Paper on

“WiTricity”

WIRELESS(ELECTRICITY) POWER

TRANSMISSION

Branch of

Electrical & Electronics Engineering

Submitted By:

G.SUDHARSHAN B.HEMANTH

09691A0249 09691A0215

Email:gsudharshan249@gmail.com Email:viky.b2000@gmail.com

+91 9494742368 +91 9701430671

WIRELESS (ELECTRICITY)POWER TRANSMISSION

Abstract:

Everything in the world of

technology is becoming wireless. The

advancement in science and technology

has paved it ways in mobile phones,

computers and other communication

systems, which access the wireless

technology.

Today power production, its

transportation and distribution faces lot

of maladies to reach the consumer

premises. So, we are in need of an

alternative way to transmit power, which

is free from the losses involved in

ordinary conventional method. It is none

other than the implementation of

‘Wireless Technology’ in power

transmission.

It is a project paper that

reveals the secret of Wireless Power

Transmission. The paper mainly throws

light on a small experiment thereby

proving the possibility of Power

Transmission without wires. ‘Wireless

Electricity’ is based on using coupled

resonant objects. It works on the

principle that Two resonant objects of

the same resonant frequency tend to

exchange energy efficiently, while

interacting weakly with extraneous off-

resonant objects and says ‘Goodbye’ to

wires.

Introduction:

Challenging criteria in the

next fifty years due to energy crisis are:

1. SPS-Solar Power Station &

2. MPT-Microwave wireless

power transmission.

‘Wireless Electricity’ is based

on using coupled resonant objects. It

works on the principle that two resonant

objects of the same resonant frequency

tend to exchange energy efficiently, while

interacting weakly with extraneous off-

resonant objects.

A Simple wireless power transmission

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Historical events:

In 1900 Nikola Tesla illuminated two

hundred incandescent lamps at a

distance of 26 miles, "with electrical

energy extracted from the earth." (no

records of documentation)

During World War II Willian C. Brown

demonstrated a microwave-powered

helicopter 2001in 1964, using 2.45 GHz

in the frequency range of 2.4 - 2.5GHz

reserved for the ISM (Industrial, Scientific

and Medical) applications of radio

waves.

In 1978 United States introduced

three-year study program called the

NASA/DOE Satellite Power System

Concept Development and

Evaluation Programor

NASA/DOE reference model.

In 1987 Canada introduced the

world’s first flight of a fuel-less airplane

powered by microwave energy from the

ground. This system was called

Stationary High Altitude Relay Platform

(SHARP).

In 2001 Europeans proposed A Sail

Tower SPS. In 2 0 0 3 a point to

p o i n t wireless power transmission

system was examined to deliver 10 kW

of electricity power to a small isolated

village in Reunion Island, France.

From 2001 to 2002 an SSP Concept

and Technology Maturation (SCTM)

program has been pursued by NASA.

Tesla’s Tower of Dreams:

Tesla left Colorado Springs on

January 7, 1900. The lab was torn down,

broken up, and its contents sold to pay

debts. The Colorado experiments

prepared Tesla for his next project, the

establishment of a wireless power

transmission facility that would be

known as Wardenclyffe. On March 21,

1900, Tesla was granted US685012

patent for the means for increasing the

intensity of electrical oscillations. The

United States Patent Office classification

system currently assigns this patent to

the primary Class 178/43

("telegraphy/space induction"), although

the other applicable classes include

505/825 ("low temperature

superconductivity-related apparatus"). A

few years later, George Westinghouse

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and J. P. Morgan stopped funding Tesla's

research when Tesla showed him that he

could offer free electricity to the whole

world by simply "ramming a stick in the

earth in your backyard". Westinghouse

said he would go bankrupt if that

happened.

Tower Raised By Tesla

Wardenclyffe tower and laboratory. The

building was designed by Stanford White,

famous architect and personal friend of

Tesla. Tesla intended this to be a

broadcasting system in the world and

transmission system of electricity to the

whole globe without wires.

Nikola Tesla began planning the

Wardenclyffe Tower facility ca. 1898, and

in 1901, construction began on the land

near Long Island Sound. Architect

Stanford White designed the

Wardenclyffe facility main building. The

tower was designed by W.D. Crow, an

associate of White. Funding for Tesla's

project was provided by influential

industrialists and other venture

capitalists. The project was initially

backed by the wealthy J. P. Morgan (he

had a substantial investment in the

facility, initially investing $150,000).

In June 1902, Tesla moved his laboratory

operations from his Houston Street

laboratory to ‘Wardenclyffe’. However, in

1903, when the tower structure was near

completion, it was still not yet functional

due to last-minute design changes that

introduced in an unintentional defect.

When Morgan wanted to know "Where

can I put the meter?”Tesla had no

answer. Tesla's vision of free power did

not agree with Morgan's worldview.

Construction costs eventually exceeded

the money provided by Morgan, and

additional financiers were reluctant to

come forth. By July 1904, Morgan (and

the other investors) finally decided they

would not provide any additional

financing. Morgan also encouraged other

investors to avoid the project.

Experimental proof:

A block diagram of the microwave

wireless power transmission

demonstration components

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Description and Working:

The primary components include a

microwave source, a transmitting

antenna, and a receiving rectenna.

The microwave source consists of a

microwave oven magnetron with

electronics to control the output power.

The output microwave power ranges

from 50 W to 200 W at 2.45 GHz. A

coaxial cable connects the output of the

microwave source to a coax-to-

waveguide adapter. This adapter is

connected to a waveguide ferrite

circulator which protects the microwave

source from reflected power. The

circulator is connected to a tuning

waveguide section to match the

waveguide impedance to the antenna

input impedance.

The slotted waveguide antenna

consists of 8 waveguide sections with 8

slots on each section. These 64 slots

radiate the power uniformly through free

space to the rectenna. The slotted

waveguide antenna is ideal for power

transmission because of its high aperture

efficiency (> 95%) and high power

handling capability.

A rectifying antenna called a

rectenna receives the transmitted power

and converts the microwave power to

direct current (DC) power. This

demonstration rectenna consists of 6

rows of dipoles antennas where 8 dipoles

belong to each row. Each row is

connected to a rectifying circuit which

consists of low pass filters and a rectifier.

The rectifier is a Gas Schottky barrier

diode that is impedance matched to the

dipoles by a low pass filter. The 6

rectifying diodes are connected to light

bulbs for indicating that the power is

received. The light bulbs also dissipated

the received power. This rectenna has a

25% collection and conversion efficiency,

but rectennas have been tested with

greater than 90% efficiency at 2.45 GHz.

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Inductive

coupling: One of the means to power a device

wirelessly is to couple it inductively with

the power source. Inductive coupling is

the phenomenon electric transformers

rely on to work properly. If you

remember correctly, transformers consist

of two coils - a primary coil and a

secondary one - coupled inductively

through an armature. Current is

circulated through the primary coil,

which generates a variable magnetic

field, carried through the armature to the

secondary coil. The magnetic field then

induces in the secondary coil an electrical

current that can be used to power a

particular device.

The same principle can be

successfully applied for wireless power

transmission. Eg: Electric toothbrushes

Resonance:

The problem with this wireless

power transmission technique is that it

generates a highly confined, small

magnetic field which acts only on short

distances. To make it more efficient on

long distances, one has to take in

consideration resonance.

Resonance is achieved

between two coils when the

electromagnetic field around them

oscillates at the same frequency. This is

done by using a curved coil as an

inductor, which is coupled with a

capacitance plate. As long as the two

coils are in resonance, the power transfer

between them will continue. When the

two coils resonate on different

frequencies, no power is transferred

between them.

Microwaves: Nevertheless, not even resonance

works when distances several kilometers

long are involved. Instead microwave

radiation comes into play. The idea is

that microwaves can be generated with

the help of ground-based transmitters

and will then be picked up by a certain

device with the help of a rectifying

antenna that converts microwaves

straight into direct current.

Properties of Microwaves:

In many ways, microwaves act like

light rays. They can be focused with

lenses made of wax or paraffin. They can

be reflected from large, plane sheets of

metal, as light is reflected from plane

mirrors. Metal parabolas may be used to

produce parallel beams. (The maximum

diameter of the parabola should be

greater than two or three times the

wave-length if reasonably parallel beams

are to be obtained.) The waves can be

diffracted by slits in metal surfaces.

Interferometers can be constructed for

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their use. In many ways, the name quasi-

optical is justified. On the other hand,

microwaves will pass through dry wood,

whereas light waves will not. The

dielectric constant of pure water for 1-

meter waves is around 80; it is around

1.3 for 1-centimeter radio waves and for

light waves. Apparently the electrical

constituents of water molecules cannot

vibrate faster than about 1 billion times

each second. Likewise, the elementary

magnets or " domains " of a piece of iron

cease to follow an applied magnetic field

if the oscillation rate is of this same order

of magnitude.

Long-Distance Wireless

Power

Transmission Experiment: One of the examples of long-distance

wireless power transmission is a 1980

experiment by Communications Research

Center in Canada. The research center

used a small unmanned airplane

designed for communications relay and

capable of being powered from a power

beamed from the station for this

experiment. The experiment managed to

prove that aircrafts can fly (2 km

diameter flight path with an altitude of

21 km) for as long as several months

without the need to land by using power

beamed from a distant station.

Basic

Principle:

One of the central devices that will

be used in long-distance wireless power

transmission technology is the rectenna

or rectifying antenna composed of dipole

antennas connected to semiconductor

diodes. These diodes direct the electrons

produced from the infrared or microwave

energy to the circuitry on the rectenna

that distributes the electrons to the

system. Magnetically coupled

resonance:

In contrast, WiTricity is based on

using coupled resonant objects. “Two

resonant objects of the same resonant

frequency tend to exchange energy

efficiently, while interacting weakly with

extraneous off-resonant objects”.

Features and Benefits

Highly Resonant Strong Coupling Provides High Efficiency over Distance

WiTricity's mode of wireless power

transfer is highly efficient over distances

ranging from centimeters to several

meters. We define efficiency as the

amount of usable electrical energy that is

available to the device being powered,

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divided by the amount of energy that is

drawn by the Witricity source. In many

applications, efficiency can exceed 90%.

And WiTricity sources only transfer

energy when it is needed. When

a WiTricity powered device no longer

needs to capture additional energy,

the WiTricity power source will

automatically reduce its power

consumption to a power saving “idle”

state. Contact WiTricity to learn the

efficiency and distance ranges that can

be achieved in your applications.

Energy Transfer via Magnetic Near Field Can Penetrate and Wrap Around Obstacles

The magnetic near field has several

properties that make it an excellent

means of transferring energy in a typical

consumer, commercial, or industrial

environment. Most common building

and furnishing materials, such as wood,

gypsum wall board, plastics, textiles,

glass, brick, and concrete are essentially

“transparent” to magnetic fields—

enabling WiTricity technology to

efficiently transfer power through them.

In addition, the magnetic near field has

the ability to “wrap around” many

metallic obstacles that might otherwise

block the magnetic fields. WiTricity’s

applications engineering team will work

with you to address the materials and

environmental factors that may influence

wireless energy transfer in your

application.

Non-Radiative Energy Transfer is Safe for People and Animals

WiTricity’s 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—and

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 chicken in a

microwave. But it doesn't respond

to magnetic fields. As far as we know the

body has almost zero response to

magnetic fields in terms of the amount of

power it absorbs." Evidence of the safety

of magnetic fields is illustrated by the

widespread acceptance and safety of

household magnetic induction cook

tops.

Through proprietary design of

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 radio frequency emissions that

interfere with other electronic devices,

and is not a source of electric and

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magnetic field levels that pose a risk to

people or animals.

Limits for human exposure to magnetic

fields are set by regulatory bodies such

as the FCC, ICNIRP, and are based on

broad scientific and medical

consensus. WiTricity technology is being

developed to be fully compliant with

applicable regulations regarding

magnetic fields and electromagnetic

radiation.

Scalable Design Enables Solutions from milliwatts to Kilowatts

WiTricity systems can be designed to

handle a broad range of power levels.

The benefits of highly efficient energy

transfer over distance can be achieved at

power levels ranging from milliwatts to

several kilowatts. This

enables WiTricity technology to be used

in applications as diverse as powering a

wireless mouse or keyboard (milliwatts)

to recharging an electric passenger

vehicle (kilowatts). WiTricity technology

operates in a “load following” mode,

transferring only as much energy as the

powered device requires.

Flexible Geometry Allows WiTricity Devices to be Embedded Into OEM Products

WiTricity technology is being designed so

that it can be easily embedded into a

wide variety of products and systems.

The physics of resonant magnetic

coupling enables WiTricity engineers to

design power sources and devices of

varying shapes and sizes, to match both

the packaging requirements and the

power transfer requirements in a given

OEM application. WiTricity has designed

power capture devices compact enough

to fit into a cell phone.

WiTricity

applications : WiTricity’s wireless power transfer

technology can be applied in a wide

variety of applications and environments.

The ability of our technology to transfer

power safely, efficiently, and over

distance can improve products by making

them more convenient, reliable, and

environmentally

friendly. WiTricity technology can be

used to provide:

Direct Wireless Power—when

all the power a device needs is

provided wirelessly, and no

batteries are required. This

mode is for a device that is

always used within range of

its WiTricity power source.

Automatic Wireless Charging—

when a device with

rechargeable batteries charges

itself while still in use or at rest,

without requiring a power cord

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or battery replacement. This

mode is for a mobile device that

may be used both in and out of

range of its WiTricity power

source.

Consumer Electronics

Automatic wireless charging of

mobile 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 (flat screen TV’s,

digital picture frames, home theater

accessories, wireless loud speakers, etc.)

… eliminating expensive custom wiring,

unsightly cables and “wall-wart” power

supplies.

Direct wireless powering of

desktop PC peripherals: wireless mouse,

keyboard, printer, speakers, display, etc…

eliminating disposable batteries and

awkward cabling.

Industrial

Direct wireless power and

communication interconnections across

rotating and moving “joints” (robots,

packaging machinery, assembly

machinery, machine tools) … eliminating

costly and failure-prone wiring.

Direct wireless power and

communication interconnections at

points of use in harsh environments

(drilling, mining, underwater, etc.) …

where it is impractical or impossible to

run wires.

Direct wireless power for

wireless sensors and actuators,

eliminating the need for expensive power

wiring or battery replacement and

disposal.

Automatic wireless charging for

mobile robots, automatic guided

vehicles, cordless tools and instruments…

eliminating complex docking

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mechanisms, and labor intensive manual

recharging and battery replacement.

Transportation

Automatic wireless charging for

existing electric vehicle classes: golf

carts, industrial vehicles.

Automatic wireless charging for

future hybrid and all-electric passenger

and commercial vehicles, at home, in

parking garages, at fleet depots, and at

remote kiosks

.

Direct wireless power

interconnections to replace costly

vehicle wiring harnesses and slip

rings

Other Applications

Direct wireless power

interconnections and automatic wireless

charging for implantable medical devices

(ventricular assist devices, pacemaker,

defibrillator, etc.).

Automatic wireless charging

and for high tech military systems

(battery powered mobile devices, covert

sensors, unmanned mobile robots and

aircraft, etc.).

Direct wireless powering and

automatic wireless charging of smart

cards.

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Direct wireless powering and

automatic wireless charging of consumer

appliances, mobile robots, etc.

Some Future Projects:

Japan's space agency planning

space-based solar power

arrays:

A space-based solar array beams

power back to Earth. The agency is set to

begin testing on the microwave power

transmission system on February 20th,

with an attempt to beam enough power

(over the 2.4GHz band to power a

household heater at 50 meters (164

feet).) That's certainly not the sort of

large-scale sci-fi power system we were

hoping for, but fret not -- if the tests are

successful, JAXA's plan is to eventually

launch a constellation of solar satellites,

each beaming power to a 1.8-mile wide

receiving station that'll produce 1

gigawatt of electricity and power

500,000 homes.

Solaren Corp to supply

California with space-based

solar power:

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California's largest energy utility, Pacific

Gas & Electric, has agreed to do just that,

inking a deal with solar power startup

Solaren Corp. The agreement calls for the

utility to purchase 200 megawatts of

electricity once the company starts

beaming power down from Earth orbit

beginning in 2016. A solar-power

satellite would consist of mirror arrays --

perhaps measuring up to several miles

wide -- which would focus sunlight onto

photoelectric cells. From there, the

electrical power is converted into a

microwave beam that is directed

downward toward Earth, where it's

converted back into electricity and then

fed into the grid. According to the

company, the system could generate

roughly 1.2 to 4.8 gigawatts of power, at

a price comparable to that of other

renewable energy sources.

Conclusion:

Thus, the implementation of

‘Witricity’-Wireless Power Transmission

which is an immediate requirement in

now-a-days of energy crisis and its

applications to the new era was shown

clearly. Further its practical

implementation is under research.

However, now it is possible to charge

laptops, cell phones without power cords

from short distances.

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References:

[1] R. G. D., Laffan, “The Serbs:

The Guardians of the Gate”, 1989

Dorset Press, ISBN 0-88029-413-2

[2] J. J. O’Neill, Prodigal Genius-

The Life of Nikola Tesla, New

York: Washburn, 1944.

[3] Nikola Tesla; C o l o r a d o

S p r i n g s N o t e s , 1 8 9 9 -1900, N o l i t ,

Belgrade, Serbia, 1978. (Published by

the Nikola Tesla museum, Belgrade,

Serbia.

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