Here's a little known fact: The human body, at any given moment, produces energy equivalent to a 100 watt light bulb. In that sense, we're always wasting our energy—energy that can be used to, well, power a light bulb. It's this line of thinking that led a 16 year old to invent the first flashlight powered entirely by body heat.

Ann Makosinski's "Hollow Flashlight" isn't the only manually-powered light out there. But whereas other products generate energy with shaking or even hand cranking, her award-winning prototype shines the moment you pick it up.

"I thought, why not body heat?" she told The Oregon Herald. "We have so much heat radiating out of us and it's being wasted."

Not until recently did researchers look into ways to capture excess body heat as a means of powering devices like hearing aids and pacemakers. Four years ago, engineers in Sweden figured out a clever (and somewhat sneaky) way to siphon the biothermal energy of passengers at a central train station to heat nearby office buildings. Still, much of the challenge in developing these technologies has to do with the fact that electricity produced from residual thermal energy is usually too weak to run most common devices. The inner ear, for instance, produces just 70 to 100 millivolts ​of potential electricity, which isn't even enough to power a sensor or Wi-Fi chip, according to a report in the Wall Street Journal.

Makosinski, a high school sophomore at St. Michaels University School in Victoria, British Columbia, initially thought of the idea after learning that a friend in the Philippines, who didn't have electricity, was failing in school because she didn't have enough time to study during daylight hours. Her friend's dilemma is surprisingly common among a growing number of people in developing regions that either can't afford or don't have access to a power grid. For Makosinski, it served as an impetus to apply what she had learned about energy-harvesting materials from experiments she's been conducting since the seventh grade.

Still, Makosinski was unsure whether heat from a person's hand was enough to fuel a flashlight equipped with an LED bulb. To capture and convert energy, she settled on Peltier tiles, which produce s electricity when the temperature differential between the two sides is 5 degrees Celsius, a phenomenon known as the Peltier effect. The durable material, which has no moving parts and an indefinite lifespan, was built into the flashlight's casing to simultaneously absorb heat from a person's hand along the outside of the flashlight along with the cool ambient air on the inside of the gadget.

But while the tiles can, according to her calculations, generate beyond the minimum wattage necessary to power a flashlight (5.7 milliwatts), she discovered that the resulting voltage output wasn't enough. To up the voltage, she added a transformer, and later, a circuit, to supply what turned out to be more than enough usable electricity (5 Volts AC).

Once she got the flashlight to turn on, Makosinski tested her new invention and found that the light tended to shine brighter as the outside air got colder. For instance, the flashlight started to work better when the outdoor temperature dropped from 10 to 5 degrees Celsius. But even in warmer environments, the hollowed flashlight sustained a strong beam of light for more than 20 minutes.

What's perhaps most impressive is the materials Makosinski used to build the product amounted to just $26; if the device is mass manufactured, the total cost is expected to be significantly less.

In the spring of last year, Makosinski submitted her patent-pending invention to the 2013 Google Science Fair, where she was awarded the top prize in the age 15-16 category and took home a $25,000 scholarship. But to commercialize her invention, she'll need to figure out a way to get it up to spec with others on the market, which have a brightness output ranging from 90 to 1,200 lumens; her version currently maxes out at 24.

Still, she's not discouraged.

"I want to make sure my flashlight is available to those who really need it," she told the The Oregon Herald.