By: Ikenna Okafor, Kyle Johnson,
Robert Mitchel.. & Hui Zheng
The Harris Company presented the
challenge of designing the system to provide a
portable source of power for mobile devices. Our
team decided to focus on a system to power a
radio for a military of wilderness park ranger.
Our team brainstormed various options to meet
their constraints of something that was light
weight, safe, economically viable, and combined
two different energy sources
Our team came up with proposals that would meet
the Harris Project’s constraints. We gathered our findings
bellow so that we could compare the benefits of each
different power source combination. We will need to
consider the constraints we identified in an earlier
meeting and use two sources of power in each proposal.
I proposed a solution that would combine
solar and kinetic energy power sources. Solar
power is low cost and produces power as long as
the sun is out. The kinetic generator will produce
power as long as the user is walking. This system
was found to provide more than ample power
while being safe and low cost.
Thermoelectric generators are a very proficient way
of generating electricity by using the surrounding heat, or
even body heat as sources of power. Along with wireless
power generating ,this manner of electrical generation
involves, series of wireless sensors used to transfer
electricity. Proposal two was the combination of these two
ideas whereby, power was generated by a heating and
cooling system attached to the user’s body. The user
would also carry around a small wireless transmitter
which converted wireless signals into electrical power.
Piezo-electric Wheel
From what I understand about PE strips, they require
little energy to bend, and have the potential to produce a lot of
power. This led me to the conclusion that they would be
effective if combined with wind power because if there was a
force to drive the strips to be bent, there would be virtually no
work to produce energy. My idea is comprised of setting up PE
strips around a wheel as some sort of flywheel design, and the
wind would spin these trips as it spins pinwheels. The
difference is that there would be objects in the paths of the
strips causing them to flex and the un-flex with every
revolution of the wheel. My thinking is that if the wheel had
very little friction and was therefore easy to turn, you could
produce a lot of speed and have many rotations per minute, or
possibly even per second. Welcome to the future.
In my design, I will combine piezoelectric
and solar power. I will use piezoelectric energy
harvesting and install it in a shoe-pad. On the
right side of shoes, solar pads will be installed.
Also, there will be a USB port connected to the
shoe. The USB port will be moveable. And the
energy produced will be store in a capacitor and
connected to USB. While people walking or
running, they will produce piezoelectric energy
and we can use it anytime just simply plug in the
USB connector with your device and the USB port
in shoe.
To choose a final design we used a design
matrix to compare the various proposals on the
elements of safety, cost, environmental impact,
ease of use, size and weight, and combining two
power sources. We weighted each proposals
score in each category based on what we thought
the relative importance of each category was.
Selection Matrix
Criteria/
Requirements
Weight
Factors of
criteria
Solar/Kinetic
Backpack Unit.
Piezoelectric
Shoe
Piezoelectric/Wind
Wind Mill
2/.6
Body heat/
wireless
power
“clothing
panels”
2/.6
Combine
energy sources
Ease of use
Size and
Weight
Safety
Impact on
environment
Economic
Viability
.3
4/1.2
.13
.07
3/.39
2/.14
2/.26
3/.21
2/.26
2/.14
2/.39
4/.28
.27
0
4/1.08
3/0
3/.81
4/0
4/1.08
4/0
2/.54
4/0
.2
3/.6
3/.6
3/.6
2/.4
19/3.41
17/2.84
17/2.68
18/2.81
4/1.2

We decided the best design to pursue was the
solar and kinetic power option. This system
received high scores in the safety and ease of
use categories. This system is composed of a
portable solar panel and a kinetic power
generator. This combination allows the system
to generate power if it is sunny or if the user is
moving. As long as it is sunny the solar panel
will generate ample power to charge the radio.
If it is cloudy or night time then the kinetic
power source will create power as long as the
user is moving.
To use the system the user will place the
nPowerPEG upright in their pack so that it will
generate power as they walk. The solar panel gets
hung off of the back of the pack so it will be
exposed to sunlight as the user walks along. Both
of these sources are connected to the charging
module which is placed in the top of the users
pack. The module will have a cord that is
connected to the radio to charge it.
The radio we are designing our system to charge
is the RF-7800S-TR personal form Harris. This radio is
lightweight and easy for the user to carry around
with them. The radio consumes 2 watts of power
during operation. For our Kinetic generator we plan
on making use of the nPowerPEG kinetic generator
which costs $200. This kinetic generator weighs 14
ounces and produces 2.5 watts of power at 5 volts
DC. For our solar power we will utilize the Brunton
Explorer folding solar panel which costs $65. This
panel weighs 4.8 ounces and folds for easy
transportation. The panel produces 5 watts of output
at 5 volts DC.