Such a simple idea that could make a big difference for many in developing nations:
The GravityLight is simply charged by a bag that is filled with around 9kg of material and hung from a cord below the light. As the bag descends, a series of gears inside the device translates this weight into energy, providing 30 minutes of light. The light strength can be adjusted, from strong task lighting to a longer-lasting low-level glow, and two terminals on the front allow it to be used as a generator so it can recharge other devices including radios and batteries.
The project originally emerged from a brief by charity Solar Aid to come up with a low-cost light source as an alternative to the ubiquitous kerosene lamps that provide the main source of light across the developing world – but which come with their own set of health problems.The World Bank estimates that 780 million women and children around the world inhale a volume of smoke equivalent to smoking two packets of cigarettes a day – leading to the statistic that 60% of female lung-cancer victims in developing nations are non-smokers. The fumes also cause eye infections and cataracts, while 2.5 million people per year suffer severe burns from kerosene lamps in India alone. It also comes with a huge financial burden: the cost of kerosene for lighting alone can account for 20% of household income.