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. My science project in tenth grade was a volcano that only worked about half the time, so I think she has me beat.

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, which is to say, when it's colder. So while the flashlights worked with an air temperature of 10° C (50° F), they emitted more light with the air temperature at 5° C (41° F). Still, she claims that both 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 just over CA$26 (US$25), but if mass-produced, the cost would obviously be substantially lower.

Makosinski and the 14 other Google Science Fair finalists will travel to Google's Mountain View, California campus in September where winners will be announced in each of the three age groups. One grand prize winner will also receive a $50,000 scholarship from Google and a trip to the Galapagos Islands.

Makosinski explains her design and demonstrates her Hollow Flashlight in the following video.