WIRELESS POWER TRANSFER · · 2017-02-17CONTENTS 1. Introduction 2. The History of Radiative Wireless Power Transfer 3. Basics and Limitations 4. Future Perspectives 5. Summary

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WIRELESS POWER TRANSFERPROF. DR. IR. HUBREGT J. VISSER

CONTENTS

1. Introduction

2. The History of Radiative Wireless Power Transfer

3. Basics and Limitations

4. Future Perspectives

5. Summary and Conclusions

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1. INTRODUCTION

1. INTRODUCTION

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DEFINITIONS

Wireless Power Transfer (WPT):A special form of energy

harvesting using dedicated electromagnetic sources.

Energy Harvesting: The process by which energy is obtained by

a device from external sources in the environment and

converted into usable electric energy.

Radiative Wireless power Transfer: WPT using radio waves.

Energy Harvesting

WPT

inductive radiative

1. INTRODUCTIONENERGY HARVESTING SOURCES

1831 Faraday dynamo WWII Philips dyno torch Modern dyno torch

1880 Curie discovery

of piezoelectricity

Enocean

wireless switchRPG7 fuse

Movement

Pressure

1821 Seebeck experiment

1948 USSR oil

lamp powered

radio

Temperature

gradients

1977 Voyager 2

Radioisotope

Thermoelectric

Generator

Light

1839 Becquerel experiment 1954 Bell Labs PV Modern PV

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1. INTRODUCTION

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APPLICATIONS AND POWER DENSITIES

APPLICATIONSReplacement of or charging batteries in small, wireless, autonomous sensors.

POWER DENSITIES

Picture source: http://smarthomeenergy.co.uk/what-smart-home

2. THE HISTORY OF RADIATIVE WIRELESS POWER TRANSFER


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1931: HARRELL NOBLE DEMONSTRATES RADIATIVE WIRELESS POWER TRANSFER

100MHz half-wave dipoles

Distance: 5 to 12m

15kW transmit power

Westinghouse laboratories

Demonstrated 1933-1934 at the

Chicago World Fair


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1964: WILLIAM BROWN DEMONSTRATES A WIRELESSLY POWERED HELICOPTER

• 5kW, 2.45GHz magnetron

• 3m diameter parabolic reflector

antenne

• 9m height

• 1.5m2 receive antenna

• 4480 diodes

• 270W DC power

• Raytheon Airborne Microwave

Platform (RAMP) project


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2017: HOLST CENTRE / IMEC & TU/E

2007

2009

2011

2013

2013

2014

2015

2016

2017

3. BASICS AND LIMITATIONS


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DECREASE OF POWER

PT

Radio waves spread spherically.

For every distance-doubling, the power density [W/m2]

decreases with a factor 4.

Restrictions are not put on the transmit power

only, but also on the transmit antenna: EIRP

For GSM: 0.003 W/m2 (0.3 W/cm2)

For a 4W (EIRP) source at 5 m distance: 0.013 W/m2 (1.3 W/cm2)


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EXPECTED RF POWER

PTPR

r

The receive antenna also determines the received power.

example: 4W EIRP at 5 m distance

Patch antenna, 6 cm x 6 cm, 2.4 GHz

RF power on antenna: 58 W


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RECTENNA (RECTIFYING ANTENNA)


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INCREASING THE DC VOLTAGE

Resonant grid with diodes


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RESONANT DIODE GRID


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POWER MANAGEMENT

• 30 W DC continuous at 10 m distance (3W EIRP source)

• 60 mW DC for 40 ms, every 2 minutes, at 10 m distance (3W EIRP source)


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RECTENNA DEMO

4. FUTURE PERSPECTIVES


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RECTENNA MINIATURIZATION AND INTEGRATION


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CHARGING PHONES ON A DISTANCE

• Use distributed radiators

• Combine radiation

patterns smartly

• Create pockets of high

energy density


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Combining in frequency


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Combining in time (pulsing)


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Combining in time (pulsing)

&

Phase-shifting (beam-steering)


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t = t0 + 10ns


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t = t0 + 30ns


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t = t0 + 50ns


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t = t0 + 68ns


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t = t0 + 90ns

5. SUMMARY AND CONCLUSIONS

5. SAMENVATTING EN CONCLUSIES

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1. For practical radiative WPT creating enough voltahe and power are challenges;

2. WPT can be realised with a large collecting aperture;

3. For a small collecting aperture we need voltage boosting;

4. Through careful co-design of rectifier and antenna radiative WPT is feasible;

5. Charging cell phones remotely will become feasible by employing distributed, transient

transmitters;

6. For that research (and funding!) is necessary.

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WIRELESS POWER TRANSFER · · 2017-02-17CONTENTS 1. Introduction 2. The History of Radiative Wireless Power Transfer 3. Basics and Limitations 4. Future Perspectives 5. Summary