2. Introduction:
The human body, at any given moment, produces energy
equivalent to 100 watt light bulb
We are wasting our energy—energy that can be used to 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.
HOLLOW FLASHLIGHT is a device that harvests energy
from the human hand to power itself.

4. Idea behind :
Ann Makosinski of Canada had invented HOLLOW
FLASHLIGHT, which won the 15-16 age group category
of the Google Science Fair.
The basic principle of the Hollow Flashlight is Peltier
Effect
Makosinksi’s flashlight runs on four Peltier tiles,
which convert heat into energy using the temperature
differential between a person’s hand and the ambient air.

5. Principle:
The thermoelectric effect is the direct conversion of
temperature differences to electric voltage and vice versa.
A thermoelectric device creates voltage when there is a
different temperature on each side. Conversely, when a
voltage is applied to it, it creates a temperature difference.
At the atomic scale, an applied temperature gradient
causes charge carriers in the material to diffuse from the hot
side to the cold side.

6. The Peltier effect is the
presence of heating or cooling at
an electrified junction of two
different conductors
When a current is made to flow
through a junction between two
conductors A and B, heat may be
generated (or removed) at the
junction.
Peltier Effect:

7. Initial Design:
Peltier tiles were tested 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.
The transformer was used to rise the voltage

8. Model:
Peltier tiles were mounted on a hollow aluminum tube that had
been inserted into a PVC pipe.
A spot was cut on the PVC tube where the hand could warm the
tiles, while ambient air from the PVC tube cooled the other side
of the tiles.
The result was a flashlight that could shine for more than 20
minutes if the outside temperature was more than 5 degrees
Celcius (about 34 degrees Fahrenheit).

10. The tiles are fixed to the outside of a hollow tube
One side of the tile is heated by the warmth of the
hand, while air flowing through the hollow tube helps
keep the other side cool.
The electricity generated by the temperature
differential between either side of the tile powers the
LED light.
Working :

11. Flashlight work better when the difference between the
ambient temperature and body temperature is greater.
So while the flashlights worked with an air temperature of
10°C (50° F), they emitted more light with the air temperature at
5°C (41° F).
It is capable to maintain a steady beam of light for 20 minutes,
even in the warmer temperature.
Better Working :

12. Only needs a five degree temperature difference to work and
produce up to 5.4 mW at 5 foot candles of brightness.
Harvesting energy, like with this flashlight, can provide a lot
of potential for powering small devices without necessarily
having to have batteries
We use an enormous amount of batteries," said Albin
Gasiewski of the Center for Environmental Technology. "Most
of them are not rechargeable and end up in landfills." Hollow
Flashlight could make a difference.
Advantage of Hollow Flashlight:

13. Conclusion:
The final prototype cost her US$26, but Makosinski
believes the product could be produced in mass quantities
for less.
Researchers look into ways to capture excess body heat
as a means of powering devices like hearing aids and
pacemaker.