6 ms·

Gravity Battery Concept

67 points by vrepsys 13y ago

alextingle 13y ago
This is a terrible idea. It would cost a fortune to build a "battery" that stores no more energy than a simple lead-acid deep cycle battery. About the only advantage is that with simple maintenance, this system should last indefinitely, while lead-acid batteries have a limited lifespan. (Oh, and didn't web-sites that are nothing but one giant image go out of fashion around the turn of the century?)
Gravityloss 13y ago
I have another idea: just throttle the hydro and nat gas plants?
jsmcgd 13y ago
I (like many people) have had this idea an energy storage mechanism. Unfortunately gravity batteries have an extremely low energy density for weight [1] or volume and so are only really a valid choice for something that operates at the scale of a hydroelectric dam. Heat batteries make more sense for energy storage at a household level, whether it's heating or cooling. They're smaller, can require almost no maintenance and have a much higher energy density. [1] https://en.wikipedia.org/wiki/Energy_density#Energy_densities_ignoring_external_components https://en.wikipedia.org/wiki/Energy_density#Energy_densitie...
- ash 13y ago
  LightSail Energy system uses heat and compressed air to store energy: http://www.lightsail.com/ http://www.lightsail.com/
1rae 13y ago
In Johannesburg we have a whole lot of deep mine shafts that are no longer being used, and one of the main ideas for reusing them is to turn them into hydroelectric power stations. During the night when the electricity is cheaper, the water will be pumped up to the top, and during peak hours the water will be allowed to fall back down and provide power if necessary. It's a similar concept but on a much larger scale.
- PeterisP 13y ago
  Are they really that big? Stored-hydro stations are efficient because of lake-sized reservoirs, and it takes uncountable miles of tunnels to have the same volume as a medium-sized lake.
devrelm 13y ago
Has anyone worked out how much energy this could actually theoretically store given the number of weights as n, the mass of each weight as m, and the height of each well as h? My physics is a little rusty, and I'm sure someone will come up with an answer before I figure it out. EDIT: If my math is right (using this [1] as reference), E = m * g * h (J) gives the energy E in joules. 1 watt hour is 3600 joules, so: E = m * g * h / 3600 (Wh) So, if this system were made up of 4 x 200kg weights suspended over a 50m well, it would hold E = 4 * 200 * 9.81 * 50 / 3600 = 109 Wh 109 Wh. That's hardly enough to run a few high-efficiency light-bulbs for an hour. I don't mean to be a naysayer, but this doesn't seem very efficient at small scales. [1]: http://physics.stackexchange.com/questions/39281/needed-energy-for-lifting-200-kg-weight http://physics.stackexchange.com/questions/39281/needed-ener...
- maxerickson 13y ago
  It's just mass * gravity * height. So, for instance, 1000 kg with a working height differential of 1000 meters can store a theoretical maximum of 2.72 kilowatt hours (9.8 million joules).
  - seniorsassycat 13y ago
    You would have to factor the efficiency motors that raise the weights, and the generator that lowers them to get a more accurate estimate.
    - maxerickson 13y ago
      That's why I used a kilometer. There's little need for an accurate estimate, capacity for such a system is very expensive, either in dealing with huge masses or huge distances. By way of comparison, a thousand dollars of lead acid batteries would have more capacity (and despite the issues with lead, such batteries are quite recyclable...).
  - danbruc 13y ago
    Which is comparable to 10 kg of lithium-ion batteries - not terrible efficient.
lylebarrere 13y ago
Using potential energy to store electricity is nothing new. Many hydroelectric damns pump water to a high reservoir when there is excess electricity generated to store it, and let it fall to a low reservoir when more is needed. EDIT: See wikipedia link explaining it, with examples. http://en.wikipedia.org/wiki/Hydroelectric_energy_storage http://en.wikipedia.org/wiki/Hydroelectric_energy_storage
mike_esspe 13y ago
Similar concept is already in use with hydroelectric power generation. It's called pumped-storage hydroelectricity: https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
- mxfh 13y ago
  And it seems to work even better submerged: http://phys.org/news/2013-05-storage-power-seabed.html http://phys.org/news/2013-05-storage-power-seabed.html
- zamalek 13y ago
  Indeed, I was about to point this out. I visited the Drankensberg one[1] in South Africa a few years back. It's amazing how big the complex was for such a simple concept (if memory serves me correctly the turbines were 50 or so stories underground). I'm very interested to see if graphene supercapacitors may eventually have a role to play here. Using gravity seems a bit "primitive". [1]: http://en.wikipedia.org/wiki/Drakensberg_Pumped_Storage_Scheme http://en.wikipedia.org/wiki/Drakensberg_Pumped_Storage_Sche...
praptak 13y ago
Any reasonable estimates of (investment, maintenance) costs per joule of capacity?
doctorwho 13y ago
This is just a large physical battery. The only way to win is if storing the energy in a weight system is more efficient or has more capacity than storing it in a chemical battery. It's certainly not as scalable as a chemical battery and requires a lot of infrastructure to pull off.
gum_ina_package 13y ago
I'd be curious to see the immediate/longterm ROI for something like this. It seems like there would be an incredible amount of resources spent on initially building a powerhouse like the one in the picture.
- jmelloy 13y ago
  There's one in England that's mainly for tea kettles after major television events, like Eastenders. They're one of the power storage options that has the quickest ability to change their output.
kijin 13y ago
At larger scales, these are called pumped-storage hydroelectric plants. There are currently more than 100 GW of pumped-storage capacity in the world, with efficiency ranging from 70% to 87% [1]. They are, in fact, some of the largest batteries we've ever built. They store electricity by pumping thousands of tons of water uphill when demand is low, and letting it fall back down past a bunch of turbines when demand is high. Water is much easier to handle than a solid block of steel, and it's much more scalable as well. You just need a hill and some water, possibly an already existing reservoir. Pumps can be turned on and off almost instantly to meet fluctuating demand. There's one about 10 minutes' drive from where I live. It's marvelous, and the two artificial lakes (one at the top, one at the bottom) also make nice parks for the public to enjoy. Since pumped-storage plants seem to work so well, I wonder if there will be any need to install smaller versions in each home. It's probably going to be difficult to match the efficiency of much larger units. Maybe these will be more useful as backup batteries. [1] https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
- hrjet 13y ago
  The only drawback I see with pumped-storage hydroelectric plants is that there could loss of stored energy due to evaporation. I don't know how much loss does it amount to on a sunny day.
  - logicallee 13y ago
    it could also rain in your pond and give you free energy.
    - Tloewald 13y ago
      This is in fact the entire principle of hydro-electric power (incidentally, a form of solar power since the water-cycle is driven by heat from the sun).
  - JshWright 13y ago
    Another drawback is that building a reservoir on top of a mountain can be a little trickier than originally thought... http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_Station#Upper_reservoir_breached http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_S...
mrgriscom 13y ago
I'm really sick of hearing about this idea. At least this one doesn't make the same mistake of suggesting it should be human powered, but the energy density of gravity is ridiculously low compared to practically any other technology we have. It works for hydroelectric plants because they have HUGE reservoirs to supply them. Assume one of these gravity batteries uses a 100m deep shaft with a counterweight the mass of a Cadillac Escalade. The energy stored is 100m * 2700kg * 9.8m/s^2 = 2.6 MJ. The first deep-cycle battery I found through google (retail price $260) is 90Ah * 12V * (assume 80% discharge cycle) = 3.1 MJ. It just doesn't add up!
puetzk 13y ago
The problem is the poor density: power stored is just mass * gravity * height. So if we want to store 1kWh, using a hole 500m deep (about the max for elevator cables, which seems analogous) this would need a 750kg weight. Storing the same amount of energy in a lead-acid battery would only take 21kg, a LiFePO battery only ~10kg. And those don't require digging out a 500m hole, or the supporting equipment to winch a car up and down a skyscraper.
Geee 13y ago
Better would be to use your whole house as the weight. And store the energy in angular momentum.. That's limitless energy storage :D
- alextingle 13y ago
  Wheeeee.....!!
tehwalrus 13y ago
I've always imagined a frictionless spinning top instead of a long shaft (using permanent magnets, perhaps with some copper coils for stabilisation). You don't need a big geometry, and you can go faster and faster, up to relativistic speeds if required, without any inefficiency. (of course, it must be in a vacuum tube.) EDIT: thanks everyone, now I know that that's what a flywheel is. Had heard the name, never found out what one was.
- wffurr 13y ago
  You mean a flywheel: http://en.wikipedia.org/wiki/Flywheel_energy_storage http://en.wikipedia.org/wiki/Flywheel_energy_storage They're in use for a number of applications, namely in datacenter UPS systems. The main downside is a catastrophic failure mode. Lots of mass, spinning at high speed. Just apply imagination. Their energy density is pretty good relative to batteries, which is to say terribad compared to hydrocarbons. Good ones are pretty expensive, and they require periodic servicing for bearings, gaskets (for vacuum sealed systems), etc. Generally limited to niche applications for now, but there are various pilot projects to look at them for train system energy recovery and grid storage.
  - pygy_ 13y ago
    For safety, they can be burried, can't they?
  - tehwalrus 13y ago
    yeah, my thought process had some pretty complicated failure systems. The thing is, with magnetic suspension, you can "catch" the thing using it's own energy. With a good and fast enough controller, you could catch the thing where it is and flood the tube with air to slow it down. since all you're doing is dissipating energy, you can use it to soften the crash. In terms of energy density, you can just *keep increasing the speed can't you?
    - pbhjpbhj 13y ago
      >In terms of energy density, you can just increasing the speed can't you? // In which case you only need a tiny mass to start with ... The speed limitation is presumably going to come in with the rate at which you can alter the magnetic field to still accelerate the mass. Also you'll get drag as it impinges on local fields (Earth's magnetic field) and there'll presumably be eddy currents and local electrical fields to cope with too which will become more significant at higher flux rates.
ghh 13y ago
GravityLight[1] applied this concept at small scale: to power a white led in e.g. rural areas without power, a bag of dirt is suspended from a dynamo. [1] http://www.indiegogo.com/projects/gravitylight-lighting-for-developing-countries http://www.indiegogo.com/projects/gravitylight-lighting-for-...
heeton 13y ago
I refuted a few of his points and got banned from commenting ;)
pkinsky 13y ago
>(H) Generator & CPU > The generator axis gets spinned I think you mean spun. Aside from that, very cool!
achy 13y ago
A pretty illustration of a terrible idea. Gravity just isn't that strong of a force. Electrostatic forces in chemical bonds on the other hand...
stox 13y ago
The ghost of Storm King rises again.

67 points by vrepsys 13y ago

This is a terrible idea. It would cost a fortune to build a "battery" that stores no more energy than a simple lead-acid deep cycle battery. About the only advantage is that with simple maintenance, this system should last indefinitely, while lead-acid batteries have a limited lifespan. (Oh, and didn't web-sites that are nothing but one giant image go out of fashion around the turn of the century?)

Gravityloss 13y ago

I have another idea: just throttle the hydro and nat gas plants?

jsmcgd 13y ago

I (like many people) have had this idea an energy storage mechanism. Unfortunately gravity batteries have an extremely low energy density for weight [1] or volume and so are only really a valid choice for something that operates at the scale of a hydroelectric dam. Heat batteries make more sense for energy storage at a household level, whether it's heating or cooling. They're smaller, can require almost no maintenance and have a much higher energy density. [1] https://en.wikipedia.org/wiki/Energy_density#Energy_densities_ignoring_external_components https://en.wikipedia.org/wiki/Energy_density#Energy_densitie...

ash 13y ago
LightSail Energy system uses heat and compressed air to store energy: http://www.lightsail.com/ http://www.lightsail.com/

1rae 13y ago

In Johannesburg we have a whole lot of deep mine shafts that are no longer being used, and one of the main ideas for reusing them is to turn them into hydroelectric power stations. During the night when the electricity is cheaper, the water will be pumped up to the top, and during peak hours the water will be allowed to fall back down and provide power if necessary. It's a similar concept but on a much larger scale.

PeterisP 13y ago
Are they really that big? Stored-hydro stations are efficient because of lake-sized reservoirs, and it takes uncountable miles of tunnels to have the same volume as a medium-sized lake.

devrelm 13y ago

Has anyone worked out how much energy this could actually theoretically store given the number of weights as n, the mass of each weight as m, and the height of each well as h? My physics is a little rusty, and I'm sure someone will come up with an answer before I figure it out. EDIT: If my math is right (using this [1] as reference), E = m * g * h (J) gives the energy E in joules. 1 watt hour is 3600 joules, so: E = m * g * h / 3600 (Wh) So, if this system were made up of 4 x 200kg weights suspended over a 50m well, it would hold E = 4 * 200 * 9.81 * 50 / 3600 = 109 Wh 109 Wh. That's hardly enough to run a few high-efficiency light-bulbs for an hour. I don't mean to be a naysayer, but this doesn't seem very efficient at small scales. [1]: http://physics.stackexchange.com/questions/39281/needed-energy-for-lifting-200-kg-weight http://physics.stackexchange.com/questions/39281/needed-ener...

maxerickson 13y ago
It's just mass * gravity * height. So, for instance, 1000 kg with a working height differential of 1000 meters can store a theoretical maximum of 2.72 kilowatt hours (9.8 million joules).
- seniorsassycat 13y ago
  You would have to factor the efficiency motors that raise the weights, and the generator that lowers them to get a more accurate estimate.
  - maxerickson 13y ago
    That's why I used a kilometer. There's little need for an accurate estimate, capacity for such a system is very expensive, either in dealing with huge masses or huge distances. By way of comparison, a thousand dollars of lead acid batteries would have more capacity (and despite the issues with lead, such batteries are quite recyclable...).
- danbruc 13y ago
  Which is comparable to 10 kg of lithium-ion batteries - not terrible efficient.

lylebarrere 13y ago

Using potential energy to store electricity is nothing new. Many hydroelectric damns pump water to a high reservoir when there is excess electricity generated to store it, and let it fall to a low reservoir when more is needed. EDIT: See wikipedia link explaining it, with examples. http://en.wikipedia.org/wiki/Hydroelectric_energy_storage http://en.wikipedia.org/wiki/Hydroelectric_energy_storage

mike_esspe 13y ago

Similar concept is already in use with hydroelectric power generation. It's called pumped-storage hydroelectricity: https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...

mxfh 13y ago
And it seems to work even better submerged: http://phys.org/news/2013-05-storage-power-seabed.html http://phys.org/news/2013-05-storage-power-seabed.html
zamalek 13y ago
Indeed, I was about to point this out. I visited the Drankensberg one[1] in South Africa a few years back. It's amazing how big the complex was for such a simple concept (if memory serves me correctly the turbines were 50 or so stories underground). I'm very interested to see if graphene supercapacitors may eventually have a role to play here. Using gravity seems a bit "primitive". [1]: http://en.wikipedia.org/wiki/Drakensberg_Pumped_Storage_Scheme http://en.wikipedia.org/wiki/Drakensberg_Pumped_Storage_Sche...

praptak 13y ago

Any reasonable estimates of (investment, maintenance) costs per joule of capacity?

doctorwho 13y ago

This is just a large physical battery. The only way to win is if storing the energy in a weight system is more efficient or has more capacity than storing it in a chemical battery. It's certainly not as scalable as a chemical battery and requires a lot of infrastructure to pull off.

gum_ina_package 13y ago

I'd be curious to see the immediate/longterm ROI for something like this. It seems like there would be an incredible amount of resources spent on initially building a powerhouse like the one in the picture.

jmelloy 13y ago
There's one in England that's mainly for tea kettles after major television events, like Eastenders. They're one of the power storage options that has the quickest ability to change their output.

kijin 13y ago

At larger scales, these are called pumped-storage hydroelectric plants. There are currently more than 100 GW of pumped-storage capacity in the world, with efficiency ranging from 70% to 87% [1]. They are, in fact, some of the largest batteries we've ever built. They store electricity by pumping thousands of tons of water uphill when demand is low, and letting it fall back down past a bunch of turbines when demand is high. Water is much easier to handle than a solid block of steel, and it's much more scalable as well. You just need a hill and some water, possibly an already existing reservoir. Pumps can be turned on and off almost instantly to meet fluctuating demand. There's one about 10 minutes' drive from where I live. It's marvelous, and the two artificial lakes (one at the top, one at the bottom) also make nice parks for the public to enjoy. Since pumped-storage plants seem to work so well, I wonder if there will be any need to install smaller versions in each home. It's probably going to be difficult to match the efficiency of much larger units. Maybe these will be more useful as backup batteries. [1] https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...

hrjet 13y ago
The only drawback I see with pumped-storage hydroelectric plants is that there could loss of stored energy due to evaporation. I don't know how much loss does it amount to on a sunny day.
- logicallee 13y ago
  it could also rain in your pond and give you free energy.
  - Tloewald 13y ago
    This is in fact the entire principle of hydro-electric power (incidentally, a form of solar power since the water-cycle is driven by heat from the sun).
- JshWright 13y ago
  Another drawback is that building a reservoir on top of a mountain can be a little trickier than originally thought... http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_Station#Upper_reservoir_breached http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_S...

mrgriscom 13y ago

I'm really sick of hearing about this idea. At least this one doesn't make the same mistake of suggesting it should be human powered, but the energy density of gravity is ridiculously low compared to practically any other technology we have. It works for hydroelectric plants because they have HUGE reservoirs to supply them. Assume one of these gravity batteries uses a 100m deep shaft with a counterweight the mass of a Cadillac Escalade. The energy stored is 100m * 2700kg * 9.8m/s^2 = 2.6 MJ. The first deep-cycle battery I found through google (retail price $260) is 90Ah * 12V * (assume 80% discharge cycle) = 3.1 MJ. It just doesn't add up!

puetzk 13y ago

The problem is the poor density: power stored is just mass * gravity * height. So if we want to store 1kWh, using a hole 500m deep (about the max for elevator cables, which seems analogous) this would need a 750kg weight. Storing the same amount of energy in a lead-acid battery would only take 21kg, a LiFePO battery only ~10kg. And those don't require digging out a 500m hole, or the supporting equipment to winch a car up and down a skyscraper.

Geee 13y ago

Better would be to use your whole house as the weight. And store the energy in angular momentum.. That's limitless energy storage :D

alextingle 13y ago
Wheeeee.....!!

tehwalrus 13y ago

I've always imagined a frictionless spinning top instead of a long shaft (using permanent magnets, perhaps with some copper coils for stabilisation). You don't need a big geometry, and you can go faster and faster, up to relativistic speeds if required, without any inefficiency. (of course, it must be in a vacuum tube.) EDIT: thanks everyone, now I know that that's what a flywheel is. Had heard the name, never found out what one was.

wffurr 13y ago
You mean a flywheel: http://en.wikipedia.org/wiki/Flywheel_energy_storage http://en.wikipedia.org/wiki/Flywheel_energy_storage They're in use for a number of applications, namely in datacenter UPS systems. The main downside is a catastrophic failure mode. Lots of mass, spinning at high speed. Just apply imagination. Their energy density is pretty good relative to batteries, which is to say terribad compared to hydrocarbons. Good ones are pretty expensive, and they require periodic servicing for bearings, gaskets (for vacuum sealed systems), etc. Generally limited to niche applications for now, but there are various pilot projects to look at them for train system energy recovery and grid storage.
- pygy_ 13y ago
  For safety, they can be burried, can't they?
- tehwalrus 13y ago
  yeah, my thought process had some pretty complicated failure systems. The thing is, with magnetic suspension, you can "catch" the thing using it's own energy. With a good and fast enough controller, you could catch the thing where it is and flood the tube with air to slow it down. since all you're doing is dissipating energy, you can use it to soften the crash. In terms of energy density, you can just *keep increasing the speed can't you?
  - pbhjpbhj 13y ago
    >In terms of energy density, you can just increasing the speed can't you? // In which case you only need a tiny mass to start with ... The speed limitation is presumably going to come in with the rate at which you can alter the magnetic field to still accelerate the mass. Also you'll get drag as it impinges on local fields (Earth's magnetic field) and there'll presumably be eddy currents and local electrical fields to cope with too which will become more significant at higher flux rates.

ghh 13y ago

GravityLight[1] applied this concept at small scale: to power a white led in e.g. rural areas without power, a bag of dirt is suspended from a dynamo. [1] http://www.indiegogo.com/projects/gravitylight-lighting-for-developing-countries http://www.indiegogo.com/projects/gravitylight-lighting-for-...

heeton 13y ago

I refuted a few of his points and got banned from commenting ;)

pkinsky 13y ago

>(H) Generator & CPU > The generator axis gets spinned I think you mean spun. Aside from that, very cool!

achy 13y ago

A pretty illustration of a terrible idea. Gravity just isn't that strong of a force. Electrostatic forces in chemical bonds on the other hand...

stox 13y ago

The ghost of Storm King rises again.