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.
> Lithium mining is an insanely tight bottleneck in LI battery production
If anything lithium refining and production into high quality is far closer to the bottleneck.
> 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)
This is also very questionable. Lithium exists basically everywhere. Basically one of the most common elements. Pretty much in every desert you have tons. There is tons in water brines all over the world. There are huge hard rock reserves all over the world (US, Wales, Canada, Australia, Czech Republic and so on). There are even larger clay reserves, Nevada alone has lithium enough for all US needs. Mexico has huge amounts of brine as well.
South American brine is losing market share quickly and they will never get it back.
> They require complicated manufacturing processes that are centralized into maybe four or five advanced manufacturing companies around the planet.
This is true but many more companies are currently working on it all over the world. It is difficult but not its not some totally crazy technology.
Other technology have a place, but I don't know if gravity battery is one of those. Liquid air batteries, liquid metal batteries and others might be better solutions.
No that I see. It's just really easy to read your comments in a haughty tone, which naturally selects for downvotes. The content of your posts, on the other hand, seems to encourage deeper investigation, so that's probably on point.
Even 400 stories would be 600 kwh. Thats like 2 tesla battery packs. Way better than 6 but still not anything that can be realistically applied at scale.
There's not many deep mineshafts that aren't filled with water. And dewatering mines is insanely expensive. And 600 Kwh is nothing. Enough to power maybe 30 houses for a day.
My math is bad, but there's no math where this will ever work out profitably
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.
In my head, liquid must be easier to play with than a solid.
So displacement of water or air should be done.
The displacement of air, being pumped into a balloon under water seems like a great idea.
I know many solutions must have been thought of, but is the inflate balloon under water , then let it float up - the most efficient way of storing energy?
Lithium batteries wear out, but are more energy dense and so arent comparable ( regardless of size).
Forgive me for ruminating I think this is a problem with an already identified solution though?
I heard conjecture about it. Possibly more realistic is high pressure gas storage in salt domes. Or hydro power based on filling and draining deep mines.
There's realistic gravity based projects, but dropping ACME style anvils down mineshafts isn't one :)
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.
Does that matter though? If it is weak to extract energy with gravity, then it should also be weak to “charge” the system against gravity. The weakness may push these systems to less “instantaneous” loads, but I don’t see why it would necessarily be bad to use gravity storage (as opposed to another mechanical method like pressure).
Because gravity is so weak, in order to store a meaningful amount of energy, the lifted object has to be very heavy or very high. Building large tall structures is expensive, and we just don't have objects that are dense enough to make the system small.
While I don't disagree with your general sentiment of the viability of gravity batteries. I don't think its a very good comparison. One is all about electricity generation and the other is all about storage. If gravity batteries ever become used in practice it would probably be in tandem with solar. You would charge the battery during the day off solar and allow it to discharge at night when there is no sun to stabilize the grid.
anyone saying gravity is strong relative to the other forces should ask themselves why they don't keep sinking or get crushed when gravity pulls there feet back to the ground.
You risk damaging the batteries and you make maintenance a pain in the ass. If you've got that amount of batteries, just put them on the ground the normal way.
I was thinking what if we used buildings built on jacks as our source of mass. Big one are largely built on pilings anyway, and even small ones on softer ground.
Going to be a lot of flexing though.
Nice thing is that some of the “inefficient” heat may be usable on-site: and you may get compressed air as an output that could be usable directly.
It’s amusing to think of whole houses getting jacked 100 ft into the air on giant stilts during the middle of the day when solar panels are operating, then slowly dropping to release the stored energy in the evening/morning.
I don't know how much a typical house weighs, but assuming 100t, raising it by 30m will give you potential energy of ... 8.2 kWh, or about $1.6 in today's electricity rate.
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.
> Sure it would cost much more, but in some applications steady power is worth it.
It would cost much more and be way more complicated & less reliable than… just getting the two separately and using battery grid storage on the output of the windfarm.
Even for a backyard turbine it wouldn't make much sense, for maintenance reasons you'd want to manage your turbine and storage separately, and if, say, you add solar panels, you want that to feed into your battery bank as well.
Why would it be more complicated and less reliable than getting them separately? I understand that it would be a more complex product for GE but for a turbine buyer it sounds extremely attractive
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.
Not true in northern European countries. The problem isn't day to day regulation, it's the massive demand in cold snaps in winter (when there is very little wind generation - cold weather tends to have little wind). You're talking balancing 20-30GW of additional demand with little solar/wind generation for weeks/months - probably at least 1TWh of storage required for the UK alone.
Keep in mind this will only get worse as heating demand is switched from natgas to electricity.
This seems like a "running before we can walk" statement. Until we can handle day to day problems, it seems weird to worry about edge cases. I imagine as we transition to renewables and storage we will still have fossil fuel peeker plants to handle these sorts of snaps.
It won't be until our power storage is far more beefed up that we'll shut those down, and that will take years.
Right, and my point is that they aren't going to decommission all backup power until they are at the point where sun/wind/storage can actually be relied on for more than just the good days.
We have a long trip to get there, so why worry about a once in 3/5 year event? We wouldn't go a year without fossil fuels and say "Ok, that was it! Demolish all the plants right now!"
A cold snap like that can happen every 3-5 years, think really cold February. If you don't have the capacity to handle it people will die and lots of things will break. It is not an edgcase
It's actually worse than that, there are many days in winter in the UK with high demand and virtually no solar/wind output. But obviously a really cold snap would be even worse (and as you said isn't an edge case - even if it is look at the damage that happened in Texas when it wasn't accounted for)
It is when we aren't running 1 year on pure renewables. Let's worry about events that happen every 3 to 5 years when we've got 1 year of renewable only figured out.
It will take years before this is potentially a problem and by that time we'll likely have gone through a few cold snaps.
Homes in the UK are poorly insulated, likely due to a previous over-reliance on fossil fuels. https://www.theguardian.com/environment/damian-carrington-bl... Better insulation and switching to district heating where applicable could yield massive savings.
District heating still needs heat to come from somewhere. Admittedly, low grade heat like is used for heating can be stored for days in the form of hot water in insulated tanks.
Long distance power transmission is a significant political and military liability, not to mention a fantastic terrorist target.
We cannot guarantee that the UK will be at peace with every county between them and the Sahara forever. Hosting the power line would grant significant political or military leverage.
You don't want a single point of failure. Having multiple lines across a geographic space is the way to go.
It's a big upfront investment, but it could be much cheaper than storage at scale.
I think ultimately you want power transmission stretching from the UK to Japan so as the sun moves the power generation continues.
I imagine it will happen one day, because it would seem to make so much sense, but this is something governments could make happen a lot sooner if they put their mind to it.
Importing energy from Sahara comes with serious geopolitical issues. Do you really want to commit to peacekeeping in a huge area of Africa? Keep in mind that oil can be stockpiled much more easily than electricity, stockpiles that let you weather small storms. Importing electricity means being on top of every hint of a blip.
Wrt cold snaps being a big problem, it seems like we could just massively insulate dwelling and improve our energy use auditing, if it became necessary? Vacuum insulation panels are a bit pricey, but they’re crazy insulative for the thickness. If we’re willing to deal with thicker walls, there are a variety of other options that are downright cheap (shredded newspaper, for example).
We’ve been designing around super cheap on-demand energy for a while now, but we did manage before that.
The problem is the UK sees maybe 1-2GW of renewable generation sometimes in winter while demand is about 50GW. So you'd have to overbuild 25x to cope with these days.
Keep in mind the UK already has about 30GW of solar and wind potential nameplate capacity. Your suggestion would result in a requirement of 700GW of solar and wind to be installed. On windy and sunny days would result in probably 350GW of generation, at least 300GW more than we need.
Actually, almost none of our trash is recyclable (despite what you've heard). Plastic is particularly bad, and it's only now, with China banning import of "recyclable" materials, that we're finally seeing just how much of a farce it is.
Burying it is a form of CO2 sequestration. Burning it just releases it into the atmosphere.
But it's already out of the ground. I'd rather burn 1T CO2 worth of plastic trash made from oil and prevent 1T CO2 worth of coal or heavy oil being extracted and burnt. Not that it's 1-to-1, point is burying plastic is probably less net carbon vs burning.
> It's a common misconception that energy storage needs to handle all the power needs of an area for a significant time.
You are only looking one half of the problem. Wind power in the UK has a power factor of about 35%. What that means is to meet the average demand from the UK electricity grid we'd need not install 3 times as much Wind Power as the demand. This is borne out in the current figures, we have some 25GW installed wind power for an average of about 6GW supplied. If we have enough renewables to meet the demand on average, a windy day across the UK is going to result in a glut of power.
If we don't have ways of storing that modestly efficiently then our only choice will be to take turbines out of service, increasing the overall cost.
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.
I think[0] we should probably be aiming for a few hours of storage, even with every affordable grid interconnect (which would help a lot with short winter days). We use less power at night — and some of what we do use is incentivised by lower nighttime electricity costs from power plants that don’t scale down well — but I expect we will continue to use some at night forever.
For the sake of Fermi estimation, I assume average electricity use in a developed nation is 1kW/person, and that average all-forms power use in the same is 5kW/person.
Transportation is almost certainly going to be batteries or synthesised fuels like hydrogen, and can only be backed by gravity storage if you have the kind of beamed power that would be banned by international treaty on the grounds of being too easily weaponizable[1].
If you’ll permit me to assume grid interconnects and lower nighttime demand than at present due to different pricing incentives, we might be able to need a mere 3kW-hours/person of electricity storage per night.
Using the lifetime cost estimates in the article, 3kWh/person/night is about $0.51/person/night for gravity storage and $1.10/person/night for LiIon. Neither is bank-breaking, but cheaper is better.
However, the volume required is a different question: 3kWh of batteries has a volume of 4.3 to 12 litres, while 3kWh of gravity storage is 1.1 metric ton kilometres[2].
You can make the distance required smaller by using more mass, but if I assume the average home mass is about 200 tons, you’d still have to raise the entire building 5.5 meters every day to store the same energy as a backpack of batteries. I do not expect construction on this scale to be the optimal solution in general, despite it being a very good idea in some specific cases such as hydro dams and preexisting deep shafts.
[0] Armchair opinion — I’m a software engineer not a civil engineer.
[1] Assuming they’ve read or watched any Larry Niven, the Bobbiverse, The Expanse, Babylon 5, or the news at any point in the decade following the second week of September 2001 — 'A reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive.'
Large scale hydro electric dams are already large scale batteries across months. The specific day of the week energy is released is not particularly relevant let alone time of day. 6.6% of US electricity is from hydro, assuming 2/3 flexable your looking at 4.4% of daily power demand or ~1 hour of full grid storage every day is already built.
Excess capacity is required for storage to work and reduces the need for energy storage. But, once you start talking excess capacity, transmission dramatically reduces the need for storage.
Assuming storage costs say 2x as much as wind generation then building excess wind capacity is worth it until ~1/2 of a wind turbines output is wasted. Thus if we are looking at 3kWh of storage that can be banked at any time of the day we are looking at a lot of excess capacity, yet somehow still supposed to have a 3kWh per night deficit.
"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.
Side note on what is currently existing with gravity.
The suiss folks are gaming the west European energy market this way.
When the French produce too much nuclear energy, the German have leftover and stop buying it 100%w
Price go down.
Swiss buy it cheap and pump water in their dam system with it.
Inevitably, the french grid align and produce a bit less. Price goes up slightly.
That when the suiss comes out, release the water into a turbine system and sell the energy for a higher price that what they bought it for to German, French and Italian grid.
I can’t even be mad at them. They have the perfect setup. But you need the Swiss alp and climate to do what they are doing.
And being freaking Swiss.
Source/Context from a Swiss news paper : le temps, in French
They describe that « system » and apparently it’s being disturb in recent years with the evolution of the German market.
Maybe I do not understand it fully (ne pas parle de francais), but where do they game the system?
You buy cheap when you have storage and sell expensive when demand goes up.
Pretty much how the market should work?
This way there is incentive to balance it out (by creating storage) - and in this case stabilize the grid.
When the grid would become more flexible, so even homeowners can do this with their solar panels and big batteries - then this should be net gain for everyone, no?
Unless gaming it, with big money, destabilises it. So some safeguards probably should remain.
You are correct, it's not gaming the system indeed. It's more something that they decided to do on their own, and rightfully so.
It's a bit innervating for French tax payers to be on that side of the bargain. But at the same time, we have nuclear power plant, those cannot react that swiftly to market demands changes... it's all fair game. They actually provide some kind of buffer service.
It's not gaming the system, it is arbitrage. However, it is pretty terrible for producers unable to exploit price swings. E.g a nuclear plant produces electricity at a fixed cost and may sell it at a loss when the price is low, but recoups the losses when the price is high. Since arbitrage smooth out the price peaks, it damages nuclear's profitability. One could say that's too bad for nuclear, others (nuclear lobbyists) say that regulation is needed to prevent electricity arbitrage.
If nuclear can offer sustained cheaper than average generation then the market would allow a long term fixed price contract — they shouldn’t need to sell their full output at spot rates. Consumers that want predictability could buy on these contracts.
How much of a swing in pricing are we talking about here? Because that storage mechanism is maybe 80% efficient. So the price swing would have to be at least that big to break even. And in that case, if they are helping to smooth out swings in demand that are that large... Sounds like they're providing a valuable service.
EDIT: Keep in mind that electricity is entirely fungible. This is no different than the Swiss turning on a power plant when prices are higher. Except it would probably be too expensive to have a power plant just sitting there idle when the price isn't "high enough".
> it would probably be too expensive to have a power plant just sitting there idle when the price isn't "high enough"
This is exactly what is done, and pretty much inevitably must be done - grids need spare capacity that can be relied on to spin up rapidly when demanded, that's usually done by gas turbine plants.
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.
Yes, but only once. This is energy storage not energy source for the purpose of human utility. The ability to pull that 1kw of potential energy back up (with some renewable source eg wind turbine) to be output over again is where the comparison breaks down.
A fairer comparison is current battery tech, you can pack something like 40kwh in 200kg of batteries (rough guess based on leaf ev battery modules). So vastly more in the same space/weight. But those are complex and energy intensive to manufacture, and have limited lifespans before further energy investment is required to recycle/replace them. The relative simplicity and long lifespan of gravity storage seems like it has potential. Not to mention the potential for owner/operator to self install, which could be great for developing nations.
Absolutely, useful just to illustrate the scale we're talking about for a given amount of energy stored as a real-world analog easy to recall.
Assuming you used cast iron as weights that has a density of ~7800kg/m³ at regular temperatures, so you're looking at about 10 cubic meters for that 1kWh of potential energy storage using an abundantly available, non-toxic material that will endure.
I can imagine this tech all packed up in a standard 40ft shipping container and dropped on premise.
This would be rather simple tech, that can supplement solar and wind on your farm, lodge, campsite or island. Another piece in the puzzle for smaller scale independence.
Not to replace metropolis-scale energy demands, as grandparent implies, but to smooth out fluctuations on hourly, household scale.
I imagine chemical batteries would be easier to ship and install, and require less maintenance. I really can't imagine any mechanical system that involves plugging and unplugging a load (or anything more complex than that) to be useful at small scales.
There will be a maximum drop rate that is supported by the machinery being built, and it seems reasonable, though not mandatory, that a 5x weight system will be designed to handle more generation than whatever it's 5x of.
Construction material is a meaningless metric. If you compare coal or gas plants you need to consider the materials they consume and infrastructure needed for fuel transport. This is a big number, many times the material used for the plant itself.
The only meaningful comparison is material used vs solar. Once these things are built they use near zero resources. For everything else you have to keep mining shitloads of material forever.
How much coal do we have to mine for coal plants? How many gas wells and pipelines for gas plants? What about transport? How much does it take to mine and process all the uranium into fissile isotopes for nuclear?
With wind and solar you plop the thing in a field and get years, maybe decades of energy with no input.
I'm convinced that all these land use and building materials costs studies are just FUD funded by the fossil fuel industry.
Please link to a source/calculation where a wind turbine uses more resources than a coal plant to build. I mean, you can even do napkin math and see that there’s no way multiple buildings and vast mining infrastructure take less material than a turbine farm.
If you want to take a coal plant, you have to compare it with something that's comparable.
A coal plant is a 1000MW machinery. A wind turbine is in the order of 10MW. Also, turbines have a very low capacity factor so you have to double them to guarantee their output and combine them with storage. So it's 1 coal plant vs 200 turbines at the very least.
But coal plants use an absurd amount of coal and everything they don't burn ends up as ash.
And have you been close to a big coal plant? They're massive. A coal plant probably used more land than 200 turbines and unlike turbines the land is unusable.
Coal plants use many times their mass in coal during their lifetime. If you're looking at total materials needed over the lifetime of the plant, I wouldn't be surprised if coal was 100X higher than 200 turbines.
It does far less damage than any other source of power. Unlike solar, it uses no space. Unlike fossil fuel and nuclear, it uses no continuous inputs.
Coal and gas plants use many times their weight in materials for a lifetime of operation. Nuclear probably does too because the massive waste involve in uranium refining.
What do you suggest as a greener power source than wind?
So? How much resources does it take to mine thousands of tons of coal a day, or billions of BTU of natural gas?
With solar and wind, you put it up and you're done. No more inputs. It chills in the field.
With coal and gas you're feeding shit tons of material into it every day. And you always need more, for the life of the plant.
It's bonkers you think the amount of steel and concrete that go into a turbine are anywhere close to comparing to the raw materials other power sources consume.
Turbines require steel and concrete. So does every other building above 5 floors
The problem with wind is storing the energy. I live in the Pacific NW and when you drive through the Columbia Gorge you see hundreds of these windmills. I have have visited the Wild Horse Wind facilities and they store energy using batteries -- terrible. The dams below can back up water, but wind blows whenever is may. The dams also provide safety from flood, a waterway, recreation, ... windmills just pollute the sky, kill song birds, and can not produce energy on demand nor store it effectively. Talk to engineers for Bonneville and they mock the windmills.
If they are going to use wind why not pump water up from the Columbia River up to the top of the surrounding hills? Use the potential energy at least.
Are you actually complaining that wind is bad because it ruins the view?
Windows, cars, and pet cats kill multitudes more birds than windmills
Hydro plants do use wind to bank energy. Either by shutting down and banking water when the wind is blowing, or even running the pumps in reverse.
I agree with you that energy storage is a big problem with wind. It is with solar too. But we can get near 50% wind and solar before it becomes a problem since much more energy is used during the day.
Dams also have a finite lifetime, something nobody really talks about. They silt up over 50-100 years until they're completely full. This is a bigger problem in places like China with turbid water but happens everywhere eventually. The sun will shine and wind will blown till long after we're gone but dam sites will be gone eventually.
You misunderstand the impact of the dams on the ecosystem. Salmon are hanging by a thread in the Columbia, and only a very aggressive hatchery program has kept them from collapse.
Essentially all buildable sites have already been built, and there's a growing awareness some existing damns need to come down. The Gorge is not some great untapped resource for pumped storage that people were too distracted by wind power to discover.
I'm friends with an environmental economist that did the analysis while working for the state of Oregon. He also was involved in the reports that shut down Boardman. The information is accurate.
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.
The cheapest "energy storage" is bandwidth and demand based billing.
The required battery storage cost to guarantee my 3 KW electric clothes dryer could theoretically operate 24x7 when needed after three weeks of cloudy windless weather at midnight is staggering. The alternative is demand based billing and program my dryer to never accept a KWh that costs more than say, seven cents. On a minute by minute basis I don't care if my "hour" dryer cycle takes 65 minutes because a cloud passed overhead and it slept for five minutes. Its also worth considering that "in theory" people who design for max theoretical load MUST assume my clothes dryer will run for 24 hours a day 7 days a week, when in practice I have never done more than five hour long loads of laundry in a row, and that was after traveling out of country for two weeks (after zero electrical demand for 14 days)
Even data centers can do stuff like vmware vmotion running virtual hosts off a cloudy cloud data center to a sunny cloud data center with no user interruption.
The idea that the wall outlet is an infinite source of energy is going away, or if its demanded for a hospital operating room or nuclear power plant or something, those KWh are going to cost like $5 or something similar and that's just how its going to be. Its not going to be that much suffering; right now my multi KW airconditioner instantly starts up when the thermostat says go, and in a decade maybe the electric company contract says it's guaranteed to start within the next ten minutes 99% of the time, and that sounds like a nice deal if it cuts my bill in half and eliminates CO2 output.
Problem is: how are you going to convince great numbers of people to alter their daily routine that might also be quite synchronized across a country's population?
Like tea time in the UK where apparently millions of people turn on their kettles (2 kilowatts each) in synchrony to get some hot water.
What if they also like to cook something with their stove (another 2 KW) to get a nice dinner, around the same time?
He told you: Dynamic rates and appliances that let you adjust their behavior based on rates. Have people pay based on the demand and the most able to alter their usage will do so.
I'm skeptical-- but probably for different reasons that you.
W/ PG&E and MCE the utility can't even manage to tell me my current rate-- determining from my bills requires solving a linear system in three unknowns, requiring three bills. And the rates change quarterly, so I can only determine the rates at the moment they no longer apply. The rate scheme also has various non-linearities such that my total rate depends on my overall usage over the year and as a result my true marginal rate is unknowable at any given time. I dunno how rates are supposed to incentivize behavior when they're so opaque.
So I like to imagine a future with smart electrical panels and appliances where their behavior can be rate shaped in realtime, ... but then I encounter the actual behavior of the PUC and utilities and a future with demand shaped by economics seems distant indeed.
Sounds like you're mostly unaware of the issue that trying to compensate region, country and sometimes even continent wide lows/peaks would require many gigawatts of transmission capacity in the form of cables in arbitrary directions. Even if the European grid is well interconnected it's painfully far from handling such situations.
And that is not even accounting for the fact that right now only a small proportion of total energy use is transmitted electrically, which means that with future energy generation becoming greener being strongly tied to having more solar/wind (which is also electrical), there will anyway have to be a massive increase in grid capacity.
> Currently, clean energy is the dominant form of energy in many countries already (e.g. Europe, China, parts of the US)
Just not true. Yes, some countries are (Iceland is one of the few) but most European countries are far from what you claim.
Maybe you meant energy transmitted as electricity instead of all energy.
> Somebody will jump to the wrong conclusion that we need to provide massive amounts of battery storage
+1 for the post, but I don't see this that much.
Whenever I see the debate come up, it's when someone is directly comparing the cost of solar to nuclear/natgas without factoring in the additional cost of batteries and DC lines, which obviously leads to an invalid (or at least incomplete) comparison.
I'd like to add that with the rapid electrification of car- and soon truck and ships- fleets, we are already rolling out that giant battery-pack, as we speak.
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.
Does it? If you use iron instead then we only need to know that it has eight times the density of water. Multiplying a volume by eight is not a lot; it's only twice the size in length, width, and depth.
So let's imagine replacing a typical hydroelectric power station [0] with a 'gravicity' system. Supposing the same depth you need a system of about one third of its length and its width and then fill it to the brim with iron. And of course do not forget to install cranes that are able to lift this iron to another space about 200m lower and back up.
By the way, for concrete blocks it would only be a volume factor of 2.5, which would mean about 36% more in length, width and height.
All in all, the amount of space that can possibly be gained with these systems seems pretty minimal to me.
Maybe our expectation that we can match generation to consumption with storage, is just plain wrong.
Maybe all we need is to have massive overcapacity of renewables - if we have 10x more solar than we need, even the most cloudy day will still provide power.
'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/
You should not use Thunderf00t as an authority on this. He has no clue what he's talking about. That seems to be a problem in general, he doesn't actually do much research on the topics he talks about. So unless he already has some understanding of the topic, he doesn't provide much insight.
He seems to think Energy Vault is an alternative to pumped hydro, which it is absolutely not. They're not solving the same problem.
Pumped hydro is best suited for regulating power over days/weeks. You do not want to use it to do frequency regulation or regulate power fluctuations over hours/days. In fact, in Norway, where there's a whole lot of hydropower, and now an increasing amount of wind power, they're considering putting battery storage inside hydro power plants. This may seem really stupid until you understand that constantly regulating the output of a hydro power plant up and down wears down all the parts of the power plant much faster, and can cause issues for life in the river downstream. So it actually makes a lot of sense, since the hydro power plant has a good grid connection and may have some spare areas for batteries.
Batteries and solutions like Energy Vault are primarily intended for frequency regulation and short term storage, and that covers most of what's needed to help balance renewables in most areas.
There's a bunch of other serious flaws in his reasoning too, such as thinking that a marketing-material picture of Energy Vault next to wind turbines means that they actually propose putting Energy Vault towers right next to wind turbines, rather than just an illustration that the Energy Vault helps regulate output from renewables.
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.
I wish that cost basis wasn't the only consideration when evaluating energy storage, but we're so accustomed to money being the great equalizer that things without a financial cost associated are often overlooked.
What is the $/MWh cost associated with mining for, recycling, and disposing of battery components? What about the third order effects of centralizing control over the fuel source within only a handful of countries[0]? What's the $/MWh of the political shifts?
I can't safely make assumptions about why you personally stopped reading after cost came up, but it seems to be a common reaction at this point. "Show me the money!" tends to end most conversations about energy these days.
Not to disagree with your underlying point, but I think it might be more constructive to frame the problem as a failure to internalize the costs, rather than a focus on money. Ultimately we do need a fungible way to compare solutions, and money is the simplest way to do that. We just need to figure out how to effectively internalize those externalities to the price.
Cost functions have an implied ethical system behind them. Using money is just waving your hands over it and going “well, money is objective, so we don't need a value system” – but there's still a value system there. It's like “machine learning” in that regard; there's no magic.
Money is a unit of measure. Any other unit of measure you choose will be fungible with it. Money is simply a way of unifying things we care about and translating them into the same space.
In order to compare two actions, you need to normalize their consequences to make them comparable. This is a fundamental requirement of making decisions. 'Money' is simply the unit we choose to do that in our complex society. We can call it utility points or something else, if you want, but it's still the same abstract object.
There's so much bullshit in mainstream energy analysis; there's too much incentive. Energy is central to civilization - what we use, where and how we get it, how we use it, how much of it there is and when we can use it - change any of those variables, change the shape of the entire civilization.
Yet the conversation around energy technologies is entirely dominated by dollar cost. This obfuscates so much, and lends a false equivalence to pricing/market/financial mechanisms - it implies that if something can be sold cheaply (low price) then it can be produced/extracted cheaply (low cost).
We are quite capable of, and actively involved in, stealing from our futures (high cost) in order to achieve low prices in the present. The economic externalities of our energy usage don't go away - by definition, that which is finite and we use now to do this, cannot be used later to do that.
That energy we'll one day need to feed ourselves, and heat our homes, and supply our medicines and materials? We're using it, right now, to make a shitload of disposable, toxic, plastic shit. Junk nobody needs that we'll convince them they want anyway.
And why are we doing this mad, insane, thing? Because we're convinced it doesn't matter, we're convinced the price of energy will always be low. We're convinced we're not the ones paying the costs.
> That energy we'll one day need to feed ourselves, and heat our homes, and supply our medicines and materials? We're using it, right now, to make a shitload of disposable, toxic, plastic shit.
We should limit it's use to making medicines and materials instead of burning it to heat our homes and propel our cars.
Not only does the latter consume a lot more fossil fuels, it does so by dumping a lot more CO2 into the atmosphere. Plastics consume 14% of global petroleum production today [1].
We could ban all the "disposable, toxic plastic shit" tomorrow (and I agree that we should find ways to create a less disposable culture) and we would still have a huge CO2 problem caused by fossil fuel powered space heating, transportation and electricity production.
> What is the $/MWh cost associated with mining for, recycling, and disposing of battery components?
A fraction of the cost of the batteries, naturally.
> What about the third order effects of centralizing control over the fuel source within only a handful of countries[0]?
The lead in car batteries is one of the most recycled materials on the plant. Your link is talking about lithium, not lead. Lithium-ion batteries only make sense in portable applications like cell phones and electric vehicles where weight is a major consideration. In stationary applications, heavier batteries like lead-acid are infinitely more practical.
The problem with batteries is that there are a bunch of grid storage chemistries using abundant elements that can scale to 1 GWh but there is almost no demand for grid storage only chemistries so lithium wins by default because it piggybacks of other developments.
> For a 25-year project, he estimates that Gravitricity would cost $171 for each megawatt-hour. Jessika Trancik, an energy storage researcher at the Massachusetts Institute of Technology, says that number is aspirational and still needs to be supported with field data. But Schmidt’s calculation of the lifetime cost per megawatt-hour for lithium-ion batteries, $367, is more than twice as much. Flow batteries, a promising grid-scale technology that stores charge in large tanks of liquid electrolyte, come in at $274 per megawatt-hour
What you have described would last for 1000 days used to even out daily (solar) power demand/supply. So for a 25yr capability it would cost 8x more? I would hope not, and I think you could get 3000 cycles by restricting temperature and charge/discharge, but that still requires 2.5-3x higher cost and puts this solution as very competitive with current battery solutions.
This doesnt account the short duration of batteries, I have to replace them every time they go past their lifetime, so in the long term their cost is much higher
The heavy machinery with moving parts lifting thousands and thousands of tons is also going to need maintenance and wear&tear replacements. The problem with scale is that all these proposed gravity batteries need much, much more machinery than an equivalent pumped capacity pumped hydro or chemical battery plant.
This is something made easier by the fact that we understand how mechanical designs age. We've built high-standing structures with parts that move in a similar way that last decades. We understand how to maintain those structures without totally replacing them.
Too bad they don't seem to provide the actual report anywhere (and neither does ICL), they just quote a single chart from that without any details. This feels fishy to me - I'd want to look into the cost basis they used, as a key problem with comparisons against batteries is that the battery cost has changed so much over the recent years (halving every 5 years or so), and many studies quote their battery price calculations on older reports that are now off by a large multiple.
$367 of LI batteries at year X is $171 of LI batteries at year X+5 and $86 at year X+10, so it's important to look at what the X is in their study. And of course, we should consider that chemical battery costs are expected to decrease in the near future, while the cost well-established mechanical components would stay stable.
Whilst I agree the components of a mechanical battery are probably going to stay stable, I think Gravitricity have an opportunity to commoditise the design and install near sporadic renewables like wind.
Bias: I participated in their crowdfunding campaign.
The only savings grace with these gravity systems is that they could last 100 years. Gravity is a very poor of storing energy. Height is limited by practicality. Reusing old mine shafts is just a code word for unaffordable. You need to increase the amount of mass that you move around, therefore your system should be infinitely scalable. By limiting yourself to mineshafts you have reduced the scalability option and the entire project becomes a scam.
It is over 25 years, I don't think your battery will last 25 year. You probably have to replace it 3-4 times over that period of time. A mechanical system can last that much, even more, with minimal maintenance.
You may have accidentally responded to the wrong comment. The comment to which your response has been attached already takes into account the limited cycle life of batteries.
Battery does not just degrade with power cycles. It also degrades with time. Not sure about the numbers for LFP, but it's something you need to take into account. For some areas time may be a more important factor than cycles. If it does a full cycle every 3 days or so, it'd take roughly 25 years to reach the cycle limit.
It's also important to remember that capacity will be reduced gradually. After 25 years both the energy storage capacity and power output of batteries will be seriously reduced, while the gravity-based system will most likely still be at full capacity.
I still think the estimate may be too high. Especially taking into account that these systems will compete in the future at a time where battery costs will be lower. But it might still make sense to build gravity based systems for a while to make sure all the lithium we mine goes to batteries for transportation.
Wow, that's amazing. But why are home battery systems still so expensive? I see system prices in the range of $700 to $1200 per kWh. Even on aliexpress, it's minimum $550/kWh. Is the inverter so expensive?
Or then we could use lot more of this pretty cheap, pretty available, pretty easy to handle stuff that we have mature technology and understanding for. Namely water. Only thing is that need nice reservoirs on top and bottom. The shaft it self can even be narrower and less sturdy...
yeah this sounds like a pendulum but geared on the y axis instead of the x. in fact a pendulum seems more practical since it doesn't need a shaft, just an enclosure. I suppose a pendum is itself is just a special case of flywheel anyway.
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
Pumped storage hydro makes far more sense. Which is why it's already in use.
Maybe the efficiency can be improved upon with a small-scale 'gravity battery', but water has massive advantages when it comes to scaling it up, as well as being able to combine it with traditional hydro, where nature moves much of the water for you.
Plenty of issues with hydro, but in the grand scheme of things, it does seem like by far the most accessible, actionable, least polluting option.
I've often wondered what scale of a system would be required to power a fully off the grid home at say 30kwh/ day, for say, 6 days? I'm imagining a tank based system with two tanks where the fluid is effectively just exchanged (so one doesn't have to account for the environmental impacts of a dam or for losses due to evaporation)..
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.
So, let's look at doing this in a distributed manner: giving every household their own gravity battery. A 1 m3 cube of concrete weighs 2400 kg; moving this over 6 meters yields (mass * gravity acceleration * height) = 140 MJ, = 39 kWh. Lets say 34 kWh after accounting for energy losses.
A european household uses approx 3500 kwh/year; americans use upwards of 10000 kwh/year.
Clearly such a slab of concrete will comfortably allow buffering an entire day's worth of power, and then some.
Edit: fuck me I'm dumb. Off by a factor 1000. 39 watthour in that cube, not 39 kWh. Ignore everything I said.
An European household rather uses 10-20kWh/day, usually closer to 10. The question is, what is cheaper, to build a 6 M tower that can lift 2 tons of concrete or a nice Lithium battery pack which uses a lot less volume too?
I know not every where is suitable for reservoirs but this seems pretty obvious. Run renewable to pump the water up hills, all the 'battery' components of the tech are well established. You're creating additional benefit by storing potentially potable water. It seems like the tech for water storage/ transport/ regeneration to electricity is all pretty well figured out. I'm thinking some place like the Columbia gorge where there is high capacity for wind and for hydro.
A long time ago I was interested in alternative ways to store energy, one good method but quite expensive is to convert it to Rotational energy of a flywheel, NASA had pretty good results with magnetic bearings and vacuum.
Gravity and electromagnetic forces are somewhat similar, they both have infinite range, decay as 1/r, one key difference is that the electromagnetic force is 10^36 stronger than gravity [0]. Just for that reason I'm always immediately skeptical of projects of this type.
On Earth, gravity has a bonus of a free massive side plate. As a battery, it might work better on Jupiter and unusable in free space, but it still stores orders of magnitude more energy than we use, in abundant cheap materials. I liked the trains-on-hills project - seems easy enough to build in large quantities and stores reasonable amounts of energy.
With electromagnetic, we are barely capable of scraping a bit of energy from the surface without the device self-destructing. Even in superconductors, only a fraction of electrons whizzes around and even high-energy plasma is a mixture of both charges.
it is strong enough at the scale of a star, on earth my foot electromagnetic repulsion against the floor is enough to counteract all of the planet pull
Does it need to expend the energy to winch it up? Would it not be simpler to have a set of these weights, and a ramp system to deliver them to the top, and use vehicles to unload at the base and drive them back to the top to be hooked up again in sequence? Surely there would be less energy loss moving it up a ramp than fighting gravity in a vertical shaft to winch it directly upwards.
If you pump one cubic meter of air 100 meter deep, the energy stored equals a tonweight at 100 meter up. That is 9.81 kJ aka 2.7 Wh. This is inifinitely scalable and suits flat places like Australia.
One and only minor problem is how we prevent the 2.7 GWh energy storage, which is 1E9 m^3 aka one cubic kilometer inflatable container, not rupturing or raising up.
Yeah, if you do the math, it turns out that you need impractically large weights lifted to unreasonable height. Like, suppose you’re lifting 100 ton weight 100 meters high. That’s a rather large and heavyweight system. How much energy you can store this way? Less than $5 worth of electricity, as it turn out.
This is basically the same as pumped water storage, but instead of immense amount of water you can pump between very large reservoirs, you’re limited to one solid weight that’s too light to store nontrivial amount of energy, but heavy enough to be significant problem from engineering perspective. It just doesn’t make practical sense.
> How about to retrofit wind turbines? They are tall, strong, and empty inside.
It's still basically piss-stakes: the largest wind turbine right now (14MWe Haliade-X) has 765t sitting on top of a 150m tower, so let's say you keep the 150m tower, rejigger it so it can move a 765t weight up and down the shaft without crumpling, and add your weight (a lead weight 4m in diameter and 5.4m tall), how much energy does that store?
250kWh, 2.5 teslas, or a medium-large electric bus battery.
And it's not like you can add that to a working turbine: the tower was set up for 765t not 1500, and you need space for the crane.
Yes, the math does not look good. I remember dreaming about a house that could go up and down like this. Then I went to buy a AAA battery... same.
That said, if they can manage to find that 1km shaft in an old mine like they hope, and put some crazy amount of weight and make it work, that would be impressive and cool.
Too me, pumping water seems like a pretty good solutiuon. If you are located on the coast, and can move let's say a million tons something like 100-200m up, that's not trivial and doesn't seem that impractical.
Great, now calculate how much a flywheel system that stores that much energy will cost vs cheap concrete blocks. Magnetic bearings and large vacuum chambers do not come cheap.
One of the downsides (or maybe double-edged swords) of kinetic energy storage is that it's relatively easy to accidentally get all of the energy out at once.
A stick of butter and an 2-tonne truck at 216 km/h both "contain" about 1 kilowatt-hour of energy.
The butter could maybe burn your house down but the truck could easily kill a couple of dozen unprotected humans in a fraction of a second.
Flywheels made for energy storage are vacuum chambered and surrounded by very very dense material, made to withstand any accidents. So it isn't an issue.
Now I want one. Home powered by solar and a flywheel is so retro-future. How does your house get electricity? Oh, power from the sun gets this flywheel spinning super fast and then it slows down and powers the house all night.
This could give a new purpose for abandoned mines all around the world. The shafts already exist and are no longer in use, they would only need some repairs.
I grew up in one such city, there were "covered holes" everywhere.
I wonder what is the limit when this kind of storage would only consist of single steel cable. As at certain point weight of cable is so big that it can't support even itself anymore.
Ok, ok, everyone, I've got it. It's great. As you know, two meh ideas together make one galaxy-brain idea so here it is. Gravity batteries + vertical farming.
This is so amazing I'm just jittering over here. So what are big shafts filled with before they are shafts? Dirt! What do plants need to grow? Dirt! So what you do is ... wow this is great ... what you do is you take the dirt out, then you make this big battery thing a stack of dirt shelves that go up and down and while they are going up and down they also grow plants in the dirt.
So now you have a big field of these dirt stacks going up and down and in the middle you have a big farmers market. Money from dirt two ways. God how is this not already a thing.
It's crazy how little we understand about gravity if you think about it. It's a perpetual energy source right in front of us, but we never really think about it, and can barely offer a basic explanation as to what powers it. It even impacts time itself[1] for christ sake. I think better understanding gravity is the solution to all human energy needs. (interesting to note I have heard stories of disappeared scientists who made advancements in gravity research years back)
> It's a perpetual energy source right in front of us
It's not. Once something has fallen down, it can't fall down again.
To draw energy from the gravitational attraction of 2 bodies, you must first separate them. That consumes energy.
On second thought, I suppose tidal energy fills the bill. Extracting that energy is really exploiting the Moon's motion, using gravity as the "conduit". Not strictly perpetual, but essentially so for our needs.
Isn’t tidal energy just harnessing some of the existing gravitational potential energy of the Moon-Earth system, which is roughly similar to any system that harnesses energy from a massive object falling due to gravity?
It basically draws energy from the moon orbiting earth. It could theoretically alter that orbit, but given that the moon/earth system has a lot of mass, the timescale for that to happen is extraordinarily large.
But that "something" keeps being pulled down until it is stopped/blocked by something (e.g. the ground). Gravity is perpetual relative to the source of the gravity. It's just that our surroundings change and give the illusion of gravity changing...i.e. we don't "run low" on gravity
I don't think Maxwell's Demon is 100% solved.
Tidal energy could play into it, some underwater tides deep in the ocean are insanely strong.
You're confusing force with work. Gravity is a perpetual force, but a force doesn't generate energy.
To generate power you need gravity to move something downwards, releasing the potential energy. And when that thing hits the bottom of the shaft you've used up all the potential every that was stored in it.
You shouldn't repeat unsubstantiated rumors like that. Can you even name these disappeared scientists or know anything at all that could be used to verify those stories?
If you dare to venture, need to follow deep rabbit holes. Look into: work of Harold Aspden (and his coworkers & previous research partners), plancks equation origins and drop offs, dewey larson physics, piesel electric effect origin and drop offs, the adams motor, ellen brown, what maxwells equation actually determines and where it selectively isn't being used
Wikipedia tells me Harold Aspden lived to 84 years old. How was he disappeared? I don't see any mention of suspicious circumstances about his death or his body never being found.
I agree but honestly I'm used to it on HN. This place is a lot of smart people but also the type of people that suffer from severe cognitive dissonance and stubbornness.
They are the types that would ridicule Christopher Columbus for even considering the notion that the Earth wasn't flat...then after proven wrong go around telling people they had a strong feeling the Earth wasn't flat.
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?