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Posted By charly,
Dec 19, 2012 at 3:26 PM
A half hour? I'm really surprised. Love it
Totally cool concept. Like the old Coo coo clocks only different.
They are cool! I was in on the initial funding and have one coming. They still need donations to get this made in quantity. http://www.indiegogo.com/projects/282006
Why is this needed? Take Liberia where just .58% of their population has electricity. Light at night means that kids can read, moms can cook without having to buy fuel or batteries.
Very cool idea.
I can picture this going into many more things than just lighting. A fantastic idea and these folks are to be congratulated.
Seems like it's American made, wow that's a rarity . Imagine making something like that but stronger, and runs longer,,,a remote location battery charger, etc.
Hmmm. Cool idea, but some perspective (do the math): A typical modern AA rechargeable battery is 2500 mAH, or 2.5 amp hours. At 1.5V, that's 3.75 watt-hours of energy. With a 20 pound weight dropping 3 feet that's 60 lb-ft of energy, which computes to 0.023 watt-hours, which means the single AA battery has 163 times the energy that one lift of the GravityLight's weight can produce.
Conversely, to use it as a battery charger you would need to lift it 163 times to charge that single penlight battery, which would take nearly 3 1/2 days.
Now, how bright can it be? A 20 lb weight falling 3 feet in 30 minutes is a power output of 2 lb-ft/minute, which works out to 0.0045 watts, An LED light which they're using, is very roughly 10X as efficient as an incandescent bulb, so you have the same light output as a 0.045W bulb. By contrast, a single candle produces about the same light output as a 1W incandescent bulb. So, the candle (which is not as bright as the kerosene lanterns they're proposing to replace) is roughly 20X brighter than the light the GravityLight can produce.
Now maybe they're dropping it 6 ft rather than 3 ft which doubles the output, but offset that by the fact that the generator is likely to be at best 50% efficient, you're back to the above numbers.
Add to that the fact that I've never heard of a cheap generator flashlight that lasted very long before breaking.
Neat, idea, but unless I've slipped a few decimal points somewhere, not practical.
And that settles that