The document discusses various techniques for wireless power transmission, including near-field techniques like inductive coupling and resonant inductive coupling, as well as far-field techniques like microwave power transmission and laser power transmission. Near-field techniques transfer power over short ranges and include using coils and capacitors to achieve resonance and maximize efficiency. Far-field techniques transfer power over longer ranges but require line-of-sight and involve converting electrical power to microwaves or lasers and using receivers to convert back to electrical power. Examples of applications discussed include wireless charging of electric vehicles and consumer electronics.

1. Wireless Power Transmission
Techniques
Presented by
A.Anantha Babu,
Master of Engineering,
Dept of Computer Science and Engineering,
Anna University Regoinal Campus,
Coimbatore.

2. Introduction
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
Wireless Power Transmission 2

3. Why not wires?
As per studies, most electrical energy
transfer is through wires.
Most of the energy loss is during
transmission
• On an average, more than 30%
• In India, it exceeds 40%
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4. Objective
Reliable
Efficient
Fast
Low maintenance cost
Can be used for short-range or
long-range.
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5. History
Nikola Tesla in late 1890s
Pioneer of induction techniques
His vision for “World Wireless 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
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6. History (contd…)
Tesla was able to transfer energy from
one coil to another coil
He managed to light 200 lamps from a
distance of 40km
The idea of Tesla is taken in to research
after 100 years by a team led by Marin
Soljacic from MIT. The project is named
as ‘WiTricity’.
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7. Energy Coupling
The transfer of energy
◦Magnetic coupling
◦Inductive coupling
Simplest Wireless Energy coupling is a
transformer
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8. Types and Technologies of WPT
Near-field techniques
Inductive Coupling
Resonant Inductive Coupling
Air Ionization
Far-field techniques
Microwave Power Transmission (MPT)
LASER power transmission
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9. Inductive coupling
Primary and secondary coils are not
connected with wires.
Energy transfer is due to Mutual
Induction
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10. Inductive coupling (contd…)
Transformer is also an example
Energy transfer devices are usually air-
cored
Wireless Charging Pad(WCP),electric
brushes are some examples
On a WCP, the devices are to be kept,
battery will be automatically charged.
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11. Inductive coupling(contd…)
Electric brush also charges using
inductive coupling
The charging pad (primary coil) and the
device(secondary coil) have to be kept
very near to each other
It is preferred because it is comfortable.
Less use of wires
Shock proof
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12. Resonance Inductive
Coupling(RIC)
Combination of inductive coupling and
resonance
Resonance makes two objects interact
very strongly
Inductance induces current
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13. How resonance in RIC?
Coil provides the inductance
Capacitor is connected parallel to the coil
Energy will be shifting back and forth
between magnetic field surrounding the
coil and electric field around the capacitor
Radiation loss will be negligible
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14. Block diagram of RIC
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15. An example
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16. WiTricity
Based on RIC
Led by MIT’s Marin Soljacic
Energy transfer wirelessly for a distance
just more than 2m.
Coils were in helical shape
No capacitor was used
Efficiency achieved was around 40%
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17. WiTricity (contd…)
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18. WiTricity… Some statistics
Used frequencies are 1MHz
and 10MHz
At 1Mhz, field strengths
were safe for human
At 10MHz, Field strengths
were more than ICNIRP
standards
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19. WiTricity now…
No more helical coils
Companies like Intel are also working on
devices that make use of RIC
Researches for decreasing the field
strength
Researches to increase the range
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20. 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
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21. 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 19/04/17 Wireless Power Transmission 21

22. 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 19/04/17 Wireless Power Transmission 22

23. 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
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24. Far-field energy transfer
Radiative
Needs line-of-sight
LASER or microwave
Aims at high power transfer
Tesla’s tower was built for this
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25. 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 energy
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26. MPT (contd…)
AC 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 to AC
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27. 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
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28. 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
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29. SPS (contd…)
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
Efficiency exceeds 95% if microwave is
used.
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30. Rectenna in US
Rectenna in US receives 5000MW of
power from SPS
It is about one and a half mile long
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31. Rectenna
Stands for rectifying antenna
Consists of mesh of dipoles and diodes
Converts microwave to its DC equivalent
Usually multi-element phased array
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32. Rectenna in US
Rectenna in US receives 5000MW of
power from SPS
It is about one and a half mile long
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33. Other projects
Alaska’21
Grand Bassin
Hawaii
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34. LASER vs. MPT
When LASER is used, the antenna sizes
can be much smaller
Microwaves can face interference (two
frequencies can be used for WPT are
2.45GHz and 5.4GHz)
LASER has high attenuation loss and also
it gets diffracted by atmospheric particles
easily
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35. 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
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36. 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
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37. Applications
Near-field energy transfer
◦ Electric automobile charging
 Static and moving
◦ Consumer electronics
◦ Industrial purposes
 Harsh environment
Far-field energy transfer
◦ Solar Power Satellites
◦ Energy to remote areas
◦ Can broadcast energy globally (in future)
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38. Conclusion
Transmission without wires- a reality
Efficient
Low maintenance cost. But, high initial cost
Better than conventional wired transfer
Energy crisis can be decreased
Low loss
In near future, world will be completely wireless
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39. References
 S. Sheik Mohammed, K. Ramasamy, T. Shanmuganantham,”
Wireless power transmission – a next generation power
transmission system”, International Journal of Computer
Applications (0975 – 8887) (Volume 1 – No. 13)
 Peter Vaessen,” Wireless Power Transmission”, Leonardo Energy,
September 2009
 C.C. Leung, T.P. Chan, K.C. Lit, K.W. Tam and Lee Yi Chow,
“Wireless Power Transmission and Charging Pad”
 David Schneider, “Electrons unplugged”, IEEE Spectrum, May
2010
 Shahrzad Jalali Mazlouman, Alireza Mahanfar, Bozena Kaminska,
“Mid-range Wireless Energy Transfer Using Inductive Resonance
for Wireless Sensors”
 Chunbo Zhu, Kai Liu, Chunlai Yu, Rui Ma, Hexiao Cheng,
“Simulation and Experimental Analysis on Wireless Energy
Transfer Based on Magnetic Resonances”, IEEE Vehicle Power and
Propulsion Conference (VPPC), September 3-5, 200819/04/17 Wireless Power Transmission 39

40. References(contd…)
 André Kurs, Aristeidis Karalis, Robert Moffatt, J. D.
Joannopoulos, Peter Fisher and Marin Soljačić, “Wireless
Power Transfer via Strongly Coupled Magnetic Resonances”,
Science, June 2007
 T. R. Robinson, T. K. Yeoman and R. S. Dhillon,
“Environmental impact of high power density microwave
beams on different atmospheric layers”,
 White Paper on Solar Power Satellite (SPS) Systems, URSI,
September 2006
 Richard M. Dickinson, and Jerry Grey, “Lasers for Wireless
Power Transmission”
 S.S. Ahmed, T.W. Yeong and H.B. Ahmad, “Wireless power
transmission and its annexure to the grid system”
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41. THANK YOU!
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