The GravityLight is powered by, well, gravity. You attach it to a strong beam, tie a 12kg weight to it (made from rocks or sand), and let gravity pull it down. As it does, it powers a set of gears inside, which drive a DC generator that produces one-tenth of a Watt. That’s enough to power the LED for up to 25 minutes at a time. When that’s over, just hoist the weight back up and keep going. This is great for developing nations which often rely on Kerosene lamps that are not only polluting, but noxious, and potentially dangerous. The makers of the GravityLight already made one last year, but this new model is brighter, more robust, easier to use, and can provide light even as it is being charged. More importantly perhaps, it is being assembled right in Kenya, which will provide some jobs to the very people it is meant to help. You can get one yourself for a $70 pledge, all the while knowing you’re contributing to a good cause.