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 Body heat/ wireless power “clothing panels” Piezoelectric/Wind Wind Mill Combine energy sources.34/1.22/.6 4/1.2 Ease of use.133/.392/.26 2/.39 Size and Weight.072/.143/.212/.144/.28 Safety.274/1.083/.814/1.082/.54 Impact on environment 03/04/0 Economic Viability.23/.6 2/.4 19/3.4117/2.8417/2.6818/2.81

 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.