This LED lamp is powered by gravity using the same technology as a grandfather clock.  The lamp last four hours per cycle when activated and is expected to remain functional for 200 years.  “To “turn on” the lamp, the user moves weights from the bottom to the top of the lamp.  An hour-glass like mechanism is turned over and the weights are placed in the mass sled near the top of the lamp.  The sled begins its gentle glide back down and, within a few seconds, the LEDs come on and light up the lamp.”  I thought this piece was interesting because of how easy it was to power and how long it was expected to last.