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ISBN-13: 978-1-59693-718-5ISBN-10: 1-59693-718-1

B O S T O N L O N D O N

www.artechhouse.com

for Autonomous systems

ENERGY Harvesting

Stephen BeeByneIL WhIte

Stephen BeeByneIL WhIte

BeeByWhIte

for Autonomous systemsENERGY Harvesting

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ERGY Harvesting

Electrical Engineering/Microsystems

• Wireless Devices and Sensor Networks• Photovoltaic Energy Harvesting• Kinetic Energy Harvesting• Thermoelectric Energy Harvesting

• Power Management Electronics• Energy Storage• Case Study: Adaptive Energy-Aware

Sensor Networks.

This unique resource provides a detailed understanding of the options for harvesting energy from localized, renewable sources to supply power to autonomous wireless systems. Professionals are introduced to a variety of types of autonomous systems and wireless networks and explore the capabilities of existing battery-based solutions, RF solutions, and fuel cells. This book focuses on the most promising harvesting techniques, including solar, kinetic, and thermal energy. Readers also learn the implications of energy-harvesting techniques on the design of power management electronics in a system. This in-depth reference discusses each energy-harvesting approach in detail, comparing and contrasting its potential in the field.

Contents Overview:

Stephen Beeby obtained his Ph.D. from the University of Southampton in 1998 in the subject of micromechanical resonators. He was awarded a prestigious EPSRC advanced research fellowship in 2001 and is currently a reader in the School of Electronics and Computer Science at the University of Southampton. His research interests include energy harvesting, MEMS, active printed materials development, and biometrics. He is the coordinator of an EU Framework Integrated Project MICROFLEX and is the principal or coinvestigator on a further 6 projects. He is a cofounder of Perpetuum Ltd. He has coauthored one other book, MEMS Mechanical Sensors, published over 150 publications in the field, and holds 7 patents.

Neil White holds a personal chair in intelligent sensor systems in the School of Electronics and Computer Science, University of Southampton, U.K. He obtained his Ph.D. from the University of Southampton in 1988. He is the author/coauthor of over 200 peer-reviewed papers and holds 10 patents in the areas of advanced sensor technologies, instrumentation, and energy-harvesting systems. He is a cofounder and former director of Perpetuum Ltd., a university spin-out company specializing in vibration energy harvesting.

v

Contents

CHAPTER 1

Introduction 1

1.1 Background and Motivation 11.2 Typical System Architecture 31.3 Intended Readership for This Book 4

Reference 5

CHAPTER 2

Wireless Devices and Sensor Networks 7

2.1 Introduction 72.2 Energy Requirements of Autonomous Devices 9

2.2.1 From Mobile Phones to MP3 Players 92.2.2 Radio Frequency Identifi cation (RFID) 102.2.3 Wireless Sensor Networks 12

2.3 Enabling Technologies: Devices and Peripherals 192.3.1 Low-Power Microcontrollers and Transceivers 192.3.2 Sensors, Peripherals, and Interfaces 20

2.4 Wireless Communication 242.4.1 Communication Protocols and Power Requirements 242.4.2 Energy-Aware Communication Protocols 27

2.5 Energy-Awareness in Embedded Software 332.5.1 Operating Systems and Software Architectures 33

2.6 Alternative Nonrenewable Power Sources 352.6.1 Direct Transmission 35

2.7 Discussion 36References 37

CHAPTER 3

Photovoltaic Energy Harvesting 45

3.1 Introduction 453.2 Background 46

3.2.1 Semiconductor Basics 463.3 Solar Cell Characteristics 49

vi Contents

3.4 Module Characteristics 503.5 Irradiance Standards 51

3.5.1 Outdoor Operation 513.5.2 Indoor Operation 54

3.6 Effi ciency Losses 543.6.1 Intrinsic Losses 553.6.2 Extrinsic Losses 563.6.3 Module Losses 65

3.7 Device Technologies 653.7.1 Silicon Wafers 663.7.2 Single Crystal and Multicrystalline Devices 673.7.3 Amorphous Silicon 693.7.4 Thin Film Polycrystalline Silicon 703.7.5 Multijunction Silicon 713.7.6 Cadmium Telluride/Cadmium Sulphide 723.7.7 Copper Indium (Gallium) Disselenide 733.7.8 Single and Multijunction III-V Cells 743.7.9 Emergent Technologies 76

3.8 Photovoltaic Systems 793.8.1 Basic System 793.8.2 Charge Controllers 803.8.3 DC-DC Converters and Maximum Power Point Tracking 803.8.4 Miniaturization and Low-Power Systems 823.8.5 Device Technology 823.8.6 Systems Considerations 83

3.9 Summary 85References 85

CHAPTER 4

Kinetic Energy Harvesting 91

4.1 Introduction 914.2 Kinetic Energy-Harvesting Applications 92

4.2.1 Human 924.2.2 Industrial 934.2.3 Transport 934.2.4 Structural 94

4.3 Inertial Generators 954.4 Transduction Mechanisms 97

4.4.1 Piezoelectric Generators 984.4.2 Electromagnetic Transduction 1004.4.3 Electrostatic Generators 1034.4.4 Transduction Damping Coeffi cients 1054.4.5 Microscale Implementations 108

4.5 Operating Frequency Range 1104.5.1 Frequency Tuning 1114.5.2 Strategies to Broaden the Bandwidth 114

Contents vii

4.6 Rotary Generators 1164.7 Example Devices 117

4.7.1 Human-Powered Harvesters 1174.7.2 Conventional Generators for Industrial and Transport Applications 1194.7.3 Microscale Generators 1234.7.4 Tuneable Generators 126

4.8 Conclusions and Future Possibilities 1284.8.1 Piezoelectric Generators 1294.8.2 Electromagnetic Generators 1294.8.3 Electrostatic Generators 1304.8.4 Summary 130Acknowledgments 131References 131

CHAPTER 5

Thermoelectric Energy Harvesting 135

5.1 Introduction 1355.2 Principles of Thermoelectric Devices 135

5.2.1 Thermoelectric Effects 1365.2.2 Thermoelectric Devices 139

5.3 Infl uence of Materials, Contacts, and Geometry 1425.3.1 Selection of Thermoelectric Materials 1425.3.2 Thermal and Electrical Contacts 1445.3.3 Geometry Optimization 1465.3.4 Heat Exchangers 148

5.4 Existing and Future Capabilities 1485.4.1 Low Power Systems 1495.4.2 Waste Heat Recovery 1515.4.3 Symbiotic Cogeneration System 1535.4.4 Commercial Thermoelectric Module Suppliers 154

5.5 Summary 155References 155

CHAPTER 6

Power Management Electronics 159

6.1 Introduction 1596.1.1 Interface Circuit Impedance Matching 1596.1.2 Energy Storage 1616.1.3 Output Voltage Regulation 1616.1.4 Overview 162

6.2 Interface Electronics for Kinetic Energy Harvesters 1626.2.1 Electromagnetic Harvesters 1646.2.2 Example of a Complete Power Electronics System for a Continually Rotating Energy Harvester 1666.2.3 Piezoelectric Harvesters 182

viii Contents

6.2.4 Electrostatic Harvesters 1886.3 Interface Circuits for Thermal and Solar Harvesters 197

6.3.1 Thermal 1976.3.2 Power Electronics for Photovoltaics 201

6.4 Energy Storage Interfaces 2046.4.1 Output Voltage Regulation 205

6.5 Future Outlook 2066.6 Conclusions 207

References 207

CHAPTER 7

Energy Storage 211

7.1 Introduction 2117.1.1 Battery Operating Principles 2127.1.2 Electrochemical Capacitor Operating Principles 2137.1.3 Comparison of Energy Storage Devices 214

7.2 Micropower Supply for Wireless Sensor Devices 2157.2.1 Microenergy Storage Considerations 2167.2.2 Materials Considerations for Microbatteries 2177.2.3 Geometry and Processing Considerations for Microbatteries 219

7.3 Implementations of 2D Microbatteries 2197.3.1 Thin Film Solid-State Microbatteries 2207.3.2 Thick Film Microbatteries 2227.3.3 Concluding Remarks for 2D Microbatteries 229

7.4 Three-Dimensional Microbatteries 2307.4.1 3D Microbattery Architectures with a Discontinuous Element 2327.4.2 3D Microbattery Architectures with Continuous Elements 2377.4.3 Prospects for Three-Dimensional Microbattery Implementation 240

7.5 Electrochemical Microcapacitors 2427.5.1 Electrochemical Capacitor Materials 2427.5.2 Microcapacitor Prototypes 2437.5.3 Conclusions and Prospects for Microcapacitors 246

7.6 Conclusion 247References 247

CHAPTER 8

Case Study: Adaptive Energy-Aware Sensor Networks 253

8.1 Introduction 2538.2 Requirements 2548.3 Energy Harvesting Sensor Node Hardware Design 254

8.3.1 Node Core Design 2548.3.2 Overview of Modular Design 2558.3.3 Choice of Microprocessor 2558.3.4 Energy Multiplexer Subsystem 2568.3.5 Supercapacitor Energy Storage Module 2578.3.6 Solar Energy-Harvesting Module 258

Contents ix

8.3.7 Vibration Energy-Harvesting Module 2608.3.8 Thermal Energy-Harvesting Module 2608.3.9 Wind Energy-Harvesting Module 2618.3.10 Other Energy-Harvesting and Storage Modules 2628.3.11 Plug-and-Play Capabilities 2628.3.12 Sensor Module 2648.3.13 Built-In Sensing Capabilities 2658.3.14 Energy Effi cient Hardware Design 265

8.4 Energy-Harvesting Sensor Node Demonstration Overview 2678.5 Energy-Harvesting Sensor Node Software Design 267

8.5.1 Node Software 2678.5.2 Intelligent Energy Management 2698.5.3 Information Reported by the Energy-Harvesting Node 270

8.6 Energy-Aware, Energy-Harvesting Node Demonstration 2718.6.1 Supporting Nodes for Demonstration 2718.6.2 Energy Sources for Demonstration 2718.6.3 Demonstration Sequence 272

8.7 Conclusions 275References 276

CHAPTER 9

Concluding Remarks 277

About the Editors 279

About the Contributors 279

Index 283