Stacking concrete blocks is a surprisingly efficient way to store energy
qz.com
qz.com
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...
The use of space to store energy is maybe double of what typical damn reservoir uses to store the same amount of energy.
http://documents.worldbank.org/curated/en/739881515751628436...
And methane is a greenhouse gas 20-80x more potent than carbon dioxide.
Concrete has the advantage of lasting "forever" in those conditions (rebar when wet ruins it, otherwise it last long, long time). Concrete also stacks perfectly as you can mold it however you want. Might bite the bullet and stick with concrete, just work on making it more efficient.
Here's some totally useless back-of-the-envelope calculations on land requirements for this sytem.
The United States, in total, used 1,819,393,805 MWh of energy in 2016. If one plant provides 35MWh of storage, that means 51,982,680 plants are required.
That comes to 84,211,942 acres of land. There are 2.3 billion acres of land in the United States, so it would require 3.66% of the US. That's obviously a huge overestimate.
The beauty of this is the simplicity. This is something we could have built 40 years ago. And unlike LIBs, there's much less worry about degradation and we can put these out in the desert near a solar power source without worry.
Imagine it combined with solar thermal, which has dropped immensely in price per KWh.
Also, concrete reabsorbs around 43% of the co2 used to create it over a period of time.
But they'd probably be mechanized before long.
> If anything, that's a plus.
That's the world you want to live in, where there are more construction crane maintenance workers than teachers, police officer, food service workers, lawyers and doctors combined and then tripled? Is there no possible better use for human potential that fixing machines that lift bricks?
"Truck Driver", however, is a common job title[0] which may go away thanks to automation. Finding a replacement role would be nice.
I'm not sure you mean to insult people whose job it is to fix machines that lift bricks, by the way?
[0] https://www.npr.org/sections/money/2015/02/05/382664837/map-...
Why is working on power storage and generation meaningless? Cheap energy is literally the basis of our civilization, tech, and standard of living. Would you consider power plant work or oil drilling work meaningless?
That's why I asked if that was the pinnacle of human achievement. If nothing was better. Because it crowds our other things at that level.
10% of that makes more sense, even if it goes, let's say, 50% solar
10% would be overkill. I don’t think we should be aiming to sacrifice our livelihoods to be concrete block stacking addicted energy horarders, but I’m not entirely against that either. It’s hard to look at a solution so tangible and transparent as concrete block stacking before ducking my head into this mangled half-commented test suite.
As others have said,they likely would be placed near the solar plant where land is cheap and dry, rather than in neighborhoods.
I'm sceptical of that. As the sibling comment noted, the technology is well-tested, yes but for a completely different usage pattern. You don't know how reliably construction cranes are in lifting heavy loads in back-to-back cycles, 24/7.
Additionally, I'd guess you will have to modify the cranes to realize the "recover energy" parts. I'm no expert, but I could imagine, traditional parts spend energy for both raising and lowering a weight because the design goal is reliable control of the load, not making energy. So you'd probably have to modify the motor assembly.
From what I've been told, the magic isn't in the generators (almost every project I'm working on is just using a standard industrial motor as a generator) but in the smart regenerative drives which both supply and harvest power from them. Harvesting power from industrial processes to keep costs down seems like it's a very common thing to do, so these drives are available off the shelf, and are designed to plug into a variety of existing motors.
That's definitely a really awkward choice of word in that context for it not to be intended, so I'm thinking pun was, in fact, intended. You can try to convince me otherwise but in order to do so I'll need to see some concrete evidence (pun not intended)
Anyway, I really didn't intend the pun! My reaction to the article was to try to get a rough estimate of how reliable tower cranes are, at which point I realized that they must be very reliable to work at all. But I only had that broad hypothesis of "very reliable", so I went looking for evidence to confirm it, and if so, what that broad hypothesis ended up looking like in practice. For whatever reason I found "concretely" when I went looking for a word for the segue. Probably concrete on the brain and a bit of luck.
In a normal building site they either do very few cycles per hour (at heavy loads) or a decent number of cycles per hour at a tiny fraction of their load capacity.
Even when you use them intensively (with concrete buckets) to lift/pour concrete, that happens for a relatively short time (a few hours) each day.
A typical cycle is 5-10 minutes and you don't actually have 12 or 6 of them per hour, each hour in a normal 8 hour shift and - with some exceptions you normally have 1 shift per day, 5/7 (it is rare that a site working with cranes operates 24/7).
Besides, in a building site you don't work when it rains, and you cannot work with cranes if there is a not-so-strong wind blowing (for safety reasons).
[1] no reference, you will need to trust my word for it, coming from some 30+ years experience in building sites
I did notice that the cylinders were around twice the quoted capacities for tower cranes I was finding. It also sounds like they're building a much more expensive crane; that many cylinders, at 35 metric tons per and $90 for a yard of concrete, is upwards of $5m, and the article says that the concrete "could" be the most expensive part. Aaaaand random googling is giving me price tags for tower cranes that can't possibly be right - <$300k?! So the quoted system might be using a crane that's ten times the cost of a "normal" tower crane? I can... sort of seeing that buy a six-armed crane with twice the lift capacity but permanent construction, no need for a counterweight assembly, and better continuous performance. But now I feel like these numbers are lining up too well and I have to have done something wrong.
1. https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-l...
2. http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+y...)
A "normal" (very large) tower crane rarely exceeds 12 tons, BUT, more than that, usually these use not "single" cable, i.e. a largish crane is usually 6 tons max, but can lift up to 12 tons doubling the cable/rope (which implies halving the lifting speed).
Moreover, cranes are rated/designed (loosely) on their reach, they are intended - within limits - to cover a whole building site, so arms of 20-30-40-50-60 meters.
An electric tower crane (a "normal" one) is well below US$ 300 K, I seem to remember we paid for a very large one, 80/100 meters tall, 50/60 meters arm, 6/12 tons at arm point around 250,000 Euro a few years ago (but costs have not increased much as it is a stale market AFAIK).
The "key factor" is the "overturning" moment at the base (that implies a much sturdier tower and heavier coounterweights), and the single tower design is aimed to have a "light", "transportable" and "easily assemblable/disassemblable unit" the actual lattice is subject to very heavy tensile cycles as it is extremely flexible.
It would make much more sense (to me at least) to have a specially designed crane with an as short as possible arm, traveling on a track (which is also a setup commonly used in building sites) or a portal crane, like the ones used in quarries or pre-fabrication sites 35 tons are a lot of weight.
Besides (reinforced) concrete is at the most 2.3 tons per cubic meter, so it is not very efficient as a weight/counterweight, though possibly it is among the lower cost per kg material.
On the other hand rebar concrete is an excellent material for the actual tower, so in a fixed place it makes much more sense to build a (say) 100 m tall pier/pylon than using a "light" lattice /truss structure for the tower.
If a tower crane did not need to be transported, how much would the design change? I’m guessing not much, but curious.
I was imagining there would be no counterweight but just opposing loads, then I realized that might be a safety hazard. But, I really don’t know about these things.
I just love the elegance of this solution and immediately obsessed. I think it just ruined my productivity for the day.
You can get around that, and they probably have to anyway, by just having a perimeter around the system that must be cleared by humans before the system can go active.
1) be easily transportable, which among other things means that the lighter it is the better it is AND that in most countries the girdles cannot exceed 2.40 meters in width
2) most would be self-erecting (there are two kinds of self erecting cranes, the one in [1] is a kind limeted to smaller/shorter/less load models and it is properly "self-erecting") but any tower crane is normally assembled on the ground (using a crane truck) up to a given size/height, usually up to 30-40 m height at the most, for taller cranes, the arm and the base is assembled on the ground, but later the crane is assembled using a self-erecting "cage" or "climber" see [2], this again calls for "the lighter, the better", and implies besides the truss design the use of high tensile strength steel (which as said before is very elastic, meaning that the operation of the cranes is not as easy as you may think, particularly when high loads are involved, it is not uncommon that the point of the arm has several cms oscillation when the load is lifted/released)
3)transport/assembly/erection/disassembly is done relatively often it is rare that a tower crane remains in the same place more than a few months, at the most a couple of years, so the points above are very relevant.
A "static" crane would resemble more than anything else a port crane, more or less like this one:
https://commons.wikimedia.org/wiki/File:Port_crane_of_Mammoe...
[1] video of a self erecting crane:
https://www.youtube.com/watch?v=pqSFxZV6OvY
[2] video/animation of a climber crane assembly:
If you build a permanent crane for 30 year operation for most weather conditions it can be heavier and made of larger and heavier body segments. More like cranes in harbors.
I think the counterweights can be removed if you have symmetric working arms lifting exactly the same weight at the same time.
> 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.
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.
You still have to build a base, which stores no energy, and then plan for different storage amounts in different layers.
Think of it as a VERY slow, VERY large TV screen. With red, green, and blue blocks, they could advertise almost anything!
The value generation from the ad would almost certainly outpace the value generation from energy storage!
Also, you could encase your bitcoin wallet in a block, creating the ultimate block-chain block-chain!
By god and the scientists, you're a genius maxxxxx!
I don’t think that works if the blocks are reflecting light rather than emitting it.
One question is... visible from the sides, from above, or both?
From a long distance the colors would merge in the eye. And this would be visible from a long distance. Imagine it on a high spot next to a city.
The nice thing about the crane idea is you don't even need a lot of cranes, you just need a lot of stackable mass. The rail idea needs a lot of movable mass on wheels, and a lot of siding to store it on. It seems like the rail idea would need more land as well, plus it only works on hillsides.
Keep in mind these will be grid-tied too, so you only need the power to be smoothed across the entire grid; it doesn't have to be at a single location. So grid storage batteries elsewhere could play a role too.
I guess the only advantage the train approach has is if you can get a lot more height out of it -- imagine an elevation difference of 1 km from top to bottom, way more than you could get with a crane. This still uses a lot more land though and needs a lot more rail; just having several crane installations might still be simpler and use less land.
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...
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.
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
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-...
[1] https://en.wikipedia.org/wiki/Cement_kiln#Carbon_dioxide
https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP39460S.htm
https://nvlpubs.nist.gov/nistpubs/jres/60/jresv60n5p441_A1b....
The thing i ponder about this is the foundations needed for a setup. Concrete stacks very well (think dams) but you need very strong foundations for tall, solid concrete structures.
From [2]:
Cement manufacturing is highly energy- and emissions-intensive because of the extreme heat required to produce it. Producing a ton of cement requires 4.7 million BTU of energy, equivalent to about 400 pounds of coal, and generates nearly a ton of CO2. Given its high emissions and critical importance to society, cement is an obvious place to look to reduce greenhouse gas emissions.
Ignoring the geographical problems, could using the power source from which energy is stored for these devices also be used to manufacture the concrete, or would you be constrained by the power plants ability to output enough energy intensity to produce concrete?
If feasible to do, then for the geography issue, would the CO2 output from lengthening the trucking route and/or high voltage transmission lines to the storage site possibly overcome the cement issue overall? If the power is ~free, loss in transmission is less important, but then you have to consider the output of manufacturing and installing transmission lines also. Although, perhaps there's spare capacity on some lines.
Actually, once the blocks are manufactured, you can ship them anywhere.
Complicated.
But you won't want to, because they're insanely heavy. At 35 tons a semi-trailer can only carry one.
You really need to build these on-site. The amount of diesel you'd burn to move them long distance is astronomical.
I know nothing about the cement business, so it's hard to have even a clue how to estimate this, even if you consider the power to be ~free..
Goodness, this doesn't seem viable at all.
Could the system work with pallets of steel drums filled with water? It looks like 4 layers is usually the height limit.
Does it depend on height to be effective, or could it stack limestone just 30' up or so?
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."
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)?
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.
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.
I also think it might be easier to do away with the crane and just put the weight on a huge moving platform. Where available, you could sink that into a disused mine shaft.
The article does mention that they expect to use 1/6th the cement of construction concrete.
This paper https://www.nature.com/articles/s41893-017-0009-5 gives an idea: 2 Gt of water per 21.3 Gt of not-water.
Assuming perfectly dry concrete (and none of the water converting to not-water mass, both of which I believe are counter-factual), that means a 2130 kg block of concrete would have needed 200 kg of water. Pumped hydro, assuming identical efficiency, would need all 2130 kg of water.
That article does go on to cover the water footprint, but what troubles me is that they switch units, and report it as 16.6km^3 of water. Which seems like they're trying to obfuscate the results (they have obfuscated them, whether that was intentional or not is another question).
That's all the water for all the concrete. Which for a hydroelectric perspective, is about 5% of the volume of water behind Grand Coulee Dam, for all the concrete we currently make every year. So maybe concrete blocks make sense for power.
True, though the paper makes a point, early on, that much of it is used in producing the aggregate, and the article makes a point of (potentially) using recycled/discarded aggregate, which would incur no additional water consumption.
> report it as 16.6km^3 of water. Which seems like they're trying to obfuscate the results
That's a remarkably harsh characterization, especially since that was parenthetical. The main reported amount was 16.6 × 10^9 m^3.
With water having the convenient density of 1000kg/m^3 (1 ton/m^3) and 10^9 being equivalent to the SI G prefix (both facts which one reasonably expect a reader of a physical sciences journal to know casually), it seems hardly obfuscatory. I'd attribute, instead, a change of units to a desire to compare it to household use, later in that paragraph, which is more typically measured by volume.
Although for commercial concrete block of 2130kg, that would, indeed, change the amount of water to be 1660kg from my original 200kg. However, I'm fairly confident that the ability to use 1/6th the cement combined with not needing any particular aggregate (even recycled) will bring the number for the article's application much closer to the smaller one than the larger one.
Which it should be - IMHO, despite the material, both systems get very similar techniques, at the core in both cases you have the loss of a motor+generator pair plus the friction of your mechanical system.
There's nothing to suggest that each tower would need to be comparable.
My reading of the article suggests the converse, that each installation is feasible at a fraction of the size of pumped hydro [1].
Although the article does mention land availability being an issue, to say the same for pumped hydro would be a gross understatement, since the latter requires not just land but a specific (vertical) shape of land in a continguous piece.
[1] Article mentions "each 35 MWh system". I found it remarkably difficult to find the usable storage capacity of a PSH station.
That would put the storage capacity at around 1000x, and, if the estimates of the cranes' generating capacity elsewhere in the thread are correct, approximately proportional to that, as well.
Sounds quite crazy at first but actually looks quite reasonable after looking at it a little closer [2].
[1] https://heindl-energy.com/ [2] https://heindl-energy.com/technical-concept/engineering-chal...
For this purpose, all freely exposed surfaces are sealed with a geomembrane and concrete.”
Any idea how they will separate the bottom of the piston?
I wonder how they will balance it too, so that it doesn't seize in the cylinder. It seems like (re)moving material would be straightforward enough, but figuring out what the current balance is, maybe not so much.
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.
Seems easier to just use that same mass on land with a crane.
They don’t need to do much underwater, only install. But I agree capital costs might be higher because of this.
> all the same concrete requirements because they need ballast
Depends on the geology of the sea bed. Where I live, the sea bottom is mostly solid rock, it’s possible to attach stuff to the bottom without putting much ballast.
> use that same mass on land with a crane.
The idea’s nice I just worry about disasters. I read in local news about falling construction cranes every couple of years, because stormy weather for a few months each year. It’s possible to make cranes strong enough even for bad weather (like bridges), but such weather proof cranes will become more expensive than regular ones.
> Depends on the geology of the sea bed. Where I live, the sea bottom is mostly solid rock, it’s possible to attach stuff to the bottom without putting much ballast.
It's likely to be more expensive to attempt to attach to the sea floor than it is to just sink large weights. In fact, I'm not aware of any large structures that are anchored to the sea floor in a way that resists an upward force rather than a downwards one. It might be a wholly unsolved problem.
> The idea’s nice I just worry about disasters.
Falling construction cranes are dangerous because they tend to happen in inhabited areas, adjacent to other buildings. The energy storage cranes, on the other hand, would likely be in the middle of nowhere where land is cheap, so even if they do fall there's nothing to damage beyond the energy storage installation.
Marine vessels can be very large and helical screws are widely used, here’s an example https://helixmooring.com/square-shaft-anchors-2/
> even if they do fall there's nothing to damage beyond the energy storage installation.
Very expensive installation. Maybe they don’t need the reliability of bridges but they need to be able to withstand any weather.
Global marine community has developed special signs to mark various locations on water, http://www.sailingissues.com/navcourse9.html
Captains normally follow these rules because the ships they’re controlling are often very expensive.
Would also make it cheaper to build extra wagons, with a storage yard at the top and bottom.
Same for all the energy from pedestrians/cars ideas, solar roadways, etc.
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.)
- 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)
The beauty of this idea is that these tower cranes are standardised and ubiquitous. So it could be implemented immediately in almost any city in the world.
I think the problem with the one big weight is that it'd require an extra structure (a gantry) to hold it, whereas this is really simple logistically. Easy to transport and assemble.
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.)
In that case, something comes along and cleans it. Maybe a rod-shaped brush (like a vacuum beater) that spins. Or a water jet.
Also, you can have more than one hole for redundancy. If one of them is clear, that should be good enough.
Hmm, or rather than holes through the middle, make them notches or grooves on the side and shine a laser through them.
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.
Those are very controlled environments. Outside where there is weather and wind, anything can happen. Also if there is a bug in the software or some hardware fails in a CNC machine then you loose some material, not a big of a deal. If the concrete tower collapses you loose a skyscraper volume full of concrete, also it takes days or weeks to clean the area up.
http://www.orbitalvector.com/Orbital%20Travel/Space%20Founta...
>Article added 2005
"Houston is experiencing its third ‘500-year’ flood in 3 years. How is that possible?" - https://www.washingtonpost.com/news/wonk/wp/2017/08/29/houst...
Huston got unlucky, but the real worry is the new 100+ year storm, because that will be even more brutal in the changed climate.
This seems like it'd be much more resistant to wind than buildings, which are hollow.
The cylinders have got to go, however. Stable stackable shapes are a thoroughly solved problem (bricks!), and stack at higher densities as well. Scaling up a press release model from the barrels they used for a real life demo saves very little time or money and implies an absence of familiarity with structural engineering, which will be this concept's #1 critical problem.
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...
I wanted to get a sense of the economics of the entire thing.
They said mining for sand could be more profitable than mining for gold.
I presume that means extracting a truckload of sand will yield more profit than a truck of ore containing rock?
I’m also now curious about sand alternatives.
A team has recently created a concrete alternative from desert sand, however, that has half the carbon footprint and is made from abundant materials.
https://www.dezeen.com/2018/03/24/desert-sand-could-offer-lo...
The idea has been around for decades, but no one has been able to really do it yet.
Just random thoughts, though...
* old empty mine in Germany. They pump air into the mine and then heat it to get extra energy when letting it out.
* big underwater bags next to wind turbines. Wind turbine directly pumps air into nearby bags. When there is no wind, the air is used to rotate the same electric generator that the wind turbine uses.
http://www.lowtechmagazine.com/2018/05/ditch-the-batteries-o...
This is an area of active and relatively promising research. Adibiatic heating and cooling is a concern.
""" While pumped hydropower storage has a charge/discharge efficiency of 70-85%, and chemical batteries reach 65-90%, the CAES plants in operation in Germany and the US have an electric-to-electric efficiency of only 40-42% and 51-54%, respectively """
http://www.lowtechmagazine.com/2018/05/history-and-future-of...
- The promoters are likely to present at least a realistic (if not optimistic) estimate of mid term cost, the technologies involved are all mature (so the potential for further reduction I'd low), and the estimated cost is not materially better than battery energy storage (worse, in fact, than near term forecasts, and much worse than midterm potential battery energy storage cost).
- The siting flexibility is poor, which means grid connection will be slow/expensive.
- The power density will be pretty bad (which wouldn't matter for bulk energy storage... but it's too expensive to compete in that market).
Maybe it could become more attractive with much taller cranes?
> Now, how much energy can it store? This is given by potential energy formula E=mgh, thus E=100kg⋅9.8m/s2⋅10m=9.8kJ≈2.7Wh.
> For comparison, a single AA-sized battery stores about 2Wh of energy.
https://physics.stackexchange.com/questions/305563/why-dont-...
Wind turbine height: 99 meters. 100 kilogram lead weight == about a large person. So, a normal turbine maybe can hold about 100 people's worth of additional weight (elephant or two) * 10 (height multiplier) = ~1,000 AA batteries worth of stored power.
Relative to combustibles such as hydrocarbons, ammonia, or hydrogen, not so much.
(It's possible to synthesize carbon-neutral hydrocarbons, though with high round-trip losses, and not yet proved at scale.)
One simple demonstration is to look at how a small magnet can combat the gravity of the entire planet when it holds an metal object in place above the ground.
At first it seems a bit silly that the bottom layers aren't lifted off the ground much at all, but if a tower is N meters high, the average height of each block is N/2, so that's only a factor of 2 loss. (For example, if each block were 1m tall, a stack of 100 of them would be 100m tall, and the average block would be 49.5m off the ground.)
And of course also because concrete is a combination of cheap, strong, and heavy. All of these serve as multipliers for energy storage practicality.
More weight means more tower, with means using an existing tower doesn't save you much money.
Or why doesn't it just have many medium motors; each permanently attached to a single medium-sized block? Why should the relationships between motors and blocks be one-to-many?
Lots of small concrete blocks, a camera and a hook to latch onto them one at a time sounds overly complicated and error-prone - Not to mention how much precious time would be wasted getting the hook through the holes and then coordinating the lifting so that each block ends up stacked nicely.
Can you, for example, make a mechanical watch by compressing liquid instead of a spring?
For such a system, time isn't precious, hardware is.
I wonder how this compares to lithium on a power store per square foot metric.
Almost everywhere has a lot of unused land, even in densely packed countries like Japan. If it's not good for farming, forestry, or leisure, it would be suitable for this sort of use.
[1]
- 3.8e12 kWh/y electrical use in the US.
- 1e10 kWh/d
- 1e10kWh / 2e4 kWh/unit = 5e5 units
- $2e6 / unit * 5e5 units = $1e12
The bad news is, the capacity is lower, but the good news is the $2M is the cost to build the first prototype, and prototypes can be extremely expensive compared to the real manufacturing costs.
It seems like the only information available about the price is their estimate that they can hit $150/kWh.
Concrete is already harder to transport (you need to correctly grasp, stack and release the blocks).
It also might make sense to use shipping containers full of heavy rubble rather than purpose-built concrete blocks. Container cranes already are designed to work fast and accurately. Containers are common and strong, and solving the saftey problem of weight integrity might be easier.
Solid material gravity storage requires vastly more low-capacity motors, of under 1 MW each, as you note.
Raw efficiency isn't everything.
I'd guess the cranes would be cheaper than locomotives and laying track.... and works on flat terrain (EG the midwest).
https://vimeo.com/124312632 (ARES, Bakersfield) https://www.snl.com/InteractiveX/Article.aspx?cdid=A-2654235... https://www.vox.com/2016/4/28/11524958/energy-storage-rail
As for lifting an entire landfill, how the hell would you accomplish that? No such machine exists, and the support columns required to do so would be utterly massive.
Also, I don't think a strong enough material exists to make that sheet out of.
I don't see a practical problem with very heavy monolithic blocks. Over a century ago, people built perfectly stable hydraulically-powered draw bridges that have opened and closed several times per day, every day, up to the present. Sounds like a solved problem to me.
Moving a counter-weighted something-heavy up and down is a distinctly different physics problem (that closely resembles moving it back and forth horizontally) than moving an unattached something-heavy up and down.
A single one of these concrete blocks is 35 tonnes. To get useful stored energy levels you need thousands of blocks. So you're looking at something like 100 kilotonnes of total mass. That's way, way, way more than any movable bridge weighs. Bagger 288, the largest mobile machine ever built, only weighs 13.5 kilotonnes, and all of that weight is supported by the ground on massive treads. To be able to lift many times the weight of Bagger 288 over 100 m in the air defies imagination as to what would be required. It would require billions of dollars to achieve, most likely.
Contrast with an off-the-shelf tower crane that costs a few million.
That said, there are a few points worth noting, if I spend a few minutes thinking about this:
* You probably want to maximize "dumb mass", with relation to the lifting mechanism, to bring down your costs this has to be optimized vs density
* You probably want to maximize the height difference in order to make the system more effective:
--* Less losses due to the "fixed costs", both in time and energy, of positioning the mechanism for the next payload
--* If you have lots of blocks to move, or are simply stacking them, it will take up a huge area when discharged, which will at least make the crane system more complicated
So, simply stacking blocks does not seem like the perfect solution to me, unless you really want to max out the energy per unit of volume. This could make sense if you were stacking goods that would be useful elsewhere (think a warehouse that doubles as a batteries). Incidentally, batteries, fuel tanks or containers would be a rather good choice if you have to pick one of these.
Following on the double-use idea, there is already one distributed, underused infrastructure that is designed for electrically lifting things (though probably not power generation). I can see a few ways that elevators could double as auxiliary power storage units.
Of course, special care would be needed to make sure the extra weight doesn't compromises the buildings' structural integrity. The same could be said about virtually any other candidates, which includes existing bridges, dams, cliffs, etc.
An interesting take on this would be to see whether it is possible to take it offshore. In theory, given perfect water-proofing (or just good pumps) and logistics, you could change the geometry of a concrete-built floating structure, and lower parts of it extremely deep. Of course, Archimedes doesn't help much with power density, but that wouldn't affect efficiency much (hydrodynamics would, if speed/geometry isn't optimized, though). As a preliminary approach, sea deeps near the coast could make it simpler. I suspect concrete composition would be the hardest part to solve, in that case.
Don't pump water up.
Convert to steam/vapor. Run a hyper-insulated pipe up the side of a mountain with repeater heaters if necessary. Condense at the top, recovering the heat, and send them both (the water and the heat) back to the bottom separately. For added points make up your losses from solar inputs.
Not convinced. Am I missing how they get to store 20 MWh of energy using gravity?
That's not an implausible object.
You want to use blocks that are as big as possible so you get more energy out of each trip. 2.4 tons isn't very much at all compared to the carrying capacity of a crane -- you want as heavy as possible while still being comfortably within the lifting capabilities of the crane. Their design says 35 tonnes and that does indeed make more sense. Where is your doubt coming from?
Don't know what the sweet spots of capacity vs power are on different markets. This could be good for long term storage.
Water permeability also has an impact. Imagime lifting the products when it's wet and dropping them when it's dry.
Notwithstanding the misspelling of "of", it seems like if this becomes popular, such "waste" materials will increase in price, making the plan unviable at scale.
Ok, sorry for the off topic, but this annoys me to no end.
Two hours by plane is about 1400 miles, by car about 120 miles, by bicycle about 25 miles, by foot maybe 6 miles, so why not give distance by miles or km? Even if we are talking by car, then how do you know there are no traffic jams on the way, or bad weather?
</please ignore rant>
Supposing that you could store the concrete blocks at a height of 50m (which is already a lot), you would need roughly 8000 tons to store 1 MWh. Taking account concrete density (2400kg/m^3), that's 19000 barrels !
Citation needed. The vast majority of current energy storage uses pumped hydro.
> Supposing that you could store the concrete blocks at a height of 50m (which is already a lot), you would need roughly 8000 tons to store 1 MWh. Taking account concrete density (2400kg/m^3), that's 19000 barrels !
Both the video and the article make it clear that the thing with the barrels is a 1/10th-scale prototype. The full-size version is slated to stand 120 meters tall and use 35-ton concrete blocks.