A flashlight powered by the heat of your hand!

[Sancho]

http://www.nbcnews.com/technology/teenager-invents-flashlight-powered-warmth-your-hand-6C10485762

A 15-year-old girl has invented a flashlight that produces a usable amount of light just by using the heat from your hand. And if the judges at the Google Science Fair like it, she may be on her way to the grand prize.

"The flashlight I have made is more of a prototype then a final product, but the components in my device are quite strong," Ann wrote. "Of course, if it was to be used and manufactured, I would try to seal off the electronic components in some sort of casing so that it wouldn’t get heavily exposed to the elements (example water), and therefore last longer."

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[MannyGoldstein]

1. It might be barely able to light an LED, but

It won't be anywhere near as powerful as any flashlight one would buy in a store. Probably barely visible in a totally-black room.

But a cute bit of technology.

[TheMadMonk]

2. They also said a clockwork radio was IMPOSSBILE. /nt

[MannyGoldstein]

3. A clockwork radio?

This is just physics. Energy out = energy in, unless mass gets converted to energy (which isn't happening here). The heat from our hands is tiny, tiny.

[TreasonousBastard]

4. As she explained in the video...

and she seems to know quite a bit about the thermal efficiency of Peltier devices. (Which aren't really all that efficient.)

She says the thing works for about 20 minutes, and I'm guessing that since a Peltier device works on a temperature differential it takes that long for the temps to equalize to where it doesn't generate anything. A fan might help, but also use half the juice it creates. Sticking it in a warmer body part might also help.

(Which body part, you ask...)

[MannyGoldstein]

9. She mentions 5 mW of power

A single AA battery can provide that continuously for around a month before going dead. Anything that can last a month on a single AA battery ain't gonna be very bright.

Cool project, though.

[TheMadMonk]

7. And it's been possible to buy/build a palmtop Stirling...

...engine for close to a century. A good Stirling engine can operate on temperature differentials of just a few Kelvin. And that's a MECHANICAL system.

Check out Joule Thief on Wiki, and US Patent 4,734,658.

[MannyGoldstein]

8. I agree that you can get energy out of the hand

But not *much* energy.

The amount of energy that you get from a temperature differential depends on the magnitude of the temperature difference, and how well, the materials conduct heat. If our hands were made of metal, we could get some more power out, but skin ain't a good conductor.

Thanks for the Joule Thief info. If I get a burst of energy, I'll fire up SPICE...

[TheMadMonk]

10. Doesn't have to be much. Just has to be ENOUGH.

IT WORKS!

When reality gets in the way of your understanding of the world you have two choices. Found a church, or update your understanding.

So what's it going to be?

[TreasonousBastard]

11. Speaking of Stirling...

and the heat of your hands...

https://www.stirlingengine.com/product/stirling-engine-stirling-4/



It's a bit pricey, but looks great and will run from the heat of your hand.

(Won't do much actual work, though.)

[struggle4progress]

5. +

[Sancho]

6. I know nothing about the materials other than those described in the article...

but I'd love to have a body heat driven LED flashlight even if I had to tape the "generator" on my backside and run wires to the light...

[Shankapotomus]

12. The more eco-friendly power sources the better

I'd buy one as a reliable emergency light.. But for impoverished communities she will have to compete with the GravityLight, another eco-friendly light that is projected to cost only $5.

http://deciwatt.org/

[canssho]

13. The best rechargeable flashlight is an option

It will be hard to use this in real life I guess. Thus, I always prefer a rechargeable flashlight for its flexibility.