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Google Science Fair Finalist Invents Peltier-Powered Flashlight 170

GTRacer writes "Ann Makosinski, a Canadian student competing in Google's Science Fair, submitted a flashlight which uses temperature differentials to power its LEDs. Her long-time interest is alternative energy because, '[she's] really interested in harvesting surplus energy, energy that surrounds but we never really use.' Using Peltier tiles and custom circuitry, her design currently runs for 20 minutes or so and costs $26. A win at the September finals in Mountain View and/or outside investment could fund further development."
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Google Science Fair Finalist Invents Peltier-Powered Flashlight

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  • by _merlin ( 160982 ) on Tuesday July 02, 2013 @08:34PM (#44171791) Homepage Journal

    It's not thermocouples with dissimilar metals. It's Seebeck effect using semiconductor junctions. (Peltier effect is the use of voltage to generate a temperature differential, Seebeck effect is use of a temperature differential to generate voltage, but you can use the same devices for both.)

  • by Anonymous Coward on Tuesday July 02, 2013 @08:44PM (#44171863)

    It's not a tiny current source, but a tiny voltage source.

    The current provided by a thermocouple can be quite significant despite the very low voltage. Many security valves like those in gas powered water heaters are operated with the current generated by a thermocouple. Even a thermocuple powered electromagnet can easily hold several pound.

  • by Ungrounded Lightning ( 62228 ) on Tuesday July 02, 2013 @08:44PM (#44171867) Journal

    Does she put it in the fridge before using it or something? Or does it use the difference in temperature between your hand and the flashlight.

    The latter.

    If you RTFA you'll see she's using the aluminum flashlight body as a heat conductor and the "head" and other exposed portions of it as an air-cooled heatsink.

    She's stuck the handle of the light into an insulating plastic pipe, cut a hole in the pipe, and stuck the peltier cell in the hole, with the "cold" side in contact with the flashlight handle and the "warm" side in contact with the hand. (I expect the next step is to wrap an outer aluminum tube around it to conduct heat from the whole hand to the cell, rather than just heating it with a patch of palm directly contacting it.)

    Voltage boost converter between the peltier assembly and the LED (because the peltier cell she used was not stcked for the right voltage to drive the LED.) The LED shines as long as you hold it, if the air is cool enough. (She's used it for 20 minutes running.)

    Also, since this is generating electricity from a temperature differential, rather than generating a temperature differential from electricity, wouldn't this be the Seebeck effect?

    Yes. Seebeck discovered current generation from heat differential (with dissimilar metal wires and a compass needle), then Peltier discovered heat-pumping with current.

    But, like most rotating electric machinery (where the same device is a motor or generator depending on whether you power it or twist it), the same effect is a heat pump or heat engine (depengding on whether you apply a temperature difference and pull power or apply power and pump heat).

    The effect is now often called the "Peltier-Seebeck effect" in textbooks. The cells are typically called Peltier Cells because the efficient ones are manufactured mainly for heat-pumping, though they work just fine both ways.

  • Re: FlashDark? (Score:3, Informative)

    by Midnight Thunder ( 17205 ) on Wednesday July 03, 2013 @07:41AM (#44174593) Homepage Journal

    It sounds like you never went to the Sahara. I went to the south of Tunisia, during the cooler months, and it was 25ÂC during the day and dropped to around or below freezing at night. The ice on the car in the morning was testiment to how cold it got.

    Reading online I see it can go from 40ÂC during the day to -6ÂC at night.

The Macintosh is Xerox technology at its best.