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Energy Vault – Gravitational Batteries

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Re: Energy Vault – Gravitational Batteries

#21

Post by tambourine_man »

moneytide1 wrote: post #6
imtringued wrote: post #2

Building cranes is most the boring part of this project. It's far more interesting to know how they are going to make the 35 ton weights. I don't know anything about the construction industry but some googling showed that 1 m^3 of concrete weighs 2.4 tons. You will need 15 m^3 weights. 1 m^3 costs $200 so each weight costs $3000. 35000kg×9.81m/s^2×100m is 34335000 Joules or 9.5kWH. $3000 / 9.5kWH is $315 per kWH. I'm…

> What materials are they using? "Just Have a Think" put out a video about this recently [1]. The project he reports on claims 30MW with 4MW available within 3s for frequency stabilization and the weight is not solid concrete (emissions penalty), but rather compressed refuse that otherwise cannot be recycled (coal ash, demolition debris). The friction would occur as long term tensile strength durability of lifting ca…

That’s where I got the link from

Re: Energy Vault – Gravitational Batteries

#22

Post by Retric »

ktpsns wrote: post #7
londons_explore wrote: post #3

Earlier quoted context omitted.

But each weight can be reused almost infinitely... The cost doesn't matter too much.

That's not right. Refinforced concrete will suffer from environmental influences and have a durability from maybe 30 years. That means you have a cost overhead of 3-4% per year for the replacement value. Water tanks certainly have a much worse life time, given that they will start lacking after a short time and you don't only have to repair the tanks but also provide liquid to refill.

Cycling stress like that is going to dramatically reduce the lifespan due to tress fractures. I think they would be lucky to get 10-20 years from the blocks.

Stress fracture are already a significant issue for concrete dams when you frequently vary the water levels, and this is much worse as different stacking is going to stress each block slightly differently every time. In theory they might be perfectly flat surfaces meeting evenly, but in practice that’s far from the case.

Re: Energy Vault – Gravitational Batteries

#23

Post by J-dawg »

I'm quite fascinated about how an idea like this gets as far as somebody founding a company when, as several people here (as well as the linked videos) have argued quite convincingly, it appears to be easily debunked.

Are the founders knowingly trying to scam investors? Are they just naive/stupid?

Or am I (and the debunkers) being too negative, and this is just the first iteration of an idea that could one day change the world?

What's really going on?

Re: Energy Vault – Gravitational Batteries

#24

Post by Tade0 »

kumarvvr wrote: post #12

I really wish humanity comes up with a good way to store large quantities of electricity (not counting Hydro Batteries). Compressed air in mines is a good alternative, with heat of compression also stored. I am actually looking for ways to make this small scale. As in, creating a storage system for domestic use. In developing countries, average energy usage per house hold, would be not more than 10 kWh per day. Compr…

We already have that in the form of LiFePO4 batteries. They last over 2000+ cycles, use no rare/expensive/conflict minerals and are safe. Also just recently they crossed the $100/kWh barrier in some markets:

https://about.bnef.com/blog/battery-pack-prices-cited-below-...

An ISO container(40ft) of those can store 10-15MWh.

For the cost of the Astravets Nuclear Power Plant in Belarus ($11bln, 2GW) you could have 80GWh worth of batteries - that's a week of backup power for one million households in the EU.

One disadvantage of them has always been their performance in terms of power and energy density, but given that they're currently installed in Chinese-made Teslas, I guess it's more or less a solved problem.

Re: Energy Vault – Gravitational Batteries

#25

Post by fsh »

simonebrunozzi wrote: post #16
imtringued wrote: post #2

Building cranes is most the boring part of this project. It's far more interesting to know how they are going to make the 35 ton weights. I don't know anything about the construction industry but some googling showed that 1 m^3 of concrete weighs 2.4 tons. You will need 15 m^3 weights. 1 m^3 costs $200 so each weight costs $3000. 35000kg×9.81m/s^2×100m is 34335000 Joules or 9.5kWH. $3000 / 9.5kWH is $315 per kWH. I'm…

I would use depleted uranium for that. Many countries have to store thousands of tons of it, and governments will pay you for storing it. Instead of making it sit idle, you might as well use one of its finest qualities (density).

Thousands of tons is a very small amount of mass for gravitational energy storage. The capacity of small pump storage reservoirs is measured in millions of tons. Also one probably wouldn't want to use a somewhat toxic and slightly radioactive material at large scale.

Re: Energy Vault – Gravitational Batteries

#26

Post by treekogreen »

kumarvvr wrote: post #11

1 Ton of mass, at 100 m height, holds 0.2778 kWh of energy. 100 tons (3 bricks as per their design) - 27.778 kWH 100 x 100 Tons (300 bricks ) - 27.78 MWH. However, as per their design, not all bricks store the same amount of energy. The lower section of bricks would not be economical. Every Ton of Concrete, on average produces 0.9 Tons of CO2 during its manufacturing process. 1 MWH of electricity generation, on avera…

Would a better design not to bore downwards instead of build upwards? This seems like such an over-engineered concept that could be simplified and compartmentalised drastically.

There's a whole host of negatives I see in this implementation, not to mention the downsides of erecting a crane-line structure and public opinion.

This is a UK company doing what I described above: https://gravitricity.com/ (i have no affiliation)

Re: Energy Vault – Gravitational Batteries

#27

Post by IanCal »

treekogreen wrote: post #26
kumarvvr wrote: post #11

1 Ton of mass, at 100 m height, holds 0.2778 kWh of energy. 100 tons (3 bricks as per their design) - 27.778 kWH 100 x 100 Tons (300 bricks ) - 27.78 MWH. However, as per their design, not all bricks store the same amount of energy. The lower section of bricks would not be economical. Every Ton of Concrete, on average produces 0.9 Tons of CO2 during its manufacturing process. 1 MWH of electricity generation, on avera…

Would a better design not to bore downwards instead of build upwards? This seems like such an over-engineered concept that could be simplified and compartmentalised drastically. There's a whole host of negatives I see in this implementation, not to mention the downsides of erecting a crane-line structure and public opinion. This is a UK company doing what I described above: https://gravitricity.com/ (i have no affili…

Drilling is also complex and expensive. You'd have to go down, reinforce it and deal with pumping at the very least. On the other hand a crane is, well, a pretty small and simple (/well known) thing. It's a crane and a stack of bricks, it doesn't feel particularly over engineered to me.

Either may make sense given the surroundings but I don't think building up is an obvious problem

Re: Energy Vault – Gravitational Batteries

#28

Post by newyankee »

J-dawg wrote: post #23

I'm quite fascinated about how an idea like this gets as far as somebody founding a company when, as several people here (as well as the linked videos) have argued quite convincingly, it appears to be easily debunked. Are the founders knowingly trying to scam investors? Are they just naive/stupid? Or am I (and the debunkers) being too negative, and this is just the first iteration of an idea that could one day change…

I think the main founder is a CalTech alumnus who also has another company (Heliogen) which promised solar heat at 1 cents/kwh. Backed by Breakthrough new energy ventures.

I believe this idea and kite power ideas are crazy but they might just work.

Re: Energy Vault – Gravitational Batteries

#29

Post by lovemenot »

ulnarkressty wrote: post #15

Water towers could also be economical and straightforward to produce / maintain as power storage sites for a small community.

A large water tank of 500m3 on a high tower at 50M above an underground storage tank yields approx 70 kWh at best.

Not much, but a bit better than nothing. Especially if the tower and upper tank can be dual-purposed. Of course in that case you'd lose some energy capacity to maintain water pressure head.

Re: Energy Vault – Gravitational Batteries

#30

Post by newyankee »

Tade0 wrote: post #24
kumarvvr wrote: post #12

I really wish humanity comes up with a good way to store large quantities of electricity (not counting Hydro Batteries). Compressed air in mines is a good alternative, with heat of compression also stored. I am actually looking for ways to make this small scale. As in, creating a storage system for domestic use. In developing countries, average energy usage per house hold, would be not more than 10 kWh per day. Compr…

We already have that in the form of LiFePO4 batteries. They last over 2000+ cycles, use no rare/expensive/conflict minerals and are safe. Also just recently they crossed the $100/kWh barrier in some markets: https://about.bnef.com/blog/battery-pack-prices-cited-below-... An ISO container(40ft) of those can store 10-15MWh. For the cost of the Astravets Nuclear Power Plant in Belarus ($11bln, 2GW) you could have 80GWh…

i have never seen retail prices of lfp batteries below 300$/kwh yet. Although i am confident near future versions of these batteries can last > 5k and may be even 10k cycles
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