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 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.
"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).
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).
They're using "composite" bricks that include waste material (I can't find any obvious references to exactly what kind of mix of materials), so my guess would be the material cost will be rather low.
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.
I wonder how they've calculated the costs of building this giant crane and concrete block system, vs building small scale pumped storage hydroelectricity. Not by the usual method of impounding a reservoir at the top of a hill, but putting a giant array of load-balancing medium sized water tanks at the top of a hill, running a pipe to the bottom where there's the pump/generator, and a similarly sized array of tanks.
A big tank is overwhelmingly cheaper than a collection of small tanks.
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.
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.
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?
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.
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 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.
To be fair, Pumped Storage is really dependent on Geography. It has downstream affects on environment due to having reservoirs where none have been and all.
It's powerful, cheap and long lasting, but not easily available.
Well, this thing also depends on geography. There aren't many places where such a construct would be easy to build: seismic situation, static stability for these enormous weights, winds (it's actually quite funny to see cranes side by side with wind turbines in their commercial)
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)
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
From a personnel safety standpoint (what a catastrophic failure looks like in each case),
a unit installation cost standpoint (fabricate x amounts of bricks with x tolerance in the grooves plus a crane with y units of generation on top) and finally from
a complexity standpoint of stacking stacking bricks (I assume is not just going to be a stored procedure and include some kind of error correction and monitoring).
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.
I wonder if these could coexist with solar farms in deserts and the concrete blocks are simply filled with sand and made there as a part of levelling the field required to install solar panels. A rough analogy would be the cut and fill process that is adopted while making roads. Similarly when a new plant is sited the sand is removed and used to create a storage system. The main idea is that it would reduce transportation costs and will share the transmission lines that exist for the giant solar farms which will be installed.
An "obvious" improvement is to push blocks up, and insert new blocks below (yes, u need gearing, and maybe lean them on a slope). But you get quadratic energy per tonne.
Its amazing how much energy a 250W panel outputs. Imagine storing energy from a 1MW wind mill (free pole? ;).
It’s the same total energy per bock. Their design starts out with 2 rings of stone. To simplify assume both piles are equivalent. The first layer of stones is raised by the width of a single stone. The next layer is raised twice the height of a single stone. The n+1 set is raised 2n+1 layers.
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.
Demand supply matching, reducing solar curtailment by innovative use cases will lead to thousands of business ideas. Although most still make sense at large scale and difficult to bypass the grid or apply anything in terms of storage at small scale like an individual house.
They are, already. They use a type of rock "glue" to fuse together rubble — in some cases old broken up concrete. The GP comment is a pretty basic HN middle-brow response.
The structure would have to be fully enclosed. Lowering and raising concrete blocks in heavy wind conditions (required for wind energy) does not sound like the most safe and deterministic process to automate.
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:
An ISO container(40ft) of those can store 10-15MWh.
For the cost of the Astravets Nuclear Power Plant in Belarus ($11bln, 2GW) you could have 80GWh worth of batteries - that's a week of backup power for one million households in the EU.
One disadvantage of them has always been their performance in terms of power and energy density, but given that they're currently installed in Chinese-made Teslas, I guess it's more or less a solved problem.
i have never seen retail prices of lfp batteries below 300$/kwh yet. Although i am confident near future versions of these batteries can last > 5k and may be even 10k cycles
I studied the topic and it appears that none of the manufacturers/retailers is willing to sell at this price to consumers - they already sell all their stock to car manufacturers and the like.
Is it because demand greatly outstrips supply at this point and will remain so for a few more years at least till new production capacity catches up ? Or is there any other reason that makes it trickier ? Would appreciate any links if you have some.
My best source was a first-hand account from a business owner who tried to switch from one-off EV projects to an a full-blown assembly line. He called up a few manufacturers and they basically told him to come back when he's at the scale of hundreds of MWh - sort of a chicken-and-egg scenario.
Retailers didn't want to talk about special pricing, regardless of scale.
I've read about using a lot of small cheap containers, like plastic bottles, as compressed air batteries, but can't find the article right now. Apparenly a lot of small containers is a significant improvement over few (or single) large compressed air containers. Many small containers offer better space efficiency, they're cheaper, because you require less pressure (regular plastic bottles v. steel tanks), and their power output is steadier.
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.
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.
> A large water tank of 500m3 on a high tower at 50M above an underground storage tank yields approx 70 kWh at best.
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.
This giant crane with three arms looks like something you would climb in a FPS stealth game (dishonored 2, deus ex series, etc). Of course it would be populated with various difficulty levels of private military company henchmen.
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.