GravityLight: lighting for a billion people

GravityLight is a revolutionary new approach to storing energy and creating illumination. It takes only 3 seconds to lift the weight which powers GravityLight, creating 30 minutes of light on its descent. For free. It will revolutionize places that currently depend upon stinking and dangerous kerosene.

Want to have a go yourself? Here’s a basic model that would be a great project for you and a kid.