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Integrated Solar Backpack

George Ingrish, Jack Hearin, Charles Tyndal

DESIGN PROJECT

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AGENDA

SOLAR BACKPACK

Identifying the problem

Outlining our design

Demonstrating prototype functionality

Discussing necessary improvements

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Identifying the Problem

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OUR MOTIVATION

“Electronic device consumers currently do not have a self-sustainable, lightweight energy source to charge their devices in portable luggage.”

Students

Need a way to charge their electronic devices around campus
Cannot rely on having a wall charger near a power outlet
Portable chargers do not integrate with daily carry backpacks

Outdoor Enthusiasts

Outdoor enthusiasts need a way to charge their devices off the grid
Portable chargers and solar panels are large and heavy
Hikers rely on electronic devices for navigation

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Compound Annual Growth Rate

11.03%¹

Increasing use of portable phones, tablets, laptops, etc. drives power consumption

Power bank usage is increasing 18.5% per year

Eliminating inefficiencies in power delivery and storage will drive Innovation in portable tech

Compound Annual Growth Rate

21.3%

Portable Electronics

Portable Solar Chargers

Governments and firms are providing large amounts of capital for sustainable energy

Increasing participation in outdoor activities and use of off-grid energy resource in developing countries

Note: All market statistics obtained from marketwatch.com

ANALYZING MARKET DEMAND

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Array Solar Backpack

ANALYZING EXISTING CONCEPTS

Cons:

Large, rigid solar panel
Not aesthetically appealing for modern consumers
The solar system leaves little room for storage

External Solar Charger

Cons:

Externally mounted system requires user input
Panels take up considerable space in the pack
Impractical for use outside outdoor recreation

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Design Concept

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CONCEPTUAL DESIGN

Initial Design Goals:

-Ease of Use (USB in/out)
-Integrate panels seamlessly with backpack style

Solar fabric design not feasible

Chose to integrate an array of flexible solar panels

Wired together to increase power output
Moves with backpack to increase flexibility

Solar manager circuit board

Regulates incoming solar power
Charges internal battery
USB output

Improve on functionality and aesthetic from existing products

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Prototype

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SOLAR PANEL SYSTEM

Flexible solar panels

1.5V operating voltage
0.25A operating current
~8% efficiency

Five pairs of 2 solar panels in parallel

Each pair wired in series

Our circuit increases power by 7.5x

0.5 Watt panels
3.75 Watt circuit

Flexible solar panels improve useability

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SOLAR MANAGER CIRCUIT HOUSING

Casing Designs:

3D Print
Laser Cutter

Solution: Laser Cutter Box

Openable Design (for tooling)
Bolts and Washers as Standoffs
Fastened in place
Screws are only point of contact

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SOLAR IN (FM)

BATT/IOS in

USB OUTPUT

POWER OUT

BATT. INPUT

SOLAR INPUT

POWER CONTROL SYSTEM

Solar Manager

Maximum Power Point Tracking

Power maximizing algorithm
Maximizes amps to battery

2500 mAh battery
Directs solar power to battery and battery to power output

IOS compatible battery booster

Converts manager output to IOS compatible charge
Input for storage battery

4400 mAh

USB Output

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Solar Panel Wiring

INTERNAL ASSEMBLY

Notes:

Two large cuts made in parallel to secure solar panels onto the front of the backpack
Wire clips thread through these slits

Control System Integration

Notes:

2-part laser cut casing to house circuit board
Glued to lower right corner of the backpack
Wiring shielded within lining

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Demonstrating Functionality

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SOLAR SYSTEM ASSEMBLY & TESTING

Tested solar panels in optimized circuit to operating characteristics

10.29 Volts and 0.51 amps at ~80 degrees fahrenheit (300K)

After 3 hours of operation during peak sunlight

9.47 Volts and 0.67 amps at ~150 degrees fahrenheit (338K)

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TESTING FINAL PROTOTYPE

Tested in direct sunlight from 8 AM to 4 PM

Output at 1.0A for 5 hours (1.5 “iPhones” of charge)

Complete iPhone charge in 2.5 hours

Output at 0.67 amps for an additional 3 hours

iPhone was being charged directly through solar output
Charging rate greatly slowed down

Solar panel temperature increased by 70 degrees leading to a decrease in performance

Charging rate was slow but self-sustained output was provided all day

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PROTOTYPE CONCLUSIONS

Succeeded in developing a self-sustainable, integrated solar charging system for backpacks
Augmented battery capacity by 2 hours and provided slowed 0.67 amp charging without stored energy
Net-charge equilibrium can be achieved with high efficiency solar panels
Small improvements in the manufacturing and design could drastically increase useability and visual appeal

DEMONSTRATING FUNCTIONALITY

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Potential Improvements

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METRICS OF SUCCESS

Customer Statement	Need Statement	Metric	Marginally Acceptable	Ideal Target Value	Prototype Value
“I would like my charger to last all day while charging my iPhone.”	The energy delivery system maintains charge equilibrium all day.	Solar input amperage during peak sunlight (Amps)	1	2.0	0.67
“I think most tech backpacks do not keep up with the latest styling trends”	The solar backpack is visually attractive and matches the latest styling trends.	Qualitative Scale (1-10)	7	9	5
“I get tired of carrying large, portable chargers in my backpack.”	The energy storage system is lightweight and does not take up space in a bag.	Percent volume occupied (%)	7%	5%	15%

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INCREASING AMPERAGE

IMPROVING SOLAR CAPABILITIES

Currently operate at 8 % solar efficiency

Operating characteristics

7.5 Volts
0.5 Amps
3.75 Watts

Need to increase power and reduce solar cell area

Decrease to 6 flexible solar panels
3 pairs of 2 solar panels in parallel
Existing circuit provides 6x power increase

iPhones draw ~ 5V at 1 amp while charge

Our model shows we need 18% solar efficiency to maintain charge equilibrium
Greater efficiency is needed to account for use with less sun exposure

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Presentations are tools that can be used as lectures and more.

OPEN SPACES

Presentations are tools that can be used as lectures and more.

ACCESSIBILITY

SEWN SOLAR PANELS

CUSTOM SOLAR MANAGER

ELECTRONICS SPACE

Existing glue seams create rough edges and gaps

Sewn solar panels for seamless edges

Increases durability
Increases aesthetic appeal

Current circuit has wasted space

Unused outputs and inputs
Uses an entire board to be IOS compatible

Print custom solar manager

The same functions contained in one unit
Takes less space in the bag

Sleek custom manufactured controller with full acrylic

Sewn into outside drink pocket of backpack
Does not take up space in the backpack

IMPROVING USEABILITY AND AESTHETICS

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KEY TAKEAWAYS

The prototype achieves its mission during ideal conditions and proves product feasibility

The design process is not unidirectional

Always be aware of project constraints

Concept development rests on team dynamics

SOLAR BACKPACK

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THANK YOU