Teen Invents Flashlight Powered by Body Heat

Portable light sources have been one of the most evolving inventions in history -- from the primitive torches and oil lamps of yesteryear, to today's battery-powered flashlights and headlamps. But through it all, most of these illuminating tools have required an outside energy source that would deplete when needed the most. But now, thanks to one particularly enlightened 15-year-old girl from Canada, your next flashlight just might be powered by the heat from your hand. 

At the tender age of 15, Canadian high school student Ann Makosinski has designed and built a flashlight powered by body heat.

Her Hollow Flashlight secured her a finalist slot in the 15-16 age group of the Google Science Fair ahead of thousands of entries from more than 100 countries.

The LED flashlight relies on the thermoelectric effect, with tiles that generate electricity from the differences in temperature to generate electricity.

The tiles are fixed to the outside of a hollow tube so that when held, one side of the tile is heated by the warmth of the hand, while air flowing through the hollow tube helps keep the other side cool. The electricity generated by the temperature differential between either side of the tile powers the LED light.

Makosinski built two different flashlights. The first was made using a tube of aluminum, which is a good heat sink material thanks to its high thermal conductivity, while the second was built using a PVC tube.

Both models work better when the difference between the ambient temperature and body temperature is greater. So while the flashlights worked with an air temperature of 75°F, they emitted more light with the air temperature at 60°F. Both flashlights were able to maintain a steady beam of light for 20 minutes, even in the warmer temperature.


The final cost of each flashlight came to only $25, but if mass-produced, the cost would be substantially lower.