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Comment by throwaway189262 | Hacker News Reader

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 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

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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.

Yeah, but mine shafts are not exactly abundant either

> 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.

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

With absolutely nothing to explain the cost estimate, so you can put away "TFA" thank you.

A system like this with only a single weight is going to be a huge amount of work to set up each unit of capacity.

Also looking up the info I can find, I think they're calculating that rate over a 60 year lifetime.

Edit: Uh, did I say something offensive?

> Uh, did I say something offensive?

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.

Communication is hard.

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.

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?

Is anyone trying to implement that gas bag idea? Not one I'd heard of before

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.

[0]: https://aresnorthamerica.com

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