Assuming the full scale version delivers peak power for 11 seconds like the prototype, 2MW peak power would be 6 kilowatt hours of energy.
That's terrible. We're taking about dropping hundreds, maybe thousands of tons down a mine shaft to get the same amount of power as $700 of lithium batteries you could carry in a backpack. For instantaneous loads you're way better off using flywheels, which we've already had for decades.
Gravity is weak, literally. The only realistic use case for gravity generation is hydro power. And MAYBE reverse hydro power where we put giant gas bags underwater and they make energy floating up
I think an important thing to note about gravity batteries is how environmentally friendly they are, even relative to lithium ion batteries. Lithium mining is an insanely tight bottleneck in LI battery production, mostly outsourced to countries where we don't think much about it (Australia is a big one right now, but in terms of untapped reserves, Chile Argentina and China are all huge). They require complicated manufacturing processes that are centralized into maybe four or five advanced manufacturing companies around the planet.
When speaking about LI packs, especially to enterprises deploying them at grid scale, their expected life has to enter into the equation. Maybe 15 years? 25? So, millions up-front, and millions more every couple decades; its not an impossible sale, but relative to other options (like hydro storage, which is excellent but also limited to areas with existing reservoirs) its not obviously the best option.
They may be better, but I don't feel that means gravity batteries don't have a place. The mechanical pieces to raise and harvest the energy likely aren't carbon-zero, but the weight itself can be built out of anything. They don't experience leakage of stored energy over time (barring a failure of the retention system keeping the weight elevated) (though, obviously, there is loss in the addition of energy to the storage, as the machines which raise the weights are not perfect). They can be reused essentially indefinitely (excepting continuing upkeep of the retention and raise/harvest systems, and proper weather protection of the weight). Their failure mode is "falls", which can be designed far, far safer than a typical LI pack failure of "explodes in a fire that literally cannot be put out". None of the systems in-play are particularly technically advanced, and a ton of the cost is up-fronted. There's a lot of reasons to think they will represent a component of green energy storage in the future; likely not as large at LIo packs, but the world is a big place.
Agreed. I'm glad that people and companies are trying different solutions for our energy challenges, but I see so many examples where the basic physics make these solutions impossible to scale, that it seems like these are primarily just schemes to suck government money.
Gravity solutions like these will never be feasible, because as you point out, gravity is just plain too weak of a force. I mean, it looks like pumped hydro will be viable, but when you think of the sheer mass of water that can be pumped behind the Hoover damn you realize stacking a bunch of bricks is ridiculous in comparison.
There was another recent article on HN about a giant tidal generator, and I was glad to see the top comment pointing out that basically over 50 years all these tidal projects have been failures (at least when it comes to ever being able to provide decent power in a fashion that shows it can scale).
It's time we start calling out these schemes for what they are, because they take funding away from solutions that we now we'll need now to fight climate change.
Well, maybe not rocks in a mineshaft. Probably not rocks in a mineshaft.
But Advanced Rail Energy Storage?[0] Different story, has potential (bad pun, I know). There are some nice synergies, like a system such as this can reuse the generators from a decommissioned coal or natural gas plant.
It can definitely play a part in a broad-spectrum energy policy.
Here's an idea: what if -- instead of digging a deep hole into the ground -- we use the tower of a wind turbine as the vertical space in which the weight is raised/lowered?
A wind turbine is already equipped with a generator, so it'd be a matter of building some sort of "switch" which would make it either: (a) generate electricity using the turbine, as per usual; (b) raise the weight using the turbine, thus not producing electricity; (c) generate electricity by connecting the weight to the rotor/generator, while lowering the weight.
> Here's an idea: what if -- instead of digging a deep hole into the ground -- we use the tower of a wind turbine as the vertical space in which the weight is raised/lowered?
First, there's not really any room in there, wind towers are built for the job, we don't add twice the amount of steel and an elevator shaft for funsies.
Second, even if there were some room it would be inconsequential, you need a lot of crap very high up to get significant amount of energy.
As demo, let us take the largest turbine available right now and lift the entire thing up and down its tower.
The Haliade-X has a hub height of 150m, a 600t nacelle, and 165t blades. In normal operations it's rated for 14MWe.
765t at 150m is 250kWh. You can get electric buses with larger battery packs than that. For reference, US households use about 29kWh/day.
That's the issue with gravity: it's really not that strong, so to store significant amounts of energy you need either ridiculous amounts of weight (hence dams and pumped hydro which can manage unfathomable weights), or extreme height difference (hence… still dams, pumped hydro a bit less so I think).
As a point of comparison, Bath County (the largest pumped-storage station in the world) has a hydraulic head of 270~385m and the upper reservoir stores 44 million tons of water.
Now taking in account that you can't really empty the entire thing, that it's not perfectly efficient, etc… Bath has a storage capacity of "only" 24GWh, it's not actually moving 44 million tons up and down 400m.
Wind turbines use the tower to take parts to the top for maintenance. Regardless, you'd need to dramatically increase the wall thickness of the tower along with the foundation for the additional load, to the point it probably wouldn't be worth it.
Bad math, let's say we can use a lead weight 2 meters in diameter, 3 meters tall (107,000 kg) with 120 meters of drop available.
All of that gets us 35 kWh, or 0.035 megawatt hours of energy. Compared to a 2 MW turbine, it's a negligably small amount of stored energy, even if we scaled every dimension up by a factor of 2 (getting us to 0.28 MWh).
I think it'd be more efficient to use a massive flywheel for a wind turbine. That flywheel could then be the battery and each turbine would come with their own.
This could be something more like a planetary gearbox or a differential that can connect 3 systems (e.g. gas engine, electric motor, wheels in a hybrid car). But if requirements are too different 2 generators may be the better option.
The tower would probably need reinforcements for the additional weight, but I have no idea about the magnitude required.
I’ve always been surprised that there is no product wind turbine with a guaranteed power output, that is, a turbine with an embedded battery. Sure it would cost much more, but in some applications steady power is worth it.
As usual everyone is fixated on price when the real hurdle will be scale. If we're going to replace our existing fossil fuel plants we need at least as much capacity. A quick grep in the article tells me these guys have a plan for a 4MW plant that involves a 1km shaft. That's the same order of magnitude as a single wind turbine, which is already one of the worst ratio of power output per quantity of resource and land use.
> As of 2018 coal power under construction was 236 GW, planned 339 GW, and 50 GW was commissioned and 31 GW retired
If we want to replace those new plants we'll need 100.000 of those shafts. And that's not counting the existing plants, and the other fossil-fuel based plants. Think of the quantity of concrete that involves. That's just insane. If we want to actively tackle electricity generation we need to use the most efficient low-carbon tech that we already know.
Also, we already have gravity-based systems, only nature does all the work of raising the payload for us in gaseous form, and we let it fall in liquid forms. But it takes so much dam place.
It's a common misconception that energy storage needs to handle all the power needs of an area for a significant time.
The most immediate need for energy storage is frequency regulation, and short hours-long dips in power output. If we can solve that we can scale renewables very far.
For days-long dips in power output, it's probably better to keep some gas power plants on stand-by. I think many areas of the world has enough of them to handle these needs already. To make it sustainable, they could be switched to using renewables fuels, like hydrogen or ammonia made from electricity. We're going to need a shit-ton of those kinds of fuels for trucks, ships and airplanes anyway, so setting aside some of it for backup power wouldn't be a huge problem.
For seasonal variations, I think trash burning power plants is a reasonable solution. Sweden and Norway has some of them, and they also provide heating to nearby homes. I mean, yeah: first of all we should reduce, reuse and recycle. But eventually our trash become unrecyclable, and burning it seems to be the best option. Modern facilities seems to be able to extract almost all harmful compounds from the waste then. There are also experiments with carbon capture from these plants, which in a fully renewable world could make them carbon-negative, and become one of several tools to help reduce CO2 in the atmosphere again over time.
And of course, nuclear would be a great help. If it can be made cheap enough again, it can be used for seasonal variations. But we're still going to need renewables. So we still need energy storage for frequency regulations and minute/hours-long dips in energy output. Nuclear power plants are NOT a good solution for that.
That's the wrong comparison. We don't need to replace generation capacity with the same capacity of batteries. Batteries don't generate any electricity after all. We need batteries to smooth out differences between demand and generation. The total amount we'll need is very much still up in the air. Better interconnects, good use of existing hydro, overbuilding renewables, shaping demand, are all other ways to balance loads and guarantee enough power at all times, all of which reduce the need for batteries.
"Also, we already have gravity-based systems, only nature does all the work of raising the payload for us in gaseous form, and we let it fall in liquid forms. But it takes so much dam place"
We actually also do have self created gravity-based systems, where we also do the work by ourself, to have a energy storage on demand:
They work reliable and with big capacity since the very beginning of electricity. The only problem is ... scale. You cannot just build them where you want them. You need rivers and height differences.
Unless you create such systems completely artificial and there are plans to do so, but that will be very expensive.
edit:
here is a paper (in german) discussing such possibilities, to create a artificial pumped-storage out of the remains of surface mining
and my opinion is, that I am not a fan of complicated solutions, like the originial solution from the article seems to be, which is also stated as "The technology is still “incredibly immature”
There are solutions to make batteries without rare elements.
They just don't reach the energy density of lithium based ones, but that is not really a problem, when you have them stationary.
So if you could scale up production of these and in the end, have a big battery in every home/factory connected to the grid - you would have a stable grid without any need for gas- or coal powered backup.
I did a bit of scratch math with the notion this might be more suited for individual, home power storage rather than grid supply - You need something in the order of a 5m tall tower bearing 73 tonnes to store 1 kilowatt hour (even then, ignoring conversion losses). So that's the weight of ~ten class-4 fully laden heavy trucks.
Once you can get it up in the air then the higher you can go you're doubling your storage in a linear fashion. Hoist one of those trucks to 50 meters (perhaps you have a handy cliff in your backyard) and you've stored as much as the ten trucks did at 5 meters.
So yeah scale seems hard, but the low technology/materials requirements and potential for gradual scale-up make this worthy of deep investigation. I think there's a lot of wandering off into dead-ends as far as limitations go though - Solutions that depend on a lot of concrete pouring, for example, are a no-go if the end goal is reducing atmospheric carbon.
Your assumption that we need that much storage is simply wrong. This pops up in just about any article on HN mentioning batteries. Somebody will jump to the wrong conclusion that we need to provide massive amounts of battery storage and that therefore we need coal/nuclear/etc. (i.e. really expensive ways to generate energy) because buying so many batteries is obviously stupendously expensive. It's a popular argument with nuclear proponents and with the fossil fuel industry.
The reasoning roughly goes like this: wind and solar capacity varies because wind doesn't always blow and the sun doesn't always shine. This is very obviously true of course. Except these effects are local, temporary and typically result in a reduced capacity rather than a complete collapse. You always get some output out of solar panels (except at night). And wind turbines might stop spinning but it's extremely rare for that to be a continent wide thing. Offshore wind is pretty reliable. Also these effects are kind of predictable via weather forecasts so we can plan for them. Same with seasonal patterns. Simple cables rather than batteries are the key technology that we need. And we mostly have that in place already.
The grid connects power plants via cables. So, we can compensate for local dips in power with remote peaks. What matters is the collective performance of the grid. That still fluctuates but not nearly so dramatically that you'd need a lot of battery. E.g. the European grid is very connected. So, you might get power from Norwegian hydro, North Sea offshore wind, German on shore wind, solar plants in Spain, France, Germany, etc. or any of the gazillions of solar panels on people's houses. And of course there are coal, gas and nuclear still on the grid as well (for now).
All of that failing 100% at the same time is simply not a thing. Not even close. It's not something grid operators plan for. It might dip by 20-30% but it might also peak by that much. And it's likely to average out over time in a very predictable way. All that means is that we need to have a little more capacity. 2x would be overkill. 1.2 to 1.3x plus some battery will probably do the trick.
Batteries on the grid are intended for and used exclusively for absorbing short term peaks and dips in both supply and demand. Short term as in hours/minutes; not days or weeks. They are very good at that.
This is why modest amounts of lithium ion batteries are being used successfully in various countries. These batteries can provide large amounts of power (MW/GW) for typically not more than a few hours. The reason that is cost effective (despite the cost of these batteries) is that taking e.g. gas peaker plants online for a few hours/minutes and then offline again is expensive and slow. And of course with cheaper wind and solar providing cheap power most of the time, gas plants are increasingly pushed in that role because they are more expensive per kwh to operate. Gas plants on stand by still cost money. And turning them on costs more money. Batteries basically enable grids to have fewer (and eventually none) of those plants. These gravity based batteries have the same role. It's a cheaper alternative to lithium ion batteries.
Currently, clean energy is the dominant form of energy in many countries already (e.g. Europe, China, parts of the US). In some countries it's well over 50%. This proves the point because these grids don't feature a lot of battery currently and the combined capacity of peaker plants (i.e. not operating continously) is far smaller than the presumed need for batteries. If you were right, these countries would be facing massive blackouts all the time as their dominant form of energy disappears for days/weeks on end. That's obviously not a thing.
So 10E6 sounds practicable and, as discussed previously, may be a significant overestimate of actual need. Suspect 50 year life cycle costs and various environmental and political externalities would be substantially lower for gravity-based solutions. But who knows?
Concrete requirements? About 10E10 tons of concrete are consumed worldwide each year.
Again, 10E6 doesn’t look so big, but might involve some engineering cleverness.
But 10E6 big, capital intensive, fairly generic things can justify a lot of engineering cleverness in that one generic design. Geotech would need a lot of thought.
You are absolutely dead on right. We need to stop trying to bang on a model that isn't working and be willing to think even more outside of the box.
All of this is essentially ways to create hydroelectric plants without the water. If we can find a way to create more of them without massive disruption it'd probably be the most effective.
We need to find a solution that isn't just based on good wishes.
> As usual everyone is fixated on price when the real hurdle will be scale
If it's way too expensive (and there's no obvious way to reduce costs), then scalability is irrelevant, which is probably why people are fixated on it. We need both scalability and price to be favorable.
Batteries do not replace power generation capacity directly.
They can, however, be configured to cover huge surge loads for short moments, or smooth out small discrepancies over a longer span, in more or less the same footprint.
If you want a GW of coal, you need a GW plant, whereas with batteries you can decide between a gigawatt-hour or a 1000 megawatt-hour using a similiar footprint (scale to capacity of chosen technology).
This reduces the need for significant unclean backup capacity, and either decommissioning them or reducing their usage.
'Switzerland-based Energy Vault wants to use a multiarmed crane with motors-cum-generators to stack and disassemble a 120-meter-tall tower made of hundreds of 35-ton bricks, like a Tower of Babel that rises and falls with the vagaries of energy demand.'
This sounds amazing. It's like the repetitive, seemingly-pointless behavior you see in the background in videogames...
This is a clever system. I remember reading about a similar system in Australia that used excess solar power to lift giant concrete bricks, and then these bricks were lowered to the ground in the evenings to drive generators.
Not sure if this is the same one I read about, but it's the same concept: https://energyvault.com/
Stopped reading at a total cost of more than $300 per MWh for batteries.
Quick back-of-the-napkin calculation: Car batteries come in at less than $100/KWh. They're good for at least 1000 cycles at 80% capacity. That gives us at least 0.8MWh for a 100$ investment.
It's very, very unlikely that initial construction of the site and operational costs more than triple that price.
The cheapest gravity storage is capable of holding itself up.
Which is why vertical glaciers are so tempting. Its just ice, you pile it up, in large columns, with a puddle of water beneath. Energy is extracted by warming the water and taking part of the pressure to a turbine.
Energy is added by pumping and freezing water on top, while the extracted heat is stored in a side tank for later usage.
Insulation against heat prevents energy loss for longer times.
Four T-beams hold up the freezing machinery on top.
Storage grows with demand.
If the ice starts to deform, added carbon-flakes, can increase tensile strength.
Pressure in the pool is kept via onion-seals
The system bring talked about here can deliver 250kW during 11 seconds max.
That is LESS than 1 kWh of energy storage.
I hope it's not the one on the picture otherwise their cost estimates are way off and two orders of magnitude larger than current lithium batteries, even taking into account battery replacement.
Another problem would be the ever-lowering price of batteries comparing unfavorably against this good old tech with stable or raising costs (human costs tend to rise over time)
I had the same thought. They do make it clear that this is a demonstration, but I'm curious how this scales with larger weights and heights; both in capital cost, and efficiency.
I'm also curious if anyone's seen a good comparison to hydro/dam based gravity batteries? Or even to the gimmicky sounding electric train based ones I've read about before?
My understanding is that anything near or past 90% efficiency gets very hard to achieve, but perhaps there are special cases where this isn't true?
Finally, I'm also curious how these compare to flywheels, which offer a similar style of energy storage, but with rotational potential instead of gravitational.
Storage is clearly one of the largest barriers to large scale adoption of many renewable sources of power we have. And, chemical batteries raise a lot of valid concerns in terms of safety and environmental impact.
Since scale and locality is such an issue here, I wonder if there are any concepts for integrating such a system in new mid-rise buildings. Similar to an elevator shaft, but with a weight of depleted uranium instead of the passenger car.
You're digging for the foundation anyway, maybe maybe the marginal cost to dig a few meters deeper is worth it. You're building with a crane anyway, maybe the marginal cost to build a steel frame tower on the roof is worth it. It's certainly not a mine shaft, but perhaps better than nothing.
Not the first time I have heard of gravity batteries, and with the exception of dams, they all look unconvincing.
To make a comparison, there is a human-scaled variant of the concept in the GravityLight by Deciwatt. The concept is clever, it involves lifting a bag of rocks to get a bit of light for 20 minutes. But if you run the numbers, it is tiny. As the name of the company suggests, the generator outputs 0.1W, enough to power a 15lm LED. For 20 minutes you need to lift a 12.5kg bag 1.8m. That's around 0.03 Wh per lift. By comparison, a good 18650 battery is around 13 Wh, about 400x more.
As a niche product, GravityLight is not a bad idea, but it is telling that their new product, NowLight operates the same way, but they replaced the bag of rocks by... a 18650 battery.
Back to the topic, it looks like that "drop a weight in a mine shaft" idea does worse than what you can do with a single Tesla car, which have more energy storage and more power at the wheels. Plus, it is cheaper and you get a whole car with it.
The numbers in this article seem off. 250kW (peak power) for 11s (time at peak power) is 2.75 MJ. That's only about 51 10000mAh D batteries. Of course, the peak power of the gravity battery is much higher than the chemical batteries, but still.
Higher materials density = higher energy density of the overall system. The more you're lifting (e.g. iron, steel, tungsten) the more you can get out in a smaller space. Kind of a cool way to increase the energy density.
Materials density is irrelevant, materials abundance and scalability is far more important. The more you spend on dense materials, the less money you have left to actually store energy.
We use pumped hydro because water is basically free and it is infinitely scalable depending on geography. Meanwhile the proposed system is limited by the size and existence of mineshafts. In other words this is a dead end.
Energy vaults is impractical but it at least tried to solve the scalability problem by taking advantage of the fact that the energy storage grows quadratically with the length of the crane arm. Assuming it is possible to actually build that system in a sealed tower to protect it from the elements (wind makes the control problem almost impossible). Given a large enough energy vaults system there will be a point where its advantages massively outweigh its downsides.
Going one step further, you could carve out a large cylinder of rock out of the landscape [0]. By using wiresaws you will only need to cut the surface area of the cylinder out. At this point your material costs are approaching 0. The only challenge is sealing the walls of the hole and sealing the walls of the cylinder to turn the system into a giant hydraulic cylinder. Storage scales with the fourth power of the radius. Considering the theoretical performance of a gravity storage system anything that is below r^2 scaling is just laughable, which is why the mineshaft idea will ultimately fail.
[+] [-] dang|4 years ago|reply
Gravity Energy Storage: Alternative to batteries for grid storage - https://news.ycombinator.com/item?id=25650551 - Jan 2021 (167 comments)
Gravity-Based Energy Storage Begins Trials 2021 - https://news.ycombinator.com/item?id=24337537 - Sept 2020 (2 comments)
To Store the Wind and Sun, Energy Startups Look to Gravity - https://news.ycombinator.com/item?id=22394154 - Feb 2020 (2 comments)
Lifting rocks as a form of long term energy storage - https://news.ycombinator.com/item?id=21736607 - Dec 2019 (1 comment)
Gravity Battery - https://news.ycombinator.com/item?id=6750276 - Nov 2013 (1 comment)
Gravity Battery Concept - https://news.ycombinator.com/item?id=6739349 - Nov 2013 (72 comments)
Others?
[+] [-] throwaway189262|4 years ago|reply
Assuming the full scale version delivers peak power for 11 seconds like the prototype, 2MW peak power would be 6 kilowatt hours of energy.
That's terrible. We're taking about dropping hundreds, maybe thousands of tons down a mine shaft to get the same amount of power as $700 of lithium batteries you could carry in a backpack. For instantaneous loads you're way better off using flywheels, which we've already had for decades.
Gravity is weak, literally. The only realistic use case for gravity generation is hydro power. And MAYBE reverse hydro power where we put giant gas bags underwater and they make energy floating up
[+] [-] 015a|4 years ago|reply
When speaking about LI packs, especially to enterprises deploying them at grid scale, their expected life has to enter into the equation. Maybe 15 years? 25? So, millions up-front, and millions more every couple decades; its not an impossible sale, but relative to other options (like hydro storage, which is excellent but also limited to areas with existing reservoirs) its not obviously the best option.
They may be better, but I don't feel that means gravity batteries don't have a place. The mechanical pieces to raise and harvest the energy likely aren't carbon-zero, but the weight itself can be built out of anything. They don't experience leakage of stored energy over time (barring a failure of the retention system keeping the weight elevated) (though, obviously, there is loss in the addition of energy to the storage, as the machines which raise the weights are not perfect). They can be reused essentially indefinitely (excepting continuing upkeep of the retention and raise/harvest systems, and proper weather protection of the weight). Their failure mode is "falls", which can be designed far, far safer than a typical LI pack failure of "explodes in a fire that literally cannot be put out". None of the systems in-play are particularly technically advanced, and a ton of the cost is up-fronted. There's a lot of reasons to think they will represent a component of green energy storage in the future; likely not as large at LIo packs, but the world is a big place.
[+] [-] Youden|4 years ago|reply
Reading the rest of your comment, I'm not sure you did the math yourself...
> Assuming the full scale version delivers peak power for 11 seconds like the prototype
The prototype is a 4-storey tower (i.e. less than 20m).
> That's terrible. We're taking about dropping hundreds, maybe thousands of tons down a mine shaft
A mine shaft can be expected to be significantly deeper than a 4-storey tower is tall.
So it seems you've invalidated the assumption upon which your argument is based in the paragraph immediately following it?
> the same amount of power as $700 of lithium batteries you could carry in a backpack
From TFA itself, they estimate they can offer a price of $171/MWh, while Lithium-ion batteries cost $367/MWh.
[+] [-] hn_throwaway_99|4 years ago|reply
Gravity solutions like these will never be feasible, because as you point out, gravity is just plain too weak of a force. I mean, it looks like pumped hydro will be viable, but when you think of the sheer mass of water that can be pumped behind the Hoover damn you realize stacking a bunch of bricks is ridiculous in comparison.
There was another recent article on HN about a giant tidal generator, and I was glad to see the top comment pointing out that basically over 50 years all these tidal projects have been failures (at least when it comes to ever being able to provide decent power in a fashion that shows it can scale).
It's time we start calling out these schemes for what they are, because they take funding away from solutions that we now we'll need now to fight climate change.
[+] [-] _liww|4 years ago|reply
[+] [-] samatman|4 years ago|reply
But Advanced Rail Energy Storage?[0] Different story, has potential (bad pun, I know). There are some nice synergies, like a system such as this can reuse the generators from a decommissioned coal or natural gas plant.
It can definitely play a part in a broad-spectrum energy policy.
[0]: https://aresnorthamerica.com
[+] [-] Kenji|4 years ago|reply
[deleted]
[+] [-] runeks|4 years ago|reply
A wind turbine is already equipped with a generator, so it'd be a matter of building some sort of "switch" which would make it either: (a) generate electricity using the turbine, as per usual; (b) raise the weight using the turbine, thus not producing electricity; (c) generate electricity by connecting the weight to the rotor/generator, while lowering the weight.
[+] [-] masklinn|4 years ago|reply
First, there's not really any room in there, wind towers are built for the job, we don't add twice the amount of steel and an elevator shaft for funsies.
Second, even if there were some room it would be inconsequential, you need a lot of crap very high up to get significant amount of energy.
As demo, let us take the largest turbine available right now and lift the entire thing up and down its tower.
The Haliade-X has a hub height of 150m, a 600t nacelle, and 165t blades. In normal operations it's rated for 14MWe.
765t at 150m is 250kWh. You can get electric buses with larger battery packs than that. For reference, US households use about 29kWh/day.
That's the issue with gravity: it's really not that strong, so to store significant amounts of energy you need either ridiculous amounts of weight (hence dams and pumped hydro which can manage unfathomable weights), or extreme height difference (hence… still dams, pumped hydro a bit less so I think).
As a point of comparison, Bath County (the largest pumped-storage station in the world) has a hydraulic head of 270~385m and the upper reservoir stores 44 million tons of water.
Now taking in account that you can't really empty the entire thing, that it's not perfectly efficient, etc… Bath has a storage capacity of "only" 24GWh, it's not actually moving 44 million tons up and down 400m.
[+] [-] DavidPeiffer|4 years ago|reply
Bad math, let's say we can use a lead weight 2 meters in diameter, 3 meters tall (107,000 kg) with 120 meters of drop available.
All of that gets us 35 kWh, or 0.035 megawatt hours of energy. Compared to a 2 MW turbine, it's a negligably small amount of stored energy, even if we scaled every dimension up by a factor of 2 (getting us to 0.28 MWh).
[+] [-] patall|4 years ago|reply
(Yes, I am aware that it is not storing the water at the top :)
[+] [-] dumbfoundded|4 years ago|reply
[+] [-] thirdlamp|4 years ago|reply
The tower would probably need reinforcements for the additional weight, but I have no idea about the magnitude required.
[+] [-] thehappypm|4 years ago|reply
[+] [-] rakoo|4 years ago|reply
For reference (https://en.m.wikipedia.org/wiki/Coal-fired_power_station):
> As of 2018 coal power under construction was 236 GW, planned 339 GW, and 50 GW was commissioned and 31 GW retired
If we want to replace those new plants we'll need 100.000 of those shafts. And that's not counting the existing plants, and the other fossil-fuel based plants. Think of the quantity of concrete that involves. That's just insane. If we want to actively tackle electricity generation we need to use the most efficient low-carbon tech that we already know.
Also, we already have gravity-based systems, only nature does all the work of raising the payload for us in gaseous form, and we let it fall in liquid forms. But it takes so much dam place.
[+] [-] audunw|4 years ago|reply
The most immediate need for energy storage is frequency regulation, and short hours-long dips in power output. If we can solve that we can scale renewables very far.
For days-long dips in power output, it's probably better to keep some gas power plants on stand-by. I think many areas of the world has enough of them to handle these needs already. To make it sustainable, they could be switched to using renewables fuels, like hydrogen or ammonia made from electricity. We're going to need a shit-ton of those kinds of fuels for trucks, ships and airplanes anyway, so setting aside some of it for backup power wouldn't be a huge problem.
For seasonal variations, I think trash burning power plants is a reasonable solution. Sweden and Norway has some of them, and they also provide heating to nearby homes. I mean, yeah: first of all we should reduce, reuse and recycle. But eventually our trash become unrecyclable, and burning it seems to be the best option. Modern facilities seems to be able to extract almost all harmful compounds from the waste then. There are also experiments with carbon capture from these plants, which in a fully renewable world could make them carbon-negative, and become one of several tools to help reduce CO2 in the atmosphere again over time.
And of course, nuclear would be a great help. If it can be made cheap enough again, it can be used for seasonal variations. But we're still going to need renewables. So we still need energy storage for frequency regulations and minute/hours-long dips in energy output. Nuclear power plants are NOT a good solution for that.
[+] [-] pedrocr|4 years ago|reply
[+] [-] hutzlibu|4 years ago|reply
We actually also do have self created gravity-based systems, where we also do the work by ourself, to have a energy storage on demand:
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
They work reliable and with big capacity since the very beginning of electricity. The only problem is ... scale. You cannot just build them where you want them. You need rivers and height differences.
Unless you create such systems completely artificial and there are plans to do so, but that will be very expensive.
edit: here is a paper (in german) discussing such possibilities, to create a artificial pumped-storage out of the remains of surface mining
https://epub.wupperinst.org/frontdoor/deliver/index/docId/72...
edit 2:
and my opinion is, that I am not a fan of complicated solutions, like the originial solution from the article seems to be, which is also stated as "The technology is still “incredibly immature”
There are solutions to make batteries without rare elements. They just don't reach the energy density of lithium based ones, but that is not really a problem, when you have them stationary.
So if you could scale up production of these and in the end, have a big battery in every home/factory connected to the grid - you would have a stable grid without any need for gas- or coal powered backup.
[+] [-] FooHentai|4 years ago|reply
Once you can get it up in the air then the higher you can go you're doubling your storage in a linear fashion. Hoist one of those trucks to 50 meters (perhaps you have a handy cliff in your backyard) and you've stored as much as the ten trucks did at 5 meters.
So yeah scale seems hard, but the low technology/materials requirements and potential for gradual scale-up make this worthy of deep investigation. I think there's a lot of wandering off into dead-ends as far as limitations go though - Solutions that depend on a lot of concrete pouring, for example, are a no-go if the end goal is reducing atmospheric carbon.
[+] [-] throwaway189262|4 years ago|reply
This is just false. Every wind turbine I've ever seen uses 50 square feet on a farm or cattle ranch.
Not once have I seen a wind farm where the land underneath isn't still used for it's previous purpose.
And at least in US we have enough farmland to power entire US with wind.
And that's not counting rapidly growing offshore wind power. Which uses no land at all
[+] [-] jillesvangurp|4 years ago|reply
The reasoning roughly goes like this: wind and solar capacity varies because wind doesn't always blow and the sun doesn't always shine. This is very obviously true of course. Except these effects are local, temporary and typically result in a reduced capacity rather than a complete collapse. You always get some output out of solar panels (except at night). And wind turbines might stop spinning but it's extremely rare for that to be a continent wide thing. Offshore wind is pretty reliable. Also these effects are kind of predictable via weather forecasts so we can plan for them. Same with seasonal patterns. Simple cables rather than batteries are the key technology that we need. And we mostly have that in place already.
The grid connects power plants via cables. So, we can compensate for local dips in power with remote peaks. What matters is the collective performance of the grid. That still fluctuates but not nearly so dramatically that you'd need a lot of battery. E.g. the European grid is very connected. So, you might get power from Norwegian hydro, North Sea offshore wind, German on shore wind, solar plants in Spain, France, Germany, etc. or any of the gazillions of solar panels on people's houses. And of course there are coal, gas and nuclear still on the grid as well (for now).
All of that failing 100% at the same time is simply not a thing. Not even close. It's not something grid operators plan for. It might dip by 20-30% but it might also peak by that much. And it's likely to average out over time in a very predictable way. All that means is that we need to have a little more capacity. 2x would be overkill. 1.2 to 1.3x plus some battery will probably do the trick.
Batteries on the grid are intended for and used exclusively for absorbing short term peaks and dips in both supply and demand. Short term as in hours/minutes; not days or weeks. They are very good at that.
This is why modest amounts of lithium ion batteries are being used successfully in various countries. These batteries can provide large amounts of power (MW/GW) for typically not more than a few hours. The reason that is cost effective (despite the cost of these batteries) is that taking e.g. gas peaker plants online for a few hours/minutes and then offline again is expensive and slow. And of course with cheaper wind and solar providing cheap power most of the time, gas plants are increasingly pushed in that role because they are more expensive per kwh to operate. Gas plants on stand by still cost money. And turning them on costs more money. Batteries basically enable grids to have fewer (and eventually none) of those plants. These gravity based batteries have the same role. It's a cheaper alternative to lithium ion batteries.
Currently, clean energy is the dominant form of energy in many countries already (e.g. Europe, China, parts of the US). In some countries it's well over 50%. This proves the point because these grids don't feature a lot of battery currently and the combined capacity of peaker plants (i.e. not operating continously) is far smaller than the presumed need for batteries. If you were right, these countries would be facing massive blackouts all the time as their dominant form of energy disappears for days/weeks on end. That's obviously not a thing.
[+] [-] onecommentman|4 years ago|reply
There are about 10E7 active oil wells in the US.
https://www.eia.gov/petroleum/wells/
There are 10E8 private water wells in the US.
https://www.epa.gov/privatewells
So 10E6 sounds practicable and, as discussed previously, may be a significant overestimate of actual need. Suspect 50 year life cycle costs and various environmental and political externalities would be substantially lower for gravity-based solutions. But who knows?
Concrete requirements? About 10E10 tons of concrete are consumed worldwide each year.
https://concretehelper.com/concrete-facts/
Again, 10E6 doesn’t look so big, but might involve some engineering cleverness.
But 10E6 big, capital intensive, fairly generic things can justify a lot of engineering cleverness in that one generic design. Geotech would need a lot of thought.
[+] [-] kjrose|4 years ago|reply
All of this is essentially ways to create hydroelectric plants without the water. If we can find a way to create more of them without massive disruption it'd probably be the most effective.
We need to find a solution that isn't just based on good wishes.
[+] [-] fighterpilot|4 years ago|reply
If it's way too expensive (and there's no obvious way to reduce costs), then scalability is irrelevant, which is probably why people are fixated on it. We need both scalability and price to be favorable.
[+] [-] arghwhat|4 years ago|reply
They can, however, be configured to cover huge surge loads for short moments, or smooth out small discrepancies over a longer span, in more or less the same footprint.
If you want a GW of coal, you need a GW plant, whereas with batteries you can decide between a gigawatt-hour or a 1000 megawatt-hour using a similiar footprint (scale to capacity of chosen technology).
This reduces the need for significant unclean backup capacity, and either decommissioning them or reducing their usage.
[+] [-] sdenton4|4 years ago|reply
This sounds amazing. It's like the repetitive, seemingly-pointless behavior you see in the background in videogames...
[+] [-] amanzi|4 years ago|reply
Not sure if this is the same one I read about, but it's the same concept: https://energyvault.com/
[+] [-] blueblisters|4 years ago|reply
These guys “solve” the wind and control problem by digging a 300m deep pipe for the weights.
[+] [-] binbag|4 years ago|reply
[+] [-] choeger|4 years ago|reply
Quick back-of-the-napkin calculation: Car batteries come in at less than $100/KWh. They're good for at least 1000 cycles at 80% capacity. That gives us at least 0.8MWh for a 100$ investment.
It's very, very unlikely that initial construction of the site and operational costs more than triple that price.
[+] [-] guerby|4 years ago|reply
This is ridiculous.
I'm charging right now my EV from a 14 kWh 16S LFP pack which costed me $1400 tax paid and delivered.
LFP properly managed will do minimum 3000 cycles, so that's 42 MWh for $1400 which gives $34 per MWh out of the battery.
Note: 5kW 48V inverter cost $500.
[+] [-] robertlagrant|4 years ago|reply
[+] [-] montag|4 years ago|reply
[+] [-] raverbashing|4 years ago|reply
[+] [-] amanzi|4 years ago|reply
[+] [-] PicassoCTs|4 years ago|reply
Which is why vertical glaciers are so tempting. Its just ice, you pile it up, in large columns, with a puddle of water beneath. Energy is extracted by warming the water and taking part of the pressure to a turbine.
Energy is added by pumping and freezing water on top, while the extracted heat is stored in a side tank for later usage. Insulation against heat prevents energy loss for longer times. Four T-beams hold up the freezing machinery on top. Storage grows with demand. If the ice starts to deform, added carbon-flakes, can increase tensile strength. Pressure in the pool is kept via onion-seals
https://imgur.com/iCg9LzY
[+] [-] Gauge_Irrahphe|4 years ago|reply
[+] [-] joss82|4 years ago|reply
That is LESS than 1 kWh of energy storage.
I hope it's not the one on the picture otherwise their cost estimates are way off and two orders of magnitude larger than current lithium batteries, even taking into account battery replacement.
Another problem would be the ever-lowering price of batteries comparing unfavorably against this good old tech with stable or raising costs (human costs tend to rise over time)
[+] [-] nixpulvis|4 years ago|reply
I'm also curious if anyone's seen a good comparison to hydro/dam based gravity batteries? Or even to the gimmicky sounding electric train based ones I've read about before?
My understanding is that anything near or past 90% efficiency gets very hard to achieve, but perhaps there are special cases where this isn't true?
Finally, I'm also curious how these compare to flywheels, which offer a similar style of energy storage, but with rotational potential instead of gravitational.
Storage is clearly one of the largest barriers to large scale adoption of many renewable sources of power we have. And, chemical batteries raise a lot of valid concerns in terms of safety and environmental impact.
[+] [-] mbar84|4 years ago|reply
You're digging for the foundation anyway, maybe maybe the marginal cost to dig a few meters deeper is worth it. You're building with a crane anyway, maybe the marginal cost to build a steel frame tower on the roof is worth it. It's certainly not a mine shaft, but perhaps better than nothing.
[+] [-] unknown|4 years ago|reply
[deleted]
[+] [-] GuB-42|4 years ago|reply
To make a comparison, there is a human-scaled variant of the concept in the GravityLight by Deciwatt. The concept is clever, it involves lifting a bag of rocks to get a bit of light for 20 minutes. But if you run the numbers, it is tiny. As the name of the company suggests, the generator outputs 0.1W, enough to power a 15lm LED. For 20 minutes you need to lift a 12.5kg bag 1.8m. That's around 0.03 Wh per lift. By comparison, a good 18650 battery is around 13 Wh, about 400x more.
As a niche product, GravityLight is not a bad idea, but it is telling that their new product, NowLight operates the same way, but they replaced the bag of rocks by... a 18650 battery.
Back to the topic, it looks like that "drop a weight in a mine shaft" idea does worse than what you can do with a single Tesla car, which have more energy storage and more power at the wheels. Plus, it is cheaper and you get a whole car with it.
[+] [-] lebuffon|4 years ago|reply
Liquid metal batteries will be better than gravity storage IMHO.
https://www.youtube.com/watch?v=NiRrvxjrJ1U
First commercial scale system is going live in 2021 so we shall see how it works out.
[+] [-] sollewitt|4 years ago|reply
[+] [-] 3dee|4 years ago|reply
But looking at the size of the project, I have a hard time believing this is viable.
https://aresnorthamerica.com/
[+] [-] SarbinBracklur|4 years ago|reply
[+] [-] accrual|4 years ago|reply
[+] [-] imtringued|4 years ago|reply
We use pumped hydro because water is basically free and it is infinitely scalable depending on geography. Meanwhile the proposed system is limited by the size and existence of mineshafts. In other words this is a dead end.
Energy vaults is impractical but it at least tried to solve the scalability problem by taking advantage of the fact that the energy storage grows quadratically with the length of the crane arm. Assuming it is possible to actually build that system in a sealed tower to protect it from the elements (wind makes the control problem almost impossible). Given a large enough energy vaults system there will be a point where its advantages massively outweigh its downsides.
Going one step further, you could carve out a large cylinder of rock out of the landscape [0]. By using wiresaws you will only need to cut the surface area of the cylinder out. At this point your material costs are approaching 0. The only challenge is sealing the walls of the hole and sealing the walls of the cylinder to turn the system into a giant hydraulic cylinder. Storage scales with the fourth power of the radius. Considering the theoretical performance of a gravity storage system anything that is below r^2 scaling is just laughable, which is why the mineshaft idea will ultimately fail.
[0] http://eduard-heindl.de/energy-storage/energy-storage-system...
[+] [-] toast0|4 years ago|reply