Fifteen year old Ann Makosinski was inspired when she was told that humans are "like walking 100-Watt bulbs." She decided to harness that bulb in a human-powered flashlight. By combining peltier tiles, a hollow aluminum tube, and a light-emitting diode (LED), the 10th graders was able to create a working flashlight powered by body heat. She got 2nd place in a science fair back home and then went on to win the 2013 Google Science Fair with her invention.
Peltier tiles generate electricity by converting thermal energy as it flows from a heat source to a cold source - that is, energy flowing from hot to cold. For those who haven't seen Ann's flashlight in action, check out this video:
Skip to the last 11 seconds of this video to see the flashlight in action.
Photo credit: Graphic of a Peltier element by michbich and founds using Creative Commons.