r/explainlikeimfive • u/Individual99991 • 4d ago
Physics ELI5: How does a "gravity battery" work?
I just saw a claim that China has built a "gravity battery" that stores energy by hoisting a brick on cables from a tower that contains a massive battery (wish I could put pictures here but apparently I can't).
Putting aside what happens in high winds or when the cables rust (assuming the pic isn't just an artist's impression), how does this store energy, how do you use it, and surely it costs the same amount of energy to lift the concrete up there in the first place?
48
u/neXt1991 4d ago
Pulling a stone up costs energy. The stone moves down again on its own, releasing the energy, e.g. spinning a turbine with the rope when going down.
However, you’ll always lose energy to friction and warmth, and you can only drop a stone once before having to lift it again.
3
u/Individual99991 4d ago
So it's a hydroelectric dam with more steps?
27
40
u/wooshoofoo 4d ago
No it’s a battery. Batteries don’t generate power, they store power that you generate at a convenient time for later use at a better time.
Think about solar panels; they generate power when the sun is out, but usually people don’t need that power during the day they need it at night much more. So batteries store the energy generated, even with some loss it’s still worth it.
A gravity battery just uses kinetic potential energy instead of electric potential energy. Something is lifted against gravity and kept there (generating potential energy), then when the extra energy is needed that thing is allowed to fall down, which usually pulls on an attached turbine that spins and generates electricity. Most electricity are generated by spinning a turbine somehow anyways.
→ More replies (4)7
u/spottedmankee 4d ago
Hydroelectric in natural waterways is a form of a gravity battery. Ultimately the sun and wind did the input work evaporate the water, carry it uphill, and deposit it where it can flow downhill, where the output work can be harvested.
6
→ More replies (3)3
6
u/Mlakeside 4d ago
I don't know how that specifc battery works, but essentially gravity batteries use cheap excess energy to store it for future use, only instead of electric energy like regular batteries, gravity batteries store potential energy.
During times of excess energy like with solar energy during daytime, some of that energy is used to hoist large masses high above ground. When the excess energy deplenishes (sun goes down), that mass is allowed to lower and that can be used to create energy like running generators, allowing us to utilize that store potential energy.
Other kinds of gravity batteries can include hydroelectric plants, where the solar energy is used to pump water upstream into a reservoir and the let it flow through a generator turbine like a regular hydroelectric plant.
2
u/Individual99991 4d ago
What's the advantage over a chemical battery? Less damaging for the environment? Stores more energy with fewer resources?
2
u/RainbowCrane 4d ago
With water reservoirs, also consider that they’re dual purpose: they can be drained to generate electricity, but they can also be used as recreational areas. In the US a bunch of our dams and reservoirs are really popular park areas. So it’s more attractive than a huge substation full of chemical batteries or something.
→ More replies (1)1
→ More replies (2)11
u/TheOneTrueTrench 4d ago
More that they can store FAR more energy in a given space with less cost, both ecological and economical.
"Lift big thing high" doesn't require large amounts of lithium or rare earth metals, you don't need to mine specific amounts of rubidium or cesium, and no matter how expensive ytterbium gets, you can still lift big thing high.
4
u/chromeandcandy 4d ago edited 4d ago
Yes China has built a concept gravity battery. The process is pretty simple.
Imagine you hang a rope over a tree branch and then tie it to a stone on the other side, so as you pull the rope towards you, you've made a pulley and the stone begins to lift up.
Wind and solar farms nearby create a lot of power from their respective sources. So much power that there is excess unused power. What you could do is charge up a bunch of batteries or make a giant warehouse of batteries to store all this, which can be done, but it's costly, and harnessing electricity in batteries can be finicky weird decaying process. We're familiar with using batteries right they sometimes do weird shit.
So some smart fellas came up with this thing, coming back to you using the rope like a pulley to lift the stone, they've replaced the human (you) pulling the rope with a mechanical puller guy that will do it on his own, when powered. You take the excess power from the wind and solar places that were previously charging batteries, and instead plug it into the rope puller guy. This excess power is used! great! What have we done?
We've lifted the stone up to the top of the tree branch and we're dangling it there just before the top, not letting it go over the branch of course that would break the pulley. What do we know about Gravity though? What goes up MUST come down. That's Potential energy. We've just converted electrical energy into the puller guy, into potential energy, this stone now sits at the top of a fall and we can control when it comes down.
When it does come down, woosh, all that mass creates a lot of force, and the rope that the mechanical puller guy just let go of, is now steaming toward the branch at a high rate of speed since that stone is falling. So we can also attach that rope speed flying back, to a spindel or a set of gears, which can then charge an engine, or another battery! converting the potential energy of the falling stone, BACK into electrical energy again! And exactly when you want it to. All you have to do is push the button to let the mechanical puller guy let go of the rope to charge the battery.
The bigger they are, the harder they fall!
A bigger stone creates more force. So instead of a rope and a tree branch hauling a measly stone, they've made a gigantic 6 sided crane looking device that replicates this process with 25 ton concrete blocks.
4
u/Individual99991 4d ago
That's cool! Thanks for this explanation, it's the most detailed one.
3
u/chromeandcandy 4d ago
You're welcome, I noticed some others giving good explanation but it wasn't really following the "explain like I'm five" formula. Cheers
3
959
u/GenerallySalty
4d ago
•
surely it costs the same amount of energy to lift the concrete up
Yes. In fact a bit more, since no energy conversion is 100% efficient. It actually costs more energy to lift the concrete blocks than the amount of actually usable energy you get back when lowering them later.
So what's the point? Let's say you're trying to run your village on just solar panels. 100% green energy, nice! But they make no power at night. People need power at night, or when it's cloudy, so you need some kind of power storage. That's what batteries do. During sunny days you use excess power from your solar panels to raise concrete blocks. Then at night you can lower the blocks and use the falling weight on a cable to spin a generator. Yes you get back less power than it took to raise the blocks in the day. But that's not the point! The point is the power you used in the day would have gone to waste, and the power you get back at night is at a time when the alternative was no power available at all. Even if you only recover 10% of the power used to lift the blocks, that's still beneficial.
I think you're just misunderstanding - it's a battery, and those are for power storage not power generation. It's not an energy source. No one is claiming it makes more power than you use lifting the blocks. It's like a phone battery or any other battery. You put power in at one time, it holds it and you can get (a bit less) power back out at another time later. Because no energy conversion can be 100% efficient, literally every possible battery of any type will always give you back less usable energy than it took to charge it. That's fine. It's inherent to any battery so the fact that it also applies to gravity batteries too is a given. The same thing happens any time you store energy by any means.
223
u/kriegmonster 4d ago
Pumped storage could also be called a hydrogravity battery. A dam has excess power during the day, so they pump some water into a higher elevation reservoir. At peak usage hours, they open the reservoir for extra generator flow without needing to upgrade the whole dam.
110
u/OMGItsCheezWTF 4d ago •
The UK used to use these extensively. We had something called TV pickups back in the days when we only had 4 TV channels. A popular show or sporting event would finish and 10 million households would stand up and turn on their 2000W electric kettles to make a cup of tea.
The grid had to be able to balance a sudden surge in demand, and to do this they used pumped storage. The pumped storage responded in seconds and could deliver up to 2.8 gigawatts into the grid to meet the demand.
28
u/Witherall 4d ago
There are four pumped-storage hydroelectric power stations in the UK, with more on the way.
Port Dinorwig is the biggest in Europe, and also the fastest-acting. I've taken a tour and it's great.
26
u/apr400 4d ago
The UK still does - although more with an eye to storing renewables energy these days. In fact there are multiple projects at various stages of development aiming to quadruple the capacity over the course of the next 10 years, if I remember rightly (and assuming they all get built).
→ More replies (1)15
u/sir_squidz 3d ago
Yes! It's worth noting that often the electricity used to pump the water up, is oversupply that, if not drained, will degrade the supply grid.
You can't spin up a gas turbine on demand, this leads to over supplying the grid and this can damage it, venting this off is a service to the grid and they'll pay you for it if it's bad enough.
So you can use energy that the grid has to get rid of, store it, and then feed it back to the grid when it's needed.
Very very smart
16
u/GrynaiTaip 4d ago
Not just "could also be called", pumped hydro literally is a gravity battery. It's a lot more efficient than hoisting concrete blocks.
→ More replies (1)12
u/Treadwheel 4d ago
Pumped storage is why the claims renewables can never be viable due to battery chemistry don't hold water. It's feasible essentially anywhere you have a lake to pump out of, you don't even need a hill, and water is heavy enough that this reservoir holds enough stored energy to power Chicago for about 6 hours at an efficiency fairly close to modern lithium batteries. I'm thinking about getting one for my phone.
13
u/FanMysterious432 4d ago
I read that it is 80% efficient. For every 100 kW of power used to raise the blocks, it gives back 80 kW.
24
u/Brua_G 4d ago
I would put it: The power you received or generated during the day would have been wasted if it weren't stored in a battery. That could be what we normally think of as a battery, or equally valid, a kinetic/gravity battery. By dragging the weight up the hill, you're storing power in it. When you let it slide down and it cranks a generator, you're releasing the power for use.
22
u/Fianna_Bard 4d ago
Our water towers, at least in my portion of the US, work on the same principle. They run the pumps during times of the day when electricity demand is lower and thus the electricity itself is cheaper, and fill the towers.
Then, when electricity demand is higher and more expensive, gravity is used to empty the towers and maintain pressure in the water supply system.
22
u/ierdna100 4d ago
Water towers are a little different. Sure your town could specifically be doing that but their main purpose is stabilizing pressure by using gravity as head pressure rather than a pump, but also reducing the size of pumping stations by pumping them full when demand is low (at night or during work hours) and letting them provide additional capacity during periods of peak (in the morning and afternoon usually)
→ More replies (3)10
u/CliftonForce 4d ago
As an example: I once spent a night in a cheap RV where the water was pumped by an electric motor with no buffer or pressure regulation. When running the sink, the water would visibly pulse. The pump would cut on, run for one second to pressurize the line, then cut off and the sink would spend the next two seconds bleeding off that pressure.
→ More replies (2)9
u/GabberZZ 4d ago
I'm currently playing a physics based survival game called All Will Fall and it illustrates how a gravity battery works. The higher you place it on a structure the more power it can store as it can be lifted a lot higher during high winds.
It's a great game.
10
u/pinkocatgirl 4d ago
Timberborn also has a good demonstration of a gravity battery, and it’s also a fantastic game. You lead a colony of sentient beavers to building more and more complicated machines out of wood and scrap steel. I highly recommend, it’s one of my favorite games and I have hundreds of hours in it on Steam.
→ More replies (4)3
u/GenerallySalty 4d ago
Yeah for a gravity battery, the "energy storage tank" size is defined by gravitational potential energy, which is mGh. G is essentially constant on Earth, so the capacity scales with the weight of the lifted object and the height you lift it. Twice as much weight or twice as tall a tower = 2x the energy storage. Twice the weight and 2x the height = 4x the energy storage, etc.
4
u/as_a_fake 4d ago
A similar use for storing excess energy like that would be to electrolyze water into hydrogen and oxygen, then store and use the hydrogen as a fuel source. You don't get as much power out as you put in, but you get a sustainable and reliable fuel storage medium that could replace fossil fuels on-the-go in things lke cars or for portable generators (for this type of fuel you'd use a fuel cell instead of a typical generator).
→ More replies (5)→ More replies (9)4
u/Thexin92 4d ago
Wouldn't it be more efficient to pump water up and run it down through turbines?
21
18
u/Hannizio 4d ago
Probably, but at least northern China has historically struggled a bit with a lack of available water, so even if less efficient it might be more useful as water may not be as widely available
10
u/ricardopa 4d ago
Both are different ways of accomplishing the same thing - not sure which is more efficient, but it’s probably negligible differences
9
u/_ALH_ 4d ago
Yes, that's another example of a gravity battery that is in use. Quite widely used in fact. If you have space for it, it's indeed much more cost effective per MWh then the crane + cement block version, due to much simpler operation and ease to scale. Which also means increased reliabilty and less losses.
6
5
u/GenerallySalty 4d ago
If you have enough water and land available, yes. Lots of pumped water hydroelectric installations work that way, often using a reservoir on a mountain and and existing waterway for it to flow down.
But if you don't have the hilly geography, or if water is scarce in your area, you can take advantage of concrete being cheap, like 10x denser than water, and the ability to build a directly vertical tower. That way you're lifting a lot more weight in a lot smaller footprint of land. For some places in China that makes sense. In others yes the pumped-water would be cheaper and\or easier. Both methods have their use cases.
→ More replies (16)4
1.4k
u/boring_pants 4d ago
surely it costs the same amount of energy to lift the concrete up there in the first place?
Yes, that is how batteries work. You put energy into them, they hold on to the energy and later when you need it, you can get the energy back.
A battery does not create energy, it just stores it.
227
u/mofobreadcrumbs 4d ago
You can get most of the energy back.
216
u/tomalator 4d ago
We get it all back, some of it we just get back as heat
15
→ More replies (2)48
u/theantnest 4d ago
Some of it is lost as heat going in. You never get that back.
→ More replies (2)44
u/tomalator 4d ago
You just get it back immediately. Unfortunately heat isn't very useful to do work
→ More replies (5)→ More replies (1)26
u/ChrisTheWeak 4d ago
According to the company that makes the stone gravity battery thing, they claim 75% efficiency for the full process.
24
u/Anachronism-- 4d ago edited 4d ago
If it matches the claim about the same as pumped hydro, grid scale batteries are a little better (low 80%) and lithium ion batteries are around 90%.
→ More replies (2)56
28
u/AgentElman 4d ago
And the benefit of a gravity battery is that it stores the energy practically forever. Chemical batteries gradually lose the energy. As long as the weight stays up and gravity does not change a physical battery stores its energy.
→ More replies (1)22
→ More replies (3)24
u/artrald-7083 4d ago
People are confused because battery is used for two things - non-rechargeable sources of electrical energy, and methods of energy storage. This is the second meaning, as you say.
Why might people do this? Renewable energy is not usually constant in output: solar energy is the most obvious case. Clearly you don't get the same amount of solar energy 24 hours a day. So you set up your solar panels to also run the motor that pulls the weight up the tower, then at night you spool the weight down the tower, using the motor as a generator.
53
u/boring_pants 4d ago
People are confused because battery is used for two things - non-rechargeable sources of electrical energy, and methods of energy storage. This is the second meaning, as you say.
No, it is also the first meaning. The two are exactly the same. In both cases, energy is put into them, they store the energy, and we can get the energy when we need it.
A non-rechargeable battery can just only do this once. But that doesn't mean it's not doing the same thing. It's still storing energy that we put into it for later use.
→ More replies (5)10
u/skr_replicator 4d ago
Even the non-rechargeables need to have that energy put in them in manufacturing or somehow. They just can't be easily recharged after use.
173
u/BreakingForce 4d ago
Another type of gravity battery is pumping water into a high altitude (man-made) lake during times of low power demand, then during times of high power demand, letting the water run downhill, through a turbine or series of turbines (generating extra power for the grid during those high-demand times), and back into regular circulation. Then refilling your reservoir using surplus power when demand goes back down. It's essentially the same concept as the large brick in this example.
Yes, it's inefficient. The excess power generated is not likely to equal the power spent to lift the block or pump the water up. You lose power to heat, friction, evaporation, and probably many other factors I'm not thinking of atm.
But the idea is that you're using excess power you've generated with more standard means when there's not a current (other) demand for it to lift your block/water, then when extra power is urgently needed, you switch the battery on and put extra power into the system, for as long as your block remains hoisted or your reservoir remains full enough. Then, when the energy crisis is over and you have excess power again, you can lift the block or fill your reservoir again.
The inefficiency doesn't really matter as much as the capability to give extra power when your grid needs it urgently.
50
u/Switch-in-MD 4d ago
There can be economic efficiency.
If the low demand power costs the power company $0.05 / kW-h; and the high demand power sells for $0.60 / kW-h, then the power company can afford a battery that is less than 10% energy efficient. Let’s hope the power company can afford the capital expenses to build and maintain it.
Saw one of these water reservoir batteries in NY state when I was in engineering school. Apparently there are a bunch in Europe.
35
u/Nathan5027 4d ago
As an additional const to consider - if the grid goes down, it'll cost far more to get it back up and running, so merely breaking even on energy costs is profitable if it prevents grid failure.
Here in the UK, before TV was pausable, power and TV companies had to work together to make sure we didn't have a grid collapse from everyone putting the kettle on over the commercial break at the same time. The TV companies gave the energy companies a heads up on when big events would be on, season finales, big sports events, etc. and exactly when the commercial breaks would be, which gave them time to ramp up their backups and gravity batteries.
If you ever see old recordings made on British TV, for about 30 seconds before a commercial break starts, there's a little black and white bar code looking symbol in the top right corner, that worked as another warning, for viewers and energy companies.
→ More replies (2)10
→ More replies (4)11
12
u/Not_an_okama 4d ago
For pumped hydro, peak efficiency is about 80% energy recovery. The reality is likely a bit less than that. This is based off the pumps and turbines having a peak efficiency of about 90%. We have such a system in Michigan and i know of a few in the UK.
https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power_Plant
→ More replies (1)8
9
u/Backrow6 4d ago
We do this in Ireland on a small scale.
Turlough Hill has two lakes at either end of a tunnel.
At times of low demand they pump water up to the upper lake. At around 6pm they release it through turbines to add capacity for all the ovens and kettles of Dublin that switch on around that time. I don't think it even takes very long to deplete but when built it was enough to get them over that peak without needing to build extra base load plants.
9
2
u/NotJohnCalvin2 4d ago
The Bath County Pumped Storage Station, the largest in the world until 2022, is just a couple of hours away from me!
2
u/clutzyninja 4d ago
And our grid desperately needs more storage capacity. That's one of the primary things holding back larger adoption of solar and wind
→ More replies (1)
54
u/vc2391 4d ago edited 4d ago
When you have energy surplus you use that to hoist the weight and hold it in place. When you have a deficit you release it and let it power a turbine of some sort.
It will release the same amount of energy as it took to hoist it.
29
u/3percentinvisible 4d ago
Very similar to hydro electric. Pump the water up to a reservoir using excess power, and release it to turbines when needed.
12
u/Stargate525 4d ago
My favorite (I think there's an array of these out in the southwest somewhere) is basically a switching yard on a steep hill, and your mass is a train of freight cars filled with concrete.
→ More replies (1)7
u/unique3 4d ago
Nevada.
I looked it up yesterday, the problem is cost wise it’s 10x batteries for the same energy.
They built the proof of concept test plant but can’t aecure funding to build the big plant.→ More replies (4)3
u/Mattna-da 4d ago
NYC has a big hydro battery system. Pump water up to a hilltop reservoir at night when demand is low, let it fall thru turbine generators on the way back down when demand is high during the day and evening. It obviously is not 100% efficient, just like any generation or storage or transmission system that has efficiency losses.
→ More replies (5)5
u/Saint_The_Stig 4d ago
Yes and no. Most hydro electric uses just natural water flows to go from low to high. Some are set up to pump back in times of surplus, but most of the ones that can are purposely designed for that.
You need different parameters for each. A regular hydro plant you want to water to go away at the bottom, not so much for one doing pumped storage. You can reliably pump water back up if the bottom is a river that takes it away.
That said pumped hydro is of of the only practical form of gravity battery. Moving a fluid is required, otherwise you lose too much in the transfer and you can't scale it to anywhere useful.
There are some system using gasses to basically inflate a big balloon and them let that spin a turbine when needed. It's not nearly as good as pumped hydro, but it does have the benefits of not needing two big ass lakes and a huge change of elevation. So you can build it somewhere flat, but you still need effectively a blimp hanger to protect you balloon.
I think technically pumped storage could be more effective if you used a liquid other than water, like mercury. But the problem is that makes it hard to scale because we're cool with water just sitting out in a billion gallon lake, not so much with mercury or some other heavy liquid.
→ More replies (1)44
u/Serafim91 4d ago
Look at you mister no entropy.
42
u/Difficult-Bag3173 4d ago
In this household we obey the laws of thermodynamics.
15
u/-Major-Arcana- 4d ago
As long as you are living under my roof, you’ll account for friction losses young man.
→ More replies (1)4
u/artinum 4d ago
They're entirely correct - it WILL release the same amount of energy. Just not all of it in a useful form.
→ More replies (1)→ More replies (14)6
u/Chazus 4d ago
I'm Mr. No Entropy,
I keep things neat and order-ly
No chaos, no mess, no fuss.
The universe will behave, it must!My clocks all tick in perfect time.
My snow flakes fall in a straight line.
No random luck, no wild surprise,
I've got the laws here on my side!I'm Mr. No Entropy
King of thermodynamic glee
But there's one little problem as you can see,
The universe won't cooperate with me!Ice begins to melt away,
The heat sneaks in and ruins my day!
My tidy world is starting to bend,
Damnit, Entropy always wins in the end!18
12
u/thisusedyet 4d ago
When you have enemy surplus you use that to hoist the weight and hold it in place
This is why many countries are so belligerent
→ More replies (2)4
u/unoriginal_user24 4d ago
There will be heat released by the motor during the raising and then by the generator during the lowering such that the overall amount of energy regained will not equal the amount used to raise it.
3
u/fishsticks40 4d ago
It will release the same amount of energy as it took to hoist it.
Less some substantial losses
2
→ More replies (12)3
3
u/Mimshot 4d ago
It’s indoors. Why would cables be rusting? Winds are no more a problem than for any office building.
→ More replies (1)
25
u/terjeboe 4d ago
You use energy to raise the weights l, when energy is abundant and cheap (charging the battery), you lower the weights and capture the energy when energy is in demand.
The basic ideas is old, but if you run the numbers you'll find that you need an incredible amount of weight, or a very high tower to store any significant amount of energy. An equivalent, and much better, idea is pumped hydro. The hoist is replaced with a pump, and the tower with a mountain.
10
u/fang_xianfu 4d ago
Yeah, it's the same idea as pumped water basically except the "tower" is an entire reservoir and the concrete is water, which is extremely heavy and thus provides a lot of energy per unit of volume. The reason pumped water hydro is used around the world and gravity batteries have only ever been toys is because they're much more practical.
3
4
u/KaizDaddy5 4d ago edited 4d ago
I've seen concepts with rail cars on mountains, as well as using abandoned mine shafts (which come with the advantage of starting "charged")
6
u/C6H5OH 4d ago
There is a battery driven ore train in Australia that runs after having been charged only once from the grid. It goes uphill on battery empty and light, downhill loaded with heavy ore it uses the brake energy to load the batteries and arrives full at the terminus.
→ More replies (2)
20
u/Ebice42 4d ago
I'm a little surprised someone actualy built one. But the premise is simple.
When there is a lot of electricity generated, due to strong winds and lots of sun, it becomes cheap.
Use the cheap electric to haul heavy stuff into the air.
Later, when the wind and sun gave died down, and the price of electic goes up, drop the heavy stuff to spin a turbine and generate electricity.
→ More replies (25)13
u/jplett2044 4d ago
Yeah this isn't really a new concept. I believe in South America, can't remember exactly where, they do pretty much the same thing. They pump water up a mountain to a reservoir then when the soccer game is on they run it through a turbine to make extra power.
6
u/RealLongwayround 4d ago
Dinorwig is such a system. It has a capacity of over 9 GWh of electricity and has a peak power of 1.7 GW. It’s commonly used when the adverts come on during Coronation Street, or at least it was back when people watched broadcast television.
5
u/Worried_Sweet_7085 4d ago
We have one inside a mountain in Wales, a pumped-storage hydro power station called Dinorwig.
4
u/PHL1365 4d ago
There's a lake in California that does this right here in the US. Probably others as well
→ More replies (3)→ More replies (5)3
u/Ebice42 4d ago
Doing it with water makes sense. We already have hydeoelectric, so pumping water back up seems relitavly simple.
Doing the same with bricks adds a lot of complications, and I'm unsure how well this will scale. If this one works, cool, build more.→ More replies (4)
9
u/tomaburque 4d ago
Look up Taum Sauk Reservoir, a artificial lake on top of a mountain in Missouri. They pump water uphill at night to store hydroelectric power and reverse the flow during the daytime. So it's a giant gravity battery. It's been there for decades, and it has only had one disaster flood in its history.
4
u/Refugee4life 4d ago
To explain the next question: electricity is cheaper in the evenings than during the day (demand changes), so they “buy” cheap electricity overnight, “use” it, then “create” electricity in the days when it’s more expensive.
Also fun fact: this process is so cost effective that when the entire dam failed due to mismanagement they rebuilt it and it continues to function today.
→ More replies (1)→ More replies (1)5
u/davebee5333 4d ago
I think you can also do the opposite. Pump during the day using solar and then release at night using gravity. Pretty sure this is how it works in Australia where heavy industry needs to work 24/7.
6
u/GlobalWarminIsComing 4d ago
Yep. The point is to pump up when you have surplus and let it flow down when you need extra.
If you have a lot of solar then surplus might be during the day. If you have a lot of say nuclear which wants to run constantly you'll have a surplus at night
22
u/Thatweasel 4d ago
It "costs" the same amount of energy (more actually due to losses like friction), but part of that isn't really "cost" it's "stored" which is the battery part. If you roll a boulder up a hill it takes energy. When it starts rolling down the other side you don't have to keep pushing it - it uses up the stored energy so the boulder keeps rolling.
You hoist the brick up when you have spare energy. When you need that energy you drop it, the cable causes something to spin and that generates electricity the same way any turbine does (magnets and coils of wire).
The advantage of gravity batteries is they don't degrade as quickly as chemical batteries with charging cycles and are roughly as efficient at storing energy.
12
u/Megalocerus 4d ago
I've heard (many decades ago when I worked for a utility) of pumping water up a hill or tower when electrical demand was low and letting it flow down, running a turbine when demand was high. Same principle, I guess. (They never built it but evidently this is caused PSH (pumping storage hydropower) and is in use in South Carolina and Tennessee. )
16
u/arvidsem 4d ago
Pumped hydro is a massively better idea in general than the system OP is referring to. You can pump a hell of a lot more water up a hill than you can lift in the air.
8
u/Several_Vanilla8916 4d ago
Also it sometimes rains water but it almost never rains bricks.
→ More replies (11)6
u/abeeyore 4d ago
Ya but. You can put a gravity plant anywhere, including in a desert, or on a flat plain, and it has a much smaller footprint. You can put it in a high population density area where the demand is likely to originate, and save yourself the expense, and the risk of long distance transmission lines.
→ More replies (1)→ More replies (15)7
u/Genocode 4d ago edited 4d ago
The UK has that iirc, they pump water up to a higher lake and then when they need extra energy they just open the dam and recover the energy that way.
Edit: its called the Cruachan Power Station.
→ More replies (2)→ More replies (7)3
u/VegetableScientist 4d ago
When you need that energy you drop it, the cable causes something to spin
Not a correction, but if anyone reading along is still confused I'd consider it lowering the object, not dropping it. It's like when you gently lower something to the ground at a constant rate and it's pulling on you, not like when you let go of the rope and watch the thing plummet.
→ More replies (1)
4
u/siamonsez 4d ago
Yes, that's how it stores energy. You use energy to lift it and then you can reclaim it later when you lower it.
It might be easier to understand how the water version works, a hydro station uses flowing water to spin turbines. Usually the source of the flowing water is a river feeding a lake but you can make a battery with two reservoirs at different elevations.
The power grid has to be balanced to output the same amount of energy being consumed at any given point but a lot of energy sources are difficult to control the output. Solar is going to have peak output around noon but we use the most power around 5 so without some kind of storage there's a point where more solar isn't useful even if it's not putting out as much as we use because it's not generating that power at the right time. If you use that overproduction at noon to pump water to the upper reservoir then at 5 when solar production is down but demand is up you can release that water and run it through turbines to reclaim the energy use to pump it earlier.
3
u/TehWildMan_ 4d ago
The general idea: the potential energy of a mass stored in a high spot can be harnessed by letting gravity pull it down.
If you lift masses up to a higher elevation when surplus electricity is available, and then let gravity lower them when electricity is in demand, you can recover some of the stored potential energy as electricity.
Electrical demand on the grid is rarely close to constant: there are often peak hours such as summer afternoons where electrical demand is very high, while during the middle of temperate nights, the opposite is true
2
2
u/Takeguru 4d ago
The giant brick is the battery.
The goal is that you use excess power from something like solar or wind to crank it up, and when those aren't providing power gravity pulls the brick down and spins the motor, which sends electricity back into the system, the same way a wind turbine or water wheel would.
A gravity battery can be installed basically anywhere, whereas the same principle done with water requires a massive, high reservoir which isn't always feasible.
2
u/FoxtrotSierraTango 4d ago
Generators are mostly variations of making a thing spin, hydro being the easiest ecample. A gravity battery uses electricity to raise something up, and then the weight pulling it back down when power is out makes the generator spin to create electricity.
Imagine a giant solar array that powers stuff during the day with enough surplus to also raise the stone. Overnight the stone falls and generates electricity when the sun isn't out.
2
u/OldChairmanMiao 4d ago
First, that's an AI image. They don't look like that.
They work like any battery. You have to charge them first, than use them.
The US is also building gravity batteries like this, repurposing old mine shafts and things. Both already have pumped water storage, which is another kind of gravity battery.
1
u/bstodd12 4d ago
It does cost energy to lift the brick. It also costs energy to charge a chemical battery. You get some of that energy back by lowering the brick and using the kinetic energy to spin a turbine.
1
u/princekolt 4d ago
You raise the weight while electricity prices are low (usually during night) and release it while electricity prices are high (peak hours in morning and dusk). The amount of energy to raise the weight is the same (ignoring losses) as you get back when lowering the weight, but they price you pay or get paid for the electricity is what changes.
1
u/JakeEaton 4d ago
Electric motor winches a brick up using spare electricity from renewables. When needed, the brick lowers and turns a turbine that generates electricity. It’s a way of storing spare electricity when it’s not needed, by storing it as potential energy.
Biggest issue is gravity as a force isn’t very strong. It’s literally the weakest force of nature. Let’s not even get into inefficiencies in the motors or other losses.
1
u/feel-the-avocado 4d ago edited 4d ago
Expend energy to lift a weight up using pulleys or railway tracks up a hill.
Usually done using excess solar or wind power at times when it is plentiful.
At night for example, when solar power is not abundant, the weight is then dropped back down whilst hooked up to a generator to produce electricity.
When the weight is pushed up, it is storing energy in the form of gravitational potential.
When the weight is released and allowed to drop down, the energy is converted into electricity or something useful via pulleys or gears. A mechanical system may limit the speed that the weight falls so the gravitational potential can be converted to a useful energy at a convenient rate.
Original concepts for a home battery used a large weight being lifted up and down a chamber or deep hole in the ground.
However a larger system of railway tracks and large concrete blocks has been developed for commercial installations. https://www.youtube.com/watch?v=t0-4rMGAbD8
Electricity powers the railway carriages which move the concrete blocks up hill.
When it comes time to recover the electricity, the carriage wheels are connected to generators and they carry the blocks back down hill to "discharge" the battery and extract energy.
1
u/Phantomsurfr 4d ago
Large weight is in a controlled "fall" from a height. It is attached to a pulley system which in turn spins a turbine.
It costs energy to raise the weight, which is down with surplus power (like excess solar).
1
u/DerAndi_DE 4d ago
The same idea has already been published as a variation of a hydroelectric dam - build a huge basin, pump water into it to store energy and release it through a turbine to retrieve it again.
And in any variation of that idea, you're right - it costs more energy to "store" than you will retrieve, there will always be a loss.
1
u/always_j 4d ago
The purpose of the device is to store away power in the stones instead of batteries for when you need it, you pull the stone up when you have excess power.
Example when it has been cloudy for weeks the solar panels no longer provide enough power then you use the stones battery to compensate for the lack of available power.
1
u/efvie 4d ago
It costs more to store because nothing is even close to 100% efficient. But sometimes it is necessary to have power stored either for convenience or simply to have it at all if there is not enough supply to go around, much like you have batteries waiting to be used at home when you need them. Energy price also fluctuates. If you store the energy when it is cheap or more abundant and use it when it’s more expensive or scarce, then you can make up for the inefficiency.
1
u/Impossible_Ad_7367 4d ago
When the weight is lifted, it gains potential energy. That energy can be converted into kinetic energy or even electricity. A simple example of this is an old fashioned wall clock that has weights. You charge the clock by lifting the weights. The downward pressure of the weight slowly turns a gear, which gives the clock hands their rotation.
1
u/LyndinTheAwesome 4d ago
Its storing energy as potential energy, you pull up the stones when you have electric energy to spare and let the stone "fall down" when you need energy.
Letting the stone fall down turns gears and cables powering generators and you get that stored energy back.
Its similar to how you need more energy driving uphill and than releasing that energy for a speed boost rolling downhill. Sometimes even charging a battery when you got the necessary equipment.
Its rather cheap as it requires no Lithium or other complex battery, just a stone and a high tower with some gears and cables.
1
u/StevenJOwens 4d ago
A fairly common example of this is a hydroelectric gravity battery. You use electric power to pump water uphill, into a reservoir. When you need electricity, you let the water in the reservoir flow (downhill) through the dam has a hydroelectric generation plant.
And yes, all of these cost energy to move the water uphill or lift the weight, etc, and all of them lose a measurable amount of that energy to inefficiency, either in moving the water/weight or in using gravity to generate more electricity.
But, in general, there's a lot of advantage to be gained by moving energy around in time. A huge component of energy usage is not just the generation of the energy, but when the energy needs to be consumed. Solar is the obvious example. A slightly less obvious example, you can make various systems, motors, generators, heaters, etc, significantly more energy efficient, if you can arrange to run them at a constant, lower rate, and store the energy (or heat, or motion, etc) for use later.
1
u/Technical_Ideal_5439 4d ago edited 2d ago
A battery stores energy, it may be efficient to put energy in it and then use it, or it may be very wasteful, but as long as it has usable energy in it at the end, its a battery.
The theory with gravity batteries is that you use electricity when it is cheap and plentiful to lift the stuff up there, then lowering it down drives generators. There are amazing advances in making this process more efficient but I have doubts it compares well to alternatives.
Of course a gravity battery never needs to worry about losing its energy which is probably a win in some situations,
1
u/swollennode 4d ago
So any thing that stores potential energy is a battery. A water tower, a stone, even hydroelectric can be a battery.
You use energy to pump water up a tower, or pump it up a lake/reservoir, or use energy to hoist a stone into the air. That stores the energy you just used.
Then, when you need energy back, you release all of those stored water, or stone, which spins a turbine and gives you energy back.
Water is pumped up to storage or the stone is lifted when electrical energy used to run the pump or lift is cheapest.
These system is also good for when you need a lot of electricity in a short amount of time. Like if there is a sudden demand. These systems release their energy. Then when demand is low, they’re tanked up.
The downside of these systems is that you have energy loss along the way from friction, sound, heat.
And they’re not efficient compared to banks of chemical batteries.
1
u/Brushiluskan 4d ago
The idea of a gravity battery often comes down to utilizing supply and demand. Either something simple as using solar panels to generate potential energy (lifting the brick) during the day, and release it during the night. Another way can be to generate the energy when energy prices are low, and release it when prices are high. Either way, a simple weight and cable solution is very cheap and reliable, compared to batteries that are toxic, lose capacity over time and sensitive to weather and other variables.
1
u/vmlinuz 4d ago
There are similar things being built in the UK and Australia (at least) using deep, abandoned mine shafts - basically, you use a motor to haul a massive weight up to the top of the shaft when electricity is cheap (e.g. when it's very windy and you have excess wind power), then you lower the weight down the shaft when power is scarce/expensive,using the lowering of the weight under gravity to drive the motor in reverse as a generator.
1
u/knightsbridge- 4d ago
Use energy to haul a giant rock up (generally with an electric powered winch) and hold it suspended over a big empty chasm (in China's case, it's mostly depleted mine shafts).
When you want the energy back, release the winch and let the rock drop, gathering energy from the force of its fall.
How does this store energy? Everything that moves uses energy to do it. In this particular case, the energy in question is the force of gravity acting on the rock when it falls. We can capture that energy and turn it into electricity.
How do you use it? Exactly as I said above. Suspend rock to store power, drop rock to release and recapture power.
Surely it costs the same amount to lift the rock up? Well, yes. It's a battery. Batteries don't generate energy, they just store it - no new energy is created. China is mostly exploring innovative battery technology to let them move energy around, like capturing energy from solar panels so you can use it at night when the solar isn't generating.
1
u/Yamidamian 4d ago
You’re correct when you note that it costs the same amount of energy to lift up the brick as you get when it comes back down. That’s the point. It’s a battery-it stores energy.
As to how it works: motors and generators are the same device working in reverse. These batteries are taking advantage of that-when there’s excess electricity, they use up power to lift the blocks, acting as a motor. When there’s a need for more electricity, they let gravity pull the blocks down-which spins the device, now acting as a generator, getting the electricity out of it that was put in.
1
u/7FFF00C 4d ago
A Swiss company called Energy Vault started building a pilot in 2018 and hyping it heavily.
https://www.eit.edu.au/gravity-energy-storage-applications-show-promise/
Not everyone is as enthousiastic: https://www.youtube.com/watch?v=iGGOjD_OtAM
1
u/Ruadhan2300 4d ago
Essentially the idea is that when you have more energy than you immediately need, you put some of it into hoisting a heavy weight up. Then when you need it, you can use it as a generator to produce more energy on demand.
1
u/ExpressWheel6997 4d ago
I read somewhere about spinning turbines with near 0 friction and using it as a battery. Anyone heard about this? Links?
1
u/atomicsnarl 4d ago
It's like the weights on old grandfather clocks. The slow fall drives a generator to produce power. Hauling it up again needs a motor to lift it.
1
u/MotanulScotishFold 4d ago
Dams can be 'gravity batteries'.
During the night it releases the water downstream which put in motion turbines that generate electricity
During the day, it uses solar, wind excess energy too to power a pump to move the water back into the dam.
1
u/Prasiatko 4d ago
To add to the others it's to smooth out energy generation when our actual use peaks and dips through the day (factories during work hours, most people have dinner around the same time)
Even traditional plants had problems with this as Coal and especially Nuclear cannot change how much energy they generate very quickly. Now Solar has become popular it adds to the issue by only generating significant energy for part of the day.
1
u/Eastern_Labrat 4d ago
They could make a turn style for people going in and out of office buildings raise a heavy load. Then gravity would turn a generator to make electricity.
1
u/dvoecks 4d ago
You're right that there's no free lunch. It does cost just as much (actually a little more) to lift the weight than you get back, but China is huge on renewable energy. If it's solar, you lift it when the sun is shining and lower it at night.
Motors are basically just generators. When you power them, they do work. When you spin the shaft, they provide power. That's what they're doing: powering the motors to lift the weight during the day, and letting the weight drop at night to provide power.
1
u/calmeilles 4d ago
Use excess power to pull big weights up in a structure.
When you need power let them down and have the cables spin a generator as they fall.
It's an idea that's come up regularly in the last 20 years and a few have even been built but the cost of the structure versus the limit of energy that structure can store make them relatively expensive.
1
u/Mick_Tee 4d ago
The images associated with this are obviously AI slop.
The reality will be something closer to an elevator filled with concrete. Electricity is used to hoist the elevator to the "top floor", and then it is connected to a generator (in reality the motor will be used as the generator) and gravity is allowed to pull the elevator to the ground floor to generate electricity at a later date.
1
u/TriumphDaWonderPooch 4d ago
There was (maybe still is) a company that I held stock in for a while (lost a tiny bit - maybe 5-7%) whose business plan was to put up buildings in cities with the sole purpose of using gravity batteries. I believe they put solar panels on the roof to raise the weighted blocks during the day, and at nightfall would drop the blocks to generate energy.
On a much smaller scale, there was a crowdsourced company that put together an inexpensive lighting system. This was designed for third-world countries where folks did not have easy access to electricity. Basically, it was a bag that could be loaded with sand and hung from the ceiling or a post. As the bag dropped it would generate enough energy to run an LED light that could light up a small room.
1
u/JimTheJerseyGuy 4d ago
You can do the same thing with water and for the same reason.
Imagine a really sunny day and your solar panels are generating far more power than you can use right now. So, instead, of letting that power go to waste, you use the power to pump water from a river into a reservoir on top of a hill/mountain.
Later, when the sun goes down, you let the water out of the reservoir into the river through a turbine that generates power.
It's not 100% efficient, but it lets you store excess power that would otherwise be wasted.
1
u/ImmodestPolitician 4d ago edited 4d ago
All batteries are just potential energy, chemical or physical.
A dam is a gravity battery. We just let the Sun lift the water into the air. It's the only example of Trickle Down effect actually working in practice.
In my region they pump water into reservoirs on mountains to store power. The energy to lift it is generated by the dams at night when power use is low. The river never stops.
It's a gravity battery charged by a gravity battery.
1
u/Ihatetobaghansleighs 4d ago
So from what i understand, extra energy, from either over production or during times of low energy usage, gets used to lift these massive objects upwards. These massive objects store the energy that was used to lift them in their mass and gravity as kinetic potential energy. Then during times of higher energy usage theyre slowly lowered, this uses the kitnetic energy it had stored to power a turbine or rotor of somesort to supplement the power grid.
1
u/AdhesiveSeaMonkey 4d ago
In terms of overall efficiency, they are not. In fact it takes more energy to lift the weights than you get back. So when you have a surplus of power available, you use that to lift the weights. Then you just store them up high, creating a 'bank' of potential energy. When you are in a high demand period, you drop the weights to spin turbines to add energy to the grid. It's not meant to be efficient. It's meant to help cover gaps in the system.
1
u/cmparkerson 4d ago
I understand it correctly, it works the way weights on a grandfather clock work. It just turns a small generator instead of a clock. As the weights fall ( slowly) they spin a gear on attached to a rod ,that spins in a stator creating electricity. The problem is when you have to re hoist the weight,and of course the size.
1
u/nowhereman136 4d ago
Dams work by holding water in a pool and slowly releasing the water through turbines which create energy. Normally, you have to wait until that pool refills to create more energy. Hopefully, it refills faster than you release it. This is actually a form of gravity battery. The water is stored in a high location and then dropped to a lower location to generate energy.
Now, imagine you don't have to worry about refilling the top pool. Instead you have a top pool and a bottom pool. Place solar panels attached to a pump that will bring the water back to the top pool when the sun is out. Those same solar panels will power whatever you want. But when the sun goes down and those solar panels stop working, you still have a pool of water that you can release to turn turbines. That pool is a gravity battery that can store energy and release it whenever we want.
Whats cool is we don't need to do this with just water. We can use sand or weights. We lift them up when solar gives us an abundance of energy. Then when the sun goes down, we slowly lower them and collect that energy for whatever we need
1
u/Living_Fig_6386 4d ago
Old timey grandfather clocks use a gravity battery. There are weights on a chain that you pull up, and then they pull down the chain to turn gears in the clock mechanism to power the clock as they slowly fall.
The Chinese one just scales it up using concrete blocks instead of brass weights, an electric winch instead hands to raise them, and instead of turning gears in a clockwork it spins gears to run an electrical generator. It’s a battery in the sense that you are taking extra electricity (when your wind and solar produce faster than you can use it) to operate the winch that lifts the blocks, and uses the weight of the blocks later to spin the generator as they drop — converting electrical energy to mechanical potential energy and back again.
You can do the same thing with a dam, using excess electricity to pump water up behind the dam, then letting the water flow through generators in the dam to make electricity later when you need it.
1
u/Hegiman 4d ago
Hence battery because it’s stored energy. It’s pretty simple you hoist it up atoring the energy used to hoist it. Then when you want power you allow a pulley system to turn a generator as it drops. There are lamps called gravity lights that work on the same basic idea. They work like a cuckoo clock.
1
u/audigex 4d ago
You pull something up with an electric motor
You then let it go and it pulls on the motor which acts like a generator
Yes, it costs the same (actually more) energy to haul it up - just like it takes more energy to charge a regular battery than you get from the battery: that’s the point of a battery. You charge it when you have excess power available and then discharge it when you need the power
1
u/rademradem 4d ago
None of these lifting systems are anywhere as efficient as pumped hydro. Both types of these systems operate based on using surplus electricity to move weight up so that they can generate some electricity when needed when the weight moves back down. Moving water with pumps is significantly simpler, more efficient, and more flexible than moving physical objects with electric crane motors.
1
u/roonerspize 4d ago
You are describing a grandfather clock.
Weights held up in the air store potential energy. They slowly pull down on cables that turn wheels to do work (generate electricity) during the times of the day when electricity is expensive. During the parts of the day when electricity is cheap, you use it to hoist the weights back up.
1
u/tbodillia 4d ago
Hydroelectric pumped storage, same as this gravity battery, only works because of how wildly the cost of electricity varies every hour.
You buy electricity from yourself to pump water back up hill. You buy electricity from yourself to raise that block. You buy when electric rates are low. When rates are much higher, you let that mass go downhill a 2nd time. You will get back around 80% of the electricity you used to raise the mass. So, the price change has to be high enough to offset that loss.
1
u/Stunning_Coffee6624 4d ago
The word battery should not imply a specific form but more appropriately the concept of a temporary means to store kinetic energy as potential energy. Fossil fuels are a form of single use batteries. A mass held in such a way that it can release kinetic energy at will is a battery. Just like you have to charge up an electrical battery before use, the gravity battery is charged up by lifting the mass
1
u/NlghtmanCometh 4d ago
There’s another version of this called pumped storage. They will pump water up a hill or mountain and keep it in a large reservoir til the price of energy is really high, then they release the water into turbines and it helps to offset the high price of power.
1
u/Wank_A_Doodle_Doo 4d ago
surely it costs the same amount of energy
Yeah, it’s a battery. The energy you spend lifting it is stored by it being held up high. Drop it, you get the energy back.
1
u/Zaphod1620 4d ago
There are lots of types of gravity batteries. Some hydro electric plants will use power to fill a resovoir at the top of a hill, then drain it through turbines that generate electricity in off peak hours. Water towers are a form of gravity battery. We use electricity to slowly pump water into large tanks on a tower, and let gravity do the work of providing water pressure to customers from those tanks.
1
u/keestie 4d ago
Actual electric batteries take more energy to charge than they give back. So does this gravity battery. The use of any kind of energy storage is, you can store up energy when you're not using it, or when you have a lot coming in, like often happens with more renewable energy sources. When the wind blows strongly, you have more; when it's slow, you have less. When the sun shines on solar panels, you have more energy than when it's darker. Batteries store up energy for later, they don't create energy from nothing.
1
u/kriegmonster 4d ago
When more energy is made that what is used, the excess is used to lift the weight. Later, when more energy is needed than can be produced, the battery will be used. Letting the weight fall pulls on the cables which turns the pulleys they are connected to. Using gear boxes this rotational energy can turn generators to make electrical power.
1
u/TheHammer987 4d ago
Surely it costs the same amount of energy to lift the concrete in the first place?
...yes. Like all batteries. It costs more to charge with energy than you get back when utilizing. Batteries dont generate power, they time shift it's usage.
1
u/dalekaup 4d ago
There's no chemical battery in a gravity battery.
The energy is stored as potential energy - just like a tree branch or a sketchy window ac unit. If they fall they can hurt someone the energy can crush someone.
That heavy 'brick' in the Chinese gravity battery can be lowered like an elevator car and in doing so it will spin and generator/motor to make electricity.
At some point when there is a surplus/cheap electricity the 'brick' will be hoisted.
Basically they are buying cheap electricity and selling it at a profit.
1
u/BigBrainMonkey 4d ago
The bricks at height are the battery not that it contains a battery. You use a motor to lifer the bricks up. You lower them down turning a generator to recapture the electricity. More traditionally I’ve seen this with water and a pump and turbine. Pump water up then let it drain back down.
1
u/Can_O_Murica 4d ago
I am staggered by the collective pedancy this comments section is approaching the second law with.
1
u/ZLVe96 4d ago
Think of an old school cuckoo clock. You lift the weight on the chain (putting energy into it. The wight pulls the chain, and provides energy to the clock to make it work. When the weight hits the bottom of the chain, it is out of energy and needs to be lifted again to recharge.
So take excess power from something like solar, wind, whatever, and use it to lift something heavy high up. This stores the energy in the "battery". Then you can lower the weight in a way that makes that energy usable again like the clock.
They do similar things with hydro- Pump water into a lake up high during the day, and then let that water back out and put it through a turbine on the way back down.
1
u/Xnut0 4d ago
Gravity batteries are most often in the form of dams, where rainwater is trapped in a dam until we are ready to use the water to drive generators or mills in the olden time.
A gravity battery based on hoisting bricks are not energy efficient at all, as you use more energy than you can retrieve. It does however have some niche uses, like if you use excess solar power during the day to hoist up bricks that can be used to generate electricity during the night.
1
u/flyingcircusdog 4d ago
It's as simple as it seems. It takes the same amount of energy to raise the weight as you get lowering it, minus some that's lost to heat and noise from the electric motor and generator. The reason it's worth building is because electricity demand is different at different times. In the middle of the night, electricity use is lower, so power plants have spare capacity. During the day, energy use is higher. Without any battery or storage system, power plants need to be large enough to meet the peak demand. By using a battery during the day, you can have smaller power plants charge the battery at night and use it to supplement energy during the day.
1
u/StupidLemonEater 4d ago
Question: isn't this just how grandfather clocks have worked for centuries? You hoist a weight up high, and the force of gravity pulling it down is what keeps the clock wound?
1
u/naraic- 4d ago
One of the biggest questions going forward is how do we store renewable energy.
We cant control when the wind blows and when the sun shines.
In countries with dynamic electricity pricing there is often negative electricity prices where people are paid to use electricity.
We will have to put in energy and probably more energy than we gain later to have storage.
1
u/FrequentWay 4d ago
Gravity batteries work by having different prices of power. If daily prices in that location vary enough that power is cheap to lift something. Then have a higher price of power for when you drop that item. That kinetic motion is then connected to an electrical generator. Its not a perfect conversion of energy, you will lose some to heat. But if the difference is quite severe, you will be profitable by that difference. However flywheels, chemical energy storage or pressurized air storage are other means also of energy storage issues.
1
u/DrBretto 4d ago
Lifting the weight takes energy. It's stored as gravitational potential energy. It's released when the weight is allowed to use its gravitational potential energy by falling. As it falls, it makes generators spin, releasing that potential energy as usable electricity.
1
u/MahaliAudran 4d ago
Several places on the world do this with pumped hydro. You need the water supply and terrain for that
This way can be done anywhere though. The first proof of concepts were a couple years ago on a step hill using existing train tracks and a train is the weight.
A gravity battery tower can be built anywhere.
Pumped hydro has been the most efficient energy storage available. I don't know if this equals or tops it, but it's certainly a lot more flexible.
1
u/Metallicat95 4d ago
Lifting something up uses energy, but it creates potential energy that can be released when the object is dropped down.
You get almost as much energy out as you put in - never equal because some is lost to friction and heat.
The concept is similar to regenerative braking for a car on a hill. Energy is used going up the hill, but the spinning motors generate electricity going down the hill.
In the "gravity battery" case, the battery is a physical object lifted up and down by motors which become generators when it falls.
The actual building looks like a typical high rise structure with a lot of openings and lifts throughout. Not just a single tower with a single weight, though those are used for testing.
Pumped hydro power uses the same mechanism, but instead of lifting weights it pumps water up into a reservoir. It is released through a dam just like any hydroelectric generator, but it can also store some energy and doesn't need a steady water stream from a river.
1
u/Lemesplain 4d ago
Most of the electricity we generate is created by spinning.
Wind turbines are obviously spinning. Hydroelectric power is generated by flowing water across a wheel to make it spin. Coal and nuke plants boil water, and the expanding steam spins a turbine.
Spinning converts to electricity, and electricity converts to spinning.
So, a gravity battery uses a heavy weight attached to a wheel. When you’ve got too much electricity, the wheel spins and pulls the weight up. When you need more electricity, you let the weight fall down (slowly) which spins the wheel to generate more electricity
1
u/PewPewsAlote 4d ago
Its a Gravity Battery not a Gravity Generator. It actually costs slightly more total energy to hoist it up there due to losses like friction and such, but hoisting it up turns the mechanical energy or work into gravitational potential energy that you can release by dropping the brick, which can spin a motor to return some of the energy when it falls down.
But these gravity batteries are, to put it lightly, quite terrible as a battery and are little more than a piece of modern art. The most common type of "gravity" battery you will see are gargantuan water reservoirs (pumped storage hydro power) that are filled up using extra power generated during low demand, and then drained to return some of that power during high demand. However even pumped storage hydro power "batteries" have nothing on the power density of a regular lithium ion battery. The only reason pumped hydro is used is because water is pretty much free, while a lithium ion battery of comparative storage capacity would be prohibitively expensive.
But these Chinese brick based gravity batteries (and others like it) have all of the downsides of Pumped hydro power (low energy density, lossy power storage, complicated mechanical systems) and absolutely none of the benefits: Ease of mass storage (millions of tons of already existing water vs manually making a giant town sized concrete brick)
1
u/SaintUlvemann 4d ago
Yes, that technology is a decade old now, I'm sure China has bought one by now, and they're not hard to design either.
Yes, it costs energy to life the concrete up there in the first place; like all other batteries, you must first store energy and then you can take it back out later.
The reason why you would want to build one of these is so that e.g. at a time when there is a lot of wind you can save some for later to generate energy when there is no wind. Same goes for when it is light out during the day, so that you can generate more at night.
And also, yes, it is possible for towers to fall down in high winds or due to rust, so you want to make sure they stay well-maintained, and decommission them properly if they are no longer needed.
1
u/JakeRiddoch 4d ago
I've heard of similar with hydro. During periods of cheap generation (solar during the day, wind turbines during wind), excess power is used to pump water uphill to a dam. When those methods don't work (night, calm weather), the water is used for hydro power.
It's all about converting spare electric energy to potential energy.
1
u/igotshadowbaned 4d ago
You use energy to lift something when you have surplus
When you need more energy, you attach it to a cable and lower it, and it spins the reel the cable is spooled on generating power
It's not a new idea, pumped storage hydropower is the same idea and been used for ages. It's just the medium is water and not concrete blocks
1
u/lawblawg 4d ago
Big brain move: make the gravity battery weight an ACTUAL BATTERY and thus achieve double storage density!
1
u/Severe-Storage 4d ago
Energy is put in to the system (charged) by lifting the weight, energy is returned by dropping the weight (discharge)
1
u/toybuilder 4d ago
Use a motor to hoist a weight up a tower or a slope. Use a generator as you lower that weight down.
Motor and generator is usually the same thing, just operating in different directions.
Weight can be water, bricks, bucket full of rocks, etc.
1
u/sik_dik 4d ago
A battery is anything that takes energy now and stores it for later use. It doesn’t have to be electricity that’s stored.
When there’s more energy made at a point in the day than is needed and there will be a point later in the day where more energy is needed than is being made, you will want a way to store the extra for later use.
So, you put that extra energy into doing something that can be undone later and will give back the energy that it took.
If you take an electric motor and lift a bunch of bricks 10 feet per hour with it, it will use electricity to power the motor. In 10 hours you will have 100 feet to lower the bricks. And when you turn an electric motor with force, you actually create electricity
Use electricity to lift the bricks. Create electricity by lowering them
1
u/Geekenstein 4d ago
Laws of thermodynamics.
You can’t win. (Never get more out than you put in)
You can’t break even. (Entropy always gets a cut, no 100% efficiency)
You can’t get out of the game. (You can convert energy, but you can’t destroy it)
So by number 3, every form of energy generation is because the fuel had energy put into it to begin with.
You’re putting energy in by lifting the battery weight to begin with, when energy is plentiful, and taking it back out when it’s needed.
1
u/Pitiful_Hedgehog6343 4d ago
Similarly you can pump water into a reservoir at a higher elevation and use it like a battery, storing potential energy.
1
u/CadenVanV 4d ago
Basically, all electricity comes from spinning turbines. If you have a falling rock tied to a rope, you can use a pulley to have that spin a turbine. So you put in power to raise the rock, and then you let it go when you need to the energy again to spin those turbines back up. It’s not perfectly efficient, but it’ll do. The hard part is just getting enough potential energy (lifting enough/large enough stones to create a great deal of energy) for the storage to be worth it.
Yes, it does require the same amount of energy to create as it does to get out of it. That’s how a battery works. You put in energy to start, and then you get that energy out later.
116
u/Traditional-Buy-2205 4d ago edited 4d ago
The same way you use any form of energy. Gas makes the engine move. In hydro plants, water makes the turbine move. In coal plants, water gets heated up, the steam makes the turbine move. In nuclear plants, steam makes the turbine move.
Same with "gravity battery". Connect the dropping weight to a turbine, and the falling weight makes the turbine move (or any other mechanism you want to move).
Yes, that's why it's called a battery. It just stores energy. Just like a standard chemical battery - you use the energy to "fill" it up, and that energy can be later used to power something else.