So where can I buy a couple of these.

I can imagine some petrochemical company is going to try to block this=20
device so they can get those pennies from the poor people of the world.

It is a fantastic  idea tho.

Bob
On 12/8/2013 3:57 AM, RussellMc wrote:
> Much talk hither and yon about a year ago re a "gravity powered light" an=
d
> it's likely capabilities and chances of getting to market.
>
> They reportedly have got to a alpha or beta release candidate version (no=
t
> what they call it).
>
> http://www.theregister.co.uk/2013/12/05/gravitylight_rolls_into_productio=
n/
>
> Home page:  http://deciwatt.org/
>
> As the name implies, output is nominally 100mW.
>
> The Register article says:
>
> Well, the initial GravityLight was just a prototype - it wouldn't hoist
> more than 10kg, and it wasn't really safe to use. It broke easily. The te=
am
> has also made it more compliant with safety regulations - and it now give=
s
> unmissable visual feedback if it's overloaded or tugged, by flashing red.
> Bearings were stripped out, and it's now a robust piece of kit, capable o=
f
> holding 7.5kg to 12.5kg of weight. And it now contains gears - so you can
> run an LED for 30 minutes at lower power, or 15 minutes of higher power,
> with an intermediate setting giving 22 minutes of light.
>
> Kits are going out to Guatemala, the Philippines and Bangladesh to gauge
> real user feedback. The proposition, Riddiford explained, is: do you want
> to save a few cents a day in fuel by lifting a weight? If people find tha=
t
> acceptable, then it's likely to go to the next stage. The economics,
> Riddiford told us, are compelling. Each hoist saves about 1 cent's worth =
of
> kerosene. Over two years this adds up to a saving of $100 - so the device
> pays for itself quite rapidly.
>
> Their $100 saved in 2 years figure infers 15 reloads/day and a break even
> time of under 3 months at a market cost of $10.
>
> A figure of 100 mW output at full power is mentioned.
> Elsewhere they say 2m (about) lift, 12.5 kg max load, and 15 minutes at
> high power.
> The mass x head gives 250 Watt second of input energy.
> 15 minutes at 100 mW is 90 Ws of LED power for an efficiency of potential
> energy to LED input of about 35%.
> If they in fact achieve that overall it's a very creditable result.
>
> 100 mW at 150 lumen/Watt (which hopefully they will equal or exceed) =3D =
15
> lumen =3D useful. One person can read a newspaper page (say A2) at a
> comfortable level with 15 lumens. (Evenly distributed that would give 60
> lux which is low by Western standards but enough for comfortable colour
> rendition). Real distribution will not be wholly even, but 15 lumen is
> still very useful.
>
> One of these could power a light in an otherwise unpowered washroom or
> toilet cubicle, with a single pull giving 15 minutes of lighting.
> (A useful addition to any remaining "pull the chain" toilets of yesteryea=
r.
>
> Make a ratchet device powered by walking on a step and small increments
> could be added as each person passes a point.
> A 10mm fall in a step would probably be unnoticed and a larger fall if
> known of would be acceptable when walking down stairs.
> 10mm gives about 5 seconds of full output and 100mm gives 50 seconds.
>
> A children's swing game that uses descent energy could provide many
> recharges per minute.
> (An idea I included in a proposal for a developing country charging syste=
m
> proposal some years before DeciWatt surfaced - it was not accepted).
>
>
> At say 25% overall, energy ~=3D
> meters_fall x kg x 10 m/s/s  x 25% W.s (=3D Joule)
> =3D 2.5 x m x kg
>
> [The idea is far from new - some early 20th century homes were lit by
> gravity powered electric lighting with weights in the ton range and
> servants using suitably geared winches to raise the weight. ]
>
>
>
>             Russell

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.