WIRELESS ELECTRICITY REPORT

1. WIRELESS ELECRICTY
(WITRICITY)
A SEMINAR REPORT
SUBMITTED BY
DEVARKSHYANJALI SRIVASTAVA
IN PARTIAL FULFILMENT FOR THE AWARDED OF THE DEGREE
OF
BACHELOR OF TECHNOLOGY
IN
ELECTRONICS & INSTRUMENTATION ENGINEERING
AT
UNITED COLLEGE OF ENGINEERING & RESEARCH
DEPARTMENT OF EC & EI
ALLAHABAD
APRIL 2016

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Table of Contents
ACKNOWLEDGEMENT 2
ABSTRACT 3
INTRODUCTION 4
HISTORY OF WITRICITTY 5
WHAT IS WITRICITY? 7
WHY WE NEED WITRICITY? 8
LOSSES IN THE WIRED SYSTEM 8
LOSS OF USING BATTERY 9
WIRELESS POWER TRANSMISSION 10
RESONANCE INDUCTIVECOUPLING 14
PRINCIPLE OF WITRICITY 15
EXPERIMENTALDEMONSTRATION 16
WITRICITY TECHNOLOGY 18
EFFICIENCY 19
APPLICATIONS OF WITRICITY 20
SAFETY ISSUES 24
FUTURE SCOPE 25
ADVANTAGES 26
DISADVANTAGES 27
ECONOMICIMPACT 28
CONCLUSION 29
REFERENCES 30

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ACKNOWLEDGEMENT
I express my sincere gratitude to Mr. H. P. SHUKLA, head of department EC & EI
Engineering, for providing me his invaluable guidance for seminar.
I extend my sincere thanks to my seminar coordinator and concerned teacher Miss.
VIBHA SHRIVASTAVA, Professor, Department of Electrical Engineering, for her
valuable and inspiring guidance towards the progress on the topic “WIRELESS
ELECTRICITY or WiTricity” and providing valuable information for the
development of my report.
Last but not the least I express my sincere and hearty thanks to all those who have
directly or indirectly helped me in completing this seminar presentation and report
successfully.
DEVARKSHYANJALI SRIVASTAVA
(1301032010)
3K

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ABSTRACT
Can we imagine the life without electrical wires? From now answer to this question
is yes. The method proposed called “Witricity” will facilitate to transfer power
without using wires. The efficient midrange power can be transmitted to any device
which usesthat range of powerby the techniqueused in this Witricity concept.Now-
a-days there is a rapid development of autonomous electronics like Laptops, Cell-
phones, House-hold robots and all the above devices typically rely on chemical
energy storage (Battery). As they are becoming daily needs to present generation,
Wireless energy transfer would be useful for many applications as above and they
need midrange energy.
Wireless electricity or witricity is the transfer of electric energy or power over a
distance without the use of wires. In order for the energy to be transferred safely
coupledresonatorsare used. When two magnetically resonating objects at “Strongly
coupled”regime tend to exchangeenergyefficiently by transfer of power in the non-
radiating fields, this is the basic principle involved in it. By taking two coils having
same magnetic resonance and one is coupled to source and other is coupled to
Device so that the energy transfer is efficient even the air gap between them is high.
This paper describesthe basic history of wireless powertransmission. Using witricity
there would be no needto replace batteries becauseenergy could be transferred from
one sensor to another.

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INTRODUCTION
Today we do live in the “wireless age”, in which the air that we breathe probably
contains more information than oxygen. However, this is also an age where mobile
phones, MP3 players, laptop computers and domestic robots exist alongside old-
fashioned power wires and bulky batteries. Unlike information, electrical energy is
still physically confined to these borderline anachronistic appliances. Overcoming
these last obstacles would finally make this a truly wireless world.
This would be achieved using big, coupled electromagnetic resonators able to
generate very large electric fields. The epitome of Tesla’s efforts to achieve his goal
was Tesla Tower, a 57 m high structure, which was meant to deliver electricity to the
entire planet. The construction was interrupted in about 1905, not because the
method was considered impractical, but because the funder, the famed financier and
banker J P Morgan, was concerned that there would be no way to bill remote
electricity users. Nowadays, more than a century after Tesla, electricity reaches
nearly every home through a global electrical grid. Nevertheless, J P Morgan’s
objections meant a premature end to the first attempt at wireless electricity. In the
near future, wireless electricity could replace the ubiquitous power cable.

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HISTORY OF WITRICITY
 1820: André-Marie Ampère develops Ampere’s law showing that electric
current produces a magnetic field.
 1864: Maxwell synthesizes the previous observations and mathematically
models the behaviour of electromagnetic radiation.
 1894: Tesla wirelessly lights up single-terminal incandescent lamps at the 35
South Fifth Avenue laboratory, and later at the 46 E. Houston Street laboratory
in New York City by means of "electrodynamic induction," that is to say
wireless resonant inductive coupling.
 1894: Jagdish Bose ignites gunpowder and rings a bell at a distance using
electromagnetic waves, showing that communications signals can be sent
without using wires.
 1896: Tesla transmits signals over a distance of about 48 kilometres (30 mi).
 1901: Marconi transmits signals across the Atlantic Ocean using Tesla's
apparatus.
 1917: Tesla's Wardenclyffe tower is demolished.
 1988: A power electronics group led by Prof. John Boys at The University of
Auckland in New Zealand develops an inverter using novel engineering
materials and power electronics and conclude that power transmission by
meansof electrodynamic induction should be achievable. A first prototype for
a contact-less power supply is built.
 2007: Using Electrodynamic Induction a physics research group, led by Prof.
Marin Soljačić, at MIT, wirelessly power a 60W light bulb with 40%
efficiency at a 2 metres (6.6 ft.) distance with two 60 cm-diameter coils.
 2008: Intel reproduces Nikola Tesla's original 1894 implementation of
Electrodynamic Induction and Prof. John Boys group's 1988 follow-up
experiments by wirelessly powering a nearby light bulb with 75% efficiency.

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 2009:A simple analyticalelectrical model of resonance power transfer system
is proposed and applied to wireless power transfer for implantable devices.
 2009:Sonyshows a wireless electrodynamic-induction powered TV set, 60 W
over 50 cm based on Prof. Soljačić’s follow-up research on Nikola Tesla's
electrodynamic induction wireless energy transmission method and the
Wireless Home Digital Interface (WHDI).
FIGURE 1 : TESLA TOWER

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WHAT IS WITRICITY?
WiTricity is nothing but wireless electricity. Transmission of electrical energy from
one object to another without the use of wires is called as WiTricity. WiTricity will
ensure that the cell phones, laptops, iPods and other power hungry devices get
charged on their own, eliminating the need of plugging them in. WiTricity
technology is transferring electric energy or power over distance without wires with
the basics of electricity and magnetism. Even better, because of WiTricity some of
the devices won't enquire batteries to operate.
In 2005, Dave Gerding coined the term WiTricity which is being used by the MIT
researcherstoday.Moreover, we all are aware of the useof electromagnetic radiation
(radio waves) which is quite well known for wireless transfer of information.
WiTricity founding technical team was the first to discover that by specially
designing the magnetic resonators, one could achieve strong coupling and highly
efficient energy exchange over distances much larger than the size of the resonator
coils.

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WHY WE NEED WITRICITY?
Now-a-days there is a Rapid development of autonomous electronics like Laptops,
Cell phones, House hold robots and all those devices typically relay on chemical
energy storage (Battery). As they are becoming daily needs to present generation,
wireless energy transfer would be useful for many applications.
LOSSES IN THE WIRED SYSTEM
Professor Rauscher showed that the earth’s magnetosphere contains sufficient
potentialenergy. Teslaalso knew that the earth could be treated as one big spherical
conductorand the ionosphereas another bigger spherical conductor, so that together
they have parallel plates and thus, comprise a “spherical capacitor”.
In 2000, about 11 Quads (quadrillion Btu) were actually used by consumers in the
US for electrical needs, which is equal to 3.2 trillion kWh. Dividing by the 8760
hours in a year, we find that only 360 million kW are needed on site to power entire

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country. This would still leave 2.6 billion kW for the rest of the world! Out of the
total electrical power, a full 2/3 is totally wasted in “conversion losses.”
Instead of trying to build 2 power plants perweek for the next20 years (only to have
additional 6 trillion kWh available), we simply need to eliminate the 7 trillion kWh
of conversion losses in our present electricity generation modality. Tesla’s wireless
transmission of power accomplishes this goal better than any distributed generation.
LOSS OF USING BATTERY
Estimated that 40 billion batteries per year add to the e-waste burden and of course
it’s not a good sign.
Figure 2: 40 billion batteries are produced per year

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WIRELESS POWER TRANSMISSION
There are various methods and theories on Wireless power transmission:-
 Near-field techniques
Inductive Coupling
Resonant Inductive Coupling
Air Ionization
 Far-field techniques
Microwave Power Transmission (MPT)
LASER power transmission
NEAR FIELD THEORY
Near field is a wireless transmission technique over distances comparable to, or a
few times the diameter of the device. Near field energy itself is non radiative, but
some radiative losses will occur. In addition there are usually resistive losses.

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INDUCTIVE COUPLING
In this method,primary and secondarycoils are not connectedwith wires and energy
transfer is due to mutual induction like transformer. Electric brush is an example.
On a Wireless Charging Pad, the devicesare to be kept, battery will be automatically
charged.The charging pad (primary coil) and the device (secondary coil) have to be
kept very near to each other.
RESONANCE INDUCTIVE COUPLING
Witricity is based on this technology. It is a combination of inductive coupling and
resonance. Resonance makes two objects interact very strongly and inductance
induces current.
RESONANCE
It is the property of certain physical systems to oscillate with maximum amplitudes
at certain frequencies.

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AIR IONIZATION
This is the toughest technique under near-field energy transfer techniques. Air
ionizes when there is a high field around 2.11MV/m. This is not feasible for
practical implementation.
FAR FIELD THEORY
Far field methods achieve longer ranges, often multiple kilometre ranges, where the
distanceis much greaterthan the diameterof the device.With radio waveand optical
devices, the main reason for longer ranges is the fact that electromagnetic radiation
in the far-field can be made to match the shape of the receiving area (using high
directivity antennas or well-collimated Laser Beam) thereby delivering almost all
emitted power at long ranges.
MICROWAVE POWER TRANSMISSION
This technique transfers high power from one place to another; two places being in
line of sight usually. AC cannot be directly converted to microwave energy. Hence,
AC is converted to DC first, and then DC is converted to microwaves using

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magnetron.Transmitted wavesare receivedat rectenna which rectifies and gives DC
as the output. Lastly, DC is converted back to AC.
MAGNETRON
Magnetron is a crossed field tube in which electrons emitted from the cathode take
cyclical path to the anode. The magnetron is self-oscillatory device in which the
anode contains a resonant RF structure. The magnetrons are also useful for
microwave ovens.
RECTENNA
The word “rectenna”is composedof“rectifying circuit” and “antenna”.Therectenna
can receive and rectify a microwave power to DC. It is a passive element with a
rectifying diode, operated without any power source. The single shunt full wave
rectifier is always used for the rectenna.
LASER POWER TRANSMISSION
LASER is highly directional and coherent. It gets attenuated when it propagates
through atmosphere. It has a simple receiver and is cost-efficient.

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RESONANCE INDUCTIVE COUPLING
Resonant inductive coupling or electrodynamic induction is the near field wireless
transmission of electrical energy. In this technique, an inductive transformer is
commonly used. A transformer typically operates up to mid-kHz frequencies. It
essentially transfers electrical energy from one circuit to another via induction: the
time-varying magneticflux produced by a primary coil crosses a secondary coil and
induces in it a voltage. The primary and the secondary coils are not physically
connected, hence the method is wireless. Transformers can be very efficient but the
distance between the coils must be very small. For distances a few times the size of
the coils, the efficiency drops significantly.
FIGURE 3: ELECTROMAGNETIC INDUCTION
Part of the underlying physics for most of the existing methods for the wireless
transfer of electricity is the fundamental principle of resonance. It follows that, for
any type of excitation (mechanical, acoustic, electromagnetic, nuclear) with a given
frequency, a receiver will pick up the transmitted energy efficiently only when

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designedto resonate atthe excitation frequency.Only then do successive excitations
add coherently in phase and lead to a build-up of energy within the receiver. To
illustrate, consider100glassesfilled with wine at different levels so that they support
acoustic resonances at different frequencies. Now, let an electric-guitar player
produce and sustain a very well-defined note. Only one of the glasses, the one
resonant with the frequency of this note, will respond to the excitation, to the extent
that it may even break, while the rest will remain unaffected.
PRINCIPLE OF WITRICITY
The main idea of the “resonance condition” between two circuits is that electrical
resonance occurs in an electric circuit at a particular resonance frequency when the
impedance between the input and output of the circuit is at a minimum (or when the
transfer function is at a maximum). Resonance of a circuit involving capacitors and
inductors occurs because the collapsing magnetic field of the inductor generates an
electric current in its windings that charges the capacitor, and then the discharging
capacitor provides an electric current that builds the magnetic field in the inductor,
and the process is repeated continually. Formula of resonance frequency:
ω =
1
𝐿𝐶
Where ω = 2πf, in which f is the resonancefrequency in hertz, L is the inductance in
henries, and C is the capacitance in farads when standard SI units are used.

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EXPERIMENTAL DEMONSTRATION
Transmitting electricity within a room, namely over distances a few times greater
than the size of the receiving devices themselves (what engineers define as mid-
range distances),is a challengefor most modernapplications. That was the challenge
for Soljačić and his collaborators at the MIT labs: John Joannopoulos, Peter Fisher,
Andre Kurs, and Robert Moffatt. For our wireless method,they used one of the most
basic electric circuits as a resonator:the LC circuit. This circuit is an electromagnetic
resonantcircuit that consists of an inductor (L), made by a wire coil, and a capacitor
(C).
The term WiTricity was used for a project that took place at MIT in 2007. The
researchers successfully demonstrated the ability to power a 60 watt light bulb
wirelessly, using two 5-turn copper coils of 60 cm (24 in) diameter, that were 2 m
(7 ft.) away,at roughly 45% efficiency. The coils were designed to resonate together
at 9.9 MHz (wavelength ≈ 30 m) and were oriented along the same axis. One was
connected inductively to a power source, and the other one to a bulb (and what can
be a clearer sign of the functionality of a system than the switch on of a light bulb?).
They suspended the coils from the ceiling with fishing wire, tuned them up, turned
them on and…there was light..

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FIGURE 4: LIGTENING A 60 WATT BULB AROUND 2M AWAY FROM THE SOURCE AT MIT
The setup poweredthe bulb on, evenwhen the direct line of sight was blocked using
a woodenpanel. Researcherswere able to power a 60 watt light bulb at roughly 90%
efficiency at a distance of 3 feet.

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WITRICITY TECHNOLOGY
Witricity power sources and capture devices are specially designed magnetic
resonators that efficiently transfer power over large distances via the magnetic near
field. These proprietary source and device designs and the electronic systems that
control them support efficient energy transfer over distances that are many times the
size of the sources/devices themselves.
FIGURE 5: WITRICITY POWER SOURCE
The WiTricity power source is connected to AC power. The blue lines represent the
magnetic nearfield inducedby the powersource.The yellow lines represent the flow
of energy from the source to the WiTricity capture coil, which is shown powering a
light bulb. This also shows how the magnetic field (blue lines) can wrap around a
conductive obstacle between the power source and the capture device.

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EFFICIENCY
FIGURE 6: EFFICIENCY GRAPH
It is observedthat efficiency decreaseswith increase in distance between source coil
and load coil.

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APPLICATIONS OF WITRICITY
Witricity has a bright future in providing wireless electricity. WiTricity technology
can be used to provide:
AUTOMATIC WIRELESS POWER CHARGING
When all the power a device needs is provided wirelessly, and no batteries are
required. This mode is for device that is always used within range of its power
source.
When a device with rechargeable batteries charges itself while still in use or at rest,
without requiring a powercord or battery replacement.This mode is for a device that
may be used both in and out of range of its power source.

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CONSUMER ELECTRONICS
Automatic wireless charging of electronics (phones, laptops, game controllers, etc.)
in home, car, office, Wi Fi hotspots while devices are in use and mobile.
Direct wireless powering of stationary devices (TV, home theatre accessories, loud
speakers, etc.), eliminating expensive custom wiring and unsightly cables.
Direct wireless powering of PC peripherals: wireless mouse, keyboard, printer,
speakers, display, etc. eliminating disposable batteries and awkward cabling.
FIGURE 7: APPLICATIONS OF WITRICITY

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INDUSTRIAL
Direct wireless powering and communication interconnections across rotating and
moving joints (robots, packaging machinery, assembly machinery, and machine
tools), eliminating costly and failure prone wiring.
Direct wireless powering and communication interconnections at points of use in
harsh environments (drilling, mining, underwater, etc.) where it is impractical or
impossible to run wires.
TRANSPORTATION
Automatic wireless charging for existing electric vehicle classes: golf carts,
industrial vehicles.
Automatic wireless charging for future hybrid: electric passenger and commercial
vehicles, at home, in parking garages, at fleet depots, and at remote kiosks.

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OTHER APPLICATIONS
Direct wireless power interconnections and automatic wireless charging for
implantable medical devices (ventricular assist devices, pacemaker, defibrillator,
etc.).
Automatic wireless charging for high tech military systems (battery powered mobile
devices, covert sensors, unmanned mobile robots and aircraft) etc.

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SAFETY ISSUES
NON RADIATIVE ENERGY TRANSFER IS SAFE
FOR PEOPLE AND ANIMALS
WiTricity technology is a non-radiative mode of energy transfer, relying instead on
the magnetic near field. Magnetic fields interact very weakly with biological
organisms. People and animals are scientifically regarded to be safe. Professor Sir
John Pendry of Imperial College London, a world renowned physicist, explains:
“The body really responds strongly to electric fields, which is why you can cook a
chickenin a microwave. Butit doesn'trespondto magneticfields. As far as we know
the body has almost zero response to magnetic fields in terms of the amount of
power it absorbs."
Evidenceof the safety of magnetic fields is illustrated by the widespread acceptance
and safety of householdmagneticinductioncook tops. Throughproprietary designof
the WiTricity source, electric fields are almost completely contained within the
source. This design results in levels of electric and magnetic fields which fall well
within regulatory guidelines. Thus WiTricity technology doesn‘t give rise to
radiofrequency emissions that interfere with other electronic devices, and is not a
source of electric and magnetic field levels that pose a risk to people or animals.
WiTricity technology is being developed to be fully compliant with applicable
regulations regarding magnetic fields and electromagnetic radiation.

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FUTURE SCOPE
MIT's WiTricity is only 40 to 45% efficient and according to Soljačić, they have to
be twice as efficient to compete with the traditional chemical batteries. The team's
next aim is to get a robotic vacuum or a laptop working, charging devices placed
anywhere in the room and even robots on factory floors.
Witricity, if successful will definitely change the way we live. Imagine cell phones,
laptops, digital camera's getting self-charged! Wow! Let's hope the researchers will
be able to come up with the commercial system soon. Till then, we wait in
anticipation! Human beings or other objects placed between the transmitter and
receiver do not hinder the transmission of power.

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ADVANTAGES
An electrical distribution system, based on this method would eliminate the need for
an inefficient, costly, and capital intensive grid of cables, towers, and substations so,
no e-waste. The system would reduce the cost of electrical energy used by the
consumer.
There are areas of the world where the need for electrical power exists, yet there is
no method for delivering power. Africa is in need of power to run pumps. Rural
areas, such as those in China, require the electrical power necessary to bring them
into the 20th century and to equal standing with western nations. The wireless
transmission will solve many of these problems.
The electrical energy can be economicallytransmitted without wires to any terrestrial
distance, so there will be no transmission and distribution loss.
It is safe and fairly efficient. There is also no need of devices to be in line of sight.
Magnetic fields interact weakly with biological masses (humans).
There would be significant decluttering of space since there would be no need for
meter rooms and electrical closets.

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Maintenancecostwill be saved.Onecan operate many devices and in any direction.
Devices using RIC technique are highly portable.
It is unaffected by the day night cycle,weather or seasons and this is an eco-friendly
technique.
WiTricity sourcesonly transfer energywhen it is needed.When a WiTricity powered
deviceno longer needsto capture additional energy, the WiTricity power source will
automatically reduce its power consumption to a power saving idle state’
DISADVANTAGES
Witricity has distance constraint: - Efficiency decreases with distance.
There is possibility of “energy theft”.
The resonance condition should be satisfied and if any error exists, there is no
possibility of power transfer. Field strengths have to be under safety levels
Initial cost is high

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In RIC, tuning is difficult and high frequency signals must be the supply.
Need for standardization and adaptation. So no overheating occurs because of
different voltages.
ECONOMIC IMPACT
The concept looks to be costly initially but the cost is still undetermined. What they
say is there are no exotic materials being used that would make it overly expensive.
The investment cost of Tesla Tower was $150,000 (1905). In terms of economic
theory, many countries will benefit from this service. Only private, dispersed
receiving stations will be needed. Just like television and radio, a single resonant
energy receiver is required, which may eventually be built into appliances, so no
power cord will be necessary!
Monthly electric utility bills from old-fashioned, fossil-fuelled, loss prone electrified
wire-grid delivery services will be optional.

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CONCLUSION
The transmission of power without wires is not a theory or a mere possibility, it is
now a reality. Theelectrical energy canbe economicallytransmitted without wires to
any terrestrial distance. Dr.N.Tesla is the pioneer of this invention.
Wireless transmission of electricity have tremendous merits like high transmission
integrity and low loss (90 – 97% efficient) and can be transmitted to anywhere in the
globe and eliminate the need for an inefficient, costly, and capital intensive grid of
cables,towers, and substations. It has negligible demerits like reactive power which
was found insignificant and biologically compatible.
It has a tremendous economic impact to human society. Many countries will benefit
from this service. Monthly electric utility bills from old-fashioned, fossil-fuelled,
loss prone electrified wire-grid delivery services will be optional, much like “cable
TV” of today. This technology is a big impediment to development in the retail
sector right now.
The wireless transfer of electricity has been a sci-fi dream up to this point, and truly,
if electricity could simply be in the air, in the same way radio waves and Wi-Fi
signals are, it would change the world.

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REFERENCES
 http://en.wikipedia.org/wiki/WiTricity
 http://www.electricitybid.com/electricity/index.php/2007/06/08/witricity/
 http://www.witricity.com/