The user fills a bag with debris – sand, rocks, whatever comes to hand – which is threaded through a proprietary electricity-generating device (see sketch below right). Each hoist of the weight provides 30 minutes of low power LED lighting. A power out socket allows other devices to be charged and GravityLights can be daisy-chained together. In keeping with its Third World target market, it costs just $10.
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 that 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.
Some guinea pigs have baulked at paying the $10 upfront cost – which is understandable in markets where wages are $1 or $2 a day and credit is hard to find. This could be solved by providing the GravityLight under a hire-purchase or loan agreement; a common model in under-developed economies.
Lifting 20lbs of weight up to six feet in the air every few minutes isn’t something everyone would want to do. But in poor parts of the world the standard fuel, kerosene, is a carcinogen that can cause skin damage and breathing problems.
“Cases of accidental poisoning by children are still relatively common,” notes the World Health Organisation.
Read more here: The Register