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.
That kind of cranes is very reliable, but in the real world they are used maybe 10% of their capacity [1].
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
No need for a reference; now that you mention it it's obvious that the duty cycle will be totally different. In fact, I'd bet that cycle time is the limiting factor - the graphic [1] shows about 100 cylindrers per layer, 18 layers already stacked, and the system looks to be around 60% loaded, so total count could be around 3k cylinders to move for a full load. Six arms, then each is doing 1000 cycles a day. Assume 4 hours down a day, 20 hours up, 50 cycles an hour, a bit less than a cycle a minute. Yikes.
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 - <$300k?! So the quoted system might be using a crane that's ten times the cost of a "normal" tower crane? I can... sort of seeing that buy a six-armed crane with twice the lift capacity but permanent construction, no need for a counterweight assembly, and better continuous performance. But now I feel like these numbers are lining up too well and I have to have done something wrong.
>I did notice that the cylinders were around twice the quoted capacities for tower cranes I was finding.
A "normal" (very large) tower crane rarely exceeds 12 tons, BUT, more than that, usually these use not "single" cable, i.e. a largish crane is usually 6 tons max, but can lift up to 12 tons doubling the cable/rope (which implies halving the lifting speed).
Moreover, cranes are rated/designed (loosely) on their reach, they are intended - within limits - to cover a whole building site, so arms of 20-30-40-50-60 meters.
An electric tower crane (a "normal" one) is well below US$ 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.
Eerecting and dismantling are key functions of typical construction cranes.
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.
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.
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:
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.
The selling point of this is low relatively low capital cost and well tested technology. Power density is not that good, but if you have land that's not a problem.
The use of space to store energy is maybe double of what typical damn reservoir uses to store the same amount of energy.
Each 35MWh system requires about 1.62 acres of land. That seems perfectly reasonable to me, especially since there are still optimizations to explore.
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.
Yeah, storing (<1%) 3 days total annual supply of electricity would be a huge over estimate... and storing 10% (35 days)would still be crazy large... I'd think the grand parent posts's numbers are high by 2-3 orders of magnitude.
As others have said,they likely would be placed near the solar plant where land is cheap and dry, rather than in neighborhoods.
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.
In this hypothetical, you also need something like ten percent of Americans to be crane maintenance workers, wouldn't you? Based on the crane numbers above it might even be more.
>> ten percent of Americans to be crane maintenance workers
> 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?
Honest question: what's wrong with being a crane maintenance worker or a crane operator? Cranes are cool, cranes help build stuff, cranes are complex. And if anything, out of the list of "desirable" jobs you mentioned at least two (police officers and lawyers) are the result of "bugs" in our societal system, they aren't productive.
Nothing is wrong with being a crane maintenance worker, and there is nothing wrong with being an accountant. But if a fifth of the workforce was accountants I would enter a panic.
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.
Gov't (fed, state, muni) employ about 23 million workers. Total workforce is about 130 million. So gov't work is roughly 1/5 of the workforce... hehehe.
Better than 10% of the US being truck drivers. Maintenance on heavy equipment like that can be remarkably complex, and the necessary skills are transferable to all sorts of industrial and fabrication jobs - not too hard to switch from fixing the hydraulics and armatures on a tower crane to fixing the same on any other sort of crane, vehicle, or chunk of factory equipment.
If all they did was make a battery, that's messed up. That many people? That's so much less useful to society than teachers, food service workers, doctors, lawyers and etc. combined. The insult to those people would be to have them spend their lives doing something so meaningless. Operating a crane in a construction crew has maybe a thousand times more dignity because they are making something people want. I have truck driver friends and that job isn't the best but they're doing something people want, they don't get out of bed unless something is out of place in the world, and they fix it.
> The insult to those people would be to have them spend their lives doing something so meaningless
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?
The system described in the article is mainly automated. They probably wouldn't need a large team to manage the system or it would be completely unfeasible. Certainly no worse than a giant battery center used to store electricity.
Reservoirs are restricted in where they can be built, because water. And that real estate is in high demand for many other uses. I think it's a safe assumption that, in general, coastal properties (including those on lakes and rivers) are more than twice as valuable as inland property on average.
Reservoirs could probably be built underground. I could also see one of these block stackers existing in the sublevels of a big skyscraper. Cost and and difficulty of access for maintenance might make either thing impractical, though.
they could make steel cages, fill them with crushed and vibrated limestone (or another aggregate). Good steel for the cage would last a lifetime but not sure if it's cheaper in $$ or CO2 emissions. Basically they need to lift /drop a heavy thing that last generations and stacks well.
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.
Probably you could throw in a small amount of nanocellulose and it could improve the strength a lot. Especially tensile strength, which is not good for concrete.
Not a true expert on the topic but from my reading it sounds like land is generally a carbon sink and water produces carbon so when you turn land into water, the net effect is additional carbon. Estimates have man-made reservoirs accounting for 0.5% of the total anthropogenic carbon emissions worldwide; fairly significant when we're considering the scale needed for energy storage with wind (blows 35% of the time, US avg.) and solar (shines 25% of the time, US avg.).
It's carbon neutral when plants decay to carbon dioxide. But they need oxygen for this to happen - and when they don't (like when they're underwater), they decay to methane.
And methane is a greenhouse gas 20-80x more potent than carbon dioxide.
< The selling point of this is low relatively low capital cost and well tested technology.
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.
I've recently started working with wave and tidal energy projects.
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.
> Concretely (pun not intended), I found a document [2] saying
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)
Not sure why you're being downvoted, it's a fair question. Maybe your post reads a bit abrasively? ¯\_(ツ)_/¯
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.
Question: can't we significantly reduce the number of moving parts by using a lever system to raise a single, giant weight, preferably from the bottom?
There was a project to carve a huge cylinder, kilometers wide, out of bedrock and raise and lower it with hydraulics. You could keep whatever's on top mostly intact. I don't know what's the latest status.
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.
They’re also a lot stronger because of steel construction, often incorporating a solid core. I don’t think we can attain skyscraper heights with blocks of concrete but I may be wrong on that.
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.
Someone would need to run the costs per GWh stored and generated. To me it looks like once you built your rail loop you could run a lot of cars on it. Still, building instead quite a lot of cranes might be cheaper.
Rolling stock isn't cheap either, though. Not even remotely close to how cheap a concrete block is. Rolling stock typically costs in the millions per car. The rail might not even be the most expensive part.
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.
You need enough cranes to smooth the dips in power generation as each crane finishes dropping one weight and has to go fetch another. The number needed would be proportional to the desired power output of the system (holding the size of the weights constant).
It looks like their prototype uses 6 cranes on a single central pillar, probably for this reason. It seems like with some basic algorithms you could get away with as few as 3 and still supply steady power as long as the cranes are tall enough.
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.
You still want each individual power plant to provide as smooth a power output as possible because each dip puts some strain on the other plants in the network as they have to increase their output to accommodate.
You could combine these ideas, though, and have only a few cars that pull weights up/down the hill, with a crane to load it off. I'm not sure but it could probably allow for a far greater total storage and kWh/$.
Now you've got more moving parts though. You have both trains and cranes involved. I think it's probably simpler and cheaper just to have the one big crane than to do a mixed mode system.
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.
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."
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.
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.
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.
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).
Worth pointing out that if you're patient with setting times, you can use portland cement substitutes (fly ash, ground blast furnace slag) as a substitute for portland cement. Slower strength times (several days longer) but same long term strength and way lower embodied carbon.
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.
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.
The point is that they would be made locally, not "shipped anywhere". Every city has a bunch of local concrete plants for a reason. If I buy aggregate, it's coming from nearby; it's not being shipped across the country.
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.
I'm not doubting it, but on the other hand I don't think that the cement will re-absorb a significant amount of its own mass in CO2 (which it would have to in order to offset this 1-to-1 CO2 footprint).
Portland cement is at least 80% CaO, so in theory it's 63% of the cement's dry mass (CaO + CO2 -> CaCO3)[1]. In practice it's ~43% that value, or 27% of the cement's dry mass.[2]
So apparently it depends on the type of cement - non-hydraulic cement hardens as you described, while hydraulic cement does not absorb CO2 but instead hardens in the presence of water. I guess they wouldn't have a reason to use hydraulic cement for this though, so it seems you're right.
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.
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.
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.
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).
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.
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.
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.
A local company [1] is taking a similar approach to the extreme and is developing a concept which involves cutting a 100-250m (328-820ft) diameter piston out of solid rock and then pumping water underneath to store up to 8GWh of energy.
Sounds quite crazy at first but actually looks quite reasonable after looking at it a little closer [2].
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.
“The Gravity Storage is cut out of surrounding rocks. Because rocks nearly always have crevasses and fine cracks through which water can flow, it is necessary to completely seal the piston and the surrounding piston cylinder against the surrounding area.
For this purpose, all freely exposed surfaces are sealed with a geomembrane and concrete.”
There still needs to be the equivalent of a series of O-rings between the piston and the cylinder bore to prevent the piston from sinking. I'd guess that it is the second-hardest technical problem, after the considerable challenge of isolating the piston.
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.
Might come down to things like, how efficient are cranes & conveyors & so forth, vs water pumps & hydro generators. The nature of each material leads to different techniques which could have very different efficiencies.
Upfront costs can sink a project, but so can ongoing maintenance. Materials that don't foul as easily have a long term advantage. And when there's a drought people won't be too happy about all that fresh water you're taking to make electricity ('course, how much water does it take to make a cubic foot of concrete, cradle to grave?).
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.
2Gt of water was mixed into the concrete, but when you're calculating water footprint you need to look at how much water went into creating all of the ingredients. That can be pretty substantial.
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.
> 2Gt of water was mixed into the concrete, but when you're calculating water footprint you need to look at how much water went into creating all of the ingredients.
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.
The efficiency is comparable, pumped hydro gets ~80% at large scale practice, while this is promised to be 85% and might turn out to be the same after all the implementation issues and wear&tear comes in.
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.
I wonder if you could compromise and use powdered concrete in a closed system? High powered fans could blow the fine powder upward in a silo so it would act like a liquid. Then large paddlewheels catching the powder could power a generator coming back down. I have no idea if powder going up a tube has less friction than blocks on a cable/pulley, however.
That's not a good idea. You would have turbulent airflow with dust, most energy would get lost, resulting in low efficiency. Weights on cables pulled by electric motors is as efficient as it gets. Not to mention dust bucking up the gears and sockets.
> So, a concrete tower, comparable to a pumped-storage hydroelectricity plant would be gigantic.
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.
There's no citation for that, so it could be what WP calls "original research". It is, however, pretty likely the right OOM.
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.
It seems to me, that for smoothing generation from solar, the important metric is more like "max power over ~8 hours", rather than "total energy storage".
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.
> Anything done deep underwater costs at least an order of magnitude more
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.
The installation process dominates overall effort, so if that's a lot harder then it ends up being a lot more expensive and thus a lot less cost competitive. It is absolutely insane how expensive an underwater oil well costs to tap compared to one on land, for example.
> 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.
Disasters are conceivable with ocean storage too. If a ship's anchor damaged the facility and caused the release of air, the rising air could well sink the ship.
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.
The amount of energy depends on how long the average cup would sit. A better critism might be complications in climates where water freezes. In any case, there is nothing so wrong with my comment that necessitates a negative attitude. I would not be surprised if it is an ‘idiotic’ form of hydro, or if it is not an idiotic form. But it’s clear that nobody has shown it to be one or the other as of yet, so your comment is negative with little justification.
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.
In the system you envision without stacking, are all of the large blocks suspended from the crane simultaneously when the system is fully "charged"? That would require the crane to support a much higher max load.
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.
Yes, you could use a pre-existing big hole, and carry concrete blocks from the bottom of the hole to the top of the hole. All you're really doing with this approach is swapping out the tower crane for a gantry crane though, for negligible savings. The hole's not really helping you out that much.
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.
Cheers. I must be missing something, but once the hole is dug, it’s dug, and i’d have thought it was pretty low maintenance and more structuraly sound than a crane. So over time, would the costs of maintenance provide a benefit?
You still need a crane to move the blocks from the bottom to the top and back. It might be a different type of crane, but I don't know that it would be any cheaper to maintain.
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.
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.)
Slap a tiny solar-powered GPS unit and transmitter on each block. ~$10 of electronics is marginal compared to the $2000 of concrete for each block. If any break, you already have a crane that you can use to move the block out of the way for repair; just hand it over to an operator who can do the special-case operation by hand. If you get a beacon unit with a MTBF of 10 years and not awful clustering you might get one to five failing per stack per day, so you'd probably be able to handle a hundred stacks with a single operator dedicated to remote failure-handling.
I suppose you'd have to clean it regularly. When the crane goes to pick up a block, it could do the optical continuity check then too. If it fails, that indicates that either the block was moved after it was stacked correctly (unlikely but possible) or it got dirty.
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.
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.
Yes, you could have 1 massive block, but the stresses and risks on the system would be much higher. Probably not achievable with current common tower cranes.
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.
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.
I don't think it would have anywhere approaching the kind of foundation a skyscraper would have. A quick google search and it looks like a tower crane sites on a 1.5m x 6.5m square footing. So 6 of those. Assuming the soil can handle it and the 'energy' weights act as their own foundations.
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?
Huh? A big stack of concrete blocks weighing 35 tonnes each seems to me exactly the opposite of being purpose-built for the wind. Maybe if you built it out of feathers then it'd be purpose-built for the wind, but gigantic concrete blocks don't get blown around a lot.
This seems like it'd be much more resistant to wind than buildings, which are hollow.
To me the most fascinating stability question is seismic. Wind is mostly predictable (apart from unusual events like microbursts). It would be easy enough to stack up a storm-stable shape before major predicted storms hit. Seismic stability would need to be considered throughout the stacking / unstacking process.
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.
As far as the crane goes, the article indicates that "Wind could cause the block to move like a pendulum, but the crane’s trolley is programmed to counter the movement." That actually seems like the most interesting part of this system.
They aren't worried about the wind's effect on the stacked blocks, just the ones suspended. If a century storm comes, just shut it all down for a day, everything is stable.
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.
The cranes also encounter corrosive water from outside the weather - and the dam of a pumped hydro station doesn't need a full replacement after a couple of decades; a crane does after 15-20 years at the most.
I would think storing energy using compressed air would be more practical. Excess electricity pumps air into a compressed air tank. When electricity supply is low, the compressed air is released turning a turbine to generate electricity. It's basically the same principle as the pumped hydro mentioned in the article but using compressed air. The advantages are size, cost, and availability. You can put it anywhere and scale when necessary.
I do not know much about engineering this sort of things, but it seems to me that working against gravity is easier than working against elastic force (as you propose), because the force of gravity is independent of the amount of energy stored, while the elastic force depends on the amount on energy stored (when the air is already pressurized it is much harder to push in some new one). And in general I believe that it is more difficult to build a motor or a generator that are efficient independently of the force they have to work against/with.
* 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.
Compressed air has been around for centuries, but:
"""
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
"""
The disadvantage is that you have made a huge compressed air bomb in the event of failure. The concrete blocks would fail in a more local way by just falling down.
Rock isn't necessarily airtight more so in mines. A fractured host material for the ore is very desirable as it means less explosives and higher ore production numbers.
There are substantial thermodynamic challenges to scaling compressed air energy storage. You either need to perfectly insulate the pressure vessel or perfectly cool/heat the air as you compress/decompress it via passive radiators.
Compressed air storage is less efficient. I think practically they have an efficiency of about 50 %, due to thermal losses (e.g. compressing air creates heat).
The article says that they can achieve an efficiency of 85 %. Which puts them in the ball park of hydro storage or lithium ion batteries. The problem with compressed air storage is that you are fighting with the fundamentals of thermodynamics i.e. compressing and decompressing air. The laws of thermodynamics try to ruin every good idea.
- 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?
I think this idea is excellent and really opens up the idea of thinking of non-traditional grid energy storage. Let's go back to the basics of what we can do to store energy and retrieve it at the basic level.
Now why couldn’t we build something like this right into a wind turbine? They’re already pretty high up. Just have it lift one giant concrete block up and down.
> Let's spin some numbers to further illustrate the poor energy density of gravity-based storage systems. Assume that you have a 100 kilogram lead weight that you can lower into a 10 meter deep hole in your yard.
> 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.
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.
If the stacking approach works at all, it must be because it is self-supporting. The material, once lifted, holds itself up.
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.
You also notice that when you go hiking on the mountains: it takes a lot of struggle to lose the weight that you gain with very little food. If you bring ham sandwiches, your net gain is probably positive...
Yes. Pretty much the opposite of the article headline, it's surprising how little energy you can store with gravity. When you do the maths, it's amazing pumped hydro works at all. And that's on the scale of cubic kilometres of water being lifted hundreds of metres - much more than any crane proposal.
Our battery tech is pretty impressive. However, this is also a clear example of how weak of a force gravity is, comparatively.
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.
Why doesn't it just lift a single extremely large block when electricity surges and then very slowly drops it back down to generate electricity (no need for complex hook-and-release)? The maximum capacity would be determined by the maximum height of the tower along which the block is lifted.
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.
The obvious answer is expense; the motor-generator part is the expensive part of the system (both in building and in maintenance) so you don't want a larger motor if a smaller will do, and you don't want more motors if fewer one will do.
For such a system, time isn't precious, hardware is.
I like the idea, but I am wondering how big these will need to be. If one of their prototype towers can store 20 MwH, at each one requires a circle 300 feet in diameter, than it will require a lot of land to do this.
I wonder how this compares to lithium on a power store per square foot metric.
They can store (not generate) 20 MWh at, according to the article, a cost of $2M. The article does not discuss how much power they can produce using one unit. That means it would cost roughly a trillion dollars to build enough storage to power the entire US for a day [1]. That's a lot, but you wouldn't need nearly that much, since daily consumption is still roughly balanced to production. You could think of that as an upper bound on the cost of backing the entire grid with this tech, assuming their numbers scale perfectly and are entirely accurate.
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.
They spent $2M on the demonstration plant, which is ~1/10th the size. It doesn't store the full 20 MWh. (Or is that 35 MWh? The article seems inconsistent on that.)
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.
How about huge helium balloons attached to a hose that lets a compressor suck the helium back down to ground level. The hose/tether would be on a spool attached to a generator. You could even do this from the ocean floor using regular surface air.
The "huge" is the problem here. In order to store any useful amount of energy, you'd need way too much. We use water because it's readily available, cheap, easy to transport, and relatively easy to store.
Concrete is already harder to transport (you need to correctly grasp, stack and release the blocks).
Does anyone see the downside that a little bug gets introduced, the concrete chips, the barrel dents, a cyber attack takes place, and suddenly your 120 meter tall stack of 35 ton blocks becomes a Jenga tower raining death into the Swiss countryside?
Not really. What are they going to hit? Presumably the realistic maximum impact radius of a failure would be fenced off (and wouldn't be that big - probably about the same size as the area fenced off for radio towers with guy wires).
Higher structural costs presumably. In the idea presented here you only need to move a small amount of mass at a time, so you don't need an especially strong crane.
If the giant block was literally just suspended and a crane would hoist it up and lower it to recover energy. Then this would put continuous stress on the crane structure. Much higher than a series of smaller blocks being lifted intermittently.
I was thinking the same but with chains or some heavy contiguous body. The problem is that you need something that can lift one super heavy load, as opposed to many lighter weight ones. I guess that's what you mean by hydraulics but then you need hydraulics
Cool. I wonder if it makes sense to make a roller-coaster-like potential energy storage system? It sounds like the electric motor-generator problem is solved. Escalator technology has many decades of safety and efficiency track record.
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.
They say the proposed version could store 20 megawatt-hours, but I wonder what the maximum output is? That is, how long does it take to produce that energy? If the maximum output is ~1-2 MW, it can support 1k or 2k homes, but it's also important to put in context that peak load of an average sized US city peak load is ~1000 MW. A med-sized wind turbine can produce ~2 MW, for comparison.
The cost is key here though, at $2m or potentially lower you're paying just $1-2k per home and maybe $100 a year maintenance thereafter. Not a bad price overall for what you get. In Australia at least, electricity costs $1-2k per year per household. Some napkin maths tells me that at 15MWH consumption per year this sort of storage could make solar (at $50 per MWH) pretty viable. As in, potentially below $1k per year even if you build enough storage to cover 80% of the day.
It's not significantly more efficient than pumped hydroelectric storage which is 70 to 80% efficient. And whilst it might be able to store quite a lot of energy, it can't release it particularly quickly I'd estimate the 6 crane motors can maybe generate a combined 1MW which is a paltry amount of power compared to even a tiny pumped storage facility.
I'd like to see a comparison of this electric-crane-block system with a system already being tested, 'rail storage', which uses electric locomotives to pull heavily loaded cars uphill.
I'd guess the cranes would be cheaper than locomotives and laying track.... and works on flat terrain (EG the midwest).
Very nice. Seems a bit finicky with all the cranes though, but what do I know. If the cost of concrete is a problem, why not put a huge sheet-like structure below a landfill and very slowly rise it up or down ... same principle, but now you're just moving waste and there's no shortage of that!
The difference is that tower cranes capable of carrying 35 tonne blocks can be bought off the shelf.
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.
Having an even number of opposing cranes might save tad of energy by hoisting the hooks and cable up by counterweight than by motor, but speed seems a more likely reason.
How about putting one or two of these _inside_ a new construction sky scraper just like one long, heavy elevator? “Charge” it at night. Release it during the day. This may not be a general solution but might be helpful at a per building level.
Why would you use a large number of small blocks to build a tower instead of one extremely large block on vertical rails, with appropriate devices to create sufficient mechanical advantage to move the block?
Because the crane has a limit of how much it can lift. If you're suggesting a custom system, it's addressed in the article, using off-the-shelf hardware is much cheaper.
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.
You're orders of magnitude off on the scale involved.
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.
Are you sure those bridges aren't counter-weighted? I don't believe I've ever seen a drawbridge that wasn't.
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.
I remember a mechanical engineer friend of mine who worked in a power plant telling me that large flywheels are still used for energy storage. Funny how basic the energy storage solutions often are.
Gravitational potential-based energy storage is nothing new. There are lots and lots of ways this is harnessed; take a grandfather clock, for example.
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.
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.
Moving ambient temperature water through an appropriately sized pipe is nearly lossless from an energetics perspective. Moving steam through a pipe of any length is far more lossy even with significant amounts of insulation.
on netflix is a show called "islands of the future" and in one of the episodes they did in fact pump excess water back up the mountain. I think their location was already hot enough that they didn't consider converting to steam.
The idea involves lifting thousands or tens of thousands of blocks, not just one. Of course it's ridiculous to have an entire tower crane dedicated to lifting a single block, but that's not what they're proposing. The linked article has a rendering showing how many blocks are involved.
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?
Idea: Stick a heavy load onto a rotating screw. Actively power it to rotate, moving the weight up; let the weight drop forcing the screw to rotate on the way down. Sounds pretty simple, I guess a lot of energy would be lost to friction.. teflon? Bearings?
Nope. Pumped storage is between 70 and 80 percent efficient, this is 85 percent efficient. Remember, with pumped storage, the pumps/turbines are usually centrifugal vanes, not displacement pumps. So, there’s quite a bit of inefficiency caused by fluid drag and leakage/backflow, like in an automatic car transmission without a torque converter. With a crane, the motor is directly geared to the weight.
IMO, that is not an important factor because the water pump option would not even be available in a desert area. This is assuming you are thinking of traditional pumped-hydro. You could probably make some sort of closed off pumped-storage where water can't escape but that would probably be very expensive.
If you have driven thru the Columbia Gorge where the highest capacity hydroelectric dams are you’ll notice that these dams are much lower than the surrounding top of the gorge. I always wonder why not pump water to the top of the gorge?
I would expect a signficant limiting factor to be the cost of dam construction (which is going to go up at least geometrically with height, assuming a V-shaped opening), not the height of the already-constructed-by-nature surrounding walls.
But it is one time cost for 30 years. Everything has an initial cost like creating traditional plant, building water reservoir (concrete too and ground formation work), photovoltaic panel grid.
Benefit here is abundance of material - existing concrete waste.
Why not do this in the ocean? Lifting and raising blocks from the sea floor provides far more potential energy, since the ocean is deeper, than any crane is tall.
Also (mostly) unrelated to the story, but the first thing I thought of when hearing about kinetic energy storage was a story I heard several years ago about a data center that protected itself from catastrophic power surges by using a massive spinning flywheel to store energy from the grid and harvest its rotation to run a generator that powered the servers.
> He’s 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.
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.
Presumably there is some kind of gearing system that causes the turbine to rotate at the optimal speed. They are probably just using the motor that they use to lift the mass in the first place.
"On a hot July morning, I traveled to Biasca, Switzerland, about two hours north of Milan, Italy"
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?
Not sure about where you are from, but in Canada distances are routinely given in hours or minutes, and it always means by car unless it is specified. As in, "Toronto to Ottawa is around five hours, or an hour by plane."
And that's the problem, tell me 10 miles and it will always be 10 miles. Where I live, in a rapidly growing city, 15 years ago it would take 15 minutes to downtown from my house, now it takes 25 or 30. It's the same distance but traffic has increased significantly in a short number of years.
Seems quite useless to me as the earth's gravitational field is not very strong.
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 !
> Seems quite useless to me as the earth's gravitational field is not very strong.
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.
I wonder why they dont put the blocks / dirt into train wagons and drive them up hill. Then generate electricity through retroactive breaking as it descends. Maybe the efficiency isn't 85%... but it sounds cheaper and simpler to make.
I wonder why just barrels, maybe to limit the scope for an academic project? I'd love to see what could be done with the cranes that load/unload container ships, daisy chained up a hillside like canal locks.
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...