Energy Vault – Gravitational Batteries
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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 generous and assume that the tower is 100m high. I haven't seen a real number on the website.
It's possible that they are using a cheaper material mix but that's the entire problem. What materials are they using? They never say so on the website. This is not rocket science. We are merely talking about how to build the cheapest 35 ton rock on earth and yet these people are silent about that.
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.
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.
it is literally rock science ;)
Seriously, in Germany, concrete costs arount 100 EUR per cubic meter. So we would end up with around 150 EUR per kwh capacity. But they would not have to use concrete for the task. They could as well use 23 m^3 gravel (which goes down to 10EUR) and some steel scaffolding. Or even just plain water (35m^3).
"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 cables and high torque electrical hoists, which are the primary material penalties. But these things may be relatively cheap to produce and rotate out of service as their known operational lifetime approaches (Tesla has designated labor that changes out public charger cables within a reasonable buffer before they are expected to wear out).
Ground water makes a remarkably capacious reservoir, which may be deeper than your hill is high, doubling the energy storage capacity, for a possible upper limit on instantaneous wattage.
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?
I believe this idea and kite power ideas are crazy but they might just work.
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 average, produces 0.417 Tons of CO2.
1 Ton of weight, lifted to 100 m and put down, if say, takes 3 minutes (Average estimate, someone correct me on this), then working without break for 7 years, it will break-even for the amount of CO2 it has saved vs. amount of CO2 it has produced.
After that, it offsets CO2 produced.
However, this is only true for those blocks that are lifted to 100 m.
Those at lower levels, will have progressively more years to break-even.
A better design would be to build the platform to store the bricks from say, 50 m or so onwards, or use natural geographic features to increase height, like on cliffs, etc.
It's powerful, cheap and long lasting, but not easily available.
One can't eat the cake and have it too.
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)
Either may make sense given the surroundings but I don't think building up is an obvious problem
I just cant see anything positive about this solution in the slightest. I wouldn't want to be anywhere near that structure. A crane truly is a simple and well known thing but I have tangible knowledge of a large community pushback in the UK where all that was installed was a relatively small turbine on the top of a hill.
Boring and reinforcement (concrete spraying) is a tried and true technology and most importantly its out of sight.
Assuming an average of 6 hours of sunlight, a 250 W solar panel can collect about 1.2 kWh of energy, or about 5 x 10^6 Joules.
In terms of potential energy that is
5000 kg x 9.8 x 100 meters.
Pretty huge for one solar panel.
I have been thinking about storing energy in underground storage tanks, with compressed air, but roundtrip efficiency does not work out.
Alternative method is to heat any material and use that heat later. Like, molten salt. But these systems are not suitable for domestic use.
Now I am exploring chemical methods to convert carbon to fuels using solar panels.
Its amazing how much energy a 250W panel outputs. Imagine storing energy from a 1MW wind mill (free pole? ;).
Starting with more piles means a lower initial height. But, the only things that matters when stacking is initial and final heights, and transmission losses.
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.
Compressed air is slightly dangerous, so are flywheel systems, not to mention complexity of operation.
Chemical conversion of captured carbon to liquid fuels seems to be a viable solution.
Mildly interesting thought: grandfather clocks have been using this form of battery for a very long time
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.
Retailers didn't want to talk about special pricing, regardless of scale.
The basic math behind the company simply doesn't work. They cannot make money out of it.
But it's not talking about using cheap things like plastic bottles. I'd be interested in reading the article you're talking about. It's hard to find much about CAES online because it's easy to run into the crazy people that think they're going to get free energy out of it or something.
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.
Correct, so if you want 70 MWh you need 1000x more water. 500.000m3 is merely a 80x80x80m cube.
Or to put it in different perspective, to lift it by 50m you need 2x this volume (another container 50m higher), which is 1.000.000m3, or 1M m3. The volume of the Pyramid of Gyza [1] is 2.5M m3. So that wouldn't even be the biggest building on Earth.