This light is powered by a hanging bag of gravel, sand or stones!
Power is generated as the bag slowly falls back down to the ground, and the rate is adjustable depending on your power requirement.
GravityLight is a new invention that could be especially life saving for the 1.5 billion people in the world who live off the grid with no electricity.
It's much cheaper than using kerosene, even cheaper than solar - and you don't have the problem of storing the solar power with a battery for night time use.
Kerosene costs can eat up 20% of a households income. This lamp will cost below $10 and after 3 months, will have paid for itself and save the owner from spending on any kerosene, which is also dangerous and unhealthy to breathe in.