WIRELESS POWER TRANSMISSION
AT A GLANCE
• What is wireless power transmission?
• History behind WPT
• Concept of electro magnetic induction and resonance
• Types of WPT’s
• whether it is virtual concept or existing
• Advantages and Disadvantages
• Applications and Conclusions
WHAT IS MEANT BY WPT?
• The transmission of energy from one place to another without using wires
which is also known as “WiTricity”.
• Generally conventional energy is transferred using copper wires
which results in large Copper loss.
• But now-a-days this wireless transmission is made possible in using various
technologies based on Resonant frequency ,Inductive coupling etc.
WHAT IS THE NEED OF WPT?
• As per studies, most electrical energy transfer is through wires.
• Most of the energy loss is during transmission as copper losses
• On an average, more than 30%
• In India, it exceeds 40%
Billions, trillions of $ is spend on wires and in their installation.
Waste management a challenge in 21 century.
40 billion disposal batteries added to e-waste every year.
PVC is non-biodegradable.
In 1891, Sir Nikola Tesla Proposed a method of Wireless Power
As it is in Radiative mode, most of the Power was wasted and
has less efficiency.
• In 2005, Dave Gerding coined the term WiTricity which is being
• Forgotton invention was reborn in 2007
A BRIEF HISTORY OF NIKOLA TESLA
• In 1891, Nikola Tesla invented a type of resonant
transformer called the Tesla coil, which was used to
generate very high voltage, low current, and high
frequency alternating electricity. He experimented
with a large variety of coils and configurations, one
of which is as:
• In1899,Tesla achieved a major
breakthrough in his work at Colorado by
transmitting 100 million volts of electric
power wirelessly over a distance of 26
miles to light up a bank of 200 light bulbs
and run one electric motor.
LIMITATION OF TESLA’S COIL
• A Tesla Coil produces high voltage electric arcs.
These arcs cause permanent damage to
electrical devices on contact
• Tesla coils also destroy hearing aids and
cardiac pacemakers in their vicinity.
• RESONANCE INDUCTIVE COUPLING
Two objects having same resonating frequency
and in Magnetic resonance at Strongly coupled
regime tend to exchange energy , while
dissipating relatively little energy to the
extraneous off-resonant objects.
The equipment used is sometimes called
a resonant or resonance transformer.
• Consider two self resonating copper coils of same resonating frequency
with a diameter 20 inches each. One copper wire is connected to
the power source , while the other copper wire is connected to the
TYPES AND TECHNOLOGIES OF WPT
• Near-field techniques
Resonant Inductive Coupling
• Far-field techniques
Microwave Power Transmission (MPT)
LASER power transmission
ELECTRO MAGNETIC INDUCTIVE COUPLING
It is based on the FARADAY’S LAW OF
Make use of coils. The coils are not connected
through wire or any other kind of material.
Transfer of energy is due to mutual induction.
Its based on the concept :- that an oscillating
electric field produces magnetic field and an
oscillating magnetic field produces oscillating
RESONANT INDUCTIVE COUPLING
Same inductive coupling(EMI) concept but
the coils here operate at their resonating
Inductance induces current.
Resonance makes both the coil to operate at
Fields are non-radiative in nature.
RIC VS INDUCTIVE COUPLING
RIC is highly efficient
RIC has much greater range than inductive coupling
RIC is directional when compared to inductive coupling
RIC can be one-to-many. but usually inductive coupling is one-to-one
Devices using RIC technique are highly portable
• 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 TECHNOLOGY
For short range transmission
Aims low power transmission
Need for battery is eliminated
Efficient energy transfer using RIC
Harmless, if field strengths under safety levels
Maintenance cost is less
DISADVANTAGES OF NEAR FIELD TECHNOLOGY
Field strengths have to be under safety levels
Initial cost is high
In RIC, tuning is difficult
High frequency signals must be the supply
APPLICATION OF NEAR FIELD
Electric automobile charging
Microwave Power Transmission (MPT)
LASER Power Transmission
Solar power Satellite(SPS)
FAR FIELD ENERGY TRANSMISSION
Aims high power transmission
For long range of transmission
Require line of sight
Radiative in nature
MICROWAVE POWER TRANSMISSION (MPT)
Transfers high power from one place to another.
Two places being in line of sight usually.
Electrical energy converted to microwave energy
Capturing microwave using retina.
Conversion of microwave energy into electrical
Transmission of electrical energy.
LASER POWER TRANSMISSION
LASER is highly directional and coherent
But, gets attenuated when it propagates
• Photovoltaic cell
Satellites are placed in geostationary orbit
Solar energy is captured using photocells
Each SPS may have 400 million photocells
Transmitted to earth in the form of
Using rectenna/photovoltaic cell, the energy
is converted to electrical energy
Efficiency exceeds 95% if microwave is used.
ADVANTAGE OF FAR FIELD TECHNIQUE
Need for grids, substations etc are eliminated
More effective when the transmitting and receiving points are along a line-of-
ADVANTAGES & DISADVANTAGES OF FAR FIELD TECHNIQUE
Need for grids, substations etc are
More effective when the
transmitting and receiving points
are along a 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
Needs positioning and GPS systems.
The Brain behind WiTricity?
• Prof. Marin Soljacic from
Massachusetts Institute of
Technology (MIT), is the one who
has proved that magnetic coupled
resonance can be utilized in order
to transfer energy without wires.
• He used Michael Faraday's principle
of electromagnetic induction
(1831) came up with WiTricity.
• Direct Wireless Power
• No device needs wires
• Immobile devices
• Automatic Wireless Charging
• Device with rechargeable batteries
• charges itself
• Mobile device
• Used in and out of range of its WiTricity power source
• Consumer Electronics
SOME MORE APPLICATIONS…….
• Safe, fairly efficient, good range:
• Magnetic fields interact weakly with biological
• Efficiency can be increased with time, most of the
60% lost is from heat radiated from the coils.
• Theoretically one stationary coil in a room could
power multiple devices with receiving coils.
• No more messy wires, and with widespread enough
use it could even eliminate costly batteries.
The resonance condition should be satisfied and if any error exists,
there is no possibility of power transfer.
If there is any possibility of very strong ferromagnetic material presence
causes low power transfer due to radiation.
• MIT's WiTricity is only 40 to 45% efficient and they
have to be twice as efficient to compete with the
traditional chemical batteries.
• Aim is to get a robotic vacuum or a laptop working,
charging devices placed anywhere in the room
• The researchers have said that in another five
years time, they will come up with a WiTricity
system for commercial use.
WHAT'S THE FUTURE OF WITRICITY?
1. An article published in the Science Magazine as “Wireless Power Transfer via Strongly Coupled Magnetic
Resonances” by Andre kurs, Science 317, 83(2007); Dol:10.1126/ science.1143254.
2. H. Haus , “Waves and Fields in Optoelectronics”, Prentice hall Publishers, Englewood
4. “Efficient Non-Radiative Midrange Energy Transfer” by Aristeidies karalis, Marlin Soljacic.
5. Nikola Tesla, My Inventions, Ben Johnston, Ed., Austin, Hart Brothers, p. 91,1982.
6. Thomas F. Valone, “ Tesla’ s Wireless Energy... For the 21st Century!!! One Step Beyond Direct TV!!!” Extra
Ordinary Technology, 1, no. 4, Oct / Nov / Dec 2003.
7. James O. McSpadden, “ Wireless Power Transmission Demonstration”, Texas A&M University, June, 1997.
8. Charych Arthur (Setauket, NY), “ System and method for wireless electrical power transmission”, Patent No.
6,798,716, September 28, 2004.
9. Joe T. Howell, et. al , “Advanced receiver / converter experiments for laser wireless power transmission”5th.
Wireless transmission conference, pp 1-8, Garanda, Spain,2004.