ENGR 103-072- Spring 2016
Freshman Engineering Design Lab
“Four Degree Utility Backpack”
Project Design Proposal
Date Submitted: April 8, 2016
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Sudhanshu Pareek, sp3263@drexel.edu
Long Nguyen , lkn25@drexel.edu
Abstract
The backpack is targeted at hikers and patients who travel in scorching summer heat and need to keep their drinks and medicines cool. It will use a Peltier Cooling unit and get power from solar photovoltaic panels. It will feature some other utilities such as USB charging ports and flashlight for emergency usage. The power and cooling systems would be detachable so the bag would be washable and could be used like a normal backpack.
The main design challenges would be to test and find the best materials for insulation, make a low power cooling system and make an efficient solar charger. A lightweight battery shall be found to provide enough power and meet the requirements.
1. Introduction
The group wants to make a utility backpack unlike any other. It will help replenish one's thirst on a hot summer day along with saving one the trouble of looking for charging ports for their phone. Be it traveling or just working all day along, this backpack will be handy and will make one’s life easier.
This project involves constructing USB phone chargers and building a cooling system within a backpack , both of which will be a new experience for the group. The entire system will be powered by a foldable solar panel, which will be located on top of the bag. The group is aiming to create a product that will be affordable, efficient and fulfill the needs of its target audiences. This project will allow the group an insight on the work that goes behind a finished product in the market.
The major task would be creating a cooling system within the front pouch of the backpack. Integrating the entire system and managing to keep the temperatures low up to ten degree celsius are the biggest obstacles on the group’s path. The group has to research and learn the installation process over the ten week period.
The group has mapped out the entire process of development throughout the course. By the end of the ninth week, the group will have a complete and tested product to present in front of everyone.
2. Deliverables
The final deliverable is going to be a photovoltaic panel powered backpack with a refrigerated chamber, USB charging ports, and an emergency flashlight. The photovoltaic cells are going to be detachable along with all the other electronics, so the backpack can be washed and kept clean.
3. Technical Activities
There are three major sections of the project. First is the selection of right solar panel. The solar panel needs to be foldable, to be able to supply enough energy to run the entire integrated system and to be economical. Second, the group needs to assemble all the required hardware and construct a fully functioning system. Third, developing the refrigeration in the backpack. The refrigerator will be made out of a material that can maintain a temperature of ten to twelve-degree celsius inside the refrigeration compartment. The system will be coolant free and will be environment friendly. The group members discussed few ideas related to the effect of the coolant in the refrigeration unit. The leading idea is usage ofPeltierr cooling unit. More is discussed in the later sections.
3.1 Refrigeration Unit Study and Assembly
The group members have studied various websites and books and are confident in their ability to assemble a refrigerated compartment from scratch. The group has to be precise in choosing the materials needed for the chamber, and it will be done by studying different material properties of our candidates.
3.2 System Integration
Matching the voltage and current output of the solar panels with that of the refrigerator and the USB ports is going to be another technical challenge. This problem can be solved by finding a proper solar panel and then using resistors and a charge controller to supply the right voltage and current to the outputs.
The energy needed by the peltier cooling unit can be calculated by using the following equation:
T1 = (−P*Itec + Itec2 *Rp/2 + Q1)/(C1 + Cp) + (Q1 + Itec2 *Rp)/(Ch + T3)
Where,
P = Peltier constant = (Qmax + Imax2 *Rp/2)/Imax
Qmax = maximum heat transfer from TEC data sheet (watts)
Rp = TEC resistance = Vmax/Imax = TEC data sheet drive ratings
Itec = TEC drive current (amperes)
Q1 = heat produced by thermal load watts)
C1 = conductivity (watts/°C) of thermal load to ambient
Cp = TEC thermal conductivity = Qmax/ΔTmax from TEC data sheet
Ch = heatsink thermal conductivity to ambient
T3 = ambient temperature
The peltier equation is going to be instrumental in our project for the procurement of the right components. The solar panel and battery have to be of the correct capacity.
Another big challenge will be making physical modifications to the backpack. This will require a bit of stitching and we will need to attain this expertise.
4. Project Timeline
Table 1: Freshman design project timeline
Week
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Task
|
1
|
2
|
3
|
4
|
5
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6
|
7
|
8
|
9
|
10
|
Refrigerator Design study
|
x
|
x
| ||||||||
Solar panel Set up
|
x
|
x
| ||||||||
Refrigerator construction and testing
|
x
|
x
|
x
|
x
|
x
| |||||
System integration
|
x
|
x
|
x
| |||||||
Testing
|
x
|
x
|
x
|
x
| ||||||
Final report preparation
|
x
|
x
|
x
| |||||||
5. Facilities and Resources
To give life to the blueprint of the product, the group needs hardwares like Foldable Solar Panel, Peltier Cooling Unit, Akasa chipset cooling kit to mention a few. The rest of the hardware list has been mentioned in the budget section. The group also needs a soldering machine to complete the circuit for the entire system. Access to the machine shop will fulfill the requirement of the specific tools needed to complete the project. Furthermore, the group also requires a work space on campus to design and build the prototype.
6. Expertise
The project will require a proper knowledge of basic circuit theory and solar panels. Both of which all the group members possesses prior to attending this class. Aman Agrawal is especially adept in the art of integration of solar panels.
For the second tier, all the members will need to achieve expertise in the art of making detachable chambers in the backpack.
7. Budget
Table 2: Freshman design project budget
Category
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Projected Cost
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Refrigerator Hardware
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$37.39
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Foldable Solar Panel
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$55.60
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Circuit hardware
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$95.98
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Back Pack
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$20.00
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TOTAL
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$207.37
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7.1 Refrigerator Hardware
This category contains all the necessary hardware we will need to build the refrigerated compartment.
The refrigerated chamber will be made up of an aluminized mylar sheet inner lining and a quilted fabric exterior, which will increase the probability of the inside the compartment The components of the chamber will be connected by using nylon strings and glue gun. The glue gun will be borrowed from the lab. The remaining hardware will be assembled to create refrigeration inside the chamber. In addition to this, all the hardware will be meticulously installed around the refrigeration chamber.
Table 3: Refrigerator Hardware Budget
Hardware
|
Projected Cost
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Aluminized Mylar Sheets
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$3.50
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Nylon Thread
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$4.99
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Quilted Fabric Square
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$6.60
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Zipper
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$2.99
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91.2W 40x40mm Peltier Cooling Unit
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$6.00
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Akasa chipset cooling kit
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$10.99
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Single hole 2.1mm DV power jack
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$3.00
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Double sided tape
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$1.00
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TOTAL
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$36.39
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7.2 Circuit Hardware
This table contains all the necessary hardware required to construct the circuit for the entire system.
Table 4: Refrigerator Hardware Budget
Hardware
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Projected Cost
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Wire
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$2.50
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Charge Controller
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$35.68
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Resistors
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$4.80
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USB cable
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$8.00
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Battery (Energy Storage)
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$45.00
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TOTAL
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$95.98
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8. Design
Figure 1 : The 4 Degree Utility Backpack
The following figure points out the location of the solar panel, pouch with the cooling system and the charging chambers. The charging chambers will have usb ports inside.
Figure 2. Energy Flow Chart
The following flowchart explains the flow of energy from the sun to different components of our system: starting with the conversion from light to electrical energy by solar panels to the charging of the battery through a charging circuit which will ultimately supply power to the cooling system, USB charging port and flashlight installed on the backpack.
9. References
- Keeping, Steven. "A Designer's Guide to Lithium Battery Charging." A Designers Guide to Lithium Battery Charging. Digi-Key, 25 Nov. 2012. Web. 01 Apr. 2016.
- "The Heatsink Guide - Peltier Cooler Information." The Heatsink Guide - Peltier Cooler Information. The Heatsink Guide, n.d. Web. 02 Apr. 2016.
- "Insulation Materials." Insulation Materials. US Department of Energy, n.d. Web. 02 Apr. 2016.
- "Solar Info: The Down Low on Everything Up High." BatteryStuff Articles. N.p., n.d. Web. 02 Apr. 2016.
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