ELECTRICITY THROUGH
WIRELESS
TRANSMISSION-
WITRICITY
by
Apoorva

Introduction
 In our present electricity generation system
we waste more than half of its resources.
Especially transmission and distribution
losses are main concern of the present
power technology.
 The transmission and distribution system
causes a loss of 26% to 30% of energy
generated.
 The transmission of power without wires is

History of Wireless Power
In 1899, Sir Nikola Tesla Proposed
a method of Wireless Power
Transmission.
Nikola Tesla – The Genius
He enlighted 200 lamps at the
distance of 40 km, Wirelessly !
The efficient midrange power
transfer concept is Witricity. In this
model source and load are in
Magnetic resonance so there is no
power loss.

Research at MIT
* Prof. Soljacic – Another
Genius
MIT-IBM Collaboration
* He did succeed to
redesign Tesla’s
experiment in safer way.
* They had lit up a 60W
bulb with a power source
at a distance of 7 feet(over
2m) with no wires

The forgotten invention is reborn in 2007
RESONANCE COUPLING
 A group of engineers at MIT came up with the idea to use
resonant induction to transmit power wirelessly.
“Resonance", a phenomenon that causes an object to vibrate when
energy of a certain frequency is applied.

Experiment demonstrated at MIT.
A 60W light bulb lit from source at a distance of 2m from
load.

Electric bulb lightened even when a barrier was
kept in between.

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

What is WiTricity ?
definition is :
* “Transmission of energy through the air”.
* A system of two electromagnetic
resonators coupled mostly through
their magnetic fields.
** Cables are going to replaced by WiTricity.
Efficient power transfer

Types and Technologies
 Near-field techniques
 Inductive Coupling
 Resonant Inductive Coupling
 Air Ionization
 Far-field techniques
 MicrowavePower Transmission (MPT)
 LASER power transmission

Inductive coupling
 Primary and secondary coils are not
connected with wires.
 Energy transfer is due to Mutual Induction

Cont…
 Energy transfer devices are usually air-cored
 Transformer is an example
 Wireless Charging Pad(WCP),electric brushes
are some examples
 The charging pad (primary coil) and the
device(secondary coil) have to be kept very
near to each other

Resonance Inductive
Coupling(RIC)
* Same concept as Inductive coupling just
that the coils operate at resonant
frequency leading to efficient transfer of
energy over a larger distance.
* Interacts weakly with extraneous off resonant
objects.
* Radiation loss will be negligible

Resonant Inductive Coupling

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.

Far-field energy transfer
 Microwave Power Transfer(MPT)
 Transfers high power from one place to another.
 Steps:
 Electrical energy to microwave energy
 Capturing microwaves using rectenna
 Microwave energy to electrical energy
 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

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

Applications
 Direct Wireless Power
 No device needs wires
 For TVs, toasters or any form of
Immobile devices
 Automatic Wireless Charging
 Device with rechargeable
batteries
charges itself
 For any form of mobile device

Some more Applications…
* Consumer electronics.
*Industrial
 would be free of heavy installation of wires and devoid
of any hazardous electric shock incidents.
*Transportation
 Could charge an electric car or automobile.

Wireless power transmission is
safe
 Human beings or other objects placed
between the transmitter and receiver do
not hinder the transmission of power.
 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.

Advantages
 Efficient and reliable power.
 Creation of a shock free environment devoid of
any chances of power thefts.
 Provides solution to the ever increasing demand
for power.
 A solution to reduce e-waste- a more safe
environment.
 A more cost effective methodology for getting
electricity to your houses which includes paying
less for use of power.
 Not affected by the day and night cycle, leads to
lesser limitations on power harvesting.

Disadvantages.
 For short and mid range transfer system
has to be set at the right frequency or
there would be no power transfer.
 For long range the installation cost is high.

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