A $5 LED Lamp Powered By Sand And Gravity

In developing countries, light at night can be a dangerous luxury. But there may be a better solution than solar.

Kerosene lamps have a certain romantic nostalgia, but for those who rely on these lamps as their sole source of light, they’re both dangerous and expensive. The fuel can cost 10-20% of someone’s income, and even the small flame contributes to high rates of disfiguring (even deadly) burns.


The GravityLight, an Indiegogo-funded skunkworks project inside Therefore Design, wants to replace the ubiquitous kerosene lamp. But rather than using new-fangled solar and lithium ion batteries (the latter of which has a devastatingly short shelf life), they’re going with older ideas–gears and weights–to drive power to an LED.

“We wanted to make a device that could provide power for light, as and when it was required, with no limit to the run time in any given night, at a price that will be affordable,” designer Jim Reeves tells Co.Design. “It’s the affordable part that has been the challenge.”

Much like an old grandfather clock, the GravityLight is powered by the force of gravity, pulling on a weight that a user has positioned. So a 22-pound bag of sand attached to a rope can generate 176 joules per lift, which is enough to illuminate a 100-square-foot room via LED for half an hour. There’s no battery backup, but that’s OK. Because when the time runs out, all someone needs to do is hang the bag of sand again. And sand is in pretty unlimited supply.

“It’s a very old idea. What has changed, and continues to change, is the power requirement of LEDs and other electronics. It’s the convergence of these factors that have made GravityLight practical,” Reeves explains. “Many have said it seems obvious, and wonder why it’s never been done before. One reason might be that it is trickier to get right than it might first appear, and I think the old cliche applies that most good ideas seem very simple.”

Indeed, when any gadget makes its way into a developing country, durability becomes of paramount importance. GravityLight is designed with such concerns in mind–the gears need no oil, they move very slowly and run dry, and the LEDs should have a 30–50-year shelf life–but working in an environment that’s often dirtier and hotter than the 72-degree vacuumed office spaces most of us spend our days, anything can happen.

“This is why the trial we are now enabled to undertake is critical,” Reeves explains. “We want to field test the design and see how well it performs with changing humidity, transit, particle ingress, and resultant wear. We have strategies that are design to cope with all these factors in the design, but the trial will be the proving ground for how well we have done.”


From my limited knowledge of LED technology, it seems like a major concern will be, not how long the LEDs can last but how long they can last burning bright enough for practical use. (Heat destroys LEDs at the transistor level, even in cooler environments.) But bigger picture, if GravityLight succeeds, it will be more than a mere lamp; it will be a relatively passive generator, capable of generating a trickle of electricity for topping off batteries or any other use case resourceful people can spot. And how exciting is that?

If you’d like to support the project and score a GravityLight of your own in the process, you can donate $60 to the project on Indiegogo.

Support it here.

[Hat tip: AEI Ideas]


About the author

Mark Wilson is a senior writer at Fast Company. He started, a simple way to give back every day.