An AA battery contains approximately the same as 1 ton raised 1m. (About 3Wh)

A Tesla Powerwall contains about 13.5kwH (about 4,000 times as much)

So you can either raise 100 tons 10m above your house, or you can have 1/13 of a Tesla Powerwall.

There is a company that claims they can store energy by lifting and lowering heavy blocks with a crane

https://www.energyvault.com/products/g-vault-gravity-energy-...

I like the picture, but the the size of the construction is enormous, especially if you're considering a tank for some kind of pumped hydro. Hydroelectric power is practical because a dam in a strategic location can back up much more than 1000x of its volume in water. If you had to build all those walls forget about it.

That is obviously a scam. Not a chance in hell.

I am giving that one a 0% chance of long term success.

Edit: no seriously. Do some back of the napkin maths. The amount of energy stored is too small. Way too small. And then the infrastructure to haul hige blocks of concrete around.

It's the same scam selling ideas that sound good to people who don't understand what a "joule" as Pavegen and the other systems that generate energy from footfall or passing cars. Mechanical energy is pretty "low grade" as energy goes.

It 100% works, but it's a system that has very specific applications and doesn't scale up well. And the best systems use a magical property of some fairly heavy materials called "being liquid" to simplify the logistics of getting millions of tonnes of weight to the lifting mechanism.

One of them is moving almost seven thousand 25-tonne concrete blocks around. I can't see how it would ever compete with something like compressed air.

It just seems so awfully wasteful.

If someone can find some real costs I would be more than happy.

7000 * 25t / 2.5t/m^3 = 70,000m^3 of water. So about 1% of the water storage of Dinorwig, which runs dry in about 6 hours of use.

Now, I know reservoirs are ecologically pretty iffy, expensive and obviously geographically sensitive, so you can't slap them around everywhere. But all these mechanical schemes have big "look what they need to mimic a fraction of our power" vibes!

I could imagine that steel-on-steel block movements could actually be quite efficient and effective in limited scenarios, but logistically it just seems like a lot of squeeze for not a lot of juice considering how much power is required to be stored for utility-scale projects. I would like to say that that they're just delusional people truly hoping it'll work, but I think there's a core of hard-nosed scammers who smell money for a shiny PPT and a plausible-to-non-engineers Wile E. Coyote/Troll Physics contraption with big numbers in the brochure: 7000 blocks! 25 tonnes per block! Megajoules! Efficiencies! Scale! Repurposed coal mining infrastructure! They even have AI in the spiel now: https://www.energyvault.com/solutions/software

Or maybe it'll work and I'll look stupid in 30 years when there are huge fields of hundreds of kilometre-deep boreholes with 100 kilotonne masses moving up and down in them. But somehow it seems quite unlikely on a practical level considering the cost of boring gigantic holes that you'd have to do to make it scale. Onsies-twosie installations in a few mines here and there may work for lucky outlying towns, but they aren't civilisational scale solutions.

Oh, but only at about 145 meters. Dinorvig has a fall of over 300m.

And this is why gravity is considered a weak force.

Sit down. Now stand up. Congratulations, you just beat the gravity force generated by a whole f*cking planet.

Now try to escape it.

You are not hiking much in the mountains, are you? 1000m of elevation gain per day are no problem for a slightly out of shape sit-all-day programmer. Not sure how high up you want me to go, but given a high enough mountain (and a thick jacket and supplemental oxygen) and most people here can do that in a few weeks or months.

That doesn't really escape the gravity well, does it?

It would if there was a mountain that kept going up, and you had oxygen to breathe.

What limits me is the lack of solid matter to push against, not lack of strength in my muscles.

Gpt says that would require about 275 million steps on a magic rigid weightless stairway. Roughly 4.1 million calories. So at Phelps level energy expenditures you are still talking over a year of climbing every day.

Well, 100kg raised 10000m is only about 2350 food calories, from a purely physics perspective.

You'd need to go to about 47km for the end of the stairs to reach escape velocity I think? Past geo. Was using 20% efficiency. Still something off there.

GPT not so good at elementary physics evidently.

Assuming you don't have to carry your food... 4.1 million calories would be around 0.5 tons of olive oil.

ok, but what do you say?

Now if it were a magnet..

And the strong force holding two protons together in an atom is on the order of 10 pounds.

I wondered when anybody would bring nuclear fission into this discussion.

Every time I see again the idea of moving big concrete blocks for storing energy, I remember the time I made the calculations, and estimated around USD100K of infrastructure to store the same amount of energy as a nissan leaf.

I did the same calculation. Gravity energy storage is a joke. Came to similar conclusions when running numbers on hydrogen-powered vehicles.

Pumped hydro storage and flywheels are cool but ultimately battery storage, distributed everywhere, will win.

Gravity storage is cool when nature has already made most of the work, I/E pumped hydro where nature has already built this huge canyon with a river in the middle just waiting for someone to put a dam at the end.

It is really perplexing when people come up with an energy storage method that is even more expensive than just straight up batteries.

Hoisting 100 tons of stuff high into the air, and then efficiently converting that into the high RPM needed to drive a generator seems like it would take a truly staggering construction effort. Suspending that amount of weight high above your house also has some... interesting potential failure modes.

Why would you put it above your house? Just construct a sort of battery tower nearby.

Why not just build a water tower? Easier to manage, it's a proven technology and it has well-known ancillary uses beyond energy storage.

I don't even think the gravity battery thing is viable for individual residential power storage at all. I was just wondering why you'd assume that the 100 ton weight would be placed directly above your house given the obvious problems with that approach, and the obvious way to avoid those problems.

The comment I was replying to literally said "For home use", and a heavy object 10m in the air does not have to be directly above something to be meaningfully (and dangerously) above something.

It's a silly scenario anyway, but I was doing a bit of guesswork about typical "home" lot sizes.

Yeah I understand it's for home use. I am imagining a tower in the back yard or something. It would be closed so that nobody can walk under the weight. Or it could be internal to the house like an elevator shaft.

Anyway I agree it's silly, definitely not a realistic idea

Right - if a tower in the back yard falls down it can still hit your house, since it isn't guaranteed to neatly collapse straight down. Worst case, it may tip over from the base and directly smash stuff up to its height away (and 10m is pretty far).

I have trees in my back yard I'm kind of worried about, which is why this immediately came to mind.

Just suspend your house, become the battery.

Gravity based with weights is generally considered not cost effective; others already did the math that your 100 ton proposal can still only store a fraction of what a consumer grade battery pack can do, but on top of inefficiency there's space and maintenance requirements. It works in situations where e.g. trains go uphill empty and full downhill, but generally it doesn't work.

Water based systems work better because water is easy to move, plentiful, and there's natural basins to pump into / flow out of that can contain billions of liters.

Gravity is weakest force of nature. Any strong force battery idea ?

Pumping water up is a super old idea, but as far as I know you'll need some natural terrain to build it efficiently.

And environmentally, that tends to be pretty bad for a long time. Looks more peaceful than a fracking site, but it's still pretty bad.

There is no magic solution. I'm happy to see all those efforts, but am missing a mention of saving energy. In the age of record-setting data centers for AI training, that's not a popular aspect to mention. Though at least we get higher res more realistic artificial cat videos out of it.

It's only bad if it's placed on and disrupts an existing river.

But PHES can be placed far from any river, even in a desert.

https://www.whitepinepumpedstorage.com/

I suspect this project may not happen, what with batteries getting so cheap.

You just need some change in elevation over moderately short distances. You don't even need rivers.

Relevant video on a pumping water on the roof + turbine system : https://youtu.be/CMR9z9Xr8GM It's quite far from powering your whole house tho !

Someone has already been thinking along the same lines: https://www.swissinfo.ch/eng/business/energy-vault_revolutio...

EnergyVault are building these GESS (Gravity Energy Storage System) arrays right now.

https://www.energyvault.com/projects/cn-rudong

Some guy on Youtube tried this. I think the conclusion was, not worth it.

https://www.youtube.com/watch?v=l19AMYd0oks

This type of plant is generally used for emergency power to balance the grid, whilst other plant come online.

> an array of ten 10-ton concrete blocks lifted 10m in the air could power a house for a day

No, that's only 2.7 kWh. Most homes use 10-20 kWh/day. A battery of that size is easily under $1k. Good luck building your ridiculous concrete block system for that.

Batteries are really good. Gravity, not so much. It only works when you can lift & store a tremendous amount of stuff "for free" because nature has done most of the work, e.g. in valleys, mountains, aquifers, caves, etc. If you have to build the whole thing it will never be viable.

Batteries are good, but you can’t repair a broken battery with odds and ends you find at the hardware store. If you’re living off grid space isn’t really an issue.

I am not sure you want to repair something holding one ton blocks in the air with odds and ends.

I’d love to buy a 20 kWh battery for under $1k. Can you give me a link to what you’re thinking of?

Sorry my wording was ambiguous; when I said "that size" I meant 2.7 kWh, which is what the hypothetical concrete blocks might provide.

Nevertheless, you can get a 16 kWh battery (which is enough for most days of a typical house) for only £2k, which is kind of insane really: https://www.fogstar.co.uk/products/fogstar-energy-16kwh-48v-...

People have been able to get their Tesla Model 3 batteries (75kWh iirc) replaced with used battery packs for around $5k, so quite close to what you’re asking.

Do they get much for the old used battery? the materials are still lithium etc are still inside it, they're just no longer in the right places..

where can I get a 20kWh battery for 1k USD?

here in Switzerland 1kWh is 1k CHF.

You need a lot of weight. IMO for home use the risks heavily outweigh the benefits for anything outside of a hobbyist project... that's just a lot of potential energy in a system that can go wrong. Weights falling quickly, pullies and cables under tension.

The same is true for batteries of course, but at the very least there are protections and checks for failures in most consumer accessible home solutions (and decades of engineering at this point). Worst case you at least have smoke detectors... not sure if there's a "cable is wearing thin and might snap and decapitate you" warning system.

Stones are typically not very dense. Iron or lead or 2-4x denser than typical stones, and so will net you better energy density.

Go all the way: depleted uranium

There are some videos on Youtube discussing the hypotheticals of this. They're never really very positive about the feasibility. Neither on a small scale nor on a country-wide scale.

If you'd want to store 1kWh at 10m height, assuming no loss at all from heat, friction, etc, you'd need about 4 of those blocks block weighing 10 tons (according to ChatGPT). So you'd need a lot of those blocks to power a house for a day, unless you're very efficient.

Please don't cite ChatGPT as a source or as a caveat, instead show the actual math, which should only be about high school level; kinetic energy formula ½mv² = e,

In perfect conditions assuming no loss through drag, you're looking at the kinetic energy formula which is ½mv² = E (in joules).

E = 1 kWh = 3,600 kilojoules, velocity v at 10 meters is 14 m/s, so we need to calculate m for v = 14 and E = 3600k, which is just under 36735 kg. "about four of those blocks" is "about" correct.

Simpler to use the potential energy formula, surely.

E = mgh

m = E/gh

m = 3.6 * 10^6 J / (9.8 m/s^2 * 10m) = 3.6735 * 10^4 kg

This is exactly what ChatGPT provided. Me, the person, then chose to describe it as 'about 4'.

You already have some decent amount of weight in the house itself, so I'd look into raising it all or parts of it

Of course it's probably not the simplest engineering effort...