
15-year-old girl invents flashlight powered by the heat of your hand - evo_9
http://www.extremetech.com/extreme/160003-15-year-old-girl-invents-flashlight-powered-by-the-heat-of-your-hand
======
pocketstar
Wow, her dad is my coworker and I heard this casually mentioned at work the
other day that his daughter was working with Peltiers and I should consult
with her because I am also working with Peltiers for characterization of phase
change materials.

Also note, calling the device a Peltier is a misnomer, her flashlight is a
thermoelectric device utilizing the Seebeck Effect, similar but opposite to
the Peltier Effect. Peltier has just become the connotation for thermoelectric
devices.

The Seebeck effect only works with a temperature gradient, the flashlight will
begin to heat up when held and the Peltier will produce less power. The next
step is to add a heat sink and fan to maintain a temperature gradient for
operation longer than 20mins.

~~~
schiffern
Wow, an encouraging comment on HN? Not assuming they're a moron?!?! You give
me hope for this place.

Speaking of phase-change materials, why not fill the flashlight with them? It
still wouldn't be steady-state of course, but I envision the fan eating up all
the power. Heat pipes might help, but they still leave the problem of heat
rejection. Evaporative cooling pad?

~~~
ChuckMcM
Paraffin would be a good choice, although just putting a slug of copper into
it and storing it in the freezer would probably work just as well. Of course
you have to be able to find your freezer in the dark ...

~~~
eksith
Paraffin would be excellent. In fact, wax + copper was such an excellent
combination to pull away thermal energy, this was the same mechanism used on
the NASA Lunar Rover :

[http://en.wikipedia.org/wiki/Lunar_Roving_Vehicle#Wheels_and...](http://en.wikipedia.org/wiki/Lunar_Roving_Vehicle#Wheels_and_power)

Basically, the heat was stored in the wax, which melted. Then, radiators would
pull the heat from the wax out into space when the Rover was resting, which
would solidify the wax again ready for the next run.

~~~
tekromancr
That's how coffee joulies work!
[http://en.wikipedia.org/wiki/Coffee_Joulies](http://en.wikipedia.org/wiki/Coffee_Joulies)

~~~
Samuel_Michon
Except that, you know, they don’t actually work. Even the creators admitted to
as much.

[http://boingboing.net/2011/10/26/coffee-joulies-review-
the-e...](http://boingboing.net/2011/10/26/coffee-joulies-review-the-effect-
is-barely-noticeable.html)

~~~
tekromancr
T.T But the idea was so neat!

------
Anonymous238
Invented is a strong word when these already exist.

[http://www.youtube.com/watch?v=pFqrx2-ENgE](http://www.youtube.com/watch?v=pFqrx2-ENgE)

~~~
sliverstorm
You don't have to be the first one to invent something, to invent it.

It doesn't suddenly become imitation if you came up with it on your own.

~~~
zerr
Of course, but with nowadays available information and possibilities to
search, it is quite easy to find that it is already done. I mean, I don't
think she invented it being sitting in some cave, without contact to outside
world. She would at least need to have done some simple research, with the
materials and etc... So some organic results would pop up.

------
gdonelli
She is more eloquent and capable of public speaking that a lot of adults.

More women should see example like these, it is a great example of woman in
engineering kicking ass.

------
ISL
Very clever!

I'll state for the purposes of prior art that, if you can get enough power to
add a little fan or other air-moving mechanism to the circuit to pull air
through the tube/heatsink, it will operate in still air for as long as a human
can keep it warm.

This opens the mind to a realm of interesting body-powered devices, especially
in environments where heat sinking is easy, like for divers, motorcycle
riders, and sailors. Want a wetsuit or jacket that lights up or operates
sensors on its own? Easy peasy.

~~~
solistice
Unless you are planning on keeping warm in those environments, which would
make strapping heat sinks all over your body a bad idea.

------
Ellipsis753
My favourite part of the article was: "The flashlight maintained a sufficient
level of light for over 20 minutes, definitely enough time to find the candles
in the dark when the power goes out."

Why not just put the candles where the flashlight was in the first place? (or
just put a reliable battery powered flashlight there.)

It sounds like it's saying "this flashlight should last long enough for you to
find your better flashlight".

------
mbell
Looks like she's just using the Peltier effect to power some LEDs. I doubt the
flashlights would work well, if at all, at room temperature but would be
useful in a cold climate.

~~~
lotharbot
> _" I doubt the flashlights would work well, if at all, at room temperature"_

I found it a bit disappointing that they mentioned one use case as finding
candles when the power is out, shortly after mentioning that it works only
marginally at 50 degrees F. It takes quite a while for a normally-heated house
to drop to that temperature.

It's a neat invention, no doubt, but the practical use cases for this
particular version are going to be outdoors.

~~~
ISL
If the exhaust from a candle (think small, like a tea light) can be made to
travel upward through the tube, and the exterior of the flashlight given
sufficient heatsinking, it's possible that this arrangement can yield more
visible light than the candle can produce.

I'd have to work through numbers to guess, and do the experiment to be sure...

~~~
schiffern
Here's the productized version of that idea:
[http://www.thepowerpot.com/](http://www.thepowerpot.com/)

The consensus of the camping community seems to be that it's not worth it.
Batteries + camping stove is easier/cheaper.

------
qwerta
Did you read the comments under the article? I usually do not buy sexism in
tech, but this got me.

~~~
alanchavez
I came here to see if anyone else noticed the sexists comments under the
article, what a shame.

However it's not difficult to find sexists pricks in tech.

~~~
atondwal
You're probably just the only two who read the comments...

~~~
alanchavez
I think the comments were removed, but one of them said that she should build
a body-powered vibrator and she would be millionaire.

------
Qantourisc
Not to complain, but how much light does it really produce ? Cause this would
be very neat ... but I still need to be able to light the room :)

~~~
fjarlq
From her project description[1]:

 _My objective in my project was to create 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, 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._

5 foot candles is about 54 lux. 30 to 50 lux is minimal illuminance for
reading.

[1]
[http://www.googlesciencefair.com/en/projects/ahJzfnNjaWVuY2V...](http://www.googlesciencefair.com/en/projects/ahJzfnNjaWVuY2VmYWlyLTIwMTJyRAsSC1Byb2plY3RTaXRlIjNhaEp6Zm5OamFXVnVZMlZtWVdseUxUSXdNVEp5RUFzU0IxQnliMnBsWTNRWXA2ZVVBZ3cM)

~~~
Qantourisc
Thanks

------
juandopazo
I guess this is a consequence of the development of the LED. LEDs being so
efficient allows for very low power sources and a thermocouple seems to be
enough to light them. Pretty cool!

------
nessus42
First I have to say that this is very cool indeed!

Practically speaking, however, I'm not sure that it would have any advantages
over the flashlights that you crank for a while. Though perhaps those crank
flashlights use a rechargeable battery that degrades over time, and this new
flashlight would have a longer shelf-life? Though I should think a good
capacitor instead of a battery would solve that potential problem with the
crank flashlights.

~~~
ht_th
Those crank-powered flashlights make a lot of noise and induce cramps in the
hand used to crank it.

~~~
iknight
It seems to work well for me. My son loves his. Granted I don't use it as a
necessity.

------
kondor6c
It's a great idea and a great science project, I just don't see how practical
it would be due to how little light it would produce. Even if I kept it in the
back of my car to aid in a possible road repair (perfect situation for a no
battery device) I don't know how effective it would be. Perhaps that's just
the skeptic in me?

~~~
arbitrage
Why focus only on the negative, or on a situation for which it would obviously
be a terrible choice? It's never going to be as powerful as a battery powered
flashlight; that's not really the point.

It might, however, be awfully useful in a stiatuion where there is no ambient
light available at all, or where equipment needs to be light and very simply
constructed. Perhaps something like in an emergency kit in case of a mine or
cave collapse. Or in a situation with very adverse operating conditions, like
a desert. Moving parts (as for a hand crank torch) would be a liability in an
environment with omnipresent particulate contamination.

~~~
aaron695
And this is why people get cranky at articles like this, people are not adult
enough to take them as what they are, puff pieces to build the esteem of
children.

Could a 15 year old child invent safety equipment for the trillion $ mining
corps. Of course not.

People with 4 year degrees in engineering have as much commitment and
inventiveness as children and money to boot. Plus a fully developed brain.

As is always the case child age x invents new way to do blah, invents object
blah they of course haven't.

As a tired cliche does it have a place on HN. Is this site aimed in part at
children is the question?

~~~
lostlogin
I don't know about mining, but I do know that some pretty damn simple things
make a hell of a difference. Hospital safety has been improved quite
impressively (or disturbingly, depending on your perspective) by using a
checklist prior to surgery. Questions identifying the surgical site feature on
the list, and writing on the site too. Staff are asked if anyone has any
concerns. It's amazing what a group of highly trained individuals can screw up
without child-like safety systems being in place.
[http://www.npsa.nhs.uk/corporate/news/surgical-safety-
checkl...](http://www.npsa.nhs.uk/corporate/news/surgical-safety-checklist-
saves-lives/)

~~~
aaron695
This stuff is really interesting but is a million miles away from child-like.

We've know for years washing your hands in hospitals saves lives.

And we've know for years people are not doing it. Even just putting up signs
helps an amazing amount, but even this isn't done.

Cause it's a really hard problem.

How does one improve the issue? Some hospitals are trying cameras, ranking
deaths in hospitals, rfid tags tracking people making sure they wash.

I'm willing to bet even though the checklist above is pretty close to proven
most hospitals don't use it.

[edit]
[http://online.wsj.com/article/SB1000087239639044462010457800...](http://online.wsj.com/article/SB10000872396390444620104578008263334441352.html)

------
twodayslate
Put this in phones to charge them when you aren't using it?

~~~
jff
Won't work very long, it operates using the temperature differential between
your hand and the interior of the flashlight. Which, based on the quoted
"still worked at 50 degrees F", means you'd have to stick your phone in the
fridge when you're not using it. And then take it out so it can charge just a
little bit before the temperature equalizes.

------
rikkipitt
Blean (n.)

Scientific measure of luminosity : 1 glimmer = 100,000 bleans. Usherettes'
torches are designed to produce between 2.5 and 4 bleans, enabling them to
assist you in falling downstairs, treading on people or putting your hand into
a Neapolitan tub when reaching for change.

~ Douglas Adams and John Lloyd

------
MojoJolo
Can this technology work in an airconditioned room? I was thinking if this
technology can provide enough electricity to even just lighting up a single
room. It can use the heat outside, and the cool air (form air condition)
inside the room.

All in all, very good invention! And also inspiring. I hope more teens will be
involve in inventing things. I hope she wins. Also, (totally unrelated) I
think she's cute. :)

~~~
ISL
It should be provable that thermodynamics guarantees that it will be more
power-efficient to generate the light directly with electricity instead of
using electricity to cool the room, then exploiting a thermal gradient with
even a lossless Peltier element.

~~~
tekromancr
True, and it is. However, if you are going to be using that energy to cool the
room anyway, why not try to reclaim that 'spent' energy?

~~~
vidarh
I think what you are forgetting is that in doing so, you would be heating the
room up again.

So to keep the temperature where you want it, you'd need to cool the room even
more.

~~~
tekromancr
Ahh, you are right.

------
samsquire
I can't help thinking of a full body suit to harvest the entire heat output of
the human body. Maybe you could use assisted sweat evaporation to provide for
the cold tile?

It could be like a Fremen suit so they can pump the water coolant around and
potentially and power electronics.

~~~
mistercow
I'm pretty sure the result of that would be that you would overheat as the
suit would prevent you from dissipating heat quickly enough.

~~~
chockablock
I think the risk is that you'd have the opposite problem: hypothermia.

~~~
mistercow
I'm a little shaky on the thermodynamics of peltiers, but it seems (and I
swear I read something years ago to back this up) that if it extracts power
from the equalization of a heat differential, it must also slow down the
conduction of heat. Two arguments for why this should be the case:

1\. If it were not the case, then assuming ideal peltiers, you should be able
to simply stack one peltier after another and get more energy than just one
from the same temperature differential. And that's clearly crazy talk. If
peltiers do not impede heat conduction, they must have some other limitation
that prevents this from being the case.

2\. Peltiers are reversible; a thermoelectric generator also acts as a
thermoelectric cooler if you put current through it. So when you heat one side
of the peltier and cool the other, generating a current, then that current
should cause it to simultaneously act as a TEC (analogously to how counter-EMF
causes an electromagnetic generator to resist as you turn it, essentially by
turning it into a motor trying to turn in the opposite direction). That is,
the very current you are generating will cause the peltier to transfer heat
from the cold side to the hot side, with the end result that it would act as
an insulator.

Edit: However, if I'm right about this, then assuming you can have efficient
and flexible peltiers, it should work quite well for winter clothing.

~~~
mistercow
I realized, thinking about this more, that my reasoning must be backwards on
point number 2. If it worked as I said, then putting a current through a
peltier would actually cause positive feedback resulting in a perpetual heat
pump, which is clearly impossible.

So the current running through a peltier acting as a generator should actually
transfer heat from the cold side to the hot side, making it act as a better
conductor of heat. I don't know how to reconcile this with argument 1, but as
far as my knowledge of thermodynamics is concerned, 2 has to trump 1.

So I figure I must be wrong, and peltier generators must conduct heat quite
well. In which case I guess it would be good for summer wear - but then, in
the summer, the differential between the human body and the surrounding air
isn't all that great.

~~~
chockablock
Yeah I was thinking of the approach used in the invention described in the OP,
with a pre-chilled slug used to set up a temporary gradient. In that case you
_could_ lose too much body heat to warming up the cold mass.

But even without pre-chilling (i.e. in the steady-state case), while you may
be right that a TE device necessarily slows down the conduction of heat across
a gradient, I don't think it follows that any such 'suit' would result in
overheating rather than hypothermia.

Consider 2 people in a 70-degree (F) room. One wearing light clothing, and the
other sitting in a tub of water. The water in the tub will equilibrate at
somewhere warmer than 70 degrees, and the person will become hypothermic,
since the capacity of their 'suit' to conduct heat to the environment is
greater than the ability of their body to generate heat to compensate. You
could have a TE device that extracted power from the gradient between the warm
water and the room without saving the person from hypothermia.

That is to say, I think we're both wrong :): a well-designed suit could keep
the amount of heat transferred within the range of the needs and capabilities
of the human body.

(Fun trivia: according to Murray Hamlet, a US Army cold weather injury
researcher, the leading cause of 'morgue wakeups' in the US is drug users who
pass out in the bath, become severely hypothermic, and are wrongly declared
dead).

------
bobsy
As someone with poor circulaton to the extremities I fear I would be walking
around in the dark holding the flash light with cold hands.

Its a really nice idea though. Its stories like this that make me wish i paid
a bit more attention in science when i was younger.

~~~
koudelka
If your extremities' temperature is cooler than the ambient temperature, maybe
all you need is a version with the heat-collection plates flipped?

~~~
schiffern
If your extremities' temperature is cooler than the ambient temperature, how
did you do that? Heat pumps in your arms? ;)

It would be trivial to put some circuitry in there to rectify the voltage so
it works in either direction. No separate version required.

 _(changing ambient temperature is the obvious answer to my joke, btw)_

~~~
chinpokomon
Although others that have responded to this thread have far more experience, I
believe Peltiers are optimized to work in one direction. That is to say there
is a hot and cold side, so I'm not sure it is as simple as adding an inverter.
Not that you'd likely be using your hands as a heat sync anyway.

Yes, I realize this was meant as a joke, but I'm still curious if current can
be reversed by just changing the gradient. Does it still work but maybe it is
less efficient? Is there no difference at all?

~~~
schiffern
Ah, good point. I hadn't considered that. It looks like you are correct! You
might sandwich two Seebeck-Peltier devices and switch between them, though.

[https://en.wikipedia.org/wiki/Thermoelectric_effect](https://en.wikipedia.org/wiki/Thermoelectric_effect)

------
stormbrew
She should be using blue LEDs. I swear those things can send light through a
wall.

~~~
vidarh
I bought a pack of 400 little round black stickers only for the purpose of
covering blue leds... For most of the devices I have with blue leds it takes
2-3 stickers on top of each others to dim them enough for me to still see them
but not feel blinded when the light in the room is dimmed..

------
hcarvalhoalves
Way to go. Good to see a girl that age interested in science and engineering.

------
kirchhoff
Reminded me of the Seiko Thermic, a wristwatch powered on the same principle.

------
circuiter
For anyone interested, here's the list of all the finalists this year - most
of them much more impressive.

[http://www.businessinsider.com/2013-google-science-fair-
fina...](http://www.businessinsider.com/2013-google-science-fair-
finalists-2013-6?op=1)

------
kailuowang
There is an old Chinese saying: I wish she was my daughter.

~~~
dsrguru
Just out of curiosity, what's the Chinese expression? Is it a 成語?

------
Architech0
Sounds similar to the fiber optic cable material found @ Roswell, NM. 1947...

~~~
krapp
Except the flashlight actually exists.

------
phy6
She should call it the Fleshlight

~~~
Kiro
Google 'fleshlight' and I'm sure you'll agree it would be a pretty bad choice
of name.

~~~
asdfologist
whoosh

------
skriticos2
So if she is using the power of the human body to power a flashlight when she
is 15, does that mean she'll design the technical foundation of the Matrix
when she is 30? (which had the purpose to harvest the human energy)

Sorry, could not resist. Great to see our youth being creative.

