WPT Wireless Charging Overview

WIRELESS POWER TRANSMISSION
AND
WIRELESS CHARGING
Pranay Gupta
5/25/2019 1Wireless Power Transmission & Wireless Charging

Overview
 What is wireless power transmission(WPT)?
 What isWPT?
 History ofWPT
 Types ofWPT
 Techniques to transfer energy wirelessly
 Advantages and disadvantages
 Applications
 Wireless Charging System
 TechnicalTrends
 Challenges
5/25/2019Wireless Power Transmission & Wireless Charging 2

What is WPT?
 The transmission of energy from one place to
another without using wires
 Conventional energy transfer is using wires
 But, the wireless transmission is made
possible by using various technologies

History
 NikolaTesla in late 1890s
 Pioneer of induction techniques
 His vision for “WorldWireless System”
 The 187 feet tall tower to broadcast energy
 All people can have access to free energy
 Due to shortage of funds, tower did not operate
 The idea ofTesla is taken in to research after 100
years by a team led by Marin Soljačić from MIT.
The project is named as ‘WiTricity’.

Types and Technologies of WPT

Inductive coupling
 Primary and secondary coils are not
connected with wires.
 Energy transfer is due to Mutual Induction
 Transformer is also an example
 Energy transfer devices are usually air-cored
 Wireless Charging Pad(WCP),electric brushes
are some examples
 On aWCP, the devices are to be kept, battery
will be automatically charged

Inductive coupling
 The charging pad
(primary coil) and the
device(secondary coil)
have to be kept very near
to each other
 Less use of wires
 Shock proof

Resonance Inductive Coupling
 Combination of inductive coupling and resonance
 Resonance makes two objects interact very strongly
 Inductance induces current
 Coil provides the inductance
 Energy will be shifting back and forth between
magnetic field surrounding the coil and electric field
around the capacitor
 Capacitor is connected parallel to the coil
 Radiation loss will be negligible

Air Ionization
 Toughest technique under
near-field energy transfer
techniques
 Air ionizes only when there
is a high field
 Needed field is 2.11MV/m
 Natural example:
Lightening
 Not feasible for practical
implementation

Advantages of near-field
techniques
 No wires
 No e-waste
 Need for battery is
eliminated
 Efficient energy
transfer using RIC
 Harmless, if field
strengths under safety
levels
 Maintenance cost is
less

Disadvantages
 Distance constraint
 Field strengths have to be under safety levels
 Initial cost is high
 In RIC, tuning is difficult
 High frequency signals must be the supply
 Air ionization technique is not feasible

Far-field energy transfer
 Microwave PowerTransmission
Solar power satellites
 LASER PowerTransmission

Microwave Power Transfer(MPT)
 Transfers high power from one place to another. Two
places being in line of sight usually
 Steps:
 Electrical energy to microwave energy
 Capturing microwaves using rectenna
 Microwave energy to electrical energyAC can not be
directly converted to microwave energy
 AC is converted to DC first
 DC is converted to microwaves using magnetron
 Transmitted waves are received at rectenna which
rectifies, gives DC as the output
 DC is converted back toAC 5/25/2019Wireless Power Transmission & Wireless Charging 13

Solar Power Satellites (SPS)
 To provide energy to earth’s increasing energy
need
 To efficiently make use of renewable energy
i.e., solar energy
 SPS are placed in geostationary orbits
 Solar energy is captured using photocells
 Each SPS may have 400 million photocells
Transmitted to earth in the form of
microwaves/LASER
 Using rectenna/photovoltaic cell, the energy
is converted to electrical energy

Solar Power Satellites (SPS)
•Rectenna in US
receives 5000MW
of power from
SPS
•It is about one
and a half mile
long

LASER transmission
 LASER is highly directional, coherent
 Not dispersed for very long
 But, gets attenuated when it propagates
through atmosphere
 Simple receiver
 Photovoltaic cell
 Cost-efficient

Advantages of far-field energy
transfer
 Efficient
 Easy
 Need for grids, substations etc are
eliminated
 Low maintenance cost
 More effective when the transmitting and
receiving points are along a line-of-sight
 Can reach the places which are remote

Disadvantages of far-field energy
transfer
 Radiative
 Needs line-of-sight
 Initial cost is high
 When LASERs are used,
 conversion is inefficient
 Absorption loss is high
 When microwaves are used,
 interference may arise
 FRIED BIRD effect

Wireless Charging System
 Transfer electric power to mobile nearby devices (less
than several meters) and charge batteries

Wireless Charging System

Technical Trends
 WiTricity-Haire
 WiTricity, a spin-off company from MIT
 Power transfer to Full HDTV in CES 2010
 Intel
 12W power transfer to netbook in 3feet
 Receiver coils in the cover of netbook
 Independent standardization activity on 100W
wireless power transfer
 Sony
 Power transfer to 22 LCDTV 60W
 Efficiency: about 80% @ 50cm
 Charging distance increases by repeaters

 Qualcomm
 Announcement of eZone, a wireless power
transfer system, in CES2009.
 Maximum supportable devices: 2
 Maximum charging distance: 0.2m
 Qualcomm-WiPower
 Takeover WiPower in 2010 for developing a
wireless power transfer system
 Developing power transfer system in vehicles
 Charging distance: 0.05m
 Fujitsu
 Simultaneous charging to two mobile phones .
 Development of a simulator which is used for analysis
of magnetic fields between multiple coils

Overview of Wireless Charging
System
 Wireless Charging System
 How to transfer power and charge efficiently
 Devices which have a battery
 Wireless PowerTransfer System
 How to transfer power efficiently
 All electric devices
 Difference from cable chargers
 Elimination of complicated wire cables
 Safety from electric shock
 Increased mobility
 Relatively low efficiency (about 90% efficiency of cable chargers)
 Considered frequency bands
 20~60 kHz
 80~370 kHz
 6.78, 13.56 MHz

Challenges
 Product Diversification
 As market is increasing, each vendor makes the Wireless
Charging system which has different structure & protocol
 Wireless Charging is possible only between systems having the
same structure & protocol
 Frequency Issues
 Each vendor considers different frequency bands forWireless
Charging which disables interoperability betweenWireless
Charging systems
 Regulation Issues
 Each nation has different regulation for EMI/EMC, SAR, etc.

THANK YOU!
5/25/2019 25Wireless Power Transmission & Wireless Charging

WPT Wireless Charging Overview

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