I visited a pumped storage facility a while back that stored electricity by pumping water uphill to store it and then draining it past a turbine to reclaim it. Ever since I’ve been intrigued by using gravity instead of batteries.
For home use, it seems like you could rig up some heavy stones on pulleys to do the same thing could be fun because you’d get to physically see your batteries filling up. Back of the envelope calculations suggest that an array of ten 10-ton concrete blocks lifted 10m in the air could power a house for a day (ignoring generator inefficiencies)
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
> 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.
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.
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.
For home use, it seems like you could rig up some heavy stones on pulleys to do the same thing could be fun because you’d get to physically see your batteries filling up. Back of the envelope calculations suggest that an array of ten 10-ton concrete blocks lifted 10m in the air could power a house for a day (ignoring generator inefficiencies)