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THE WEARABLE THERMAL GENERATOR: A BATTERY FREE POWER SUPPLYPRESENTED BY: NATE BEEMER

ADVISOR: PROF. HAL BROBERG

INSTRUCTOR: PROF. PAUL LIN

5/1/2015

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OUTLINE:

• Executive Summary

• Introduction

• Problem and Solution

• System Requirements and Validation

• System Analysis

• System Design

• System Integration and Testing

• Conclusion

• Demo/Q & A 2

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EXECUTIVE SUMMARY

• The Wearable Thermal Generator project sought to build a prototype for an

affordable apparatus that would generate power in cool, dark environments

with some ambient wind by harnessing only the waste heat dissipated from

the human body. The power generated could then be used to power efficient

light emitting diodes (LEDs), charge cell phones, or be stored in a

rechargeable battery pack for future use.

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INTRODUCTION

• This project consisted of a plan for the design, construction, and testing of a

wearable thermoelectric generating device. It was the hopes of the designer

that this project would inspire others to look into other ways of utilizing

alternate sources of power in everyday life.

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PROBLEM AND SOLUTION

“Where there’s a need, there’s a niche in the market.”

-Me

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SO WHY?

• Typical AA weighs between 15-31g

• Spelunkers carry at least 12 AA’s per headlamp (usually 3 lamps)

• Average person throws away 8 non-rechargeable batteries / year

• All mobile devices rely on batteries

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GO ON… I’M LISTENING…

• By the end of 2015, the estimated market for lithium-ion batteries alone will

reach almost 13.2 billion U.S. dollars

• Several ways to recharge batteries…

• Consider that a Samsung Galaxy S4 phone can last ~1,051 minutes making a

call or ~405 minutes using the internet

• Duration plays key role in purchases

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SO THAT MEANS…

• A need exists for a device that can help recharge portable electronics when

no other alternate energy source is available

• Potential market

• Cut down on chemical waste

• Lighter and longer

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SYSTEM REQUIREMENTS AND VALIDATION

• Wearable

• Operates in 70o F max (with some ambient air)

• Generates enough power to light an LED

• Ability to charge batteries / portable devices

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SYSTEM ANALYSIS

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SYSTEM ANALYSIS CONT.

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SYSTEM ANALYSIS CONT.

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SYSTEM ANALYSIS CONT.

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Combined surface area of TEG units: 8cm x 8cm = 64cm2

Average power dissipated by humans: ~97 Watts

Average surface area of human skin: 1.7m2 or 17,000cm2

Average power dissipated per cm2 of human skin: 97

17,000 2 x 1000 = 5.7

2

Power expected to be generated by total area of TEG units: 5.7

2 x 64cm2 = 364.8mW

With 10% TEG efficiency, actual power expected to be generated by the total area of the TEG units: (364.8 mW) x (0.1) = 36.48 mW

Target voltage generated from TEG units: ~50mV DC

Target current generated from TEG units: 36.48

50 = 0.73A

SYSTEM ANALYSIS CONT.

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Potential (mv)

Time (seconds)

Decay Rate

ARM

THIGH

NECK

NECK

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SYSTEM ANALYSIS CONT.

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SYSTEM ANALYSIS CONT.

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SYSTEM ANALYSIS CONT.

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SYSTEM ANALYSIS CONT.

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SYSTEM ANALYSIS CONT.

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SYSTEM ANALYSIS CONT.

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0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

2.4

62

2.1

44

1.8

26

1.5

81

.18

10

0.8

61

20

.54

14

0.2

21

59

.91

79

.58

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9.2

62

18

.94

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8.6

22

58

.32

77

.98

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7.6

63

17

.34

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7.0

23

56

.73

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.38

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6.0

64

15

.74

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5.4

24

55

.14

74

.78

49

4.4

65

14

.14

53

3.8

25

53

.55

73

.18

59

2.8

66

12

.54

63

2.2

26

51

.96

71

.58

69

1.2

67

10

.94

73

0.6

27

50

.37

69

.98

78

9.6

68

09

.34

82

9.0

28

48

.78

68

.38

88

8.0

69

07

.74

92

7.4

29

47

.19

66

.78

98

6.4

61

00

6.1

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02

5.8

21

04

5.5

10

65

.18

10

84

.86

11

04

.54

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24

.22

11

43

.91

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3.5

81

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3.2

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Vol

tage

(m

V)

Time (seconds)

Refined LabVIEW Arm TestVoltage vs. Time

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SYSTEM ANALYSIS CONT.

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.73

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.57

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94

.31

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.71

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.11

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.51

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.91

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.32

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.72

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.12

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.52

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.92

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.32

96

.73

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.13

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.53

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.93

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.33

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.74

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.14

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.54

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.94

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.34

80

.74

99

.15

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.55

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.95

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.35

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.75

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.36

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.76

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.17

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.11

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8.3

Vol

tage

(m

V)

Time (seconds)

Refined LabVIEW Cranial (Temple) TestVoltage vs. Time

SYSTEM ANALYSIS CONT.

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SYSTEM DESIGN

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V1

4 V 0.1 Ω

V212 V

T2C2

1nF

C3

470pF

C447µF

C52.2µF

U1

LTC3109

12345678910 11

121314151617181920

Q1

BST100

U2

LTC4070

1234 5

678

C6

47µF

C7

200µF10%

S2

C8

1nFC9

470pF

T1

V312 V

V412 V

V512 V

LED1

SYSTEM DESIGN CONT.

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C2

1nF

C3

470pF

C447µF

C52.2µF

U1

LTC3109

12345678910 11

121314151617181920

Q1

BST100

U2

LTC4070

1234 5

678

C6

47µF

C7

200µF10%

C8

1nFC9

470pF

U3pinsocket

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U4pinsocket

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U5pinsocket

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U6pinsocket

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U7pinsocket

12

U8

pinsocket

12

U9dipswtich

1 2 3 4 5 6 7 8910111213141516

U10

transformer

12 3

4

U11

transformer

12 3

4

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

• First prototype breakout boards failed to work

• Cut circuit board wouldn’t have worked anyway, due to transformer glitch

• Back to the drawing board…

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

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SYSTEM DESIGN CONT.

• Hand-soldered transformers to the circuit board…

• It worked!

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SYSTEM INTEGRATION AND TESTING

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SYSTEM INTEGRATION AND TESTING CONT.

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SYSTEM INTEGRATION AND TESTING CONT.

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SYSTEM INTEGRATION AND TESTING CONT.

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SYSTEM INTEGRATION AND TESTING CONT.

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CONCLUSION

• Prototype succeeded in producing enough voltage to power a 1-

Watt, CREE LED

• One prototype could produce a sustained 3.3V, ~1mA at 70oF,

while the other prototype could produce a sustained 5V, ~1mA at

70oF

• Power needs lasted well beyond 20 minutes in proper conditions

• Further testing needed to determine whether trickle-charger circuit

works42

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CONCLUSION CONT.

• Future designs might include head-mounted systems, piezoelectric

power sources, and water-proof circuitry

• Ideas for start-up business? Kickstarter campaign?

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DEMO / Q & A

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