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GravityLight – What a GREAT idea!

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re: GravityLight - What a GREAT idea!
1/4/2013 8:29:28 PM
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There was an article on this at The Register a few weeks ago: http://www.theregister.co.uk/2012/12/12/deciwatt_gravity_light/ One advantage of this device is that, other than the LEDs (I think), it is relatively low tech and could be mostly manufactured or at least assembled locally (an economic advantage, not just a hand-out but partly a hand-up) and quite possibly maintained/repaired locally. I still think that the child-powered (merry-go-round) water well pumps are a little more clever in terms of exploiting an abundant energy source and providing fun.

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re: GravityLight - What a GREAT idea!
1/5/2013 2:30:25 AM
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Has someone done the math on this? a 20 pound bag lifted 5 feet has 100 foot-pounds of potential energy. At an efficiency of 20%, how long will a 20ma LED provide light?

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re: GravityLight - What a GREAT idea!
1/6/2013 11:02:00 PM
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Well, based on the calculator at http://convert-to.com/159/energy-units.html 100 ft-lb = 135.58 J, and by my calculations a 3V LED powered by a 100% efficient generator that draws 20 mA will stay lit for 37.7 minutes. I would estimate for the 3-LED system shown with a 50% efficient power conversion system would give about 6 minutes of light per 5 foot 100 pound lift. That is some big bag to hold 100 lb. The Gravity Light web page talks about a 20-pound weight, and says 18 to 30 minutes of light output per lift. I agree something seems a little off...

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re: GravityLight - What a GREAT idea!
1/7/2013 8:26:47 AM
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Simple and Genious! :)

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re: GravityLight - What a GREAT idea!
1/7/2013 8:35:43 AM
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In total darkness, you dont need 3 led's at 20mA.. I'm pretty sure 3 leds at 20mA would blind you. It would be more useful to get this amount of light spread on a large area, but that is a different challenge. Dont forget to compare it to the current alternative, not to a modern flashlight.

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re: GravityLight - What a GREAT idea!
1/7/2013 5:02:29 PM
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Hello Max, Nice going. I think you just cost me \$50.00. :-) Just too good an investment to pass up. Also, I want one to play with. Cheers, Ralph

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re: GravityLight - What a GREAT idea!
1/9/2013 8:35:56 AM
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I feel the term Gravity Light is a bit mis-leading. Indeed, this light is powered by burning of bio-mass - the difference being that the bio-mass must comply to human nutritional standards and is burnt inside a human body. While this may look as an advantage in obesity-ridden countries like USA or Western Europe, I feel this may be look quite different for those countries which are currently using kerosene-lamps or open fires for lighting ..

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re: GravityLight - What a GREAT idea!
1/9/2013 1:19:13 PM
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Pulsing the LED (at a high enough freq to avoid flickering) will extend the duration for the same amount of energy.

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re: GravityLight - What a GREAT idea!
1/9/2013 3:07:21 PM
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At first glance, it reminded me of a cuckoo clock and the weight mechanism that drives it. The idea is so deceptively simple that it makes me wonder why I didn't think of it. And it's rechargeable too (in a convoluted lifting soft of way). Brilliant! While the principle is not innovative, using it for lighting is. Expect some sort of spin-off to take advantage of naturally occurring forces instead of using human energy ... tidal and air pressure changes come to mind, or perhaps the Seebeck effect could be used when day changes to night.

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re: GravityLight - What a GREAT idea!
1/10/2013 12:27:22 AM
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Nothing new, look at this project: http://www.core77.com/competitions/greenergadgets/projects/4306/ It never made it to production, reasons outlined above. Please note, that the "Gravity Light' people won't say anything about the energy generated by the device (other than it won't charge an iPhone). It don't doubt that it will generate some light, but whether this is enough to allow people to read is more than questionable.

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