Author Topic: EnergyVault gravitational energy storage  (Read 5529 times)

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Offline AlbertL

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EnergyVault gravitational energy storage
« on: January 22, 2022, 11:46:31 pm »
Raising and lowering concrete blocks; apparently comes in two flavors:

 

Online ejeffrey

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Re: EnergyVault gravitational energy storage
« Reply #1 on: January 23, 2022, 02:43:19 am »
The energy density works out pretty bad for this.  That's why it's normally done with water and reservoirs where you can have a tremendous volume.  I have a hard time imagining this would ever beat batteries on any metric.
 

Offline f4eru

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Re: EnergyVault gravitational energy storage
« Reply #2 on: January 24, 2022, 10:27:17 pm »
It's just simply hopeless.

Offline dmills

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Re: EnergyVault gravitational energy storage
« Reply #3 on: January 28, 2022, 03:08:07 pm »
Two lakes, a set of turbines and a set of big pumps, that's the way you use GPE for energy storage, and that version works just fine.
I am not sure, but they may even use the turbines as the pumps when power is cheap?
 
I think concrete blocks would need an AWFUL lot of cycles on the system before just making an equivalent amount of CO2 in a CCGT wasn't greener. 
 

Offline voltsandjolts

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Online station240

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Re: EnergyVault gravitational energy storage
« Reply #5 on: January 28, 2022, 05:33:47 pm »
Making a huge number of new concrete blocks for this storage system is just nuts.
Cement production is very CO2 intensive, and then you add the gravel you have to mine/process.
Plus you've going to crack blocks moving them around all the time, resulting in having to replace them for safety reasons.

Makes the other idea with railcars hauling containers up/down hill and filled with something look positively mainstream. As at least you could use concrete from demolition sites, dirt, garbage or anything cheap or waste.
 

Online ejeffrey

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Re: EnergyVault gravitational energy storage
« Reply #6 on: January 28, 2022, 06:32:18 pm »
Using concrete for the weight really creates a huge CO2 deficit you have to overcome before it is even CO2 negative, but the bottom blocks need enormous strength.  A lightweight box filled with gravel or other cheap fill isn't going to be strong enough to hold up the tower.  The blocks at the bottom aren't doing much for you in terms of energy storage but you need to have them and they have to be strong and stable.  Building a high load capacity skyscraper is expensive it turns out.  It would be much better to use a natural cliff and lift the blocks up and down.  Unfortunately natural cliffs aren't particularly stable for the same reason the tower would have problems.  So you really want a natural hill with modest slope.  Unfortunately that makes the crane not work particularly well, better to have some sort of ground based conveyance up the hill, like some rolling carts filled with gravel.  Gravel is kind of annoying to load and unload without wasting a lot of the energy you hope to store, so its probably better to use something like water that is cheap and easy to move.  Of course then the moving carts can just be replaced with a pipe.

Another way to look at it is this: if a battery short circuits it overheats and catches on fire.  If you drop a rock from the top of a skyscraper, how much does it heat up when it hits the ground?  Not much.  The energy density difference for feasible gravitational storage is enormous.  The only way to compensate for that is to have a truly enormous volume of ballast.  A lake or reservoir can meet this requirement much better than anything we can practically build.
 

Online Gyro

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Re: EnergyVault gravitational energy storage
« Reply #7 on: January 28, 2022, 06:53:14 pm »
It's just simply hopeless.

https://gravitricity.com/

12000 Tonnes running up and down a 300m mineshaft does sound like a decent amount of energy storage.
Regards, Chris

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Offline uer166

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Re: EnergyVault gravitational energy storage
« Reply #8 on: January 28, 2022, 07:25:38 pm »
It's just simply hopeless.

https://gravitricity.com/

12000 Tonnes running up and down a 300m mineshaft does sound like a decent amount of energy storage.

Does it?

That is 10764316800 Joules, which is 2990.088 kWh, which is just under 30 Tesla Model S packs. Something tells me 30 of those packs is much, much cheaper than the 12kT conveyance mechanism. Or another way: this is equivalent to a single Tesla Megapack, which is the size of one shipping container. It seems like all this stuff sounds cool and great until you do some minimal napkin math.

Edit, I think I'm off by a factor of m->ft conversion. So it's more like 3 Megapacks, and 90 Teslas, but the general message stands  :-/O
« Last Edit: January 28, 2022, 07:32:34 pm by uer166 »
 

Online ejeffrey

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Re: EnergyVault gravitational energy storage
« Reply #9 on: January 28, 2022, 07:34:12 pm »
Its 30 MJ or 9 MWhr, so more like 90 model S cars or 3 megapacks, but the point is still similar.  Using deep mineshafts makes more sense than stacking bricks, but it's really hard to find any way other than hydroelectric where gravity storage can reach a scale where they are better than batteries.  For a few megawatts hours batteries are fine.  If your storage tech doesn't scale to GWhr it's pretty much going to be fighting a losing battle against batteries.
 
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Offline uer166

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Re: EnergyVault gravitational energy storage
« Reply #10 on: January 28, 2022, 09:40:53 pm »
Well, I'm sure stacking bricks is better than circulating current in superconducting coils, or spinning fidget spinners really, really fast! It seems like thermal storage is one of the most promising alternatives to batteries, scales okay as well, lots of moving parts though. 1 m^3 of water over a 100C is approx. equal to one Model S pack, more if it's a phase change system. Turbines and heat pumps sure seem to be a pain though.
 

Online ejeffrey

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Re: EnergyVault gravitational energy storage
« Reply #11 on: January 28, 2022, 10:10:01 pm »
Yeah, thermal storage seems like a reasonable option for longer term storage than batteries can accommodate.  It's been fairly well studied in the context of concentrated solar thermal but could be implemented as stand alone storage. They usually use some type of molten salt at ~550 C as the storage mechanism, the energy density can be quite high.  Making an insulated tank that loses < 1%/day is totally feasible.  The main problems are that the efficiency is low and the capital cost of the turbine/generator is somewhat expensive (same as a thermal plant because that is what it is).

The traditional problem with pumped hydroelectric is that every location with the right configuration for hydroelectric power already has it.  But there has been some renewed interest in off-river pumped hydroelectric storage recently, I'd guess some combination of that + thermal storage + batteries will be able to handle most of our storage needs
 

Offline rob77

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Re: EnergyVault gravitational energy storage
« Reply #12 on: January 28, 2022, 10:26:24 pm »
3.7 millions cubic meters of water in the upper lake (that's 3.7 million tons) , 425meters of elevation difference, 735MW of installed power, yearly production ~ 200GWh , built in 1982.

replacing the water with concrete blocks is just trying to re-invent a wheel using a square shape instead of a circle.

Edit: adding a link to a time lapse of draining the upper lake in 2017 during a maintenance.

« Last Edit: January 28, 2022, 11:38:43 pm by rob77 »
 
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Online ejeffrey

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Re: EnergyVault gravitational energy storage
« Reply #13 on: January 28, 2022, 11:54:04 pm »
To be fair, that only works when your geology supports it.  There are several US midwestern and southern states that are each bigger than many european countries and have a total elevation span less than that, much less having locations for the upper and lower reservoirs that are acceptably close to each other.
 

Offline rob77

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Re: EnergyVault gravitational energy storage
« Reply #14 on: January 29, 2022, 12:34:46 am »
To be fair, that only works when your geology supports it.  There are several US midwestern and southern states that are each bigger than many european countries and have a total elevation span less than that, much less having locations for the upper and lower reservoirs that are acceptably close to each other.

agree, can't be done anywhere.. but you still have many locations where it's possible and would be a much better option. for locations where pumped hydro is not feasible, there are other options much better than 12kiloton worth of concrete blocks hanging on ropes. even pumped electrolyte battery storage is much better than those concrete blocks hanging on ropes. pumped electrolyte can be scaled by size of the tanks.. for the concrete blocks you need to replicate the whole setup to scale it. not talking about maintenance costs.. steel cables, cogs and pulleys wear out after some time especially under heavy loads coming from those concrete blocks.
 

Offline voltsandjolts

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Re: EnergyVault gravitational energy storage
« Reply #15 on: February 01, 2022, 11:37:18 am »
.. steel cables, cogs and pulleys wear out after some time especially under heavy loads coming from those concrete blocks.

Everything wears out.
Heck, some battery storage grid balancers catch fire before they are even commisioned :P
What is the long term cost of batteries at grid scale?...we don't know yet. Ask in 20 years.

I like the solutions that use basic principles and engineering, easy to build, predicatable installation and maintenance costs with minimal rare earth materials.
This also enables cost-effective solutions for less developed countries which they can implement themselves, so they don't have to depend on foreign technologies.
Pumped hydro is a great solution when you have the geology, although I don't know how efficiency compares to other options.
Molten metal batteries sounded interesting but seems to have gone nowhere since 2014 :-\
 

Offline Marco

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Re: EnergyVault gravitational energy storage
« Reply #16 on: February 01, 2022, 11:45:10 am »
I think pulling deep water concrete spheres vacuum is the most promising gravitational storage technology (it's not compressed air storage). You can sink it filled with fresh water and pump to a bladder to avoid salt water corrosion of the pump. Near infinite locations available at generally much greater effective height difference than with on shore reservoir pumped hydro.
« Last Edit: February 01, 2022, 11:46:44 am by Marco »
 

Offline f4eru

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Re: EnergyVault gravitational energy storage
« Reply #17 on: February 02, 2022, 08:35:50 am »
The main problem with deep underwater vacuum technology is that it exists only in Powerpoint-Lala-Land
Nobody found out yet how to solve it's many problems in reality.
For example: how to anchor the sphere to the bottom ?
Ha, I know! You just need 2x the pumped water mass in concrete blocks. Duh.

Meanwhile, here on earth :
https://de.wikipedia.org/wiki/L%C3%BCnerseewerk

Built 1958.
Head is nearly a kilometer. Water arrives downstairs with 100 bars, at a speed of 500km/h generating 230MW.
Very impressive.

BTW :
https://professional.hydropower.org/page/map-pumped-storage-tracking-tool
« Last Edit: February 02, 2022, 08:58:58 am by f4eru »
 

Offline voltsandjolts

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Re: EnergyVault gravitational energy storage
« Reply #18 on: February 02, 2022, 12:48:58 pm »
The main problem with deep underwater vacuum technology is that it exists only in Powerpoint-Lala-Land

Every solution at some point was or is, only a concept in Powerpoint-Lala-Land, as you put it. So that's a mute point.
Also, in this context it's not entirely true either.

But I agree that if you have the geology, pumped hydro looks like a very good option.
 

Online Gyro

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Re: EnergyVault gravitational energy storage
« Reply #19 on: February 02, 2022, 01:06:18 pm »
Meanwhile, here on earth :
https://de.wikipedia.org/wiki/L%C3%BCnerseewerk

Built 1958.
Head is nearly a kilometer. Water arrives downstairs with 100 bars, at a speed of 500km/h generating 230MW.
Very impressive.

The UK one, 288MW... https://www.electricmountain.co.uk/Dinorwig-Power-Station

I once went on the tour, but it didn't include the surge pond at the top of the vertical shaft. I bet that's a sight to see when they shut the valves!
« Last Edit: February 02, 2022, 01:08:01 pm by Gyro »
Regards, Chris

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Offline f4eru

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Re: EnergyVault gravitational energy storage
« Reply #20 on: February 02, 2022, 02:35:56 pm »
Also, in this context it's not entirely true either.
Interesting.
Butr looking at the numbers, it's not really tempting:
https://www.iee.fraunhofer.de/en/topics/stensea.html#1665982880

- quite bad efficiency (why only 72% ? seems to be without the cable-to-shore losses)
- 23 000 tons of concrete for 12 000 tons of water displaced -> my guesstimate was exactly on point ! Too much...
- nightmarish maintenance

It would be really intersting in comparison to have numbers on a typical concrete usage for pumped hydro...

Offline Marco

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Re: EnergyVault gravitational energy storage
« Reply #21 on: February 02, 2022, 03:45:15 pm »
You might be able to get away with an anchor made as a container with a small amount of virgin concrete filled with rubble.

If the the costs work out so you can have one pump/generator per sphere maintenance is easy, decouple it from the anchor and do maintenance at the surface.
 

Online ejeffrey

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Re: EnergyVault gravitational energy storage
« Reply #22 on: February 02, 2022, 04:43:25 pm »
It's an interesting concept, but I'm generally skeptical of cost estimates for anything involving deep sea construction. There are also proposals to do artificial pumped hydro using deep mineshafts, essentially the on-land version of this concept with similar issues.

Available geology for conventional pumped hydroelectric is certainly an issue, but there have been some recent research showing that there may be a fair a bit of potential (ha!) untapped resources for closed loop systems using existing lakes:  https://www.sciencedirect.com/science/article/pii/S2542435120305596

It still doesn't work everywhere, but possibly in enough locations that when combined with more HVDC transmission it could cover most of our needs.

 

Offline voltsandjolts

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Re: EnergyVault gravitational energy storage
« Reply #23 on: February 02, 2022, 04:52:49 pm »
Also, in this context it's not entirely true either.

- quite bad efficiency (why only 72% ? seems to be without the cable-to-shore losses)

Same ball park as pumped hydro:
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
Quote
The round-trip energy efficiency of PSH varies between 70%–80%,[4][5][6][7] with some sources claiming up to 87%
 

Offline rob77

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Re: EnergyVault gravitational energy storage
« Reply #24 on: February 03, 2022, 01:02:28 am »
Also, in this context it's not entirely true either.
Interesting.
Butr looking at the numbers, it's not really tempting:
https://www.iee.fraunhofer.de/en/topics/stensea.html#1665982880

- quite bad efficiency (why only 72% ? seems to be without the cable-to-shore losses)
- 23 000 tons of concrete for 12 000 tons of water displaced -> my guesstimate was exactly on point ! Too much...
- nightmarish maintenance

It would be really intersting in comparison to have numbers on a typical concrete usage for pumped hydro...

don't have the exact numbers, but the efficiency of a lake to store water is much better than a bunch of spheres.. and in the lake you don't have to enclose the water from the top. furthermore the concrete lining of the lake doesn't have to take the pressure of a 750m water column.. so it's much less concrete.

maintenance will be insane in the depth of 750m ... there is no such thing as "ok sending a technician down"... saturation diving takes time and is expensive.
pumped hydro you can drain the upper lake and the shafts and then use conventional technology for the maintenance , you take you everyday cranes, trucks, dudes in hard hats...

and i would be curious what kind of turbine are they using.. the say 12200 cubic metres will last 4.5 hours.. that's less than 1 cubic meter per second with the head of 750m - that would be a pelton wheel considering the head and flow.
 


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