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Google Science Fair Finalist Invents Peltier-Powered Flashlight
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."
So if you're hanging around the desert and the ambient temp is warmer than your hand, will it make things darker? That would be cool.
-- "Oh. This guy again."
Makosinski admitted there were points in the experiment when she thought it would never work, but said "You just kind of have to keep going.
Way more important lesson than the circuit design.
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.
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The thing her presentation is missing is any acknowledgment that she has actually learned something, and realizes now that her flashlight is a neat little science trick, but otherwise terribly impractical.
It only works for a few minutes, as the flashlight heats up to match your body temperature, and wouldn't work at all where ambient temps are remotely similar to body temperature. She also got only a tiny amount of power and light out of it, which could be provided for weeks or months by a watch battery without the expensive peltier in the mix.
Slightly more interesting than vinegar and water mixed together in a model volcano, but the real question is whether she learned something valuable in all of this.
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This is how it starts.
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The summary and article are incorrect. The Peltier effect is converting a voltage difference into a temperature difference. In this case, it is the Seebeck effect being used to convert a temperature difference into a voltage difference. So-called "Peltier devices" can work both ways, but aren't typically called thermocouples ("thermocouple" usually used for a device intended to convert temperature to voltage), even if they are in strictly technical terms.
The Seebeck effect was discovered first, so referring to it as the Peltier effect should be considered inappropriate (if not insulting to Thomas Johann Seebeck).
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She "invented" it by finding an circuit online, copying it, and buying some Peltier tiles off of eBay? WTF?
This stupid girl just did what every working engineer does - even the NASA engineers - take shit off the shelf and design from it!
If she was REALLY smart, she's mine her own copper, done her own research, discovered chemistry and physics on her own, and well, just did it without all this nonsense of living in an industrial society!
REAL inventors reinvent in the wheel everytime they need one!
She "invented" it by finding an circuit online, copying it, and buying some Peltier tiles off of eBay? WTF?
Yeah, and if you think that's bad, you should see how Intel does pretty much the same thing and they are making billions of dollars off of it! All they did was look up a transistor design from 50 years ago, hook up billions of them in an integrated circuit, stamp their name on it and sell it for hundreds (or even thousands!) of dollars to unsuspecting users that could have built it themselves if they wanted to.
Losers! (sorry for the correct spelling, stupid autocorrect didn't let me type Loosers!")
I can not believe the comments I am reading here. There are initiatives all over the world to get more females into STEM stuff and everyone here seems to quibble about the technical details! She's a teenager. I first learned about the Peltier effect in my 4th year at University, yes that was 40 years ago. My kids didn't learn about it in their High Schools either. So much for the U.S. education system. Give the kid a break!
Losers! (sorry for the correct spelling, stupid autocorrect didn't let me type Loosers!")
Wait a minute.
She just invented a new flashlight, and wants to use "energy that surrounds but we never really use."
Like, the energy that surrounds us and penetrates us, and binds the galaxy together? Her "long time interest" is clearly building a light saber.