Huh, I'm less doubtful of this than I thought I'd be. Tower cranes are apparently surprisingly low-maintenance. I assume this is because they have to actively participate in their own disassembly [1] and major breakages are super difficult to deal with because they're at altitude, so they need to operate reliably enough that they can always take themselves down at the end of a job or if they need a major repair (cracks found in main pivot ring, etc). Concretely (pun not intended), I found a document [2] saying that 10 tradesmen and $35k/month in parts (together a bit more than $1m/year) can keep a fleet of 70 tower cranes (15 metric ton lift capacity each) at ~80% utilization over a one-year period. So, yeah, I'd definitely believe that you could run these things at the quoted price.
If they don't call themselves Sisyphus Energy they're missing out on a great poetic opportunity.
> In Greek mythology Sisyphus was the king of Ephyra (now known as Corinth). He was punished for his self-aggrandizing craftiness and deceitfulness by being forced to roll an immense boulder up a hill only for it to roll down when it nears the top, repeating this action for eternity.
Its quite an ingenious idea. Could even hollow out a mountain to do this, avoiding the co2 cost of concrete.
"The round-trip efficiency of the system, which is the amount of energy recovered for every unit of energy used to lift the blocks, is about 85%—comparable to lithium-ion batteries which offer upto 90%."
That's quite efficient. Maybe they can get creative and build something different every day. One day you get a big pyramid, the next day you get a big elephant. That would be quite entertaining.
There's the horizontal version, so to speak, at https://www.aresnorthamerica.com/grid-scale-energy-storage -- it's running heavy weights up a hill on a closed rail loop to store and use them coming down to generate energy. 78% efficiency is claimed (in the press kit, the web page says "approaching 80%"). It claims to be able to store tens of gigawatt hours of energy.
The crane idea appeals to me more because the infrastructure appears simpler. Rather than having to build a lot of rail and a whole switching infrastructure, you just install the one crane and a shitload of heavy concrete blocks for it to lift. Seems like it would be cheaper.
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.
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."
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.
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).
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).
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.
I wonder though, the density of concrete is only about 2.5 higher than that of water. So, a concrete tower, comparable to a pumped-storage hydroelectricity plant would be gigantic. Seems infeasible to me.
The majority of the world’s economy is at or near the seaside. I find this approach more practical, similarly low tech (which is a good thing, simple and reliable) but uses hydrostatic pressure instead of gravity. http://theliquidgrid.com/2016/12/27/marine-energy-storage/
Sea floor is underutilized, but you can do a lot of things on a piece of land.
Below certain small depth the sea is always calm, atmosphere is not, I anticipate catastrophic consequences with these tall cranes when hurricanes, tornados or lightnings.
That seems harder to me. Anything done deep underwater costs at least an order of magnitude more, plus they still have all the same concrete requirements because they need ballast to keep the air balloons from rising to the surface.
Seems easier to just use that same mass on land with a crane.
The Ares Project (https://www.aresnorthamerica.com/) did something like this with robot trains shuttling concrete blocks up and down a slope. No news on that project in awhile tho. I hope this idea is more successful.
Quick question: how does the electricity get from the train (in motion) to the grid? Using the rails as conductors could work, but I'm not sure how efficient that would be.
They may as well make the concrete blocks in the shape of cups. Open a drain hole when the cups are on the ground. When the cups are on top of the towers, let them fill with rain.
This is why there are so many harebrained energy ideas - because people suggest ideas like this that sound vaguely plausible but when you spend a few seconds thinking about how much energy you'd get you realise it is pointless or just an idiotic version of an existing idea (hydro in your case).
Same for all the energy from pedestrians/cars ideas, solar roadways, etc.
What I don't get, why the complicated design to assemble the blocks into stacks? This seems to add a lot of non-essential complexity: Now you need cranes, a hooking/unhooking mechanism (that seems to even require cameras and image recognition!), the ability to move blocks horizontally and lots of computing power to coordinate the whole thing.
Even more, the up-front cost to recover energy is higher because you need to lift the blocks from the stacks before you can drop them.
Why not simply use a fixed hook/rope/motor/generator assembly per concrete block? Or, if there are too many blocks for that, use a hydraulic system? (But then again, what is the advantage of using many small blocks instead of a few large ones?)
Nothing against the company - the idea is awesome - but it seems weird that almost all the advertised innovations are solutions to problems that wouldn't exist without the "put the blocks into stacks" design:
>The innovation in Energy Vault’s plant is not the hardware. Cranes and motors have been around for decades, and companies like ABB and Siemens have optimized them for maximum efficiency. The round-trip efficiency of the system, which is the amount of energy recovered for every unit of energy used to lift the blocks, is about 85%—comparable to lithium-ion batteries which offer upto 90%.
Pedretti’s main work as the chief technology officer has been figuring out how to design software to automate contextually relevant operations, like hooking and unhooking concrete blocks, and to counteract pendulum-like movements during the lifting and lowering of those blocks.
(Not counting the described innovation of finding a new mixture that includes waste and reduces the amount of cement needed.)
The tower in the video looks like it contains hundreds of these blocks. You would therefore need hundreds of assemblies to do it that way, and each one has to lift the same weight that the crane is lifting. All of this to save on the cost of making the crane complex enough to move about, and the cost of the software involved.
Honest question. Is there a reason to use a crane rarther than digging a hole? It seems all that needs to happen is for a weight to be lifted and then allowed to fall. If that was done below ground, that would cut out the weather issues and I feel like the structure itself would be a lot more robust.
The general principle is converting kinetic energy -> potential energy (storage) and vice versa (consumption). My intuition is that using existing technology to lift a weight through lower atmosphere by >= X required meters is waaaaay more efficient than displacing ((X required meters of height) * required storage surface area) volume of Earth crust.
Why do you say that? We have fully automated CNC machines and 3D printers that can make things to amazing tolerances without human intervention. Stacking blocks neatly isn't a hard AI problem like self-driving cars are.
> If there is a single error the whole tower can collaps and do a lot of damage.
My reading of it is that the whole thing is fenced off anyway, since it contains an autonomous crane. Just put it somewhere that land isn't too valuable. If it all does collapse, the worst that can happen is it damages itself. Most wind turbines are similarly situated in places where, if they fail, there's nothing else really there to damage anyway.
> Is the low-cost-concrete a strong enough building material?
Presumably so, or if it's not, then it won't be used. I'd leave that to the engineers.
> The generator needs cooling (in hydro pump it is cooled by the water flowing through)
Cooling is not a hard problem. There are much larger plants generating way more power that operate 24/7 that handle cooling just fine. This idea is only generating as much power as a tower crane typically uses anyway, so whatever a tower crane has for cooling its motors should be fine. Probably some kind of closed loop liquid cooling system going to a big radiator with fans, like for a typical automobile engine.
It seems pretty easy to verify the blocks are stacked properly.
First, make them out of a shape that naturally fits together.
Then, build them with a vertical hole (shaft) through them. Put a reflector under the bottom one. Before the crane releases a block, it shines a light down the hole and checks if it is reflected back. Misalignment will block the light. (Or, you can do something similar with electricity, connected contacts on the top and bottom, and a check that current flows through the entire stack.)
Everybody seems fixated on the stacking, but it's clearly not central to the system, merely an artifact of the demonstration-scale (and presumably demonstration-budget) implementation. They could just as easily be lifting a tremendously massive object a small distance and then letting it back down again with fixed hoists, which eliminates all of the structural problems this stack of barrels faces. Also, that would allow a single unit to sink and source power continuously instead of intermittently like this crane.
How big an expensive of a foundation do you think it would need? I can't even imagine that being a major cost driver, compared to other elements of the system.
There is a similar idea using metal pellets fired from electromagnetic accelerators in a "space fountain". The energy would be stored there in the form of kinetic and potential energy, and it is relatively effortless to tap into that stored energy to even out something like the energy grid. Has the nice side effect of being able to launch things to space on it.
Good point. We know that large shifts in mass, like huge landslides caused by earthquakes, can measurably affect earth's rotation. What happens when we start using multi-gigaton masses for energy storage -- that are within a couple orders of magnitude of those landslides -- in a cyclic pattern? I wonder if we could even get resonant effects.
Q: A big stack of concrete blocks seems to be almost purpose built for the wind (or a gigantic mutant toddler/cat) to push over. Cranes are also extremely susceptible to wind. I suppose the blocks could be engineered to interlock, but the pictures show cylinders. How do they plan to counteract the wind?
One crane can store 20 megawatt hours. The wholesale price of a megawatt hour varies between US$-40 and US$120, normally being around US$60; if you manage to hit those peaks and valleys, which usually happen once a day, you make US$160. If you manage to do this 20 days a month, you make US$3200 a month or US$38400 a year. Given saulrh's comment https://news.ycombinator.com/item?id=17790442 that each tower crane requires US$500 a month in parts to keep it running, it seems plausible that this could be economically viable.
[+] [-] saulrh|7 years ago|reply
1: https://www.youtube.com/watch?v=Nww6MN_Lxeo&t=24s
2: Annex 9, "Example of the Use of Key Performance Indicators for Maintenance", in this PDF: https://www.mantiscranes.ie/wp-content/uploads/2017/01/CPA-T...
[+] [-] npunt|7 years ago|reply
> In Greek mythology Sisyphus was the king of Ephyra (now known as Corinth). He was punished for his self-aggrandizing craftiness and deceitfulness by being forced to roll an immense boulder up a hill only for it to roll down when it nears the top, repeating this action for eternity.
Its quite an ingenious idea. Could even hollow out a mountain to do this, avoiding the co2 cost of concrete.
[+] [-] maxxxxx|7 years ago|reply
That's quite efficient. Maybe they can get creative and build something different every day. One day you get a big pyramid, the next day you get a big elephant. That would be quite entertaining.
[+] [-] chx|7 years ago|reply
[+] [-] CydeWeys|7 years ago|reply
[+] [-] newman314|7 years ago|reply
[+] [-] montalbano|7 years ago|reply
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-...
[1] https://www.thespruce.com/difference-between-cement-concrete...
[+] [-] abalone|7 years ago|reply
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."
[+] [-] MauranKilom|7 years ago|reply
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/18.5922281715bdaebede9559/149604...
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/ (randomly sampled some states)
[1] https://www.umweltbundesamt.de/sites/default/files/medien/37... (German statistics)
[2] https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-...
[3] https://sans10400.co.za/concrete-mixes-by-weight/
[+] [-] pas|7 years ago|reply
[+] [-] seanmcdirmid|7 years ago|reply
[+] [-] unknown|7 years ago|reply
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[+] [-] JudasGoat|7 years ago|reply
[+] [-] baron816|7 years ago|reply
[+] [-] FrojoS|7 years ago|reply
I wonder though, the density of concrete is only about 2.5 higher than that of water. So, a concrete tower, comparable to a pumped-storage hydroelectricity plant would be gigantic. Seems infeasible to me.
[+] [-] Const-me|7 years ago|reply
Sea floor is underutilized, but you can do a lot of things on a piece of land.
Below certain small depth the sea is always calm, atmosphere is not, I anticipate catastrophic consequences with these tall cranes when hurricanes, tornados or lightnings.
[+] [-] CydeWeys|7 years ago|reply
Seems easier to just use that same mass on land with a crane.
[+] [-] jefurii|7 years ago|reply
[+] [-] theunamedguy|7 years ago|reply
[+] [-] sagebird|7 years ago|reply
[+] [-] dmurray|7 years ago|reply
[+] [-] gunn|7 years ago|reply
[+] [-] grenoire|7 years ago|reply
[+] [-] IshKebab|7 years ago|reply
Same for all the energy from pedestrians/cars ideas, solar roadways, etc.
[+] [-] tomxor|7 years ago|reply
[+] [-] xg15|7 years ago|reply
Even more, the up-front cost to recover energy is higher because you need to lift the blocks from the stacks before you can drop them.
Why not simply use a fixed hook/rope/motor/generator assembly per concrete block? Or, if there are too many blocks for that, use a hydraulic system? (But then again, what is the advantage of using many small blocks instead of a few large ones?)
Nothing against the company - the idea is awesome - but it seems weird that almost all the advertised innovations are solutions to problems that wouldn't exist without the "put the blocks into stacks" design:
>The innovation in Energy Vault’s plant is not the hardware. Cranes and motors have been around for decades, and companies like ABB and Siemens have optimized them for maximum efficiency. The round-trip efficiency of the system, which is the amount of energy recovered for every unit of energy used to lift the blocks, is about 85%—comparable to lithium-ion batteries which offer upto 90%.
Pedretti’s main work as the chief technology officer has been figuring out how to design software to automate contextually relevant operations, like hooking and unhooking concrete blocks, and to counteract pendulum-like movements during the lifting and lowering of those blocks.
(Not counting the described innovation of finding a new mixture that includes waste and reduces the amount of cement needed.)
[+] [-] ubercow13|7 years ago|reply
[+] [-] becasuretarded|7 years ago|reply
[deleted]
[+] [-] tomelders|7 years ago|reply
[+] [-] tempestn|7 years ago|reply
https://www.gravitricity.com/ https://news.ycombinator.com/item?id=8646787
http://gravitybattery.info/ https://news.ycombinator.com/item?id=6739349
[+] [-] tantalor|7 years ago|reply
[+] [-] pharrington|7 years ago|reply
[+] [-] progfix|7 years ago|reply
- Someone needs to watch the stacking process. If there is a single error the whole tower can collaps and do a lot of damage.
- You need a big (and expensive) foundation for a tower like this.
- Is the low-cost-concrete a strong enough building material?
- The generator needs cooling (in hydro pump it is cooled by the water flowing through)
[+] [-] CydeWeys|7 years ago|reply
Why do you say that? We have fully automated CNC machines and 3D printers that can make things to amazing tolerances without human intervention. Stacking blocks neatly isn't a hard AI problem like self-driving cars are.
> If there is a single error the whole tower can collaps and do a lot of damage.
My reading of it is that the whole thing is fenced off anyway, since it contains an autonomous crane. Just put it somewhere that land isn't too valuable. If it all does collapse, the worst that can happen is it damages itself. Most wind turbines are similarly situated in places where, if they fail, there's nothing else really there to damage anyway.
> Is the low-cost-concrete a strong enough building material?
Presumably so, or if it's not, then it won't be used. I'd leave that to the engineers.
> The generator needs cooling (in hydro pump it is cooled by the water flowing through)
Cooling is not a hard problem. There are much larger plants generating way more power that operate 24/7 that handle cooling just fine. This idea is only generating as much power as a tower crane typically uses anyway, so whatever a tower crane has for cooling its motors should be fine. Probably some kind of closed loop liquid cooling system going to a big radiator with fans, like for a typical automobile engine.
[+] [-] adrianmonk|7 years ago|reply
First, make them out of a shape that naturally fits together.
Then, build them with a vertical hole (shaft) through them. Put a reflector under the bottom one. Before the crane releases a block, it shines a light down the hole and checks if it is reflected back. Misalignment will block the light. (Or, you can do something similar with electricity, connected contacts on the top and bottom, and a check that current flows through the entire stack.)
[+] [-] ebikelaw|7 years ago|reply
[+] [-] VectorLock|7 years ago|reply
[+] [-] jaggederest|7 years ago|reply
http://www.orbitalvector.com/Orbital%20Travel/Space%20Founta...
[+] [-] vidanay|7 years ago|reply
[+] [-] amelius|7 years ago|reply
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[+] [-] infogulch|7 years ago|reply
[+] [-] DonHopkins|7 years ago|reply
[+] [-] IshKebab|7 years ago|reply
[+] [-] csours|7 years ago|reply
[+] [-] tpurves|7 years ago|reply
[+] [-] 7952|7 years ago|reply
[+] [-] ada1981|7 years ago|reply
We are also facing a global sand shortage crisis due to increased demand for concrete.
https://theconversation.com/the-world-is-facing-a-global-san...
[+] [-] kragen|7 years ago|reply
[+] [-] baron816|7 years ago|reply