Clean Power

Published on July 6th, 2013 | by Nicholas Brown


High School Girl Invents Flashlight Powered By Body Heat

July 6th, 2013 by  

I remember when I powered a small electric motor with heat (and a good amount of it) using a thermoelectric module. However, I had a hard time achieving more than 1 volt. A 15-year-old girl in tenth grade from Victoria, British Columbia, Canada recently got around this problem using a circuit that she discovered on the internet. She was able to power a flashlight/torch that produced 5 lumens of light per square foot (5 foot candles) using only heat from the human hand, which could be useful.

The high efficiency of LEDs makes impressive technologies such as these possible! LED efficiency can now exceed 120 lumens per watt (not the same as lumens/square foot).

The parts required to construct the flashlight cost only $26 and doesn’t need batteries or any complex mechanical systems to generate electricity.

“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 [sic] of Peltier differential. The flashlight worked!”

“Using four Peltier tiles and the temperature difference between the palm of the hand and ambient air, ” she said in her project statement, “I designed a flashlight that provides bright light without batteries or moving parts. My design is ergonomic, thermodynamically efficient, and only needs a five degree temperature difference to work and produce up to 5.4 mW at 5 foot candles of brightness.”

This flashlight landed her the position of finalist at the Google Science Fair. If she wins, she would receive a $50,000 scholarship and a trip to the Galapagos Islands.

The award ceremony is to commence in September. Winners will be chosen in the age categories: 13-14, 15-16, 17-18.

Check out our new 93-page EV report, based on over 2,000 surveys collected from EV drivers in 49 of 50 US states, 26 European countries, and 9 Canadian provinces.

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About the Author

writes on CleanTechnica, Gas2, Kleef&Co, and Green Building Elements. He has a keen interest in physics-intensive topics such as electricity generation, refrigeration and air conditioning technology, energy storage, and geography. His website is:

  • bussdriver78

    Clever; but it won’t work after the handle warms up or in hot climates. In canada, great. The idea would be better when combined with a shaker light which has a coil and magnet in it’s hollow center. Of course the best thing would be to use a crystal set AM radio… but the FCC would fine you severely…

    It would be more practical to make a heat sink for the ground and replace the solar lights with these things… since those solar lights do not work that well and their batteries are a problem… especially when they don’t last if you let them freeze (which is ok because people are constantly buying the things every few years – my current ones don’t expect you to change the batteries… and don’t say to move them in for winter. Super capacitors are still too expensive.)

    • Bob_Wallace

      Wouldn’t work with ambient temperatures between 93 and 103.

      Adjust that for personal body heat. And you might have to turn the Peltiers around at 103 and up….

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