“Wireless Electricity”
PRESENTED BY: SHAIK SARTAJ
AHMED

 What do you mean by Wi Tricity ?
 Need of witricity
 History of wireless power
 Witricity Basics
 Detailed Principle
 How Safe is Wi Tricity ?
 What's the Future of WiTricity ?
 Advantages
 Limitations
 Bibliography

 The Transfer of Electricity from one place to
another without wires is known as “WiTricity”.
 On June 7 ’07, a team of researchers at MIT
announced the successful operation of WiTricity
concept.
 They had lit up a 60W bulb with a power source
at a distance of 7 feet(over 2m) with no wires.

In 1891, Sir Nikola Tesla
Proposed a method of Wireless
Power Transmission.
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 used today.
 Forgotton invention was reborn in 2007

 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.

 Cell phones, i pods, laptop computers are capable
of re-charging themselves without ever being
plugged in.

 Currently, wired electricity powers have concured
nearly everything.
 In present electricity generation system we
waste more than half of its resources. Especially
the transmission and distribution losses are the
main concern of the present power technology.

 The resistance of the wire used in the electrical
grid distribution system causes a loss of 26-30%
of the energy generated
 The transmission of power without wires may be
one noble alternative for electricity transmission.

 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.

 There are 3 major types of wireless energy
transfer:
 – Short range; Inductive Coupling
 – Medium range; Resonant Induction
 – Long range; Electromagnetic Wave Power
Transfer

 What Is Inductive Coupling?
 Inductive Coupling is a method for short range
wireless energy transfer.
 Its range can vary, but it’s often very short.

 Inductive coupling works on the
principles of electromagnetism:
When a current (electricity) passes
through a wire, it generates a magnetic
field perpendicular to the wire.
When a wire is in proximity to a
magnetic field, it generates a current in
that wire.
Magnetic fields decay quickly , making
inductive coupling effective only at very
short ranges.

 What Is Resonant Induction?
 A group of engineers at MIT came up with
the idea to use resonant induction to
transmit power wirelessly. They deemed
their result “WiTricity” (like Wi-Fi) .
WiTricity can transmit electricity
wirelessly at 40% efficiency to about 7
feet.

 Resonant induction still uses the same
principles as magnetic induction (magnetic fields
to transfer current) , but it uses resonance to
increase the range at which the transfer can
efficiently take place.
 “Resonance", a phenomenon that causes an
object to vibrate when energy of a certain
frequency is applied.

 Everything resonates at a certain frequency,
based on its shape and material.
 Energy transfers easily between resonating
objects. An example of this is when an opera
singer shatters wine glasses by singing at the
frequency at which the glasses resonate.
 With resonant induction, power is transmitted
between two resonating coils.

 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 device.

 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.

 Is WiTricity safe?
 How much power can be transferred?
 What about the range of transferred?
 How efficient is WiTricity?
 What's the Future of WiTricity?

 The rate of energy transfer between the emitter
and the receiver is greater than the rate of
energy dissipation.
 Efficiency is mesured by measuring the current
at the midpoint of the self resonant coils with a
current probe.
 This gives a measurement of the current
parameters

 We then compute power dissipated in each coil from:-
 Then the efficiency can be calculated .

 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
 Industrial
 Transportation
 Miscellaneous

 Will it harm me?
 Will it harm the environment?
 Will it interfere with important communication?

 Human beings or other objects placed between
the transmitter and receiver do not hinder the
transmission of power.
 However, does magnetic coupling or
resonance coupling have any harmful effects on
humans?
 magnetic fields tend to interact very weakly
with the biological tissues of the body, and so
are not prone to cause any damage to any living
beings.

 Safe, fairly efficient, good range:
 Magnetic fields interact weakly with biological
masses (humans),
 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.

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
3. http://electron9.phys.utk.edu/optics507/modules/m6/coupled_resonators.htm
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. Thom as F. Valone, “ Tesla’ s Wireless Energy... For the 21 st 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.