Author Topic: Great Idea - Gravity Powered Light  (Read 14509 times)

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Offline SLJTopic starter

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Great Idea - Gravity Powered Light
« on: January 10, 2013, 11:38:33 am »
Here's a great idea.  Coo Coo Clock power meets high efficiency LEDs:

http://www.indiegogo.com/projects/282006

Heck,  I'd get some of these for around my house.

Offline Dago

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Re: Great Idea - Gravity Powered Light
« Reply #1 on: January 10, 2013, 12:13:49 pm »
Does not seem terribly useful when you do the math. Assuming the bag weighs say 5kg and its raised to a height of two meters, it will contain about a hundred joules of potential energy. Assuming a (low powered) LED light that uses 1W and no conversion losses the light would light up for about 1min and 40 seconds. In reality it will light up for maybe half or at max 2/3 of that time.

And it scales linearly so hanging 50kg to two meters would make the light light up for a maximum of around 17minutes.
« Last Edit: January 10, 2013, 12:16:37 pm by Dago »
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Offline amyk

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Re: Great Idea - Gravity Powered Light
« Reply #2 on: January 10, 2013, 12:47:24 pm »
Looks a little more realistic than some previous attempts but still,
Quote
GravityLight's output is better than a kerosene lamp.
I doubt it.
 

Offline FrankBuss

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Re: Great Idea - Gravity Powered Light
« Reply #3 on: August 01, 2015, 05:41:27 am »
There is a new campaign with an improved version, GravityLight 2. From the FAQ: "A 6ft [1.8m] drop gives over 20 minutes of light.". Sounds useful. You can lift it in seconds to recharge.
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Online PlainName

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Re: Great Idea - Gravity Powered Light
« Reply #4 on: August 01, 2015, 09:35:30 am »
Quote
Does not seem terribly useful when you do the math.

Maths isn't everything :)

I bought into the original and acquired one. It does what it says on the box and provides gravity-powered light. It is useless in my office or home, but it was brilliant during out bonfire night party to light between the pools of light out the back. Well, providing someone lifted the weight as they went past so it didn't run down.

And that's where this is aimed. It's not to be compared with lights as we know them, but with no light at all. Once acquired, it is free light - nothing to charge, no fuel to use, just a weight to lift five feet twice an hour. And the light it puts out may not be enough to read by from ten feet away, but it's a hell of a lot better than nothing and allows you to do stuff you'd otherwise not be able to do. Or just sit there and see things.

I have a couple of issues with mine (not waterproof, so not so hot in the garden, for instance, and the bags could be a little bigger to allow for less dense packing material than soil) but it is a brilliant idea and execution of same IMO.


 

Offline FrankBuss

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Re: Great Idea - Gravity Powered Light
« Reply #5 on: August 01, 2015, 09:57:58 am »
@dunkemhigh, cool, can you post some photos what's inside? I guess nothing interesting, a rectifier, capacitor and maybe not even a voltage regulator, because the description for the old version says it is brighter if the weight is higher. I could already think of some improvements, like blinking when the weight is at the bottom (could use a bigger storage capacitor and measure the power source), because if you are focussed on doing your homework or something (as intended for Africa), you might not notice the position of the sand bag and then I guess it shuts off quickly.

I just backed the new version.
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Offline rs20

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Re: Great Idea - Gravity Powered Light
« Reply #6 on: August 01, 2015, 10:05:04 am »
Maths isn't everything :)

 :wtf:

Aim your criticism the right way at least; the faulty assumption was a 1W led. The maths was fine. Evidently, the LED actually runs on less than 80mW, so it must just be a pretty excellent LED.
 

Online mikeselectricstuff

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Re: Great Idea - Gravity Powered Light
« Reply #7 on: August 01, 2015, 10:18:37 am »
The eye is very good at adapting - if there is total darkness, 100mW will easily provide enough to see where you're going, and read by if reasonably close.
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Offline bookaboo

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Re: Great Idea - Gravity Powered Light
« Reply #8 on: August 01, 2015, 11:02:44 am »
In addition to that effect all LEDs become really efficient towards the bottom of their drive current curve. So you have both these working together.

As for the project it's a neat idea and all but for a lot of the developing country applications I don't see what's wrong with a solar solution.
 

Online PlainName

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Re: Great Idea - Gravity Powered Light
« Reply #9 on: August 01, 2015, 11:15:31 am »
Quote
can you post some photos what's inside?

Sure, but not for a while - I am tied up elsewhere for a bit.
 

Online Zero999

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Re: Great Idea - Gravity Powered Light
« Reply #10 on: August 01, 2015, 11:37:07 am »
Maths isn't everything :)

 :wtf:

Aim your criticism the right way at least; the faulty assumption was a 1W led. The maths was fine. Evidently, the LED actually runs on less than 80mW, so it must just be a pretty excellent LED.
Yes, I thought that was a faulty assumption too. 10mA or so into an LED can provide enough light to see and is much better than total darkness.
 

Offline matseng

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Re: Great Idea - Gravity Powered Light
« Reply #11 on: August 01, 2015, 11:41:38 am »
As for the project it's a neat idea and all but for a lot of the developing country applications I don't see what's wrong with a solar solution.
Not sure if you're being serious or just joking...  Solar requires an expensive battery that needs to be replaced every now and then, and it requires *enough* sun during the day to last during the dark hours - if not you're out of luck until the next day.   I'd say that those two arguments against solar powered lights are more than enough to dismiss them compared to "wind-up" lights.
 

Offline bookaboo

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Re: Great Idea - Gravity Powered Light
« Reply #12 on: August 01, 2015, 11:52:27 am »
As for the project it's a neat idea and all but for a lot of the developing country applications I don't see what's wrong with a solar solution.
Not sure if you're being serious or just joking...  Solar requires an expensive battery that needs to be replaced every now and then, and it requires *enough* sun during the day to last during the dark hours - if not you're out of luck until the next day.   I'd say that those two arguments against solar powered lights are more than enough to dismiss them compared to "wind-up" lights.

The indigogo unit was $25.00, you can get a lot of solar rechargable LED for that. Alibaba is full of them. Granted the batteries will probably only last a few years but then that's all I'd expect from this thing.
Furthermore, proper micro generation small scale solar with quality batteries is a very feasible solution to bring "proper" lighting solutions.

As for needing "a lot of light" you can get similar units that work as garden lights that work fine in northern European winters.

So yeah Im serious.
 

Offline rs20

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Re: Great Idea - Gravity Powered Light
« Reply #13 on: August 01, 2015, 12:20:20 pm »
The indigogo unit was $25.00, you can get a lot of solar rechargable LED for that. Alibaba is full of them. Granted the batteries will probably only last a few years but then that's all I'd expect from this thing.
Furthermore, proper micro generation small scale solar with quality batteries is a very feasible solution to bring "proper" lighting solutions.

As for needing "a lot of light" you can get similar units that work as garden lights that work fine in northern European winters.

So yeah Im serious.
I agree, and don't forget that this gravity thing only puts out 80mW for 20 minutes, vs an 18650 cell which can power 13 of these LEDs for 8 hours. So saying "rechargeable batteries are hard to get into developing countries" might be looking past just how miniscule these batteries could be while still outperforming the GravityLight.
 

Offline EEVblog

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Re: Great Idea - Gravity Powered Light
« Reply #14 on: August 01, 2015, 12:40:59 pm »
The eye is very good at adapting - if there is total darkness, 100mW will easily provide enough to see where you're going, and read by if reasonably close.

Yes, there are whole bunch of ultralightweight bushwalking nerds who obsess over weight so much they custom design their own torches and headlamps for long treks, shaving every last gram. That means lasting weeks of nighttime walking and camping and reading etc on a single AAA or whatever. And yes they swear you can navigate with bugger-all light, and certainly read.
I've gone nighttime canyoning with my princeton Tec Eos on the lowest setting, and it would be way under 100mW IIRC.
 

Offline EEVblog

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Re: Great Idea - Gravity Powered Light
« Reply #15 on: August 01, 2015, 12:42:09 pm »
Don't those wind up torches store vastly more energy? If so then what's the point of the gravity one apart from marketing buzz?
 

Offline EEVblog

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Re: Great Idea - Gravity Powered Light
« Reply #16 on: August 01, 2015, 12:46:35 pm »
I've gone nighttime canyoning with my princeton Tec Eos on the lowest setting, and it would be way under 100mW IIRC.

I just checked. The EOS gets 50hrs regulated and 120hrs total on 3xAAA's on the low setting.
1.4Wh per AAA = 4.2Wh = 84mW.
So yes I can (not so easily, but I can) do nighttime canyoning with less than 100mW of light. And that was 5+ years ago, LED efficiency has improved much since then.
 

Offline nctnico

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Re: Great Idea - Gravity Powered Light
« Reply #17 on: August 01, 2015, 01:11:14 pm »
There is a new campaign with an improved version, GravityLight 2. From the FAQ: "A 6ft [1.8m] drop gives over 20 minutes of light.". Sounds useful. You can lift it in seconds to recharge.
Suddenly I picture streets lights with weights hanging from the top and a cord to rewind them...  8) Still I doubt it's well to wheel efficiency isn't that great because our bodies aren't very energy efficient.
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Offline LukeW

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Re: Great Idea - Gravity Powered Light
« Reply #18 on: August 01, 2015, 02:18:00 pm »
Quote
GravityLight's output is better than a kerosene lamp.

Kerosene energy density: 46 MJ/kg.

Gravitational "energy density" (at 1 meter displacement): 9.8 * 10^-6 MJ/kg.
 

Offline amyk

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Re: Great Idea - Gravity Powered Light
« Reply #19 on: August 01, 2015, 02:27:16 pm »
Even better idea: store the energy in a spring that gets wound up...? No need to lift a weight to absurd heights for longer light, springs can store the energy much more densely.
 

Offline rs20

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Re: Great Idea - Gravity Powered Light
« Reply #20 on: August 01, 2015, 02:38:58 pm »
Kerosene energy density: 46 MJ/kg.

Gravitational "energy density" (at 1 meter displacement): 9.8 * 10^-6 MJ/kg.

Heh, so kerosene can lift itself 4693 kilometers vertically (assuming the engine and the oxygen weighs nothing and gravity remains constant). I guess that proves that rockets are feasible!

Interesting to note that the potential energy required to reach geosynchronous orbit is about 50 MJ/kg, incredibly close to the energy density of kerosene. Clearly staging is required for an actual kerosene rocket to get there!
 

Online PlainName

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Re: Great Idea - Gravity Powered Light
« Reply #21 on: August 01, 2015, 03:48:40 pm »
Quote
The indigogo unit was $25.00

Wrong.

Really - I paid $50, and for that I got a unit PLUS some villager got one GRATIS. The $25 perk just sent one to a villager for nothing. i.e. zero cost to the person that counts. How many solar woznames and replacement batteries can you buy for nowt?

The whole point of this campaign wasn't to provide 1st world geeks with a crap toy but to apply modern technology to a 3rd world problem, and have the 1st-worlders pay for it. I reckon they got a result.
 

Online PlainName

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Re: Great Idea - Gravity Powered Light
« Reply #22 on: August 01, 2015, 03:54:26 pm »
Quote
If so then what's the point of the gravity one apart from marketing buzz?

Ever tried charging a wind-up torch? I have many of them, and once they run flat they are shelf fodder. This gravity light gets another half-hour of use just by lifting a bag off the floor - fast, simple, free. If a wind-up torch was like this I would have just the one and it would used all the time...

Battery torch is probably OK if you have a charger, but when it runs out at 10pm that's your day gone. The gravity job never runs out at the wrong time (or, rather, it doesn't matter when that happens because 2 secs later you have another half hour of output).

And... how many peeps are going to buy one of these nice torches and send them, sight unseen, not even an unpack video made, to some 3rd world place? I dont' think you'd run out of fingers working that one out.
 

Offline nitro2k01

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Re: Great Idea - Gravity Powered Light
« Reply #23 on: August 01, 2015, 04:25:51 pm »
Kerosene energy density: 46 MJ/kg.

Gravitational "energy density" (at 1 meter displacement): 9.8 * 10^-6 MJ/kg.
Now if only we could increase the energy held by 1 kg of kerosene by 46 MJ, by lifting it 1 m, the world would no longer have any energy problems...
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Offline bookaboo

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Re: Great Idea - Gravity Powered Light
« Reply #24 on: August 01, 2015, 05:50:40 pm »
Quote
The indigogo unit was $25.00

Wrong.

Really - I paid $50, and for that I got a unit PLUS some villager got one GRATIS. The $25 perk just sent one to a villager for nothing. i.e. zero cost to the person that counts. How many solar woznames and replacement batteries can you buy for nowt?

The whole point of this campaign wasn't to provide 1st world geeks with a crap toy but to apply modern technology to a 3rd world problem, and have the 1st-worlders pay for it. I reckon they got a result.

I don't doubt the neatness of the idea or the well meaning behind it, I just think there is already an existing superior solution in solar.
They would have been better off taking your $25 and giving the people some solar gear.
 


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