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Gravity batteries try to beat chemical ones with winches, weights, mine shafts

sciencemag.org

221–230 of 278 posts

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#221
post #179

Earlier quoted context omitted.

> That's the issue with gravity: it's really not that strong The weakest of all forces, isn’t it?

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). I’d love for someone to explain more though.

It's just impractical. You only need a 21x21 foot square of ground covered in solar panels to generate the same amount of electricity this does.

It doesn't make sense to invest so much land, machinery, and labor into something that generates and stores so little energy

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#222

This is an obvious scam if you do the math. 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 us…

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 pump…

Please excuse me if I am terribly ignorant.

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?

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#223
post #179

Earlier quoted context omitted.

> That's the issue with gravity: it's really not that strong The weakest of all forces, isn’t it?

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). I’d love for someone to explain more though.

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.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#224

Earlier quoted context omitted.

> I was thinking what if we used buildings built on jacks as our source of mass. Then you've got no height. Plus buildings are not dense so it's a pain in the ass, and when (not if) the jacks fail you're out a building.

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.

:-) Perfect for quarantine.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#225

This is an obvious scam if you do the math. 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 us…

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.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#226

This is an obvious scam if you do the math. 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 us…

> This is an obvious scam if you do the math.

Reading the rest of your comment, I'm not sure you did the math yourself...

> Assuming the full scale version delivers peak power for 11 seconds like the prototype

The prototype is a 4-storey tower (i.e. less than 20m).

> That's terrible. We're taking about dropping hundreds, maybe thousands of tons down a mine shaft

A mine shaft can be expected to be significantly deeper than a 4-storey tower is tall.

So it seems you've invalidated the assumption upon which your argument is based in the paragraph immediately following it?

> the same amount of power as $700 of lithium batteries you could carry in a backpack

From TFA itself, they estimate they can offer a price of $171/MWh, while Lithium-ion batteries cost $367/MWh.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#227
post #192

Earlier quoted context omitted.

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 just a fungible unit of comparison for types of value, nothing more.

In that case, gas plants are the best peaker option in most places as in most place CO2 and methane emissions cost $0.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#228
post #160

Earlier quoted context omitted.

> This seems like a "running before we can walk" statement. Europe tries to be at a forefront of green energy. No sun/wind is a real issue there, not just an edge case.

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!"

Arguably, if a gas plant hasn't run for a year then it'll go bankrupt and shut down pretty soon.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#229
post #179

Earlier quoted context omitted.

> That's the issue with gravity: it's really not that strong The weakest of all forces, isn’t it?

We should always hold out for some new discovery that is weaker.

Design forces are very weak...

btw anyone saying that gravity is weak should try getting of this planet...

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#230

Earlier quoted context omitted.

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 i…

> " a 5m tall tower bearing 73 tonnes to store 1 kilowatt hour " By comparison, a pint of gasoline stores about 4 kilowatt hours.

Too bad we can't just synthesize gasoline with electricity at a decent efficiency.
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