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A company is building a giant compressed-air battery in the Australian outback | |
0xE1337DAD wrote 15 hours 14 min ago: | |
Totho, has graduated from snap bows. | |
coryfklein wrote 20 hours 39 min ago: | |
What happens when you get a leak in a random seal in the chamber deep | |
under ground, does all the compressed air escape? How do you ensure | |
such a large reservoir stays air-tight for 20 years? | |
psadri wrote 21 hours 28 min ago: | |
While at it⦠they could try to extract some atmospheric CO2 from the | |
more concentrated air. | |
ck2 wrote 21 hours 29 min ago: | |
Why not lift super heavy but cheap objects like rocks or dirt and then | |
let gravity be your battery? | |
time0ut wrote 21 hours 22 min ago: | |
A company called Energy Vault[0] is (was?) working on this. I think | |
it is relatively capital intensive compared to what the company in | |
the article is doing. Of course storing underground requires | |
particular geology. | |
I also remember reading about a system that moved dirt/rock up a | |
mountain on a train. Canât find a link, but that also seems capital | |
intensive and requires different geology. | |
There is also pumped hydro storage that works via gravity. Thatâs | |
been around a while. My dad worked as an engineer on one in the 80s | |
[1]. | |
[0] [1] | |
[1]: https://www.energyvault.com/ | |
[2]: https://en.m.wikipedia.org/wiki/Helms_Pumped_Storage_Plant | |
samcheng wrote 21 hours 23 min ago: | |
They definitely do that with water. It's called "pumped storage" and | |
there are megawatt-scale installations all over the world. | |
ninju wrote 16 hours 43 min ago: | |
[1]: https://en.m.wikipedia.org/wiki/Pumped-storage_hydroelectr... | |
Pxtl wrote 21 hours 48 min ago: | |
I couldn't see in the article - is this using natural caverns or did | |
they excavate? I know the pilot versions of this tech generally use | |
old salt-caverns, like the one in Germany. | |
I'm actually pretty excited about this tech - it seems like solar and | |
wind are getting cheap faster than batteries will be able to meet the | |
needs for grid-scale energy storage, so a cheap-but-inefficient energy | |
storage tech is an exciting prospect. Massively overbuild the | |
solar/wind and use these things to defer the overflow. | |
pfdietz wrote 23 hours 0 min ago: | |
From a thermodynamic point of view, it should be noted that compressed | |
air does not actually store energy! The internal energy of a | |
compressed gas is from the kinetic energy of its molecules, and this is | |
a function only of temperature(*). | |
What a compressed gas represents is not stored energy, but stored | |
(negative) entropy. It is a resource that allows low grade heat to be | |
converted to work at high efficiency. This is what's to happen in this | |
facility: the heat of compression is separated out and stored, then | |
used to reheat the compressed air at discharge time. The energy is | |
actually being stored in that thermal store. | |
But there are other ways to do this that don't involve compressed air | |
storage. Instead, after the heat of compression is removed and stored | |
the compressed air could be reexpanded, recovering some of the work. | |
This would leave the gas much colder than when it started. This cold | |
could be stored (heating the gas back to its initial temperature) and | |
the gas sent around again. To discharge, the temperature difference | |
between the hot and cold stores could be exploited. | |
This is called "pumped thermal storage". I believe Google/Alphabet | |
has/had a group looking at this (called Malta). It has no geographical | |
limitations. | |
(*) Highly compressed air will store some energy because the molecules | |
become so crowded some energy is stored in intermolecular repulsion, | |
but that should be a small effect in this system. | |
schiffern wrote 18 hours 15 min ago: | |
Funny, when I saw the headline I thought, "I hope they're using a | |
trompe / Canot compressor or similar for efficient isothermal | |
compression and expansion." [1] [2] [3] Sad to see people are | |
misinterpreting the cleverness of isothermal compression, and | |
thinking it's "just" thermal storage. | |
[1]: https://www.youtube.com/watch?v=50fJ8Av_g7Q | |
[2]: https://www.youtube.com/watch?v=uvf0lD5xzH0 | |
[3]: https://news.ycombinator.com/item?id=27066295 | |
pfdietz wrote 18 hours 10 min ago: | |
How does that have anything to do with what I was saying? The | |
internal energy (per unit mass) of the compressed air at given | |
conditions is not a function of how those conditions were reached. | |
schiffern wrote 10 hours 45 min ago: | |
>The internal energy... is not a function of how those conditions | |
were reached. | |
How the conditions are reached makes a big difference in | |
efficiency. | |
I'm baffled at why you focus on minor implementation details like | |
internal energy at a particular snapshot in time, as opposed to | |
highly salient metrics like overall round-trip system efficiency. | |
zamadatix wrote 20 hours 36 min ago: | |
If I'm remembering this correctly from physics class then in math | |
terms this is described as U=C*n*R*T where U is the energy, the | |
constant C varies depending on the degrees of freedom the molecules | |
of the gas have, n is the molar amount of the gas, R is the ideal gas | |
constant, and T is the temperature. From that perspective it seems | |
impossible to raise the pressure without also raising n resulting in | |
a higher U even if you maintained a constant T while you did so? | |
pfdietz wrote 20 hours 15 min ago: | |
I'm talking about internal energy per mass of air, not per volume. | |
Sorry that wasn't clear. | |
foota wrote 20 hours 47 min ago: | |
Would it make sense to compress air, discard the heat generated, and | |
then use the compressed air later to increase the efficiency of a | |
turbine on a combined cycle plant? | |
pfdietz wrote 20 hours 41 min ago: | |
Yes, that's how old style CAES systems worked (although those were | |
not combined cycle). There are two of them. | |
[1]: http://www.eseslab.com/ESsensePages/CAES-page | |
crazygringo wrote 20 hours 52 min ago: | |
I understand what you're saying, but your claim seems misleading to | |
me. | |
Compressing air absolutely does store energy. It takes work to | |
compress it, and work will be done when it is allowed to expand. | |
Yes, one way of measuring the stored energy is by the resulting | |
increased temperature. Compressing air necessarily raises its | |
temperature. And then if you want to you can transfer that heat | |
elsewhere, go ahead. That's how air conditioners and refrigerators | |
work, after all. | |
But in the basic case, it seems entirely accurate to say that | |
compressing air does actually store energy. Just like raising a heavy | |
object against gravity stores energy. | |
SkyPuncher wrote 7 min ago: | |
Itâs absolutely misleading. The compressed air absolutely has | |
potential energy. Nail guns, air wrenches, etc convert that | |
potential energy into kinetic energy. | |
It seems like either this is describing an additional energy | |
storage/extraction method thatâs possible with these systems. | |
Either to improve the efficiency or something thatâs actually far | |
more efficient than utilizing kinetic energy compressed air can | |
create. | |
Itâs kind of like saying the water in a hydropower plant | |
doesnât store energy. The turbines arenât extracting energy | |
from the water itself. Theyâre extracting energy from gravity | |
acting on water. It doesnât matter if the water is nearly | |
freezing or nearly boiling, it has roughly the same amount of | |
hydropower available. | |
schiffern wrote 10 hours 21 min ago: | |
>Compressing air necessarily raises its temperature. And then if | |
you want to you can transfer that heat elsewhere, go ahead. That's | |
how air conditioners and refrigerators work, after all. | |
The oh-so-clever trick is to transfer heat elsewhere while you're | |
compressing the gas, so you actually reduce back-loading on the | |
piston instead of having it 'fight' the temperature rise. This can | |
be accomplished via water spray, or by compressing a gas bubble | |
that's surrounded by water (eg in the trompe). | |
By continuously removing heat as you compress the gas, it | |
effectively acts like a train of compressors and intercoolers with | |
an infinite number of stages, ie true isothermal compression. No | |
magic, just physics. | |
[1]: https://news.ycombinator.com/item?id=40278128 | |
pfdietz wrote 10 hours 18 min ago: | |
I want to note that in this system, where the heat is stored to | |
reheat the gas at discharge time, you want to produce heat during | |
compression. Doing adiabatic compression means you are storing | |
more heat, and therefore can produce more energy at discharge | |
time, than you could with isothermal compression (for a given | |
storage volume and pressure.) | |
This is unlike traditional CAES, where the air is reheated by | |
burning a fuel. There, fuel use is minimized by isothermal | |
compression. | |
opwieurposiu wrote 18 hours 11 min ago: | |
You can store about 10kWh of heat energy in your water heater at | |
home. | |
[1]: https://www.pvh2o.com/faq | |
KorematsuFredt wrote 19 hours 5 min ago: | |
Is compressed air in itself source of energy ? Or does it depend on | |
the external air pressure as well ? For example I compress air in a | |
canister and move it to outer space or deep underwater, does the | |
energy we can exploit out of it goes up or down ? | |
jmolinski wrote 9 hours 35 min ago: | |
Yes, if you take such a container into space, the gauge pressure | |
(pressure relative to ambient atmospheric pressure) goes up. A | |
cold gas thruster is a type of rocket engine that is basically a | |
pressurized tank of gas with a valve connected to a propelling | |
nozzle. The nozzle takes a high-pressure, low-velocity gas and | |
converts it to a low-pressure, high-velocity gas, and directs its | |
output generating thrust (which is a reaction force - Newton's | |
3rd law). The lower the ambient pressure, the higher the | |
expansion ratio of the nozzle can be, which results in a higher | |
output velocity of the gas, which directly increases the thrust. | |
It would give you a higher specific impulse, which is a measure | |
of fuel efficiency for reaction (thrust) engines. | |
pfdietz wrote 20 hours 44 min ago: | |
It doesn't store energy in the sense that all that work you did | |
compressing it doesn't increase its internal energy. It just has | |
the energy it started with, floating around in the atmosphere. | |
Now, some of that energy can be converted to work, if the air is | |
adiabatically expanded, but particularly at high compression it's | |
not large compared to the energy that went into compressing the air | |
(and that was dissipated as heat when the hot compressed air was | |
cooled.) | |
crazygringo wrote 20 hours 2 min ago: | |
But it does increase its internal energy. Its temperature goes | |
up. | |
Obviously if you let the compressed air cool, then you're letting | |
the energy dissipate. So if you want to preserve all the energy, | |
don't do that. | |
pfdietz wrote 19 hours 19 min ago: | |
The air that is stored underground has been cooled, so yes, the | |
energy that was added isn't there. | |
kobalsky wrote 20 hours 58 min ago: | |
the article doesn't mention how heat is stored, it just says "the | |
system extracts heat from the air and stores it above ground for | |
reuse". | |
do you know how they do it? | |
pfdietz wrote 20 hours 48 min ago: | |
I don't know in detail, but they could do something like this: | |
compress the air, making it hot, then run the hot air through a | |
packed bed of small objects (pebbles, bits of iron). As the air | |
goes through the bed the heat is transferred to the material. This | |
ends with a temperature gradient across the bed (hot at one end, | |
cooler at the other). To discharge, the flow of air is reversed: | |
in at the cool end, out at the hot end. | |
This sort of design (a counterflow heat exchanger, basically) keeps | |
the delta-T at each point low, so the system has low entropy | |
production. | |
A similar heat exchanger could be designed with a liquid thermal | |
storage medium, where the air and the liquid are flowed past each | |
other in opposite directions (separated by solid walls, most | |
likely). The hot storage tank would be insulated. An advantage of | |
this design is the pressure of the liquid storage tanks needn't be | |
high, unlike the vessel containing the pebbles in the earlier | |
described system. | |
All these may need to dump some waste heat to the environment as a | |
consequence of inefficiencies in the system. | |
foobarian wrote 21 hours 8 min ago: | |
I'm trying to reconcile how a consumer-grade compressor fits into | |
this. Clearly such a device can compress a few gallons of gas, which | |
could be allowed to cool to room temperature, and then used to spin a | |
small dynamo. This action clearly converts some amount of energy, | |
but where does it come from? Perhaps the problem is we're not | |
looking at a closed system at that point. | |
pfdietz wrote 20 hours 34 min ago: | |
The room temperature compressed air still has some internal energy, | |
and some of that energy can be converted to work by expanding the | |
air through a turbine. The air at the outlet of the turbine will | |
be really cold. Expanding compressed air through expanders like | |
this is part of how air liquefaction plants operate. | |
gparke wrote 20 hours 49 min ago: | |
I think you are right about the closed system. When the compressed | |
air spins the dynamo, it will cool, and then absorb heat from the | |
environment. In an ideal, lossless scenario, that heat is equal to | |
the heat given off when it cooled. So maybe you can view it as a | |
battery that stores the energy in the environment? | |
lazide wrote 21 hours 1 min ago: | |
If you empty that compressed gas, it cools everything it comes in | |
contact with. Room temperature gas still has a lot of thermal | |
energy. | |
The effect the prior poster was discussing is most apparent at | |
large scales when someone is doing actual efficiency analysis - | |
compressed air is not a very efficient way of storing or | |
transporting energy in most contexts. No one would use compressed | |
air for a power grid, because it would quickly be apparent how | |
terrible it is. | |
It is however a great way to transfer and use energy in many | |
industrial contexts, as turbines and pistons using high pressure | |
compressed air can be very compact while also being very powerful, | |
and have built in cooling. | |
At the level of typical household use, the efficiency effects | |
arenât notable. No one is going to care or even notice if it cost | |
1/2 cent of electricity (at the compressor) to use that air impact | |
wrench vs 1/10th of a cent to use an electric one. Especially when | |
the electric one is heavier and has less torque. | |
danhau wrote 22 hours 1 min ago: | |
Insightful, thanks! | |
pfdietz wrote 20 hours 47 min ago: | |
I should add that there's also some energy stored lifting water. | |
So this is not entirely a thermal store. I didn't run the numbers, | |
but I guess the thermal store stores > energy than is stored | |
lifting water. | |
watershawl wrote 23 hours 7 min ago: | |
This is a good solution (storing in rock) to get around the heat and | |
corrosion (from water) that above-ground tanks go through when storing | |
compressed air. | |
gcanyon wrote 1 day ago: | |
No mention of how efficient the energy cycle is? Without checking | |
sources, I think I've read that batteries and pumped hydro end up in | |
the 80-90% range round trip? Without knowing what this method produces | |
it's almost pointless to consider. | |
One advantage this has (I assume) is almost limitless cycle lifespan. | |
Pxtl wrote 21 hours 43 min ago: | |
Compressed air energy-storage is notoriously low-efficiency compared | |
to the alternatives. | |
The idea is that this is a hedge: if it turns out that solar/wind | |
become "too cheap to meter"? Then "efficiency" is meaningless and | |
what matters is cost-per-unit-storage and the hope is that | |
compressed-air will be able to store and output more | |
joules-per-dollar than any other storage method (regardless of how | |
many more joules you had to put in first). | |
usrusr wrote 18 hours 39 min ago: | |
Compressed air is notoriously low-efficiency when you do it like in | |
ye olden days, by venting the compression heat to the environment. | |
A-CAES means capturing that heat, storing it separately and | |
transferring it back into the decompression stream in discharge. | |
Yes, this means that there will be some trickle discharge loss when | |
using the storage scheme for long duration, but heat storage is a | |
happy square-cube law thing, at a certain scale it even become | |
viable for seasonal storage. A-CAES usually claim about 70% round | |
trip efficiency. | |
But you are right in that this number really isn't all that | |
important in the renewables age: when we are anywhere close to | |
getting to 100% renewables on a point of median supply and median | |
demand, production capacity (conversion capacity from sunshine and | |
air movement) at times when sun coincides with wind will so far | |
outpace demand that any energy sink will do that can still pay a | |
positive rate. We're a long way from fully renewable were I live, | |
and some days I see two thirds of turbines stopped in nice wind. | |
It's really all about capex per W and per Wh. Admittedly, A-CAES | |
isn't necessarily excellent in this right now, but it might scale | |
quite nicely with routine. | |
Recently there was a gravity storage scheme linked here on hn about | |
lowering mining refuse back into old mines to discharge, and | |
digging it back up to charge, which comes with the curious property | |
that it never really reaches a point of saturated capacity: in | |
theory you could keep digging new tunnels forever when energy | |
surplus keeps coming in. | |
littlestymaar wrote 1 day ago: | |
How do they work around the âheat problemâ with compressed air | |
storage. When you compress the air, it heats up, and actually there's a | |
big part of the energy that get stored in the form of heat, not | |
pressure. When you want the energy out the pressured air cools down | |
during depressurization. | |
If you were able to keep the air hot the whole time the process is | |
almost symmetrical so that's not an issue, the âheat problemâ as I | |
call it is how do you store this heat for an extended period of time? | |
At scale, it's much harder to keep than just the pressurized air. | |
The prototypes I've seen in the past were not storing the heat, but | |
relied on industrial fatal heat (that was lost anyway) but this also | |
has scale problem as you don't have that much available power except | |
near very specific industries (NPP are an option, as are other heavy | |
industries, but the supply is necessarily limited) | |
lolc wrote 13 hours 21 min ago: | |
They store the heat in a tank and feed it back on decompression. | |
littlestymaar wrote 5 hours 23 min ago: | |
Do you have any additional info about how they do that? (especially | |
cost-efficiently) | |
bluGill wrote 23 hours 37 min ago: | |
If the energy input is free/renewable they can ignore this to some | |
extent. Yes they lose a lot of energy, but who cares if the wind is | |
blowing/sun is shining making more energy than you need right now - | |
the other option is turning those systems off - either way they cost | |
the same $$$. | |
littlestymaar wrote 23 hours 20 min ago: | |
The problem is that you need this energy when you want to provide | |
electricity from the storage, which isn't the moment where energy | |
in general is cheap. | |
The positive aspect of such a system is that the thermal energy you | |
need is not subject to Carnot's law, so the temperature of the heat | |
source doesn't matter unlike most use of thermal energy (and that's | |
why you can use waste thermal energy in the first place) but you | |
still need a way to get that energy. | |
bluGill wrote 21 hours 51 min ago: | |
The air still is there whes you need it. The thermal energy is | |
lost but the pressure isn't. | |
littlestymaar wrote 19 hours 43 min ago: | |
Yes, but without the thermal energy you cannot depressurize it | |
in a turbine, because it gets so cold the air will start | |
condensing, and then you'll have droplets of nitrogen | |
destroying your turbines! | |
ourmandave wrote 1 day ago: | |
Well this changes the whole look and feel of future Bartertown | |
entirely. | |
They probably won't even have a Thunderdome. =( | |
hinkley wrote 10 hours 20 min ago: | |
Oh they'd still have Thunderdome. The population of pigs might be a | |
bit lower, however. | |
jimnotgym wrote 1 day ago: | |
What stops the air from just bubbling up the water pipe? | |
nashashmi wrote 23 hours 27 min ago: | |
. pipe | |
| | | | | |
|---|-|---water level --| | |
| |_| pipe end below | | |
|_______________________| | |
When the pipe is below the water level, air can't travel up the pipe. | |
caf wrote 1 day ago: | |
The water tunnel/bore would be connected to an opening at the bottom | |
of the chamber, not the top. | |
masteruvpuppetz wrote 1 day ago: | |
I found another technique quite fascinating.. When electricity is | |
surplus, spin large disk-shaped rocks levitated by magnets in a | |
vacuumed enclosure. Use this spinning motion to create electricity when | |
required. | |
okl wrote 1 day ago: | |
Exists, just not with rocks. I think the modern versions use heavy | |
metal blocks embedded in carbon fibre. | |
[1]: https://en.m.wikipedia.org/wiki/Flywheel_storage_power_syste... | |
mikewarot wrote 1 day ago: | |
I always wondered why compressed air storage systems work against | |
ambient pressure instead of having two tanks at high and higher | |
pressures. This would greatly increase the density of the gas, as well | |
as lowering the temperature differential. | |
It would take a long time to get it up to initial pressure, as there | |
would be a lot of heat to dissipate, but then it differential mode, the | |
gradient would be much better. | |
pjc50 wrote 22 hours 43 min ago: | |
I would have thought this is like the Carnot cycle: the greater the | |
difference across which you're generating energy, the better. So you | |
want the low side at as low a pressure as possible. | |
amluto wrote 23 hours 23 min ago: | |
Several reasons. | |
The first is fundamental: density is not really helpful for this sort | |
of application. The work done in expanding material (including gas) | |
at a given pressure is P dV, and the work done in moving material | |
across a pressure difference is V dP. Notably, mass doesnât appear | |
at all here, so adding more mass or density doesnât add energy | |
storage capacity in and of itself. | |
You can compute this more explicitly, and, for an ideal gas, the | |
useful energy extractable from a tank of gas at pressure P (under | |
ideal, isothermal conditions) is proportional to the change in log P. | |
So itâs actually rather more important to achieve low pressure | |
than high pressure. | |
On top of this, thereâs a practical consideration: the atmosphere | |
is an effectively infinite source of gas at 1 atm. If you are | |
working between high and higher pressure, you need two reservoirs. | |
All youâre gaining is less temperature change per unit pressure | |
change, but itâs probably the same amount of heat for any practical | |
purpose, so you still need an intercooler of some sort for good | |
efficiency. | |
bluGill wrote 23 hours 39 min ago: | |
Because with the tanks are not infinite size. That means as you | |
release pressure the differential between the two tanks equalizes in | |
the middle. Mean while in the current system the low pressure vessel | |
is effectively infinite and so you have more usable volume to work | |
with. Plus of course you can use both vessels to store energy instead | |
of one. | |
ssl-3 wrote 1 day ago: | |
Suppose we are driving a turbine. | |
Does having an increase in the density of gas present an advantage | |
over having a higher pressure delta by dumping to ambient for a given | |
volume of compressed-gas storage? | |
Why would I want one tank at "high" pressure, and another tank at | |
"higher" pressure, when I could just have one tank of "higher" | |
pressure to begin with? Or, better: Two tanks of "higher" pressure | |
in even less space than one of "high" and one of "higher" pressure? | |
(If the answer is "Because turbines work better with higher | |
densities," then: Do they work more-betterer-enough to make up for | |
the size and complexity?) | |
tromp wrote 1 day ago: | |
> the system extracts heat from the air and stores it above ground for | |
reuse. As the air goes underground, it displaces water from the cavern | |
up a shaft into a reservoir. | |
> When itâs time to discharge energy, the system releases water into | |
the cavern, forcing the air to the surface. The air then mixes with | |
heat that the plant stored when the air was compressing, and this hot, | |
dense air passes through a turbine to make electricity. | |
By "releases water into the cavern", do they mean simply opening the | |
air valve to let the air (pressured by the water) come back out? | |
usrusr wrote 1 day ago: | |
They don't really release water into the cavern, they release air out | |
(through the turbine stages). The water is never really held back. | |
It's a floating counterbalance for keeping the air pressure constant | |
(or mostly constant, considering surface reservoir level differences | |
which would never exceed a tiny fraction of the total water head, | |
unless the facility runs into extreme water shortage) | |
ajb wrote 1 day ago: | |
Yes, the diagram shows that the same water is used | |
foreigner wrote 1 day ago: | |
How does the air "push the water up"? What mechanism prevents the air | |
from simply bubbling up through the water column? I'm assuming some | |
kind of valve or piston, but would be interested to see what it looks | |
like. | |
Cthulhu_ wrote 1 day ago: | |
As long as the water pipe inlet is below the water level that isn't | |
going to happen. Think of a plant spray or super soaker, same | |
principle. | |
Nothing personal to the commenter I'm replying to, but I love | |
watching HN re-engineer long existing basic systems. | |
Slartie wrote 1 day ago: | |
Put the air inlet/outlet at the top of the cavern, and the water | |
inlet/outlet at the bottom. Then just stop pumping air while the | |
water level in the cavern is still above the water outlet. A little | |
water has to remain in the cavern at all times. | |
ulrikrasmussen wrote 1 day ago: | |
I wondered the same thing. I guess it would work if the water shaft | |
was actually U-shaped, but that would mean drilling three shafts | |
instead of one. | |
ajb wrote 1 day ago: | |
Why three? Their diagram shows two (plus the cavern, which must | |
already exist) | |
ulrikrasmussen wrote 23 hours 56 min ago: | |
To build a trap, the pipe would have to go almost all the way up | |
to the reservoir, then down, and then up again to connect to the | |
reservoir: [1] But there might another way to avoid bubbling | |
which I have missed. Maybe the compressed air is under so much | |
pressure that it becomes denser than the water? | |
[1]: https://en.wikipedia.org/wiki/Trap_(plumbing) | |
ajb wrote 21 hours 34 min ago: | |
It doesn't need to be denser than the water because the | |
incoming air is always above the water. | |
Imagine an cavern shaped like the great pyramid of Giza, full | |
of water. They dig two pipes, an air entry pipe to the point at | |
the top, and a water exit pipe to one of the corners at the | |
base. Air pumped in at the top pipe will almost evacuate the | |
cavern, before the water level drops to the point where air | |
could get to the exit pipe. | |
What this means is that depending on the shape of the cavern, | |
they may not be able to utilise its whole volume. In the worst | |
case, if its roof were entirely flat, they would not be able to | |
use any. They can use the volume of a section, bounded by | |
horizontal planes, from the air entry pipe either down as far | |
as the exit pipe, or (if the roof dips down between the two) | |
down as far as the lowest point on the highest possible path | |
between the two. | |
That's assuming totally vertical pipes. I know they can curve | |
them a bit, but I don't know if they can curve them enough to | |
enter a cavern from below. If they could, then they can utilise | |
the entire volume, as long as they can identify the lowest and | |
highest points | |
liftm wrote 1 day ago: | |
I'll assume the inlet is below water level / at the bottom of the | |
tank⦠| |
hackerlight wrote 1 day ago: | |
> The next project would be Willow Rock Energy Storage Center, located | |
near Rosamond in Kern County, California, with a capacity of 500 | |
megawatts and the ability to run at that level for eight hours. | |
Their California battery will be 4GWh capacity with a $1.5 billion | |
cost, which is $375/kWh. Their Australian one will be 1.6GWh for $415 | |
million USD, working out to be $260/kWh. Both are more expensive than | |
lithium ion, so I wonder what the case is for it. | |
jeffbee wrote 21 hours 38 min ago: | |
Also curious since the CPUC storage credit maxes out at 4h, so 8h | |
seems particularly pointless. | |
aoeusnth1 wrote 22 hours 3 min ago: | |
Probably these costs have a lot faster learning curves as they are | |
not as widely deployed yet. | |
humansareok1 wrote 22 hours 23 min ago: | |
>I wonder what the case is for it. | |
That there is a finite supply of Lithium available on Earth? | |
jillesvangurp wrote 23 hours 39 min ago: | |
The economics of batteries are a function of cycle limits (none in | |
this case, probably) and how much energy you can store and discharge | |
over time and the price difference between charging and discharging. | |
All that minus the upfront installation cost. | |
The article says this thing should last at least fifty years. There's | |
no good reason it couldn't last longer as it shouldn't really degrade | |
over time. If you assume daily charge/discharge cycles, that would be | |
about 18250K cycles over 50 years. Times 4GWh is about 73TWh of | |
energy sold to the grid at, hopefully, some profit. Of course that | |
all depends on demand, utilization, and whether there are any cheaper | |
ways to store energy. It's probably going to end up some percentage | |
of that. But best case that's energy you buy cheap and sell at a | |
higher price. Even a few cents difference starts adding up to | |
billions pretty quickly. And that's before you consider the | |
alternatives (buying energy on the open market from another provider, | |
investing in more energy generation, etc.). | |
The prices you cite are just the purchase price. And of course | |
lithium batteries don't last forever. So you'd be writing them off at | |
some point. But in fairness, there are some battery chemistries that | |
are getting quite good cycle times. So, the comparison might become a | |
bit more fair over time. | |
usrusr wrote 1 day ago: | |
One thing that hasn't been mentioned in siblings yet: the bulk of the | |
money, more if you lean further towards capacity in the capacity vs | |
throughput decision, is in the excavation. This is not only a | |
"forever" investment, it's also money spent on the local economy. | |
This isn't the case at all for battery cost, unless you happen to be | |
the world center of the battery business, all the way from mine to | |
recycling. | |
Another aspect, completely unrelated and I'm not sure hydrostor | |
already makes that part of the design (but it could totally be | |
introduced later, without invalidating any of the excavation | |
investment): some of the energy stored in an A-CAES system is stored | |
as heat. When you do need heat, for a district heating system, for a | |
swimming pool site or whatever, you can decouple some of the heat | |
from the pressure storage. Worst case some of the joules repurposed | |
end up missing in discharge, but it's also possible that they are | |
simply joules not lost to cycle inefficiency. And if you happen to | |
need cooling (datacenter on site?), at the time of discharge you can | |
just keep some of the stored heat untapped, substituting with energy | |
from the warm end of the coolant cycle that you want to freeload on | |
the A-CAES. Compared to other waste heat/cold coupling schemes, at | |
hydrostor pressure levels you would get considerably higher heat/cold | |
deltas to work with. Huge potential, and with the reservoir shaft | |
having very few site requirements, coupling opportunities should be | |
plentiful (as compared to e.g. opportunities that only ever arise in | |
remote valleys) | |
davedx wrote 1 day ago: | |
Yeah, also it takes 3 years to build. I predict that there will be so | |
much more lithium-ion batteries deployed by the time this is finished | |
that it will change the economics of operating it. | |
Ekaros wrote 1 day ago: | |
How do cycles and lifetime compare? More cycles over long time would | |
lower final unit cost. That is price of kWh at time of release. Which | |
I don't think will ever go down for load shifting. | |
In the end 3 figures really matter total capacity, power output and | |
cost per "generated" kWh on average over lifetime. | |
usrusr wrote 1 day ago: | |
The compressor/turbine part will have predictable wear rates, not | |
substantially different from what you see in fossil plants. | |
The reservoirs will at some point see noticeable sediment buildup, | |
but not at all comparable with surface pumped hydro based on | |
blocking valleys, due to the cyclic nature of the water flow in the | |
hydrostor facility. And occasional cleanout (measured in decades or | |
centuries?) will be trivially cheap compared to construction cost. | |
Very much unlike cleanout cost behind valley dams, which are | |
would-be cleanout costs because that never ever happens as it would | |
utterly dwarf the cost of the original dam. There's been an article | |
linked here a few months ago (can't find it, unfortunately) about | |
how the total capacity of pumped hydro is getting increasingly | |
smaller each year, despite new sites getting built. This is because | |
sedimentation already outpaces the buildup, and it will only get | |
worse the more we build. The volumes accumulating behind a dam are | |
just too big, unless you have zero natural flow from rainwater (and | |
then just getting the working volume of water to the site would be | |
prohibitively expensive, per capacity, even before you factor in | |
evaporation - the cycle capacity per unit of water is just so much | |
lower than what a hydrostor site would achieve with its much larger | |
head plus the energy stored in air compressionand heat) | |
RedRider73 wrote 23 hours 56 min ago: | |
Me I work with a turbine (Rankin Cycle) we use about perhaps | |
every day 22 or 3 reservoirs of 20 m3 just for the air | |
instrumentationâ¦. | |
richardw wrote 1 day ago: | |
"VanWalleghem said there is room to push costs down as the company | |
gains experience from these first few plants. The storage systems | |
have a projected lifespan of about 50 years, which is an important | |
data point when comparing it to battery systems, which have much | |
shorter lives" | |
So both longevity and working towards reduced costs for future | |
plants. I guess someone thinks the long-term costs will end up below | |
Li-ion, and likely lower environmental impact, at least compared to | |
the battery component. | |
hackerlight wrote 1 day ago: | |
Another benefit is it's all onshore, the US has energy security and | |
independence of critical industries from China as a priority. | |
hinkley wrote 1 day ago: | |
Installing power capacity is not O(1) complexity. | |
A battery UPS under my desk doesnât really affect my rent or | |
mortgage. Buildings not only need to get built they also need to be | |
maintained. | |
pier25 wrote 1 day ago: | |
What about emissions from lithium batteries manufacturing? | |
And how long do lithium batteries last? | |
dzhiurgis wrote 1 day ago: | |
> Both are more expensive than lithium ion | |
Are you comparing battery cell cost vs battery pack + structures + | |
electronics + lines + land + installation + different continent + N | |
other things I have no idea about? | |
zidel wrote 1 day ago: | |
BloombergNEF reports a cost of $115 per kWh for turnkey energy | |
storage systems (in China) so their comparison is likely to hold up | |
for complete systems in Australia and the US. | |
[1]: https://about.bnef.com/blog/global-energy-storage-market-r... | |
aplummer wrote 1 day ago: | |
Surely to prove and improve the technology? Being able reuse gas | |
technology as the article says, in Australia would be a boon - | |
thereâs an enormous CSG industry | |
affgrff2 wrote 1 day ago: | |
These are the costs of installation, but what about maintenance and | |
replacement costs? | |
dhaavi wrote 1 day ago: | |
My guesses: | |
1. no degradation | |
2. cheap to expand? - simply expand the cave | |
lukan wrote 1 day ago: | |
"cheap to expand? - simply expand the cave" | |
That is not cheap. And we have very high pressure here and not only | |
cave and rock, but technic around it. And pushing air in and | |
letting air out again will have degradation of that expensive | |
equipment. | |
greenbit wrote 1 day ago: | |
I must have missed something. Why not just use the water without the | |
compressed air, i.e., pumped hydro? There must be some advantage, but | |
they didn't seem to say. I'd guess maybe if your lower reservoir were | |
underground, the water-only would require the generator systems to be | |
down there, too, which would mean access for people as well, and being | |
down a mine with a small lake's worth of water overhead seems pretty | |
hazardous. Whereas by forcing air down to push water up, that whole | |
below ground aspect can be almost entirely passive. Maybe? | |
walrus01 wrote 22 hours 5 min ago: | |
The australian outback is not exactly known for its hills and | |
mountains... | |
Pumped hydro done on a large scale needs a reservoir that is at a | |
considerable elevation gain. | |
example: | |
[1]: https://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_... | |
BurningFrog wrote 23 hours 37 min ago: | |
Most places don't have a suitable mountain where you can destroy the | |
natural beauty with a dam. | |
In contrast, there is underground everywhere on Earth. | |
mozman wrote 1 day ago: | |
Have you heard of Snowy 2.0? Massive failure. Pumped storage in AU. | |
stefs wrote 23 hours 21 min ago: | |
I have not - why is it a massive failure? | |
pfdietz wrote 23 hours 8 min ago: | |
They've had problems with tunneling, I believe. | |
davedx wrote 1 day ago: | |
Yeah, I have to wonder how it compares to pumped hydro operationally | |
too. They talk about capital costs but didn't explore what opex would | |
be like at all. I would think with heat, air and water (as opposed to | |
water in pumped hydro), maintenance and operations will be more | |
expensive. | |
usrusr wrote 1 day ago: | |
I know of some pumped hydro sites that have been given up due to | |
opex, with no clear change of mind due to changing circumstances in | |
the decarbonisation age yet in sight. What they do have in common, | |
I think, is low head. There's just a lot of water to carry traces | |
of sediment into the mechanism, and so much reservoir ground to | |
keep from leaking for a given amount of capacity. | |
But you don't arrive at isobaric storage looking at mineshaft | |
pumped hydro wondering if it could be improved upon. You start | |
looking at constant volume (A-)CAES, either in high pressure tanks | |
at/near the surface or in salt caverns, and go from there, what of | |
we did not have to deal with a very wide range of operation | |
pressure. | |
taneq wrote 1 day ago: | |
The water's not there to directly store gravitational potential | |
energy, it's there to provide a variable sized containment vessel | |
under nearly constant pressure conditions. This has two advantages: | |
1) You're not losing thermal energy from the main body of air | |
(assuming their thermal recovery at the compressor works well enough) | |
because the change in air pressure only occurs at the compressor. | |
2) You get constant pressure and constant power output for the entire | |
volume of your compressed air storage, instead of both dropping | |
rapidly as air is released. This gives you far better bang for buck | |
per unit volume of pressurized air. | |
I haven't done the calcs but I'd guess that if they're bothering | |
doing all this extra stuff the energy stored in a cubic meter of | |
compressed air at these pressures is significantly higher than the | |
energy you'd get from just lowering a cubic meter of water down to | |
the reservoir. | |
usrusr wrote 1 day ago: | |
Compressed air and water head are in a balance, my physics | |
instincts strongly suggest that the hypothetical sum is 2x the | |
amount of energy stored by raising the water alone. But just like | |
you I do hope that my instincts are missing something! | |
(see nephew comment [1] ) | |
[1]: https://news.ycombinator.com/item?id=40273030 | |
taneq wrote 22 hours 40 min ago: | |
Hmm.. the more I think about it the more I agree with your | |
intuition. If the air's at constant pressure then the work it's | |
doing as it exits the chamber is coming directly from the water | |
entering the chamber. There's no difference (in terms of energy) | |
between having a turbine at the bottom of the column of water vs. | |
having the water push the air and then the air spin a turbine. | |
The whole thing seems like they started with "let's do compressed | |
air energy storage" and realised half way through that the best | |
way to do compressed air energy storage is for it to actually be | |
pumped hydro. | |
usrusr wrote 20 hours 54 min ago: | |
It's more capacity than just pumped hydro of identical head x | |
volume: even if we ignore the "compressed spring" of the air | |
involved, charging would require at least the energy for | |
lifting the water plus the energy for heating up their heat | |
source. If you close a valve in the water connection, then pop | |
open the air pressure vessel letting all energy still in the | |
compressed gas you to waste, you'd still have the heat storage, | |
and you could let the water rush into the lower reservoir | |
through a turbine, harvesting the entire energy contained in | |
the water (minus inefficiency). So it's definitely more, the | |
heat and the gas discharge we just wasted. | |
The question is how much more, whether the symmetry suggested | |
by the balanced state implies 2x energy storage or not. | |
Another mental model to further separate the two storage media | |
(water lift and air compression) is this: you could charge | |
separately, first raising the water with a pump, with the dry | |
cavity at ambient pressure via an open connection to daylight, | |
then seal the cavity an charge it as a compression vessel in | |
the non-isobaric way. I still can't decide between trusting the | |
"balance implies 2x" intuition or not, but it should be easy | |
enough to calculate. At least the thought experiments show that | |
it can't be 1x the energy stored by lifting water alone. | |
I consider starting with "let's do compressed air energy | |
storage" as a given, the "do it by pumped hydro" does not come | |
into play because pressure vessels are hard, it comes into play | |
because building compressors and turbines that have good | |
efficiency over a wide range of pressure is hard. | |
ajb wrote 1 day ago: | |
I think your answer is the correct one, rather than the replies. By | |
keeping all the machinery at the top, initial build and maintenance | |
costs are cheaper, they can use a cavern of any shape and at any | |
depth, and they only need to use drilling techniques not mining | |
techniques, which will be far cheaper . | |
hydrox24 wrote 1 day ago: | |
The short answer is that pumped hydro is mature technology with a | |
pretty wide range of places it can be implemented (at least in | |
Australia[0], which has a mountain range going down the east coast | |
where everyone lives). A-CAES has three advantages, which are in my | |
opinion aren't very fundamental: | |
1. It takes up less space on the surface than most PHES. This... is | |
almost always a marginal benefit. | |
2. It doesn't require building a reservoir or dam. These are very | |
well regulated in Australia and elsewhere, and the downsides are | |
known so they are quite slow to get approval. | |
3. It's a bit quicker at 2.5 - 3.5 years as opposed to 3-7 years.[1] | |
This is a bigger advantage than it looks if you have some tricky | |
renewable energy targets to hit by 2030 (see our 42% emissions | |
reductions target as well as an 82% renewable energy target) | |
I can't see this gaining traction outside of a few locations in | |
Australia, at least. I wouldn't be surprised if A-CAES is only | |
briefly viable as a result of subsidies and cheap government | |
financing. | |
[0]: [1]: | |
[1]: https://re100.anu.edu.au/#share=g-fa5a20c9c63f6ed6343a7e7573... | |
[2]: https://www.csiro.au/-/media/Do-Business/Files/Futures/23-00... | |
verelo wrote 23 hours 51 min ago: | |
I'd expand on your point (2) with these points. | |
1. Dams require water. Australia has suffered water supply | |
challenges as long as I've been alive. | |
2. Dams can be environmental disasters. Both building, maintaining | |
and one day destroying these has a lot of challenges and expenses | |
that we're not great at measuring. | |
pfdietz wrote 23 hours 14 min ago: | |
Pumped hydro consumes much less water than evaporative cooling of | |
a thermal power plant with the same energy throughput. Pumped | |
hydro doesn't have to be on an existing watercourse, so it | |
doesn't cause the environmental issues that come along with that. | |
rtkwe wrote 23 hours 30 min ago: | |
Not having to build and maintain a dam and find an appropriate | |
area to flood is a pretty large upside. Big thing in the US is | |
that we already have a lot of dammed lakes in mountains in some | |
places so we're really talking about making the water level more | |
variable and adding some infrastructure instead of building net | |
new lakes. | |
denton-scratch wrote 1 day ago: | |
Pumped hydro won't work unless you have a suitable mountain to | |
hand. Compressed air can be built in flat country. | |
usrusr wrote 1 day ago: | |
> with a pretty wide range of places it can be implemented | |
How so? Yes, if you dammed up most valleys you could build a lot | |
more capacity than humanity currently has, but that's because we | |
don't really have that much. A factor of two or so might be well | |
within range. But the total amount reasonably buildable simply | |
isn't enough, except for some very local scopes where demand is low | |
in both energy and in other use for the landscape that would be | |
taken over by reservoirs. And that's before you start considering | |
the geological realities required for actually building a dam, you | |
don't just need the geometric shape of a valley, you need the | |
bedrock to brace the dam against and the impermeability of the | |
ground required to not have leakage wash out pathways for ever | |
increasing leakage. Viable sites for pumped hydro are extremely | |
rare and quite a few have actually been given up decades after | |
building the dam, because the geology wasn't quite as cooperative | |
as hoped. | |
The promise of deep site water head CAES is that you can just throw | |
money at the problem (excavation) and get as much capacity as you | |
want to buy. The price per capacity is higher than that of a low | |
hanging fruit pumped hydro site, but many of those buildable have | |
already been built. | |
bryanlarsen wrote 1 day ago: | |
Most viable hydro sites are gone, yes. But you don't need a | |
viable hydro site for pumped hydro. What you need is water at | |
the bottom of a hill. That's common. | |
pfdietz wrote 23 hours 15 min ago: | |
Most primary hydro sites are gone. Pumped hydro can work in a | |
much wider variety of places, including in deserts. | |
[1]: https://www.whitepinepumpedstorage.com/ | |
jefftk wrote 1 day ago: | |
If you just have water at the bottom of the hill you'll need to | |
build a giant tank on the top of the hill. The best spots for | |
pumped hydro have a natural depression elevated above a water | |
source, so you can use that instead. | |
(I agree that this is different from traditional hydro | |
locations, and so there are many good spots still available) | |
bryanlarsen wrote 23 hours 53 min ago: | |
The best spots already have a reservoir up top, or most of | |
one. Pumped hydro is so much cheaper than other long term | |
storage options you can spend a little extra on the reservoir | |
and still come out ahead of competitors. | |
50 year old example: | |
[1]: https://en.wikipedia.org/wiki/Ludington_Pumped_Stora... | |
olau wrote 1 day ago: | |
The sources I've seen point out plenty of places. They may be | |
overoptimistic. But excavation is really expensive, and in a | |
competitive market, you cannot just throw money at the problem. | |
It's the same reason nuclear fission is dead in many markets. | |
Intermernet wrote 1 day ago: | |
Australia loves excavation. If you could double up mining with | |
pumped hydro you'd be the belle of the ball. | |
taneq wrote 1 day ago: | |
I've thought for a while that old open-cut iron ore pits | |
could be prime spots for 'inside-out' pumped hydro, like that | |
system that some German researchers were working which pumped | |
water out of submerged concrete spheres instead of up a | |
mountain. | |
psd1 wrote 22 hours 11 min ago: | |
If you have abandoned deep shafts, they may be smaller in | |
volume than an open pit, but they have several hundred | |
metres of head, so every kilogram of water is much more | |
effective than in schemes with less head. | |
globalise83 wrote 1 day ago: | |
It could make a nice option for huge abandoned open cast | |
mines - build a dam across the pit, flood it and then pump | |
water from one side to the other using solar-generated | |
electricity, allowing it to flow back to generate electricity | |
as and when needed. | |
For example: | |
[1]: https://www.news.com.au/technology/environment/aband... | |
rtkwe wrote 23 hours 28 min ago: | |
A big problem is those mines usually leave behind pretty | |
toxic remains so the water you're pumping around is | |
extremely hostile to the people and equipment you're | |
thinking of putting it through/near. Then there's the | |
chance of a dam collapse releasing that toxic water outside | |
the mine. | |
gregoryl wrote 1 day ago: | |
Let's not forget the extreme environmental impact a dam has. | |
pfdietz wrote 23 hours 12 min ago: | |
Those are for dams on rivers. PHES doesn't have to be on | |
rivers. | |
audunw wrote 1 day ago: | |
I suspect the maximum stored energy for the compressed air solution | |
is significantly higher. | |
Not only can you store the energy required to lift the water to the | |
surface, but after all the water is lifted you can keep compressing | |
the air in the closed reservoir to store even more energy. | |
If you only used water you could of course build an open reservoir | |
with more storage capacity instead. But maybe these will be built in | |
areas where thatâs not feasible. Itâd take much more space on the | |
surface, and you need to deal with evaporation. | |
usrusr wrote 1 day ago: | |
I do wonder, regarding the hydrostor approach, if the stored energy | |
(theoretical best, excluding all losses) is 2x the amount that | |
would be stored if it was just the water head (mass x height), with | |
air displacement served by an open connection to the surface, or if | |
there can be more to it: | |
Constant volume CAES would store energy without any water lift | |
involved, and with water mediated constant pressure CAES the lifted | |
water is added to the amount of energy contained in the "air | |
spring". But that's balanced at equal force in the force x surface | |
area x underground reservoir level system. My bird's eye view | |
understanding suggests that it would come down to 2x the amount of | |
energy stored in either (minus losses, of course) due to the | |
balance. Is that the maximum energy a water-column mediated | |
constant pressure A-CAES could hold, per water displacement volume | |
x head height, or am I missing something? That 2x would surely be | |
an improvement over conventional mineshaft pumped hydro, but it | |
would also define a somewhat sobering limit to the amount of | |
theoretical best case capacity. | |
Minor but perhaps very relevant detail: afaik, or rather as far as | |
I don't know, hydrostore aims at a shaft depth equivalent to a | |
pressure either right below of where pure CO2 would liquefy, or | |
right above where that happens (no idea about the boiling points of | |
N2, O2 and all those other main components of ambient air). I think | |
the target depth is not quite that deep, as in carefully avoiding | |
the "transliquid" range (as in transonic). | |
jusssi wrote 1 day ago: | |
You need to get replacement air to the cavern when you pump the water | |
up, and let the air to make room for the water when it's going down. | |
So you need a separate shaft for airflow anyway. I assume the rest is | |
just economics, it's probably a lot cheaper to have all the moving | |
parts easily accessible on the surface. | |
Edit: Also the fact, that if the pump was at the very bottom and it | |
failed, you'd need to have an alternative way to clear the cavern of | |
water in order to go down and fix the pump. | |
mywittyname wrote 22 hours 17 min ago: | |
Edit: Also the fact, that if the pump was at the very bottom and it | |
failed, you'd need to have an alternative way to clear the cavern | |
of water in order to go down and fix the pump. | |
Put the pump on a chain and hoist it up with a crane, like they do | |
with pumps in lift stations. | |
foota wrote 1 day ago: | |
I think you can store energy here not just in the gravitational | |
potential energy of the water, but also in the compression of the | |
air. I _think_ this means that you can get away with a smaller cavern | |
than you could for just pumped hydro. | |
You might think that you'd need a large amount of water to make the | |
energy release work, but I think it works like this. The force of the | |
water on the air/water interface is dependent not on the reservoir | |
volume, but on the weight of the water in the column (which depends | |
only on the height of the shaft). | |
By digging a very deep shaft, you can have a very large force of | |
water on the interface, and moving that interface an equal distance | |
hence releases more energy than it would with a shorter shaft. | |
This way, you can store an arbitrary (up to your ability to compress | |
air to a sufficient pressure, dig a deep shaft, and keep everything | |
from blowing up) amount of energy. | |
I think if you have a 1 square meter cross section of shaft, and the | |
shaft is 1 kilometer deep, then at the bottom the force of the water | |
above is the weight of 1 square meter * 1 kilometer, or 1000 cubic | |
meters of water, or 1 million kg. | |
The force then is 9.8Ã10^6 newtons. | |
Pressure is force/area, or 9.8Ã10^6 newtons/square meter here (since | |
we have a unit area). | |
There's a formula for the energy in compressed air, it's... involved. | |
I downloaded an excel file from here: [1] It says under this | |
pressure, a 1000 cubic meter tank of air at this pressure stores | |
~5000 KWh. | |
The one planned in California is supposed to store 4000 MWh, so I | |
guess they have a tank that is ~a million cubic meters. | |
A water tank of the same size would store ~2700 MWh of energy (e.g., | |
pumping that much water up a 1KM shaft requires that much energy), so | |
it does seem to be more efficient. | |
It may also be that hot air turbines are cheaper and easier to | |
maintain than hydropower turbines, but I'm not certain. | |
[1]: https://ehs.berkeley.edu/publications/calculating-stored-ene... | |
eastbound wrote 17 hours 55 min ago: | |
Did you mean 5000KWh (air) and 2700KWh (water), or MWh for the | |
second? | |
Also, 1000m3 in air is just a cube of 10m. It seems like a good | |
illustration of the convenience of air vs water. | |
foota wrote 17 hours 9 min ago: | |
The same size here is a million cubic meters, what I figure the | |
size of the planned California plant must be in order to store | |
4000MWH. | |
westurner wrote 22 hours 12 min ago: | |
Is there any pump efficiency advantage to multiple pressure vessels | |
instead of one large? | |
You could probably move the compressed air in a GPE gravitational | |
potential energy storage system, or haul it up on a winch and set | |
it on a shelf; but would the lateral vectors due to thrust from | |
predictable leakage change the safety liabilities? | |
Air with extra CO2 is less of an accelerant, but at what | |
concentration of CO2 does the facility need air tanks for hazard | |
procedures? | |
FWIU, you can also get energy from a CO2 gradient: | |
"Proof-of-concept nanogenerator turns COâ into sustainable power" | |
(2024) [1] And, CO2 + Lignin => Better than plastic; "CO2 and | |
Lignin-Based Sustainable Polymers with Closed-Loop Chemical | |
Recycling" (2024) [2] From "Oxxcu, converting COâ into fuels, | |
chemicals and plastics" [3] : | |
> "Solar energy can now be stored for up to 18 years [with the | |
Szilard-Chalmers MOST process], say scientists" | |
> [...] Though, you could do CAES with captured CO2 and it would be | |
less of an accelerant than standard compressed air. How many CO2 | |
fire extinguishers can be filled and shipped off-site per day? | |
> Can CO2 can be made into QA'd [graphene] air filters for [onsite] | |
[flue] capture? | |
"Geothermal may beat batteries for energy storage" (2022) [4] : | |
> FWIU China has the first 100MW CAES plant; and it uses some | |
external energy - not a trompe or geothermal (?) - to help compress | |
air on a FWIU currently ~one-floor facility. | |
[1]: https://news.ycombinator.com/item?id=40079784 | |
[2]: https://news.ycombinator.com/item?id=40079540 | |
[3]: https://news.ycombinator.com/item?id=39111825 | |
[4]: https://news.ycombinator.com/item?id=33288586 | |
pjc50 wrote 1 day ago: | |
> The force of the water on the air/water interface is dependent | |
not on the reservoir volume, but on the weight of the water in the | |
column (which depends only on the height of the shaft). | |
Just wanted to highlight this, since it's the key insight which | |
caused this to "click" for me. | |
The difference between a 1km shaft and a 1km deep reservoir, when | |
both are used for pumped hydro, is the amount of energy stored. | |
Running a turbine at the bottom of the shaft (to where?!) would | |
drain very quickly. But using air, which has very different | |
properties, enables you to use the water as a "piston" to keep the | |
air at a certain constant pressure underground. And you can store a | |
larger volume of (more compressible) air in a space which is easier | |
to access. | |
logtempo wrote 1 day ago: | |
also water tend to be scarse nowaday and valuable nowaday. | |
867-5309 wrote 1 day ago: | |
they say, writing from an ocean planet | |
droopyEyelids wrote 23 hours 52 min ago: | |
Salt water is a nightmare to include in any sort of mechanical | |
system. It is super corrosive itself, enables galvanic | |
corrosion, and is so âfertileâ biologic fouling is a big | |
issue. | |
trenchgun wrote 1 day ago: | |
>I think you can store energy here not just in the gravitational | |
potential energy of the water, but also in the compression of the | |
air. I _think_ this means that you can get away with a smaller | |
cavern than you could for just pumped hydro. | |
+ they are storing the heat extracted from compressing the air. | |
fanf2 wrote 1 day ago: | |
I want to know how this heat storage works. It seems kind of | |
important? | |
lucioperca wrote 1 day ago: | |
isn't that used when decompressing the air, i.e. closed loop | |
jagged-chisel wrote 19 hours 2 min ago: | |
You just pull that from the atmosphere. | |
Compress to store [potential] energy, take the heat generated | |
during compression and use it, decompress at time of need and | |
let the [hot?] atmosphere supply energy to the decompressing | |
gas. | |
I wouldnât call it a closed loop, but maybe a lack of | |
deficit. | |
JoeAltmaier wrote 1 day ago: | |
A solution to deep water pumping is to lower the pump(s) into | |
boreholes. Nobody has to go down there. | |
willvarfar wrote 1 day ago: | |
Yes this is normal even in normal residential wells. Boreholes are | |
just a few inches across so obviously nobody ever goes down them! | |
I have an injector pump that sits at the top of the borehole and | |
has a pipe that pushes water down to pump water up through a second | |
pipe, but it's more common to have a submersible pump down at the | |
bottom of the bore. | |
JoeAltmaier wrote 1 day ago: | |
I've wondered how well the inject-pump style works! Do you have | |
experiences to relate? All the electronics are up top where you | |
can get at them. Has the mechanism at the bottom ever needed to | |
be serviced? Can it be retrieved easily? | |
bluGill wrote 23 hours 51 min ago: | |
You can pull the parts out of the hole anytime you want to - | |
special equipment is normally used, but a rope and a tripod to | |
hold a pulley over the hole works (might not be safe). | |
What is at the bottom of the hole is a "injector" which is | |
basically a U shaped pipe and a small jet to push water back | |
up. If the well water is only 25 feet below the ground a pump | |
at the top along works. This jet system gets down to 60 feet. | |
The pump down the hole gets to 600 feet (check the pump specs - | |
many are rated to only 250). After that you need oil well type | |
pumps where the motor is at the top of the hole but the pump is | |
lowered down. | |
willvarfar wrote 23 hours 26 min ago: | |
(I can't find any English lit on it, but my Grundfos | |
Ejektorpump (had to go out and look at it to see what it's | |
called; perhaps the correct translation is ejector pump | |
rather than injector pump?) is in a 85m deep borehole and | |
works great. It's 40 years old, heavily used and never | |
serviced and quite a puzzle how it's still going. I have no | |
idea if they can pump from deeper than that) | |
JoeAltmaier wrote 22 hours 24 min ago: | |
Some designs might have no moving parts down there? Nothing | |
to go wrong. | |
willvarfar wrote 22 hours 10 min ago: | |
You made me more curious to find out about it. [1] Two | |
normal plastic water pipes descend down to the bottom of | |
the borehole. At the bottom is a brass u-shaped fitting | |
with a inlet with a non-return valve. | |
[1]: https://www.vvsbutiken.nu/product.html/ejektorer... | |
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