The device, a gravity-powered LED lamp called 'GravityLight', works by attaching a weighted bag below it from a cord. As the bag slowly descends, gears convert the weight into energy — providing users with up to 30 minutes of light, depending on the weight of the bag. There are also settings to provide brighter light for a shorter period.
Each device comes with an empty bag, which can be filled with up to 12 kilograms of material such as earth, rocks and sand. It needs no battery.
The idea behind GravityLight was to overcome the limitations of options such as solar lamps, which need sunlight and have a limited battery life, and kerosene lamps, which cause indoor pollution and are expensive to refuel, says co-designer Jim Reeves, associate director at Therefore Product Design in London.
After four years of development, the device is now ready for field testing.
Around 7,000 GravityLights are being manufactured, paid for by a 40-day crowd-funding project which raised around US$400,000 against a target of US$55,000.
One thousand lights will be sent predominantly to Asia and Africa for testing in the coming months. The remaining units will be distributed to those who helped crowd-fund the GravityLight trial.
"These contributors will also be feeding back on the performance of the product," Reeves tells SciDev.Net.
The field tests will examine the performance of the device over time — including the effects of varying weather conditions on its internal components — with help from local partners such as NGOs.
Once the tests have been conducted, production will be scaled-up early next year, says Reeves. Each device is expected to cost between US$5 and US$10.
He is currently exploring two ways of approaching the market — manufacturing the devices centrally and distributing them globally, or manufacturing the components centrally and distributing them for local assembly, which would provide jobs.
“It doesn't have any pollution disadvantages.”
He also plans to fine-tune the light for Western markets to help subsidise the main activity of the GravityLight project — to provide much larger quantities to developing countries.
Mary Willcox, principal energy consultant at Practical Action, a UK-based international development charity, says developing countries need a variety of lighting options and that GravityLight will make a huge contribution to this.
"It doesn't have any pollution disadvantages and given that it uses LED it should provide better lighting."
She adds that it is important to undertake field testing as, "that's the only way to understanding whether something is really robust in use".