7 ms·

GravityLight: Generate light with gravity

384 points by dimitrideag 11y ago

Orinocco 11y ago
Loads of great social tech ideas including this one on Social Tech Guide (http://socialtech.org.uk/ http://socialtech.org.uk/), nominations are open for new ones at the moment if you come across any more..
- carapace 11y ago
  Why downvote this? Seems legit.
bcg1 11y ago
This is wonderful. I plan to buy at least one for emergencies, and also to help make them cheaper for others.
- IshKebab 11y ago
  A battery powered LED torch is far superior for emergencies. The only reason you'd really want to use this is if you really can't afford a solar-rechargable battery. (But for some reason can afford this, which I'd expect to be more expensive.)
  - giarc 11y ago
    Although that might be true, battery powered flashlights/torches suffer from the problem of leaky batteries. I've tried to use many flashlights that don't work, only to find the batteries have started to leak acid and ruined the flashlight. Sure, one should check the batteries every year or so, but who really does that? I'm not saying the gravitylight is a good replacement, just that battery powered flashlights do have some drawbacks.
    - libria 11y ago
      This is what lithium primaries are for; they don't leak.
      - Vexs 11y ago
        And before anyone jumps in and says "lithium batteries self discharge!" Yes, yes they do. But it's really, really small. It discharges quickly initially, but then tapers off to about 1% per month.
  - dragonwriter 11y ago
    > A battery powered LED torch is far superior for emergencies. The only reason you'd really want to use this is if you really can't afford a solar-rechargable battery. Rechargeable batteries can be reused, but still need to be replaced; this may prove lower maintenance, which means once you can get it, you are more secure with it with a less secure distribution system. In many of the places where people are without electricity in the world, that's potentially a significant benefit. (Also, solar recharging in places that experience long periods of darkness, e.g., the arctic, may not be an ideal solution. There aren't any places that experience extended periods without gravity, at least not on Earth.)
    - Someone 11y ago
      That's true, but the statement was as to its usefulness in emergencies. This thing is fixed to the wall, limiting what you can use it for in an emergency. For example, if you have to find your car keys in a different room, make emergency repairs to your water mains after an earthquake, or figure out how to get a friend out from a collapsed wall in the dark, a torch is more useful. For emergencies, I would prefer a mechanically powered flashlight with a supercapacitor over this thing.
manveru 11y ago
Here's what people said about it 3 years ago: https://news.ycombinator.com/item?id=4889266 https://news.ycombinator.com/item?id=4889266
- scribscrob 11y ago
  It's amazing the amount of people who immediately cry hoax. Someone raised a good point about taking money from locals and bringing it to Europe/America/China, but clearly this isn't breaking the law of physics.
  - blacksmith_tb 11y ago
    The original OLPC attempted to ship a pull-cord generator. Trevor Bayliss, of Freeplay radio fame, proposed a generator based on hoisting a weight on a branch of a tree. The principle is sound. As for taking money from locals, I would be surprised if kerosene was produced locally... and even if it was, this is a one-time expense, versus an ongoing outlay.
    - eggie 11y ago
      I worked at OLPC. We didn't ship any kinetic charging systems as the most reliable ones had a mean time to failure on the order of ~three full charges. The scheme was cute and captured the imagination of people in the developed west but is fundamentally unsound due to the cost of high precision, reliable manual chargers and their miniscule power output. In addition to yielding only several full charges before the $50 charging unit failed, each charge would require tens of thousands of revolutions of a hand crank. As wonderful as the laptop was I think it would be a very strange thing for a child to do when they could easily play with something more immediate. In practice most of the laptops are charged like other laptops--- from national power grids. Those that aren't are charged from diesel generators and solar power.
  - dang 11y ago
    It's gratifying to see how much more substantive and less dismissive this thread is than that one from 2012. Partly it may be that the project itself has developed, but I'd like to think that HN threads have improved too.
mabbo 11y ago
There's a lot of reasons why this is cool, but I'm skeptical about it's aims to get rid of kerosene lamps. Kerosene lamps are made with garbage. They can be replaced in minutes if there's a problem. Fuel costs are high, yes, but capital costs and maintenance are low. Those matter. To really make this a long term win, you need to make it indestructible and easy to repair with on-hand parts. I hope they can do that.
- Vexs 11y ago
  I can see that potentially being a problem, especially if dirt or something gets caught in it. However, the most delicate part of it is the most replaceable, that band could be easily made out of cloth or leather, and motors are usually fairly available. It's most certainly a better argument than "it's not much power" etc, but I'm not convinced it matters too much. I doubt just as much as the next guy these things will change the world, but it's a noble idea and a noble purpose.
- daenz 11y ago
  > To really make this a long term win, you need to make it indestructible and easy to repair with on-hand parts. That was the first thing I looked for. The materials, at least from this image, look plastic and very custom made. http://static1.squarespace.com/static/552aca94e4b0c75f5b87b0fe/55313052e4b0d019cecfee93/5534b842e4b0c15a1026ee7d/1431037170998/GL_example_asitcomes.jpg?format=1000w http://static1.squarespace.com/static/552aca94e4b0c75f5b87b0... If these parts get brittle and break/crack, how are they repaired?
- metasean 11y ago
  It looks like they are trying to make them in a locally sustainable manner... >We're doing this in our approach to distributing GravityLight >We are partnering with local networks of people earning a living by selling products such as GravityLight, rather than disrupting local markets and jobs with free giveaways. >We're doing this in our manufacturing strategy >We aim to create jobs and skills in the regions where GravityLight will be sold, firstly by establishing an assembly line in Kenya. from http://gravitylight.org/our-approach-3/ http://gravitylight.org/our-approach-3/ --- And it looks like they've already run into robustness issues, but they weren't due to cheap plastic components, and it looks like they've modified the system to deal with them... >GL01 had a protection mechanism that clearly indicated an overload with a red light, and helped reduce damage to the gear teeth by allowing it to run more swiftly, but this did not make it indestructible. An entirely novel way of protecting the system has been designed for GL02. It will allow an overloaded bag to descend to the ground in a safe and controlled manner, repeatedly. >GL02 suspends the bag from a pulley, which reduces the strain on the cord and the gearing. This also decreases the loading on the drive system and permits a smaller gearbox ratio, which helps to improve efficiency. from http://gravitylight.org/coming-soon-gl02/ http://gravitylight.org/coming-soon-gl02/
hanoz 11y ago
You need to lift a 10KG weight about 2 kilometres to get a teaspoon of kerosene's energy, so it's not a great replacement on that front, and having 10KG weights dangling around at variable points between ceiling and floor sounds if anything even more of a liability than a lamp with a naked flame, which does at least stay where its put. Sorry to be negative but it's difficult to conceive of a realistic scenario where decent battery plus solar doesn't knock this into a cocked hat.
- icebraining 11y ago
  The amount of energy is not directly comparable if the efficiency of its use is very different. A kerosene lamp is multiple orders of magnitude less efficient than decent LEDs, so while you might have to lift 2KM to get the same energy, you'd have to lift much, much less to get the same amount of lumen-hours. A kerosene lamp has an efficiency of 0.1-1 lumens/watt, while a white LED has anything around 80-100 lumens/watt.
- astrobiased 11y ago
  Regarding the energy of lifting a 10KG weight 2 KM high is not a 1:1 comparison with the tech here. It's using an LED which much more efficient than a Kerosene powered flame, since most of the energy in the flame is spent in infrared.
- beardicus 11y ago
  > You need to lift a 10KG weight about 2 kilometres to get a teaspoon of kerosene's energy, so it's not a great replacement on that front This says nothing of light output. If you want light, and most of kerosene's output is heat, your energy calculation is not helpful. > and having 10KG weights dangling around at variable points between ceiling and floor sounds if anything even more of a liability than a lamp with a naked flame This seems like an incredibly contrived "problem". What's the liability? Somebody may bump into a somewhat heavy object that is moving downwards at a barely perceptible clip? Somebody may tweak their back lifting the weight? That seems lower risk than my housing burning down with me in it.
  - hanoz 11y ago
jpeterson 11y ago
The basic idea here is actually a very old approach -- clocks have been powered this way for centuries. But it's very cool and refreshing to see a modern electrical spin on it.
- Vexs 11y ago
  Might be fun to make an electric clock that uses gravity, go full circle.
  - fla 11y ago
    Rotor systems like in some automatic watches produce very little energy. Even at 100% efficiency it wouldn't be able to sustain an electronic circuit. Edit: I was wrong. See below.
    - aidenn0 11y ago
      My automatic watch contains an electronic circuit, so I'm not sure what your point is.
      - fla 11y ago
        Interesting. What is the circuit for ? Are you sure it's not powered by a standard watch battery ?
        aidenn0 11y ago
        Yes, it is a quartz movement with a capacitor that is charged by a mechanism similar to a mechanical auto-winding watch. https://en.wikipedia.org/wiki/Automatic_watch#Automatic_quartz_or_kinetic_movement https://en.wikipedia.org/wiki/Automatic_watch#Automatic_quar...
    - mattgrice 11y ago
      Seiko Kinetic watches are quartz watches that are powered by movement. That's 30 year old technology.
montecarl 11y ago
Its cool our energy problems are being solved in two directions at once. We are (slowly) making better energy storage and generation devices. At the same time many of our energy needs go down by the rapid decrease in energy needed to power the electronics. It would be cool to see a graph of the watts/lumen efficiency of light bulbs over the last 50 years and of the joules/operation of CPUs.
- tdaltonc 11y ago
  Manhour/lumen is the only measure I know of that captures all of the elements of economic growth and can be estimated for every culture and back to before the development of spoken language.
ajuc 11y ago
Nitpick, I know, but: it's not powered by gravity it's powered by human muscles, so in the end - by food.
- romaniv 11y ago
  I don't think it's a nitpick. I think this is a very important point. Is the hypothetical fuel more expensive than food?
  - ajuc 11y ago
    LED is much more efficient than kerosene lamp, so I guess yes.
  - daveloyall 11y ago
    I think your muscles are pretty energy efficient. The kinetic potential battery (the weight lifted against gravity) is also very efficient. Food is very energy dense. https://what-if.xkcd.com/128/ https://what-if.xkcd.com/128/ (sandwich vs battery) Uh, change of topic: isn't the caloric value of a food how much heat can be released by burning it (probably when it is dehydrated)? Plenty of energy stored in a sandwich, sure. But a car battery could power a small spaceheater-like thing for... a while. There's a lot of potential for heat production in a car battery (even without BURNING it). Did Mr. Munroe get this one wrong?
    - gus_massa 11y ago
      From Wikipedia: https://en.wikipedia.org/wiki/Muscle#Efficiency https://en.wikipedia.org/wiki/Muscle#Efficiency > The efficiency of human muscle has been measured (in the context of rowing and cycling) at 18% to 26%. The efficiency is defined as the ratio of mechanical work output to the total metabolic cost, as can be calculated from oxygen consumption.
- haxiomic 11y ago
  I take your point, but the food ultimately gets its energy from the sun, which gets its energy from collapsing under gravity. I don't think there's a clear place to stop, but I'd say the name Gravity Light gets the idea across anyhow
achr2 11y ago
Years ago there was a similar 'potential energy to electricity' buzz and I was initially quite excited. Then I did the math on how much energy is actually available (even at 100% efficiency) from such a scheme. Spoiler - it's minuscule. E = mass x 9.81 x height So a 10kg mass at 2 meters can (@ 100% efficiency) provide 196 joules of energy. A modern cell phone battery has about 25000 joules. To charge said phone would require raising that weight well over 127 times.
- pavel_lishin 11y ago
  But this isn't for charging a phone; it's for having light, right now.
  - achr2 11y ago
    I get it, I am just saying that there are a lot of ways to make a single LED light shine, potential energy from a weight is likely the least sensical.
    - bnegreve 11y ago
      > potential energy from a weight is likely the least sensical. potential energy is very easy to produce, keresene is not always available. I think this is the #1 benefit.
    - deleted 11y ago
      [deleted]
  - Gravityloss 11y ago
    1 watt of led light would require 1 Newton at 1 meters per second. Assuming 100 kg is the highest practicable mass, so that's 1000 Newtons -> 1/1000 m/s for each watt. Assuming a height of 2 meters, you could operate a very dim 2 watt led light for 17 minutes. I think that's not practical.
    - CyberDildonics 11y ago
      You can use it to read and it is free.
nirai 11y ago
what is the deep difference between this mechanism and a simple spring / coil?
- yconst 11y ago
  Precisely the same question I have as well. Especially given that the energy you could store in a spring or coil could be much more, and you are not limited by one's lifting capacity or maximum height. Anyone have an idea?
deleted 11y ago
[deleted]
biot 11y ago
Perhaps a bit of a novelty given the rechargeable battery argument others have mentioned. I imagine distributing a bunch of these with batteries and having a central dynamo-powered recharging station that gets shared throughout a community would be even more practical. The first thing that came to mind when I saw that it lasts 20 minutes would be to use it as a pomodoro timer. Code for 20 minutes, then be forced to take a break, stand up, lift the weight, etc. You get a micro-workout as a small bonus. Again, it's a novelty but sort of a cool one at that.
ris 11y ago
I implore people to support something far more practical like http://www.solar-aid.org/ http://www.solar-aid.org/ than this. Solar lights are many times more thermodynamically efficient, cheaper to make, smaller and much more robust (no moving parts!). This "lifting weights" thing is a silly gimmick. A lifted weight stores a miniscule amount of energy compared to a battery that's been charged by the sun.
- kbenson 11y ago
  Don't both have their places? There are benefits to having a power source that is a) not dependent on a resource that is not available at all times and b) does not require a charging period. It's sort of like people in the late 19th century saying you shouldn't support the development of automobiles, because boats are much more efficient way to move cargo. While true, it does nothing to address the fact that in some cases the use of a boat makes no sense, such as transporting to a land-locked location.
  - ris 11y ago
    "Don't both have their places?" It's more that this "invention" has been bouncing around for a while and gets an unwarranted amount of attention for the amount of energy it can provide. Weird to think, but solar isn't "sexy" in the same way.
    - kbenson 11y ago
      Maybe that "unwarranted amount of attention" is because it has a different set of requirement for use than solar which makes it particularly attractive. Considering only the energy efficiency and not how it could or would actually be used by the target consumers seems shortsighted to me. It may yield a the most efficient product, but it may not yield the most effective product.
      - ris 11y ago
        Yeah, sure, but that set of requirements is, I'd argue anyway, probably more appropriately served by something clockwork or something crank-based that charges a battery.
electic 11y ago
For those interested on exactly how to set one up and how it works, there is a great Vimeo video outlining installation and operation: https://vimeo.com/128802766 https://vimeo.com/128802766
jackdawjack 11y ago
I was rather hoping this would be a hawking radiation method, i.e. actually generating light using gravity
- chinpokomon 11y ago
  You and I both. This isn't even carbon neutral. I mean technically this is burning carbon molecules.
  - Vendan 11y ago
    burning carbon molecules sourced from photosynthesis. Carbon positive, but the fuel generation is carbon negative, so it balances out.
jackdawjack 11y ago
I was rather hoping this would be a hawking radiation method, i.e. actually generating light using gravity
brannon 11y ago
A 12kg weight hanging 6 feet in the air seems a little dangerous to me. Definitely less dangerous than a kerosene lamp, but I'd be worried about poorly attached weights falling if someone bumps their head on it.
- ricardobeat 11y ago
  Do you own a TV? It's certainly way more dangerous than that.
userbinator 11y ago
It looks quite a bit more plausible than the specs in http://www.howtospotapsychopath.com/2008/03/03/stop-press-pixie-dust-unsuitable-for-household-lighting/ http://www.howtospotapsychopath.com/2008/03/03/stop-press-pi... , but based on my experience with things like shake/crank torches, the light output would have to be really low to last as long as they claim it does.
dnautics 11y ago
12kg * 10 m/s^2 * 1 m = 120j. Best 100 w equivalent led is 18 watts, 120j/18w < 10s. Let's say optimistically a next gen led gets 10x efficiency (this might violate laws of physics), you're buying one minute of good light per 1 m lift.
jheriko 11y ago
these look interesting... but like all things like this i wonder what the actual costs are of lifting the weight is?
mhb 11y ago
Doing Good Better - http://marginalrevolution.com/marginalrevolution/2015/07/doing-good-better.html http://marginalrevolution.com/marginalrevolution/2015/07/doi...

384 points by dimitrideag 11y ago

Loads of great social tech ideas including this one on Social Tech Guide (http://socialtech.org.uk/ http://socialtech.org.uk/), nominations are open for new ones at the moment if you come across any more..

carapace 11y ago
Why downvote this? Seems legit.

bcg1 11y ago

This is wonderful. I plan to buy at least one for emergencies, and also to help make them cheaper for others.

IshKebab 11y ago
A battery powered LED torch is far superior for emergencies. The only reason you'd really want to use this is if you really can't afford a solar-rechargable battery. (But for some reason can afford this, which I'd expect to be more expensive.)
- giarc 11y ago
  Although that might be true, battery powered flashlights/torches suffer from the problem of leaky batteries. I've tried to use many flashlights that don't work, only to find the batteries have started to leak acid and ruined the flashlight. Sure, one should check the batteries every year or so, but who really does that? I'm not saying the gravitylight is a good replacement, just that battery powered flashlights do have some drawbacks.
  - libria 11y ago
    This is what lithium primaries are for; they don't leak.
    - Vexs 11y ago
      And before anyone jumps in and says "lithium batteries self discharge!" Yes, yes they do. But it's really, really small. It discharges quickly initially, but then tapers off to about 1% per month.
- dragonwriter 11y ago
  > A battery powered LED torch is far superior for emergencies. The only reason you'd really want to use this is if you really can't afford a solar-rechargable battery. Rechargeable batteries can be reused, but still need to be replaced; this may prove lower maintenance, which means once you can get it, you are more secure with it with a less secure distribution system. In many of the places where people are without electricity in the world, that's potentially a significant benefit. (Also, solar recharging in places that experience long periods of darkness, e.g., the arctic, may not be an ideal solution. There aren't any places that experience extended periods without gravity, at least not on Earth.)
  - Someone 11y ago
    That's true, but the statement was as to its usefulness in emergencies. This thing is fixed to the wall, limiting what you can use it for in an emergency. For example, if you have to find your car keys in a different room, make emergency repairs to your water mains after an earthquake, or figure out how to get a friend out from a collapsed wall in the dark, a torch is more useful. For emergencies, I would prefer a mechanically powered flashlight with a supercapacitor over this thing.

manveru 11y ago

Here's what people said about it 3 years ago: https://news.ycombinator.com/item?id=4889266 https://news.ycombinator.com/item?id=4889266

scribscrob 11y ago
It's amazing the amount of people who immediately cry hoax. Someone raised a good point about taking money from locals and bringing it to Europe/America/China, but clearly this isn't breaking the law of physics.
- blacksmith_tb 11y ago
  The original OLPC attempted to ship a pull-cord generator. Trevor Bayliss, of Freeplay radio fame, proposed a generator based on hoisting a weight on a branch of a tree. The principle is sound. As for taking money from locals, I would be surprised if kerosene was produced locally... and even if it was, this is a one-time expense, versus an ongoing outlay.
  - eggie 11y ago
    I worked at OLPC. We didn't ship any kinetic charging systems as the most reliable ones had a mean time to failure on the order of ~three full charges. The scheme was cute and captured the imagination of people in the developed west but is fundamentally unsound due to the cost of high precision, reliable manual chargers and their miniscule power output. In addition to yielding only several full charges before the $50 charging unit failed, each charge would require tens of thousands of revolutions of a hand crank. As wonderful as the laptop was I think it would be a very strange thing for a child to do when they could easily play with something more immediate. In practice most of the laptops are charged like other laptops--- from national power grids. Those that aren't are charged from diesel generators and solar power.
- dang 11y ago
  It's gratifying to see how much more substantive and less dismissive this thread is than that one from 2012. Partly it may be that the project itself has developed, but I'd like to think that HN threads have improved too.

mabbo 11y ago

There's a lot of reasons why this is cool, but I'm skeptical about it's aims to get rid of kerosene lamps. Kerosene lamps are made with garbage. They can be replaced in minutes if there's a problem. Fuel costs are high, yes, but capital costs and maintenance are low. Those matter. To really make this a long term win, you need to make it indestructible and easy to repair with on-hand parts. I hope they can do that.

Vexs 11y ago
I can see that potentially being a problem, especially if dirt or something gets caught in it. However, the most delicate part of it is the most replaceable, that band could be easily made out of cloth or leather, and motors are usually fairly available. It's most certainly a better argument than "it's not much power" etc, but I'm not convinced it matters too much. I doubt just as much as the next guy these things will change the world, but it's a noble idea and a noble purpose.
daenz 11y ago
> To really make this a long term win, you need to make it indestructible and easy to repair with on-hand parts. That was the first thing I looked for. The materials, at least from this image, look plastic and very custom made. http://static1.squarespace.com/static/552aca94e4b0c75f5b87b0fe/55313052e4b0d019cecfee93/5534b842e4b0c15a1026ee7d/1431037170998/GL_example_asitcomes.jpg?format=1000w http://static1.squarespace.com/static/552aca94e4b0c75f5b87b0... If these parts get brittle and break/crack, how are they repaired?
metasean 11y ago
It looks like they are trying to make them in a locally sustainable manner... >We're doing this in our approach to distributing GravityLight >We are partnering with local networks of people earning a living by selling products such as GravityLight, rather than disrupting local markets and jobs with free giveaways. >We're doing this in our manufacturing strategy >We aim to create jobs and skills in the regions where GravityLight will be sold, firstly by establishing an assembly line in Kenya. from http://gravitylight.org/our-approach-3/ http://gravitylight.org/our-approach-3/ --- And it looks like they've already run into robustness issues, but they weren't due to cheap plastic components, and it looks like they've modified the system to deal with them... >GL01 had a protection mechanism that clearly indicated an overload with a red light, and helped reduce damage to the gear teeth by allowing it to run more swiftly, but this did not make it indestructible. An entirely novel way of protecting the system has been designed for GL02. It will allow an overloaded bag to descend to the ground in a safe and controlled manner, repeatedly. >GL02 suspends the bag from a pulley, which reduces the strain on the cord and the gearing. This also decreases the loading on the drive system and permits a smaller gearbox ratio, which helps to improve efficiency. from http://gravitylight.org/coming-soon-gl02/ http://gravitylight.org/coming-soon-gl02/

hanoz 11y ago

You need to lift a 10KG weight about 2 kilometres to get a teaspoon of kerosene's energy, so it's not a great replacement on that front, and having 10KG weights dangling around at variable points between ceiling and floor sounds if anything even more of a liability than a lamp with a naked flame, which does at least stay where its put. Sorry to be negative but it's difficult to conceive of a realistic scenario where decent battery plus solar doesn't knock this into a cocked hat.

icebraining 11y ago
The amount of energy is not directly comparable if the efficiency of its use is very different. A kerosene lamp is multiple orders of magnitude less efficient than decent LEDs, so while you might have to lift 2KM to get the same energy, you'd have to lift much, much less to get the same amount of lumen-hours. A kerosene lamp has an efficiency of 0.1-1 lumens/watt, while a white LED has anything around 80-100 lumens/watt.
astrobiased 11y ago
Regarding the energy of lifting a 10KG weight 2 KM high is not a 1:1 comparison with the tech here. It's using an LED which much more efficient than a Kerosene powered flame, since most of the energy in the flame is spent in infrared.
beardicus 11y ago
> You need to lift a 10KG weight about 2 kilometres to get a teaspoon of kerosene's energy, so it's not a great replacement on that front This says nothing of light output. If you want light, and most of kerosene's output is heat, your energy calculation is not helpful. > and having 10KG weights dangling around at variable points between ceiling and floor sounds if anything even more of a liability than a lamp with a naked flame This seems like an incredibly contrived "problem". What's the liability? Somebody may bump into a somewhat heavy object that is moving downwards at a barely perceptible clip? Somebody may tweak their back lifting the weight? That seems lower risk than my housing burning down with me in it.
- hanoz 11y ago

jpeterson 11y ago

The basic idea here is actually a very old approach -- clocks have been powered this way for centuries. But it's very cool and refreshing to see a modern electrical spin on it.

Vexs 11y ago
Might be fun to make an electric clock that uses gravity, go full circle.
- fla 11y ago
  Rotor systems like in some automatic watches produce very little energy. Even at 100% efficiency it wouldn't be able to sustain an electronic circuit. Edit: I was wrong. See below.
  - aidenn0 11y ago
    My automatic watch contains an electronic circuit, so I'm not sure what your point is.
    - fla 11y ago
      Interesting. What is the circuit for ? Are you sure it's not powered by a standard watch battery ?
      - aidenn0 11y ago
        Yes, it is a quartz movement with a capacitor that is charged by a mechanism similar to a mechanical auto-winding watch. https://en.wikipedia.org/wiki/Automatic_watch#Automatic_quartz_or_kinetic_movement https://en.wikipedia.org/wiki/Automatic_watch#Automatic_quar...
  - mattgrice 11y ago
    Seiko Kinetic watches are quartz watches that are powered by movement. That's 30 year old technology.

montecarl 11y ago

Its cool our energy problems are being solved in two directions at once. We are (slowly) making better energy storage and generation devices. At the same time many of our energy needs go down by the rapid decrease in energy needed to power the electronics. It would be cool to see a graph of the watts/lumen efficiency of light bulbs over the last 50 years and of the joules/operation of CPUs.

tdaltonc 11y ago
Manhour/lumen is the only measure I know of that captures all of the elements of economic growth and can be estimated for every culture and back to before the development of spoken language.

ajuc 11y ago

Nitpick, I know, but: it's not powered by gravity it's powered by human muscles, so in the end - by food.

romaniv 11y ago
I don't think it's a nitpick. I think this is a very important point. Is the hypothetical fuel more expensive than food?
- ajuc 11y ago
  LED is much more efficient than kerosene lamp, so I guess yes.
- daveloyall 11y ago
  I think your muscles are pretty energy efficient. The kinetic potential battery (the weight lifted against gravity) is also very efficient. Food is very energy dense. https://what-if.xkcd.com/128/ https://what-if.xkcd.com/128/ (sandwich vs battery) Uh, change of topic: isn't the caloric value of a food how much heat can be released by burning it (probably when it is dehydrated)? Plenty of energy stored in a sandwich, sure. But a car battery could power a small spaceheater-like thing for... a while. There's a lot of potential for heat production in a car battery (even without BURNING it). Did Mr. Munroe get this one wrong?
  - gus_massa 11y ago
    From Wikipedia: https://en.wikipedia.org/wiki/Muscle#Efficiency https://en.wikipedia.org/wiki/Muscle#Efficiency > The efficiency of human muscle has been measured (in the context of rowing and cycling) at 18% to 26%. The efficiency is defined as the ratio of mechanical work output to the total metabolic cost, as can be calculated from oxygen consumption.
haxiomic 11y ago
I take your point, but the food ultimately gets its energy from the sun, which gets its energy from collapsing under gravity. I don't think there's a clear place to stop, but I'd say the name Gravity Light gets the idea across anyhow

achr2 11y ago

Years ago there was a similar 'potential energy to electricity' buzz and I was initially quite excited. Then I did the math on how much energy is actually available (even at 100% efficiency) from such a scheme. Spoiler - it's minuscule. E = mass x 9.81 x height So a 10kg mass at 2 meters can (@ 100% efficiency) provide 196 joules of energy. A modern cell phone battery has about 25000 joules. To charge said phone would require raising that weight well over 127 times.

pavel_lishin 11y ago
But this isn't for charging a phone; it's for having light, right now.
- achr2 11y ago
  I get it, I am just saying that there are a lot of ways to make a single LED light shine, potential energy from a weight is likely the least sensical.
  - bnegreve 11y ago
    > potential energy from a weight is likely the least sensical. potential energy is very easy to produce, keresene is not always available. I think this is the #1 benefit.
  - deleted 11y ago
    [deleted]
- Gravityloss 11y ago
  1 watt of led light would require 1 Newton at 1 meters per second. Assuming 100 kg is the highest practicable mass, so that's 1000 Newtons -> 1/1000 m/s for each watt. Assuming a height of 2 meters, you could operate a very dim 2 watt led light for 17 minutes. I think that's not practical.
  - CyberDildonics 11y ago
    You can use it to read and it is free.

nirai 11y ago

what is the deep difference between this mechanism and a simple spring / coil?

yconst 11y ago
Precisely the same question I have as well. Especially given that the energy you could store in a spring or coil could be much more, and you are not limited by one's lifting capacity or maximum height. Anyone have an idea?

deleted 11y ago

[deleted]

biot 11y ago

Perhaps a bit of a novelty given the rechargeable battery argument others have mentioned. I imagine distributing a bunch of these with batteries and having a central dynamo-powered recharging station that gets shared throughout a community would be even more practical. The first thing that came to mind when I saw that it lasts 20 minutes would be to use it as a pomodoro timer. Code for 20 minutes, then be forced to take a break, stand up, lift the weight, etc. You get a micro-workout as a small bonus. Again, it's a novelty but sort of a cool one at that.

ris 11y ago

I implore people to support something far more practical like http://www.solar-aid.org/ http://www.solar-aid.org/ than this. Solar lights are many times more thermodynamically efficient, cheaper to make, smaller and much more robust (no moving parts!). This "lifting weights" thing is a silly gimmick. A lifted weight stores a miniscule amount of energy compared to a battery that's been charged by the sun.

kbenson 11y ago
Don't both have their places? There are benefits to having a power source that is a) not dependent on a resource that is not available at all times and b) does not require a charging period. It's sort of like people in the late 19th century saying you shouldn't support the development of automobiles, because boats are much more efficient way to move cargo. While true, it does nothing to address the fact that in some cases the use of a boat makes no sense, such as transporting to a land-locked location.
- ris 11y ago
  "Don't both have their places?" It's more that this "invention" has been bouncing around for a while and gets an unwarranted amount of attention for the amount of energy it can provide. Weird to think, but solar isn't "sexy" in the same way.
  - kbenson 11y ago
    Maybe that "unwarranted amount of attention" is because it has a different set of requirement for use than solar which makes it particularly attractive. Considering only the energy efficiency and not how it could or would actually be used by the target consumers seems shortsighted to me. It may yield a the most efficient product, but it may not yield the most effective product.
    - ris 11y ago
      Yeah, sure, but that set of requirements is, I'd argue anyway, probably more appropriately served by something clockwork or something crank-based that charges a battery.

electic 11y ago

For those interested on exactly how to set one up and how it works, there is a great Vimeo video outlining installation and operation: https://vimeo.com/128802766 https://vimeo.com/128802766

jackdawjack 11y ago

I was rather hoping this would be a hawking radiation method, i.e. actually generating light using gravity

chinpokomon 11y ago
You and I both. This isn't even carbon neutral. I mean technically this is burning carbon molecules.
- Vendan 11y ago
  burning carbon molecules sourced from photosynthesis. Carbon positive, but the fuel generation is carbon negative, so it balances out.

jackdawjack 11y ago

I was rather hoping this would be a hawking radiation method, i.e. actually generating light using gravity

brannon 11y ago

A 12kg weight hanging 6 feet in the air seems a little dangerous to me. Definitely less dangerous than a kerosene lamp, but I'd be worried about poorly attached weights falling if someone bumps their head on it.

ricardobeat 11y ago
Do you own a TV? It's certainly way more dangerous than that.

userbinator 11y ago

It looks quite a bit more plausible than the specs in http://www.howtospotapsychopath.com/2008/03/03/stop-press-pixie-dust-unsuitable-for-household-lighting/ http://www.howtospotapsychopath.com/2008/03/03/stop-press-pi... , but based on my experience with things like shake/crank torches, the light output would have to be really low to last as long as they claim it does.

dnautics 11y ago

12kg * 10 m/s^2 * 1 m = 120j. Best 100 w equivalent led is 18 watts, 120j/18w < 10s. Let's say optimistically a next gen led gets 10x efficiency (this might violate laws of physics), you're buying one minute of good light per 1 m lift.

jheriko 11y ago

these look interesting... but like all things like this i wonder what the actual costs are of lifting the weight is?

mhb 11y ago

Doing Good Better - http://marginalrevolution.com/marginalrevolution/2015/07/doing-good-better.html http://marginalrevolution.com/marginalrevolution/2015/07/doi...