# Student's flashlight works by body heat, not batteries

##### July 1, 2013 by Nancy Owano weblog

(Phys.org) —Ann Makosinski from Victoria, British Columbia, has an LED flashlight powered by body heat. This inventor has a flashlight that glows when she holds it. The story gets more interesting, though. She is 15 years old and her flashlight has got her into the finalist ranks for the Google Science Fair. Her work is a result of a general interest in alternative energy. She said that she is "really interested in harvesting surplus energy, energy that surrounds but we never really use." Enter the Hollow Flashlight, which works according to the thermoelectric effect—creating electric voltage out of temperature difference. As a Grade 10 student at St. Michaels University School in Victoria, she was deciding on a topic for a science project when she discovered the Peltier tile, producing electricity when one side of the tile is heated while the other side is cooled.

"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 to work and produce up to 5.4 mW at 5 foot candles of brightness."

She ran some calculations to see if the warmth from a human hand could generate enough energy via a tile to power a flashlight. She presented her hypothesis:" If I can capture enough heat from a human hand and convert it efficiently to electricity, then I can power a flashlight without any batteries or ." She presented her objective: "To make a flashlight that runs on the heat of the human hand."

To begin, she bought Peltier tiles and tested them to see if they could produce sufficient power to light an LED. The power was no problem but getting the needed voltage was, as the tiles did not generate enough of the voltage needed. As she learned, making some changes to the circuit design might turn a page. She used the Internet for information, experimented with different circuits, and got lucky, finding an energy-harvesting article on the Internet that made note of a circuit that could provide enough voltage when used with a recommended transformer.

She talked about a point where she realized her battery-free flashlight could behave as she had hoped: "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!" In conclusion, she said, she succeeded in powering a flashlight using only the heat of the hand. Out of two flashlights that she made, neither which needed batteries, they worked.

Materials for the flashlight project cost her \$26. Considering that the effort has qualified her as a finalist in the Google Science Fair, where 15 finalists from around the world are competing for the prizes, that is not an unwise investment. The top winner gets a \$50,000 scholarship and trip to the Galapagos Islands. The prize ceremony takes place in September. Winners will be chosen in different age categories—13-14, 15-16, 17-18.

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##### jalmy
Jul 01, 2013
This comment has been removed by a moderator.
##### antialias_physorg
3.8 / 5 (12) Jul 01, 2013
For emergency use fill the flashlight with ice and it will work better when the power goes out it may be some time before the ice in your icebox melts, so you can use that.

Cold water should also increase efficiency fo a bit.

But all in all: Kudos to her for getting this to work!
##### axemaster
4.2 / 5 (5) Jul 01, 2013
Oh! That's pretty cool. I assume she used a charge pump to get the required voltage (I had to watch the video muted). I'm sure she has a *bright* future as an engineer/scientist!
##### Moebius
1 / 5 (1) Jul 01, 2013
Nice. I've been using LED flashlights I made for years. I got sick of smacking flashlights to make them work and realized only one battery solves that problem, the 9 volt. I've had these things for almost 10 years and have changed the batteries only 3 times. I use them all the time and they ALWAYS work.
##### Eikka
3 / 5 (4) Jul 01, 2013
I assume she used a charge pump to get the required voltage

Google for "joule thief". That's probably it.
not rated yet Jul 01, 2013
At \$26 for a prototype, this could probably be mass produced for less than \$2. Way better than a gravity-powered LED, the concept could be used to make a lamp that used sunlight to heat a small water reservoir for nighttime use.
##### ValeriaT
1 / 5 (7) Jul 01, 2013
she used a charge pump to get the required voltage
it doesn't have any electronic, just more Peltier diodes in serii.
##### Doc Brown
Jul 01, 2013
This comment has been removed by a moderator.
##### Sanescience
2.3 / 5 (6) Jul 01, 2013
Way to bring Mr. Caveman to the party Jalmy.

I will be interested in metrics for various weather conditions and extended use.

I wonder if something like a hybrid design could extend the life of a battery and/or use a rechargeable battery.

antialias_physorg is on the right track with ice and cold water. Perhaps some evaporator cloth and a liquid reservoir that you can fill for extended duration cooling.

##### Doc Brown
Jul 01, 2013
This comment has been removed by a moderator.
##### Anda
3 / 5 (4) Jul 01, 2013
Hey waterripples-valeria-natello-etc. You know you are sick ... and sad.
And now doc brown won't let you use CF... in your aether brain.
I'm so sorry for you.

And you @jalmy, you happy to be a pederast? Get the fuck out of here.

##### antialias_physorg
4.3 / 5 (6) Jul 02, 2013
Perhaps some evaporator cloth

Hadn't thought of that - but that does sound like a good idea.

Salt may be useful, too (its used in ice machines, after all)
##### Mike_Massen
1 / 5 (2) Jul 02, 2013
jalmy betrayed something here with
I have a few ideas how I could help her to generate vast quantities of excess exothermic heat.
If you say this on a public forum, then what will you possibly say on a private forum... In any case given her age, you should be ashamed.

As to her mother, if she is unattached, I might be prepared to ask for a date ;-)

In any case, hats off the the girl, she re-examined assumptions and was not misled by a static belief system, had the focus and intelligence to make an advancement which has prompted others to consider the same paradigm, which has been around for decades, as far more practical and with a much lower threshold than ever before.

I really think she will go far and I vote for her to win the top prize for all sorts of combinations of approaches, well done :-)

*grin* Oh and with a surname like that, she is Polish too ;-)
##### jalmy
1.7 / 5 (6) Jul 02, 2013
jalmy betrayed something here with
I have a few ideas how I could help her to generate vast quantities of excess exothermic heat.
If you say this on a public forum, then what will you possibly say on a private forum... In any case given her age, you should be ashamed.

Yes. In my own defense I admit to missing the third sentence where it said her age. I just read the title and it said "student" which pretty much always on this forum means college student. For some reason it will not let me edit or delete my post, or I would have like 5 minutes after I posted it.
##### ValeriaT
1 / 5 (5) Jul 02, 2013
Google science project of Ann Makosinski, previous project of piezoelectric flashlight. She didn't use the Joule thief, but a four component circuit based on transformer and commercial power converter LTC3108, because the Peltier tiles used generated only 50 mV at the temperature difference given.
##### Feldagast
1 / 5 (2) Jul 04, 2013
I would insert fins into the inside of the tube to act as a heat sink. Wouldn't increasing either heat on one side or cold on the other increase the voltage?
##### roldor
not rated yet Jul 04, 2013
I had a car, that runs by moving the feet !
##### Neinsense99
3.2 / 5 (9) Jul 04, 2013
I would insert fins into the inside of the tube to act as a heat sink. Wouldn't increasing either heat on one side or cold on the other increase the voltage?

Perhaps, but then it might be harvested for torch fin soup, with the rest thrown back to die a slow death on your garage shelf.