Deciwatt GravityLight
GravityLight
By taking advantage of an immutable force, the GravityLight may be the most reliable electric light source of all. A person simply lifts a 22-pound bag of ballast up to the base of the device; the weight falls over a period of 30 minutes, pulling a strap that spins gears and drives a motor, which continuously powers an LED. Peripheral LEDs can be attached to focus light on certain spots. DeciWatt is field-testing units to replace kerosene lamps in developing countries and plans to sell them there for $10 next year.
Array
     |