
Stacking concrete blocks is a surprisingly efficient way to store energy - nabla9
https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-efficient-way-to-store-energy/
======
saulrh
Huh, I'm less doubtful of this than I thought I'd be. Tower cranes are
apparently surprisingly low-maintenance. I assume this is because they have to
actively participate in their own disassembly [1] and major breakages are
super difficult to deal with because they're at altitude, so they _need_ to
operate reliably enough that they can always take themselves down at the end
of a job or if they need a major repair (cracks found in main pivot ring,
etc). Concretely (pun not intended), I found a document [2] saying that 10
tradesmen and $35k/month in parts (together a bit more than $1m/year) can keep
a fleet of 70 tower cranes (15 metric ton lift capacity each) at ~80%
utilization over a one-year period. So, yeah, I'd definitely believe that you
could run these things at the quoted price.

1:
[https://www.youtube.com/watch?v=Nww6MN_Lxeo&t=24s](https://www.youtube.com/watch?v=Nww6MN_Lxeo&t=24s)

2: Annex 9, "Example of the Use of Key Performance Indicators for
Maintenance", in this PDF: [https://www.mantiscranes.ie/wp-
content/uploads/2017/01/CPA-T...](https://www.mantiscranes.ie/wp-
content/uploads/2017/01/CPA-TCIG-0801-Maintenance-Inspection-and-Thorough-
Examination-of-Tower-Cranes.pdf)

~~~
nabla9
The selling point of this is low relatively low capital cost and well tested
technology. Power density is not that good, but if you have land that's not a
problem.

The use of space to store energy is maybe double of what typical damn
reservoir uses to store the same amount of energy.

~~~
michaelchisari
Each 35MWh system requires about 1.62 acres of land. That seems perfectly
reasonable to me, especially since there are still optimizations to explore.

Here's some totally useless back-of-the-envelope calculations on land
requirements for this sytem.

The United States, in total, used 1,819,393,805 MWh of energy in 2016. If one
plant provides 35MWh of storage, that means 51,982,680 plants are required.

That comes to 84,211,942 acres of land. There are 2.3 billion acres of land in
the United States, so it would require 3.66% of the US. That's obviously a
huge overestimate.

The beauty of this is the simplicity. This is something we could have built 40
years ago. And unlike LIBs, there's much less worry about degradation and we
can put these out in the desert near a solar power source without worry.

Imagine it combined with solar thermal, which has dropped immensely in price
per KWh.

Also, concrete reabsorbs around 43% of the co2 used to create it over a period
of time.

[https://www.nature.com/articles/ngeo2840.epdf](https://www.nature.com/articles/ngeo2840.epdf)

~~~
raverbashing
You don't need to store everything that's consumed, that's where the absurd
number of plants and needed people comes from

10% of that makes more sense, even if it goes, let's say, 50% solar

~~~
kurthr
Yeah, storing (<1%) 3 days total annual supply of electricity would be a huge
over estimate... and storing 10% (35 days)would still be crazy large... I'd
think the grand parent posts's numbers are high by 2-3 orders of magnitude.

As others have said,they likely would be placed near the solar plant where
land is cheap and dry, rather than in neighborhoods.

------
npunt
If they don't call themselves Sisyphus Energy they're missing out on a great
poetic opportunity.

> In Greek mythology Sisyphus was the king of Ephyra (now known as Corinth).
> He was punished for his self-aggrandizing craftiness and deceitfulness by
> being forced to roll an immense boulder up a hill only for it to roll down
> when it nears the top, repeating this action for eternity.

Its quite an ingenious idea. Could even hollow out a mountain to do this,
avoiding the co2 cost of concrete.

~~~
asdfman123
I can imagine living next to one of these facilities and thinking "What the
hell are they trying to build?"

~~~
onetimemanytime
or after 18000 years, after they reboot the civilization and only a few
structures remain. Give a +- few years :)

------
maxxxxx
"The round-trip efficiency of the system, which is the amount of energy
recovered for every unit of energy used to lift the blocks, is about
85%—comparable to lithium-ion batteries which offer upto 90%."

That's quite efficient. Maybe they can get creative and build something
different every day. One day you get a big pyramid, the next day you get a big
elephant. That would be quite entertaining.

~~~
csours
I think you've actually hit on the real selling point here - ADVERTISING!

Think of it as a VERY slow, VERY large TV screen. With red, green, and blue
blocks, they could advertise almost anything!

The value generation from the ad would almost certainly outpace the value
generation from energy storage!

Also, you could encase your bitcoin wallet in a block, creating the ultimate
block-chain block-chain!

By god and the scientists, you're a genius maxxxxx!

~~~
Lxr
> Think of it as a VERY slow, VERY large TV screen. With red, green, and blue
> blocks, they could advertise almost anything!

I don’t think that works if the blocks are reflecting light rather than
emitting it.

~~~
csours
Don't worry we've already pivoted. We're no longer using concrete blocks, now
it's giant LEDs.

~~~
LanceH
Unfortunately we lost the entire first floor when we dropped a block and
filled it in.

~~~
TallGuyShort
And efficiency's down to 12% because of all the backlights for the ads and all
the graphics chips got hacked and are mining bitcoin.

------
chx
There's the horizontal version, so to speak, at
[https://www.aresnorthamerica.com/grid-scale-energy-
storage](https://www.aresnorthamerica.com/grid-scale-energy-storage) \-- it's
running heavy weights up a hill on a closed rail loop to store and use them
coming down to generate energy. 78% efficiency is claimed (in the press kit,
the web page says "approaching 80%"). It claims to be able to store tens of
gigawatt hours of energy.

~~~
CydeWeys
The crane idea appeals to me more because the infrastructure appears simpler.
Rather than having to build a lot of rail and a whole switching
infrastructure, you just install the one crane and a shitload of heavy
concrete blocks for it to lift. Seems like it would be cheaper.

~~~
chx
Someone would need to run the costs per GWh stored and generated. To me it
looks like once you built your rail loop you could run a lot of cars on it.
Still, building instead quite a lot of cranes might be cheaper.

~~~
CydeWeys
Rolling stock isn't cheap either, though. Not even remotely close to how cheap
a concrete block is. Rolling stock typically costs in the millions per car.
The rail might not even be the most expensive part.

The nice thing about the crane idea is you don't even need a lot of cranes,
you just need a lot of stackable mass. The rail idea needs a lot of _movable_
mass on wheels, and a lot of siding to store it on. It seems like the rail
idea would need more land as well, plus it only works on hillsides.

~~~
rtkwe
You need enough cranes to smooth the dips in power generation as each crane
finishes dropping one weight and has to go fetch another. The number needed
would be proportional to the desired power output of the system (holding the
size of the weights constant).

~~~
CydeWeys
So a few cranes?

Keep in mind these will be grid-tied too, so you only need the power to be
smoothed across the entire grid; it doesn't have to be at a single location.
So grid storage batteries elsewhere could play a role too.

~~~
rtkwe
You still want each individual power plant to provide as smooth a power output
as possible because each dip puts some strain on the other plants in the
network as they have to increase their output to accommodate.

------
montalbano
This is absolutely fascinating.

Interestingly, the cement industry produces ~5% of global c02 emissions [0].
(Cement is an important binding element in concrete [1].)

As this technology is presumably most useful for storing surplus energy from
unpredictable renewable sources (e.g. wind, solar) I wonder if there is a
conflict of interest? I'd love to know more about the carbon economics
involved, perhaps they could use reclaimed (i.e. recycled) cement.

[0] [https://blogs.ei.columbia.edu/2012/05/09/emissions-from-
the-...](https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-cement-
industry/)

[1] [https://www.thespruce.com/difference-between-cement-
concrete...](https://www.thespruce.com/difference-between-cement-concrete-and-
mortar-2130884)

~~~
MauranKilom
Let's investigate this!

For reference, a common electricity mix currently generates about 0.5 tons of
CO2 per MWh [0][1].

Now, for the device in question: Creating 1 ton of cement releases about 1 ton
of CO2 [2]. A common ratio of cement per mass of concrete is maybe 1/5 [4].
The article says they found a way to reduce that to a sixth, so we are at
about 1/30 of the concrete mass in cement. From the article, each block weighs
35 tons. So we'll just assume 1 ton of cement (and CO2) per block.

The graphic in the article shows ~40 layers of no more than 20x6 concrete
blocks can be stacked around the tower, each weighing 35 tons. Therefore, each
such installation would cost about 5000 tons of cement or CO2.

So its building cost in cement alone is the equivalent of 10000 MWh. Fully
"charged", it stores 20 MWh. It would therefore have to complete 500 full
cycles of taking energy available for free (and otherwise lost) and feed it
back. Roughly assuming it can do that every week (no idea, really depends),
that would be ten years to become CO2 neutral, just in terms of cement. So
there's your reference value.

However, I haven't seen this kind of calculation for other energy sources.
That would be interesting.

Edit: Here is a review of CO2 from lithium-ion batteries:
[https://www.ivl.se/download/18.5922281715bdaebede9559/149604...](https://www.ivl.se/download/18.5922281715bdaebede9559/1496046218976/C243+The+life+cycle+energy+consumption+and+CO2+emissions+from+lithium+ion+batteries+.pdf)

They say 150-200 tons of CO2-equivalent (!) per MWh stored, which is very
close to the device in the article (in the above estimate it would be 250 tons
of CO2 per MWh, although I did not check whether that is pure or CO2
equivalent).

[0]
[https://www.eia.gov/electricity/state/](https://www.eia.gov/electricity/state/)
(randomly sampled some states)

[1]
[https://www.umweltbundesamt.de/sites/default/files/medien/37...](https://www.umweltbundesamt.de/sites/default/files/medien/376/bilder/entwicklung_der_spezifischen_kohlendioxid-
emissionen_des_deutschen_strommix_1990-2016.png) (German statistics)

[2] [https://blogs.ei.columbia.edu/2012/05/09/emissions-from-
the-...](https://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-cement-
industry/)

[3] [https://sans10400.co.za/concrete-mixes-by-
weight/](https://sans10400.co.za/concrete-mixes-by-weight/)

~~~
mistermann
Nice work.

From [2]:

Cement manufacturing is highly energy- and emissions-intensive because of the
extreme heat required to produce it. Producing a ton of cement requires 4.7
million BTU of energy, equivalent to about 400 pounds of coal, and generates
nearly a ton of CO2. Given its high emissions and critical importance to
society, cement is an obvious place to look to reduce greenhouse gas
emissions.

Ignoring the geographical problems, could using the power source from which
energy is stored for these devices also be used to manufacture the concrete,
or would you be constrained by the power plants ability to output enough
energy intensity to produce concrete?

If feasible to do, then for the geography issue, would the CO2 output from
lengthening the trucking route and/or high voltage transmission lines to the
storage site possibly overcome the cement issue overall? If the power is
~free, loss in transmission is less important, but then you have to consider
the output of manufacturing and installing transmission lines also. Although,
perhaps there's spare capacity on some lines.

Actually, once the blocks are manufactured, you can ship them anywhere.

Complicated.

~~~
CydeWeys
> Actually, once the blocks are manufactured, you can ship them anywhere.

But you won't want to, because they're insanely heavy. At 35 tons a semi-
trailer can only carry one.

You really need to build these on-site. The amount of diesel you'd burn to
move them long distance is astronomical.

~~~
lenzm
If you build it on site won't you still have to haul in all of the materials
to produce it which will weigh more than the final product?

~~~
CydeWeys
The point is that they would be made locally, not "shipped anywhere". Every
city has a bunch of local concrete plants for a reason. If I buy aggregate,
it's coming from nearby; it's not being shipped across the country.

------
FrojoS
Similar concept using trains: [https://www.aresnorthamerica.com/grid-scale-
energy-storage](https://www.aresnorthamerica.com/grid-scale-energy-storage)

I wonder though, the density of concrete is only about 2.5 higher than that of
water. So, a concrete tower, comparable to a pumped-storage hydroelectricity
plant would be gigantic. Seems infeasible to me.

~~~
st26
Might come down to things like, how efficient are cranes & conveyors & so
forth, vs water pumps & hydro generators. The nature of each material leads to
different techniques which could have very different efficiencies.

~~~
hinkley
Upfront costs can sink a project, but so can ongoing maintenance. Materials
that don't foul as easily have a long term advantage. And when there's a
drought people won't be too happy about all that fresh water you're taking to
make electricity ('course, how much water does it take to make a cubic foot of
concrete, cradle to grave?).

~~~
mmt
> how much water does it take to make a cubic foot of concrete

The article does mention that they expect to use 1/6th the cement of
construction concrete.

This paper
[https://www.nature.com/articles/s41893-017-0009-5](https://www.nature.com/articles/s41893-017-0009-5)
gives an idea: 2 Gt of water per 21.3 Gt of not-water.

Assuming perfectly dry concrete (and none of the water converting to not-water
mass, both of which I believe are counter-factual), that means a 2130 kg block
of concrete would have needed 200 kg of water. Pumped hydro, assuming
identical efficiency, would need all 2130 kg of water.

~~~
hinkley
2Gt of water was _mixed_ into the concrete, but when you're calculating water
footprint you need to look at how much water went into creating all of the
ingredients. That can be pretty substantial.

That article does go on to cover the water footprint, but what troubles me is
that they switch units, and report it as 16.6km^3 of water. Which seems like
they're trying to obfuscate the results (they _have_ obfuscated them, whether
that was intentional or not is another question).

That's all the water for all the concrete. Which for a hydroelectric
perspective, is about 5% of the volume of water behind Grand Coulee Dam, for
all the concrete we currently make every year. So maybe concrete blocks make
sense for power.

~~~
mmt
> 2Gt of water was mixed into the concrete, but when you're calculating water
> footprint you need to look at how much water went into creating all of the
> ingredients.

True, though the paper makes a point, early on, that much of it is used in
producing the aggregate, and the article makes a point of (potentially) using
recycled/discarded aggregate, which would incur no additional water
consumption.

> report it as 16.6km^3 of water. Which seems like they're trying to obfuscate
> the results

That's a remarkably harsh characterization, especially since that was
parenthetical. The main reported amount was 16.6 × 10^9 m^3.

With water having the convenient density of 1000kg/m^3 (1 ton/m^3) and 10^9
being equivalent to the SI G prefix (both facts which one reasonably expect a
reader of a physical sciences journal to know casually), it seems hardly
obfuscatory. I'd attribute, instead, a change of units to a desire to compare
it to household use, later in that paragraph, which is more typically measured
by volume.

Although for commercial concrete block of 2130kg, that would, indeed, change
the amount of water to be 1660kg from my original 200kg. However, I'm fairly
confident that the ability to use 1/6th the cement combined with not needing
any particular aggregate (even recycled) will bring the number for the
article's application much closer to the smaller one than the larger one.

------
Const-me
The majority of the world’s economy is at or near the seaside. I find this
approach more practical, similarly low tech (which is a good thing, simple and
reliable) but uses hydrostatic pressure instead of gravity.
[http://theliquidgrid.com/2016/12/27/marine-energy-
storage/](http://theliquidgrid.com/2016/12/27/marine-energy-storage/)

Sea floor is underutilized, but you can do a lot of things on a piece of land.

Below certain small depth the sea is always calm, atmosphere is not, I
anticipate catastrophic consequences with these tall cranes when hurricanes,
tornados or lightnings.

~~~
CydeWeys
That seems harder to me. Anything done deep underwater costs at least an order
of magnitude more, plus they still have all the same concrete requirements
because they need ballast to keep the air balloons from rising to the surface.

Seems easier to just use that same mass on land with a crane.

~~~
Const-me
> Anything done deep underwater costs at least an order of magnitude more

They don’t need to do much underwater, only install. But I agree capital costs
might be higher because of this.

> all the same concrete requirements because they need ballast

Depends on the geology of the sea bed. Where I live, the sea bottom is mostly
solid rock, it’s possible to attach stuff to the bottom without putting much
ballast.

> use that same mass on land with a crane.

The idea’s nice I just worry about disasters. I read in local news about
falling construction cranes every couple of years, because stormy weather for
a few months each year. It’s possible to make cranes strong enough even for
bad weather (like bridges), but such weather proof cranes will become more
expensive than regular ones.

~~~
CydeWeys
The installation process dominates overall effort, so if that's a lot harder
then it ends up being a lot more expensive and thus a lot less cost
competitive. It is absolutely insane how expensive an underwater oil well
costs to tap compared to one on land, for example.

> Depends on the geology of the sea bed. Where I live, the sea bottom is
> mostly solid rock, it’s possible to attach stuff to the bottom without
> putting much ballast.

It's likely to be more expensive to attempt to attach to the sea floor than it
is to just sink large weights. In fact, I'm not aware of any large structures
that are anchored to the sea floor in a way that resists an upward force
rather than a downwards one. It might be a wholly unsolved problem.

> The idea’s nice I just worry about disasters.

Falling construction cranes are dangerous because they tend to happen in
inhabited areas, adjacent to other buildings. The energy storage cranes, on
the other hand, would likely be in the middle of nowhere where land is cheap,
so even if they do fall there's nothing to damage beyond the energy storage
installation.

~~~
Const-me
> I'm not aware of any large structures that are anchored to the sea floor in
> a way that resists an upward force rather than a downwards one

Marine vessels can be very large and helical screws are widely used, here’s an
example [https://helixmooring.com/square-shaft-
anchors-2/](https://helixmooring.com/square-shaft-anchors-2/)

> even if they do fall there's nothing to damage beyond the energy storage
> installation.

Very expensive installation. Maybe they don’t need the reliability of bridges
but they need to be able to withstand any weather.

------
jefurii
The Ares Project
([https://www.aresnorthamerica.com/](https://www.aresnorthamerica.com/)) did
something like this with robot trains shuttling concrete blocks up and down a
slope. No news on that project in awhile tho. I hope this idea is more
successful.

~~~
theunamedguy
Quick question: how does the electricity get from the train (in motion) to the
grid? Using the rails as conductors could work, but I'm not sure how efficient
that would be.

~~~
tgsovlerkhgsel
One way would be using a funicular: The "train" is just the weight, pulled
up/lowered on a cable that's connected to a motor-generator at the top.

Would also make it cheaper to build extra wagons, with a storage yard at the
top and bottom.

------
sagebird
They may as well make the concrete blocks in the shape of cups. Open a drain
hole when the cups are on the ground. When the cups are on top of the towers,
let them fill with rain.

~~~
dmurray
Rainfall is 50 cm/month in the absolute wettest parts of the US, and less than
half that in most of it. This wouldn't really move the needle.

------
tomxor
Finally a useful application of block and chain based storage... _Hides_

------
xg15
What I don't get, why the complicated design to assemble the blocks into
stacks? This seems to add a lot of non-essential complexity: Now you need
cranes, a hooking/unhooking mechanism (that seems to even require cameras and
image recognition!), the ability to move blocks horizontally and lots of
computing power to coordinate the whole thing.

Even more, the up-front cost to recover energy is higher because you need to
lift the blocks from the stacks before you can drop them.

Why not simply use a fixed hook/rope/motor/generator assembly per concrete
block? Or, if there are too many blocks for that, use a hydraulic system? (But
then again, what is the advantage of using many small blocks instead of a few
large ones?)

Nothing against the company - the idea is awesome - but it seems weird that
almost all the advertised innovations are solutions to problems that wouldn't
exist without the "put the blocks into stacks" design:

> _The innovation in Energy Vault’s plant is not the hardware. Cranes and
> motors have been around for decades, and companies like ABB and Siemens have
> optimized them for maximum efficiency. The round-trip efficiency of the
> system, which is the amount of energy recovered for every unit of energy
> used to lift the blocks, is about 85%—comparable to lithium-ion batteries
> which offer upto 90%.

Pedretti’s main work as the chief technology officer has been figuring out how
to design software to automate contextually relevant operations, like hooking
and unhooking concrete blocks, and to counteract pendulum-like movements
during the lifting and lowering of those blocks._

(Not counting the described innovation of finding a new mixture that includes
waste and reduces the amount of cement needed.)

~~~
ubercow13
The tower in the video looks like it contains hundreds of these blocks. You
would therefore need hundreds of assemblies to do it that way, and each one
has to lift the same weight that the crane is lifting. All of this to save on
the cost of making the crane complex enough to move about, and the cost of the
software involved.

~~~
xg15
But what is the advantage of having a large number of small vs a small number
of large blocks?

~~~
surrealize
In the system you envision without stacking, are all of the large blocks
suspended from the crane simultaneously when the system is fully "charged"?
That would require the crane to support a much higher max load.

------
tomelders
Honest question. Is there a reason to use a crane rarther than digging a hole?
It seems all that needs to happen is for a weight to be lifted and then
allowed to fall. If that was done below ground, that would cut out the weather
issues and I feel like the structure itself would be a lot more robust.

~~~
tantalor
Holes are expensive

~~~
adiusmus
Not all of them. Sometimes they are waste products of some other industry. Eg
old mines / quarries.

~~~
CydeWeys
Yes, you could use a pre-existing big hole, and carry concrete blocks from the
bottom of the hole to the top of the hole. All you're really doing with this
approach is swapping out the tower crane for a gantry crane though, for
negligible savings. The hole's not really helping you out that much.

------
progfix
A few thoughts:

\- Someone needs to watch the stacking process. If there is a single error the
whole tower can collaps and do a lot of damage.

\- You need a big (and expensive) foundation for a tower like this.

\- Is the low-cost-concrete a strong enough building material?

\- The generator needs cooling (in hydro pump it is cooled by the water
flowing through)

~~~
adrianmonk
It seems pretty easy to verify the blocks are stacked properly.

First, make them out of a shape that naturally fits together.

Then, build them with a vertical hole (shaft) through them. Put a reflector
under the bottom one. Before the crane releases a block, it shines a light
down the hole and checks if it is reflected back. Misalignment will block the
light. (Or, you can do something similar with electricity, connected contacts
on the top and bottom, and a check that current flows through the entire
stack.)

~~~
kardos
Sounds good except what do you do about biology that decides to take up
residence in the holes?

~~~
adrianmonk
I suppose you'd have to clean it regularly. When the crane goes to pick up a
block, it could do the optical continuity check then too. If it fails, that
indicates that either the block was moved after it was stacked correctly
(unlikely but possible) or it got dirty.

In that case, something comes along and cleans it. Maybe a rod-shaped brush
(like a vacuum beater) that spins. Or a water jet.

Also, you can have more than one hole for redundancy. If one of them is clear,
that should be good enough.

Hmm, or rather than holes through the middle, make them notches or grooves on
the side and shine a laser through them.

------
jaggederest
There is a similar idea using metal pellets fired from electromagnetic
accelerators in a "space fountain". The energy would be stored there in the
form of kinetic and potential energy, and it is relatively effortless to tap
into that stored energy to even out something like the energy grid. Has the
nice side effect of being able to launch things to space on it.

[http://www.orbitalvector.com/Orbital%20Travel/Space%20Founta...](http://www.orbitalvector.com/Orbital%20Travel/Space%20Fountains/Space%20Fountains.htm)

~~~
vidanay
That page made my eyes bleed.

~~~
NullPrefix
Looks like something hosted on Geocities. Just like with old paintings, when
judging, you have to take into account the period it was produced in.

>Article added 2005

------
amelius
What will happen to Earth's rotation if we start lifting objects on the side
where the Sun shines, and dropping them on the other side?

~~~
infogulch
Good point. We know that large shifts in mass, like huge landslides caused by
earthquakes, can measurably affect earth's rotation. What happens when we
start using multi-gigaton masses for energy storage -- that are within a
couple orders of magnitude of those landslides -- in a cyclic pattern? I
wonder if we could even get resonant effects.

~~~
samatman
y'all remember we got tides right

------
csours
Q: A big stack of concrete blocks seems to be almost purpose built for the
wind (or a gigantic mutant toddler/cat) to push over. Cranes are also
extremely susceptible to wind. I suppose the blocks could be engineered to
interlock, but the pictures show cylinders. How do they plan to counteract the
wind?

~~~
jvandonsel
As far as the crane goes, the article indicates that "Wind could cause the
block to move like a pendulum, but the crane’s trolley is programmed to
counter the movement." That actually seems like the most interesting part of
this system.

~~~
csours
I'm sure they've accounted for winds they expect to encounter on a yearly
basis, but "century" storms do happen, just ask Houston TX.

"Houston is experiencing its third ‘500-year’ flood in 3 years. How is that
possible?" \-
[https://www.washingtonpost.com/news/wonk/wp/2017/08/29/houst...](https://www.washingtonpost.com/news/wonk/wp/2017/08/29/houston-
is-experiencing-its-third-500-year-flood-in-3-years-how-is-that-
possible/?utm_term=.09e98bacffa8)

~~~
lenzm
They aren't worried about the wind's effect on the stacked blocks, just the
ones suspended. If a century storm comes, just shut it all down for a day,
everything is stable.

------
tpurves
Why not stack or lift heavy lead-acid batteries? 2 for 1 deal on energy
storage.

~~~
7952
Or make a fly wheel out of batteries and lift that

~~~
dmurray
With a mirrored surface, so it could contribute to a concentrated solar farm.

------
ada1981
This is neat.

We are also facing a global sand shortage crisis due to increased demand for
concrete.

[https://theconversation.com/the-world-is-facing-a-global-
san...](https://theconversation.com/the-world-is-facing-a-global-sand-
crisis-83557)

~~~
legohead
India's sand mafia: [https://www.youtube.com/watch?v=ugT-
zyXGNIY](https://www.youtube.com/watch?v=ugT-zyXGNIY)

~~~
ada1981
Great film.

I wanted to get a sense of the economics of the entire thing.

They said mining for sand could be more profitable than mining for gold.

I presume that means extracting a truckload of sand will yield more profit
than a truck of ore containing rock?

I’m also now curious about sand alternatives.

------
kragen
One crane can store 20 megawatt hours. The wholesale price of a megawatt hour
varies between US$-40 and US$120, normally being around US$60; if you manage
to hit those peaks and valleys, which usually happen once a day, you make
US$160. If you manage to do this 20 days a month, you make US$3200 a month or
US$38400 a year. Given saulrh's comment
[https://news.ycombinator.com/item?id=17790442](https://news.ycombinator.com/item?id=17790442)
that each tower crane requires US$500 a month in parts to keep it running, it
seems plausible that this could be economically viable.

------
baron816
If this became a real thing, can the employees who operate the cranes be
called "Sisypheceans?"

~~~
CydeWeys
Per the article, the cranes are automated. Having paid operators would
probably kill all the cost advantages and then some.

~~~
azernik
At least give that name to the cranes.

------
fizx
I wonder what religious purpose future archeologists will think this served :)

------
zethraeus
Does anyone have a sense of what maintenance for a system like this would look
like relative to maintenance for a dam? It seems expensive as hell.

~~~
0xfeba
Are you serious? A crane vs corrosive water?

~~~
PeterisP
The cranes also encounter corrosive water from outside the weather - and the
dam of a pumped hydro station doesn't need a full replacement after a couple
of decades; a crane does after 15-20 years at the most.

------
joshuaheard
I would think storing energy using compressed air would be more practical.
Excess electricity pumps air into a compressed air tank. When electricity
supply is low, the compressed air is released turning a turbine to generate
electricity. It's basically the same principle as the pumped hydro mentioned
in the article but using compressed air. The advantages are size, cost, and
availability. You can put it anywhere and scale when necessary.

~~~
JohnJamesRambo
The disadvantage is that you have made a huge compressed air bomb in the event
of failure. The concrete blocks would fail in a more local way by just falling
down.

~~~
crispyambulance
The compressed air would be located in deep inside abandoned mines. The volume
and thus energy storage potential of such places is vast.

The idea has been around for decades, but no one has been able to really do it
yet.

~~~
cgdcraig
Rock isn't necessarily airtight more so in mines. A fractured host material
for the ore is very desirable as it means less explosives and higher ore
production numbers.

------
dojomouse
If the promoters themselves are only claiming $150/kwh as a goal this doesn't
have a chance of success given its other limitations.

~~~
dojomouse
I should qualify that a bit...

\- The promoters are likely to present at least a realistic (if not
optimistic) estimate of mid term cost, the technologies involved are all
mature (so the potential for further reduction I'd low), and the estimated
cost is not materially better than battery energy storage (worse, in fact,
than near term forecasts, and much worse than midterm potential battery energy
storage cost).

\- The siting flexibility is poor, which means grid connection will be
slow/expensive.

\- The power density will be pretty bad (which wouldn't matter for bulk energy
storage... but it's too expensive to compete in that market).

Maybe it could become more attractive with much taller cranes?

------
anonymous5133
I think this idea is excellent and really opens up the idea of thinking of
non-traditional grid energy storage. Let's go back to the basics of what we
can do to store energy and retrieve it at the basic level.

------
mrfusion
Now why couldn’t we build something like this right into a wind turbine?
They’re already pretty high up. Just have it lift one giant concrete block up
and down.

~~~
kordlessagain
> Let's spin some numbers to further illustrate the poor energy density of
> gravity-based storage systems. Assume that you have a 100 kilogram lead
> weight that you can lower into a 10 meter deep hole in your yard.

> Now, how much energy can it store? This is given by potential energy formula
> E=mgh, thus E=100kg⋅9.8m/s2⋅10m=9.8kJ≈2.7Wh.

> For comparison, a single AA-sized battery stores about 2Wh of energy.

[https://physics.stackexchange.com/questions/305563/why-
dont-...](https://physics.stackexchange.com/questions/305563/why-dont-we-use-
weights-to-store-energy)

Wind turbine height: 99 meters. 100 kilogram lead weight == about a large
person. So, a normal turbine maybe can hold about 100 people's worth of
additional weight (elephant or two) * 10 (height multiplier) = ~1,000 AA
batteries worth of stored power.

~~~
aeleos
Wow, I never really realized how good our current chemical battery technology
is at being extremely dense.

~~~
noir_lord
Decades of incremental small percentage gains really adds up in overall terms.

------
jondubois
Why doesn't it just lift a single extremely large block when electricity
surges and then very slowly drops it back down to generate electricity (no
need for complex hook-and-release)? The maximum capacity would be determined
by the maximum height of the tower along which the block is lifted.

Or why doesn't it just have many medium motors; each permanently attached to a
single medium-sized block? Why should the relationships between motors and
blocks be one-to-many?

Lots of small concrete blocks, a camera and a hook to latch onto them one at a
time sounds overly complicated and error-prone - Not to mention how much
precious time would be wasted getting the hook through the holes and then
coordinating the lifting so that each block ends up stacked nicely.

~~~
canam
Or maybe one block per house. Solar raises it though the day, generates
electricity at night as it lowers. No grid required.

~~~
jondubois
Nice, that sounds even better.

------
aeleos
I like the idea, but I am wondering how big these will need to be. If one of
their prototype towers can store 20 MwH, at each one requires a circle 300
feet in diameter, than it will require a lot of land to do this.

I wonder how this compares to lithium on a power store per square foot metric.

~~~
oihoaihsfoiahsf
They can store (not generate) 20 MWh at, according to the article, a cost of
$2M. The article does not discuss how much power they can produce using one
unit. That means it would cost roughly a trillion dollars to build enough
storage to power the entire US for a day [1]. That's a lot, but you wouldn't
need nearly that much, since daily consumption is still _roughly_ balanced to
production. You could think of that as an upper bound on the cost of backing
the entire grid with this tech, assuming their numbers scale perfectly and are
entirely accurate.

Almost everywhere has a lot of unused land, even in densely packed countries
like Japan. If it's not good for farming, forestry, or leisure, it would be
suitable for this sort of use.

[1]

\- 3.8e12 kWh/y electrical use in the US.

\- 1e10 kWh/d

\- 1e10kWh / 2e4 kWh/unit = 5e5 units

\- $2e6 / unit * 5e5 units = $1e12

~~~
adrianmonk
They spent $2M on the demonstration plant, which is ~1/10th the size. It
doesn't store the full 20 MWh. (Or is that 35 MWh? The article seems
inconsistent on that.)

The bad news is, the capacity is lower, but the good news is the $2M is the
cost to build the first prototype, and prototypes can be extremely expensive
compared to the real manufacturing costs.

It seems like the only information available about the price is their estimate
that they can hit $150/kWh.

------
phy6
How about huge helium balloons attached to a hose that lets a compressor suck
the helium back down to ground level. The hose/tether would be on a spool
attached to a generator. You could even do this from the ocean floor using
regular surface air.

~~~
tgsovlerkhgsel
The "huge" is the problem here. In order to store any useful amount of energy,
you'd need way too much. We use water because it's readily available, cheap,
easy to transport, and relatively easy to store.

Concrete is already harder to transport (you need to correctly grasp, stack
and release the blocks).

------
JonasJSchreiber
Does anyone see the downside that a little bug gets introduced, the concrete
chips, the barrel dents, a cyber attack takes place, and suddenly your 120
meter tall stack of 35 ton blocks becomes a Jenga tower raining death into the
Swiss countryside?

~~~
mdorazio
Not really. What are they going to hit? Presumably the realistic maximum
impact radius of a failure would be fenced off (and wouldn't be that big -
probably about the same size as the area fenced off for radio towers with guy
wires).

------
nielsbjerg
Why not use a single mega block, and hydrolics? Seems to me there would be
less mechanical wear, and the system would be simpler?

~~~
juancampa
I was thinking the same but with chains or some heavy contiguous body. The
problem is that you need something that can lift one super heavy load, as
opposed to many lighter weight ones. I guess that's what you mean by
hydraulics but then you need hydraulics

~~~
pas
Hundreds of small pumps and pistons would be easy and reliable though.

~~~
juancampa
Reliability of a system is the reliability of each component multiplied
together. It gets exponentially less reliable as you add components

------
OliverJones
Cool. I wonder if it makes sense to make a roller-coaster-like potential
energy storage system? It sounds like the electric motor-generator problem is
solved. Escalator technology has many decades of safety and efficiency track
record.

It also might make sense to use shipping containers full of heavy rubble
rather than purpose-built concrete blocks. Container cranes already are
designed to work fast and accurately. Containers are common and strong, and
solving the saftey problem of weight integrity might be easier.

------
keypusher
They say the proposed version could store 20 megawatt-hours, but I wonder what
the maximum output is? That is, how long does it take to produce that energy?
If the maximum output is ~1-2 MW, it can support 1k or 2k homes, but it's also
important to put in context that peak load of an average sized US city peak
load is ~1000 MW. A med-sized wind turbine can produce ~2 MW, for comparison.

~~~
ShinTakuya
The cost is key here though, at $2m or potentially lower you're paying just
$1-2k per home and maybe $100 a year maintenance thereafter. Not a bad price
overall for what you get. In Australia at least, electricity costs $1-2k per
year per household. Some napkin maths tells me that at 15MWH consumption per
year this sort of storage could make solar (at $50 per MWH) pretty viable. As
in, potentially below $1k per year even if you build enough storage to cover
80% of the day.

------
barbegal
It's not significantly more efficient than pumped hydroelectric storage which
is 70 to 80% efficient. And whilst it might be able to store quite a lot of
energy, it can't release it particularly quickly I'd estimate the 6 crane
motors can maybe generate a combined 1MW which is a paltry amount of power
compared to even a tiny pumped storage facility.

~~~
proto-n
Ok but the whole premise was that hydroelectric storage is infeasible in most
places.

------
8bitsrule
I'd like to see a comparison of this electric-crane-block system with a system
already being tested, 'rail storage', which uses electric locomotives to pull
heavily loaded cars uphill.

I'd guess the cranes would be cheaper than locomotives and laying track....
and works on flat terrain (EG the midwest).

[https://vimeo.com/124312632](https://vimeo.com/124312632) (ARES, Bakersfield)
[https://www.snl.com/InteractiveX/Article.aspx?cdid=A-2654235...](https://www.snl.com/InteractiveX/Article.aspx?cdid=A-26542351-12594)
[https://www.vox.com/2016/4/28/11524958/energy-storage-
rail](https://www.vox.com/2016/4/28/11524958/energy-storage-rail)

------
anon1253
Very nice. Seems a bit finicky with all the cranes though, but what do I know.
If the cost of concrete is a problem, why not put a huge sheet-like structure
below a landfill and very slowly rise it up or down ... same principle, but
now you're just moving waste and there's no shortage of that!

~~~
CydeWeys
The difference is that tower cranes capable of carrying 35 tonne blocks can be
bought off the shelf.

As for lifting an entire landfill, how the hell would you accomplish that? No
such machine exists, and the support columns required to do so would be
utterly massive.

Also, I don't think a strong enough material exists to make that sheet out of.

------
matt_the_bass
How about putting one or two of these _inside_ a new construction sky scraper
just like one long, heavy elevator? “Charge” it at night. Release it during
the day. This may not be a general solution but might be helpful at a per
building level.

------
billsmithaustin
If there isn’t a steampunk novel featuring this technology, there should be.

------
quotemstr
Why would you use a large number of small blocks to build a tower instead of
one extremely large block on vertical rails, with appropriate devices to
create sufficient mechanical advantage to move the block?

~~~
tomp
Because a block on the top of a tower of blocks is way more stable than a
hanging block 100x heavier.

~~~
quotemstr
That's why you mount the heavy block on rails.

I don't see a practical problem with very heavy monolithic blocks. Over a
century ago, people built perfectly stable hydraulically-powered draw bridges
that have opened and closed several times per day, every day, up to the
present. Sounds like a solved problem to me.

~~~
CydeWeys
You're orders of magnitude off on the scale involved.

A single one of these concrete blocks is 35 tonnes. To get useful stored
energy levels you need thousands of blocks. So you're looking at something
like 100 kilotonnes of total mass. That's way, way, way more than any movable
bridge weighs. Bagger 288, the largest mobile machine ever built, only weighs
13.5 kilotonnes, and all of that weight is supported by the ground on massive
treads. To be able to lift many times the weight of Bagger 288 over 100 m in
the air defies imagination as to what would be required. It would require
billions of dollars to achieve, most likely.

Contrast with an off-the-shelf tower crane that costs a few million.

------
calebm
I remember a mechanical engineer friend of mine who worked in a power plant
telling me that large flywheels are still used for energy storage. Funny how
basic the energy storage solutions often are.

------
MayeulC
Gravitational potential-based energy storage is nothing new. There are lots
and lots of ways this is harnessed; take a grandfather clock, for example.

That said, there are a few points worth noting, if I spend a few minutes
thinking about this:

* You probably want to maximize "dumb mass", with relation to the lifting mechanism, to bring down your costs this has to be optimized vs density

* You probably want to maximize the height difference in order to make the system more effective:

\--* Less losses due to the "fixed costs", both in time and energy, of
positioning the mechanism for the next payload

\--* If you have lots of blocks to move, or are simply stacking them, it will
take up a huge area when discharged, which will at least make the crane system
more complicated

So, simply stacking blocks does not seem like the perfect solution to me,
unless you really want to max out the energy per unit of volume. This could
make sense if you were stacking goods that would be useful elsewhere (think a
warehouse that doubles as a batteries). Incidentally, batteries, fuel tanks or
containers would be a rather good choice if you have to pick one of these.

Following on the double-use idea, there is already one distributed, underused
infrastructure that is designed for electrically lifting things (though
probably not power generation). I can see a few ways that elevators could
double as auxiliary power storage units.

Of course, special care would be needed to make sure the extra weight doesn't
compromises the buildings' structural integrity. The same could be said about
virtually any other candidates, which includes existing bridges, dams, cliffs,
etc.

An interesting take on this would be to see whether it is possible to take it
offshore. In theory, given perfect water-proofing (or just good pumps) and
logistics, you could change the geometry of a concrete-built floating
structure, and lower parts of it extremely deep. Of course, Archimedes doesn't
help much with power density, but that wouldn't affect efficiency much
(hydrodynamics would, if speed/geometry isn't optimized, though). As a
preliminary approach, sea deeps near the coast could make it simpler. I
suspect concrete composition would be the hardest part to solve, in that case.

------
bacon_waffle
I like that this scheme doesn't put the local food/water supply at odds with
the local energy supply, like hydro schemes can do.

------
carapace
(ya got me)

Don't pump water up.

Convert to steam/vapor. Run a hyper-insulated pipe up the side of a mountain
with repeater heaters if necessary. Condense at the top, recovering the heat,
and send them both (the water and the heat) back to the bottom separately. For
added points make up your losses from solar inputs.

~~~
edent
And if there are no mountains nearby?

~~~
sebazzz
Exactly. The point of this idea is that it is supposed to be doable when you
lack geographical features, like in the Netherlands.

------
ktzar
9.8m/s2 * 120m * 35000kg = 41160000 J = 11.4 kWh

Not convinced. Am I missing how they get to store 20 MWh of energy using
gravity?

~~~
CydeWeys
The idea involves lifting thousands or tens of thousands of blocks, not just
one. Of course it's ridiculous to have an entire tower crane dedicated to
lifting a single block, but that's not what they're proposing. The linked
article has a rendering showing how many blocks are involved.

~~~
ktzar
No way one a single block weights 35 tons. A concrete cubic meter weights 2.4
tons.

~~~
CydeWeys
Then they're clearly bigger than a cubic meter.

You want to use blocks that are as big as possible so you get more energy out
of each trip. 2.4 tons isn't very much at all compared to the carrying
capacity of a crane -- you want as heavy as possible while still being
comfortably within the lifting capabilities of the crane. Their design says 35
tonnes and that does indeed make more sense. Where is your doubt coming from?

------
dudeonthenet
Yeah, imagine passing by a field with about a hundred of those while they're
dropping the blocks.

------
hasperdi
This is gravity lamp all over again.

~~~
CydeWeys
It's not, because the gravity lamp math didn't check out, whereas the math on
this does.

------
radarsat1
Idea: Stick a heavy load onto a rotating screw. Actively power it to rotate,
moving the weight up; let the weight drop forcing the screw to rotate on the
way down. Sounds pretty simple, I guess a lot of energy would be lost to
friction.. teflon? Bearings?

~~~
CydeWeys
Sounds less efficient than just using a high efficiency electric motor to
power a crane as in this proposal.

------
Gravityloss
I guess with a harbor crane type of system where the crane is on rails, you
could scale to a higher energy storage with similar power.

Don't know what the sweet spots of capacity vs power are on different markets.
This could be good for long term storage.

~~~
Jarmsy
Yes, I was surprised they showed a tower crane rather than a bridge/gantry
type, which I'd imagine is much more stable for heavy loads.

------
nashashmi
They are better off using metal products in place of concrete blocks because
they have higher weight densities. About 3 times more.

Water permeability also has an impact. Imagime lifting the products when it's
wet and dropping them when it's dry.

~~~
Jarmsy
Higher density, but also surely much higher cost.

~~~
malydok
Exactly, especially if they get most of the weight material for free or even
get paid to take it.

------
personjerry
I would assume the water pump is more efficient than the motor moving the
concrete though.

~~~
anonymous5133
IMO, that is not an important factor because the water pump option would not
even be available in a desert area. This is assuming you are thinking of
traditional pumped-hydro. You could probably make some sort of closed off
pumped-storage where water can't escape but that would probably be very
expensive.

~~~
waynecochran
If you have driven thru the Columbia Gorge where the highest capacity
hydroelectric dams are you’ll notice that these dams are much lower than the
surrounding top of the gorge. I always wonder why not pump water to the top of
the gorge?

~~~
mmt
I would expect a signficant limiting factor to be the cost of dam construction
(which is going to go up at least geometrically with height, assuming a
V-shaped opening), not the height of the already-constructed-by-nature
surrounding walls.

------
mhb
Energy Storage Using a Rock-Filled Train on a Hill:

[https://news.ycombinator.com/item?id=17794547](https://news.ycombinator.com/item?id=17794547)

------
VBprogrammer
Im surprised no one had mentioned the CO2 cost of producing concrete.

~~~
krallja
Presumably because the CO2 cost of cement is thoroughly discussed in the
article.

------
pirocks
Why not do this in the ocean? Lifting and raising blocks from the sea floor
provides far more potential energy, since the ocean is deeper, than any crane
is tall.

~~~
joe-collins
Transmission costs and greater wear and tear from saltwater, off the top of my
head.

------
adamlett
I find it incredibly funny that a company in Switzerland has invented a way to
store energy that basically uses the same mechanism as… a Swiss clock!

------
Kagerjay
Not related but the first thing I thought of was flywheel regenerative braking
in cars, except that is storage in kinetic energy not potential energy

~~~
romdev
Also (mostly) unrelated to the story, but the first thing I thought of when
hearing about kinetic energy storage was a story I heard several years ago
about a data center that protected itself from catastrophic power surges by
using a massive spinning flywheel to store energy from the grid and harvest
its rotation to run a generator that powered the servers.

------
ENOTTY
Who knew Tetris could be used to solve climate change

------
anderspitman
Really cool. I wonder how efficiently (and safely) you could operate a small-
scale version in your back yard for personal solar panels.

------
Hello71
> He’s developed a machine that can mix substances that cities often pay to
> get rid off, such as gravel or building waste, along with cement to create
> low-cost concrete blocks. The cost saving comes from having to use only a
> sixth of the amount of cement that would otherwise have been needed if the
> concrete were used for building construction.

Notwithstanding the misspelling of "of", it seems like if this becomes
popular, such "waste" materials will increase in price, making the plan
unviable at scale.

~~~
svachalek
If they're so successful they've cleared the market for construction junk, I
think they're well past the viable stage.

------
dandare
This doesn't make a sense to me. Why not instead of a crane use a rope into a
deep well with a shaft with a conveyor belt?

------
v-yadli
Can we attach such things to the high buildings? Thus we can build low cost
distributed systems across a city.

------
Liron
How can a falling block generate electricity? Is it like a turbine that spins
very slowly as the block falls?

~~~
dagss
All/most electric motors are also electric generators. Similar to how electric
cars convert braking energy back to electricity.

------
kwelstr
"On a hot July morning, I traveled to Biasca, Switzerland, about two hours
north of Milan, Italy"

Ok, sorry for the off topic, but this annoys me to no end.

Two hours by plane is about 1400 miles, by car about 120 miles, by bicycle
about 25 miles, by foot maybe 6 miles, so why not give distance by miles or
km? Even if we are talking by car, then how do you know there are no traffic
jams on the way, or bad weather?

</please ignore rant>

~~~
Naga
Not sure about where you are from, but in Canada distances are routinely given
in hours or minutes, and it always means by car unless it is specified. As in,
"Toronto to Ottawa is around five hours, or an hour by plane."

~~~
kwelstr
And that's the problem, tell me 10 miles and it will always be 10 miles. Where
I live, in a rapidly growing city, 15 years ago it would take 15 minutes to
downtown from my house, now it takes 25 or 30. It's the same distance but
traffic has increased significantly in a short number of years.

------
skookumchuck
The blocks don't have to be concrete all the way through. Just need a shell,
and fill it with rubble.

------
mark-r
Would it be possible to use shaped blocks of rock instead of concrete? Would
that make it cheaper?

------
ryeguy_24
Earthquake = Big Waste of Energy

~~~
giomasce
That is true for other plant types as well: see for example
[https://en.wikipedia.org/wiki/Vajont_Dam](https://en.wikipedia.org/wiki/Vajont_Dam)
and
[https://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disa...](https://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disaster).

------
post_break
This is so cool! Could you replace the crane with mine shafts and lead
elevators?

~~~
CydeWeys
Not at even remotely the same cost, no.

------
Faaak
Seems quite useless to me as the earth's gravitational field is not very
strong.

Supposing that you could store the concrete blocks at a height of 50m (which
is already a lot), you would need roughly 8000 tons to store 1 MWh. Taking
account concrete density (2400kg/m^3), that's 19000 barrels !

~~~
monk_e_boy
I wonder why they dont put the blocks / dirt into train wagons and drive them
up hill. Then generate electricity through retroactive breaking as it
descends. Maybe the efficiency isn't 85%... but it sounds cheaper and simpler
to make.

~~~
andruby
See [https://www.aresnorthamerica.com/grid-scale-energy-
storage](https://www.aresnorthamerica.com/grid-scale-energy-storage)

------
rumcajz
Digging holes and filling them in again may be yet another way to go.

------
hayksaakian
How does it actually generate power from the stacked blocks?

~~~
pas
When it lets the down, they pull on the generator.

------
FrozenVoid
It would be much cheaper to use sand in reservoir.

~~~
pas
Sand is very abrasive, hard to pump, you need to build a reservoir, etc.

------
matell
instead of concrete blocks, they could be lifting LiPo blocks :)

------
cagenut
I wonder why just barrels, maybe to limit the scope for an academic project?
I'd love to see what could be done with the cranes that load/unload container
ships, daisy chained up a hillside like canal locks.

~~~
gonesilent
most dockside cranes recapture power on the way down as is.

