A finalist in Google's online science fair, 15 year old Canadian Ann Makosinski, has created a flashlight that runs solely on the heat of the human hand. Using four Peltier tiles and the temperature difference between the palm of the hand and ambient air, Makosinski designed a flashlight that provides bright light without batteries or moving parts.
Makosinski decided to use Peltier tiles for her flashlight design, if one side of these tiles is heated, and the other is cooled, electricity is produced. During her research she calculated that our bodies radiate 5.7 mW/cm2, but only 0.5 mW is needed to generate a bright light at the LED. The final design included mounting the Peltiers on a hollow aluminum tube which was inserted in a larger PVC pipe with an opening that allowed ambient air to cool the tube. The palm wrapped around a cutout in the PVC pipe and warmed the tiles. The result was a bright light at 5 degree Celcius of Peltier differential.
The flashlight does not use any batteries, toxic chemicals, or kinetic energy, does not create any noise or vibrations and will always work. The flashlight's only limitation is its need for at least a 5°C temperature difference to provide usable light.
In the future, Makosinski hopes to work on improving efficiencies of the converter, increase the flashlight brightness, and perhaps use this technology for powering wireless medical sensors. She said "My unique circuit and design has infinite possibilities and uses for the future! For example, imagine holding your phone, and at the same time charging it just from the heat of your hand! Or perhaps all school chairs in classrooms having Peltier tiles, and we could harvest the heat and amplify it into electricity using my method. I am very excited for the possibilities my project has! It is but a means of showing what this concept, and what human heat energy, can do."
Source: Google Science Fair 2013
Top image: Tech2