone 8y ago

So it uses concrete which is VERY BAD and also needs a lot of it, but at maybe 1/6th the impact of regular concrete.[1] It's unclear how this works out in the end. Exactly how much cement do they need to scale this up? What's the CO2 impact per MW of storage, for example? I would say anything that involves significant CO2 emissions is not an ideal candidate for renewable energy storage. [1] From the article: "Energy Vault would need a lot of concrete to build hundreds of 35-metric-ton blocks... [but they've] developed a machine that can mix substances that cities often pay to get rid off, such as gravel or building waste, along with cement to create low-cost concrete blocks. The cost saving comes from having to use only a sixth of the amount of cement that would otherwise have been needed if the concrete were used for building construction."

montalbano 8y ago
I missed that bit in the article, thanks for pointing it out. So they are already developing ways to reduce c02 output of concrete production, nice. This would change c02 balancing estimates greatly.
- azernik 8y ago
  You may have meant this, but just to clarify - they're developing methods of lowering the CO2 output (and financial cost) of their concrete weights, not concrete in general; they do this by not having to meet the structural strength requirements of regular concrete.
Fjolsvith 8y ago
So, how does the CO2 emissions of concrete production compare to that of Lithium ion battery production? Wouldn't it be mitigated by only being created once and then have a very long lifetime of utilization (vs the battery form of storage)?
- pinko 8y ago
  Depends on how much the inferiority of the concrete vs. that used for construction affects its durability and longevity. It needs to be able to withstand weight from blocks above, impact whenever it or an adjacent block is moved, and corrosion from any metallic material within. I could almost imagine these blocks needing to be tougher over time than something made from cement used in construction, to avoid crumbling under those conditions.

baron816 8y ago

Couldn't they just use recycled concrete (from broken up roads and buildings) or just rocks instead?

deleted 8y ago
[deleted]
VectorLock 8y ago
Presumably they would need to build a vessel to hold the concrete rubble in, as opposed to casting their concrete directly in the shape they desire.
CydeWeys 8y ago
No, the whole point is that they need to stack these blocks up very high. You need uniformly shaped blocks for this, so no rock, and recycling concrete doesn't let you reuse the cement as binding agent -- it's already inactivated. You just get to use reuse the aggregate, which isn't the environmentally expensive component to manufacture.
- dagss 8y ago
  People have turned rocks into uniformly shaped objects for thousands of years...
  - onetimemanytime 8y ago
    at a huge cost.... https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQlz2Q6AHm2JjaXwIxXEgUXVtEgCCT8XH3DuQGOBryDDAXEQUEaxA https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQlz2Q6...

pas 8y ago

They could make the concrete (the cement) in plants with CO2 capture. Sure, costs a lot more, but then it'd CO2 negative (as curing concrete binds CO2 from the air).