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1.ABSTRA

CT :

WIRELESS POWER TRANSMISSION (WITRICITY)

K.Komal Prakash#1 , G.Abhiraj#2

094G1A0433#1 , 094G1A0444#2,

Srinivaa Ra!an"an In$i$"$% &' T%n&*&+

kprakash.433@gmail.com#1, abhiraj401@gmail.com#2,

mailto:kprakash.433@gmail.com#1mailto:kprakash.433@gmail.com#1mailto:kprakash.433@gmail.com#1mailto:kprakash.433@gmail.com#1mailto:abhiraj401@gmail.com#2mailto:abhiraj401@gmail.com#2mailto:abhiraj401@gmail.com#2mailto:abhiraj401@gmail.com#2mailto:kprakash.433@gmail.com#1mailto:abhiraj401@gmail.com#2

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The aim of this paper is to

introduce a new system of transmitting the

power which is called wireless electricity orwitricity. Witricity is based upon coupled

resonant objects to transfer electrical energy

between objects without wires. The systemconsists of a Witricity transmitter (power

source), and devices which act as receivers

(electrical load). It is based on the principle ofresonant coupling and microwave energy

transfers. The action of an electrical

transformer is the simplest instance of wireless

energy transfer. There are mainly two types oftransfers i.e. short range and long range

transmission. The short range are of 2-metres

where as the long range are of few !ilometers.

"ireless transmission is ideal in cases whereinstantaneous or continuous energy transfer is

needed, but interconnecting wires are

inconvenient, ha#ardous, or impossible. The

tangle of cables and plugs needed to rechargetoday$s electronic gadgets could soon be a thing

of the past. The concept e%ploits century-old

physics and could wor! over distances of manymetres. &onsumers desire a simple universal

solution that frees them from the hassles of

plug-in chargers and adaptors. '"ireless powertechnology has the potential to deliver on all of

these needs.' owever, transferring the power is

the important part of the solution.

"itricity, standing for wireless electricity, is a

term coined by IT researchers, to describe theability to provide electricity to remote objects

without wires. *sing self- resonant coils in a

strongly coupled regime, efficient non-radiativepower transfer over distances of up to eight

times the radius of the coils can be done.. *nli!e

the conduction-based systems, "itricity usesresonant magnetic fields to reduce wastage of

power. &urrently the project is loo!ing for

power transmissions in the range of+ watts.

"ith wireless energy transfer, the efficiency is a

more critical parameter and this createsimportant differences from the wireless data

transmission technologies. To avoid the conflicts

li!e recharging and carrying its appliances ofelectrical and electronic devices, wireless power

transmission is desirable. "ireless power

transmission was originally proposed to avoidlong distance electrical distribution based

mainly on copper cables. This can be achieved

by using microwave beams and the rectifying

antenna, or rectenna, which can receiveelectromagnetic radiation and convert it

efficiently to & electricity. esearchers have

developed several techni/ues for moving

electricity over long distances without wires.0ome e%ist only as theories or prototypes, but

others are already in use. agnetic resonancewas found a promising means of electricity

transfer because magnetic fields travel freely

through air yet have little effect on the

environment or, at the appropriate fre/uencies,on living beings and hence is a leading

technology for developing witricity.

-OW IT WOR.S/

Wir%*% *i+$ Researchers used magneticresonance coupling to power a 60-watt light

bulb. Tuned to the same frequency, two 60-

centimeter copper coils can transmit electricityover a distance of two meters, through the air

and around an obstacle.

The researchers built two resonant copper coils

and hung them from the ceiling, about two

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meters apart. When they plugged one coil into

the wall, alternating current flowed through it,

reating a magnetic field.The second coil, tuned to the same frequency

and hoo!ed to a light bulb, resonated with the

magnetic field, generating an electric current thatlit up the bulb--even with a thin wall between the

coils.

-& ir%*% %n%r+ &"* &r-

"Resonance", a phenomenon that causes anob#ect to vibrate when energy of a certain

frequency is applied. Two resonant ob#ects of

the same frequency tend to couple very

strongly." Resonance can be seen in musicalinstruments for e$ample. "When you play a tune

on one, then another instrument with the sameacoustic resonance will pic! up that tune, it will

visibly vibrate,"

%nstead of using acoustic vibrations, system

e$ploits the resonance of electromagnetic waves.

&lectromagnetic radiation includes radio waves,

infrared and '-rays. Typically, systems that useelectromagnetic radiation, such as radio

antennas, are not suitable for the efficient

transfer of energy because they scatter energy inall directions, wasting large amounts of it into

free space. To overcome this problem, the team

investigated a special class of "non-radiative"ob#ects with so-called "long-lived resonances".

When energy is applied to these ob#ects it

remains bound to them, rather than escaping to

space. "Tails" of energy, which can be manymetres long, flic!er over the surface. %f another

resonant ob#ect is brought with the same

frequency close enough to these tails then itturns out that

the energy can tunnel from one ob#ect to another.

(ence, a simple copper antenna designed to

have long-lived resonance could transfer energy

to a laptop with its own antenna resonating at the

same frequency. The computer would be truly

wireless. )ny energy not diverted into a gadget

or appliance is simply reabsorbed. The systems

that are described would be able to transferenergy over three to five metres. This would

wor! in a room let*s say but can be adapted to

wor! in a factory. %t could also be scaled downto the microscopic or nanoscopic world.

(+W W%R&& +W&R +/ W+R1

1. ower from mains to antenna, which is made

of copper

2. )ntenna resonates at a frequency of 6.23(4,emitting electromagnetic waves

3. *Tails* of energy from antenna *tunnel* up to

5m 76.2ft8

4. &lectricity pic!ed up by laptop*s antenna,which must also be resonating at 6.23(4.

&nergy used to re-charge device

. &nergy not transferred to laptop re-absorbed

by source antenna. eople9other ob#ects not

affected as not resonating at 6.23(4.

S&r$ ran+% 5&%r $ran!ii&n an

r%%5$i&n 6

ower supply for portable electronic devices is

considered, which receives ambient radio

frequency radiation typically in an urbanenvironment8 and converts it to electricity

that is stored in a battery for use by the portable

device. ) ower transmission unit T/8 isconnected to the electrical utility, typically in a

domestic and office environment, and uses the

electricity to generate a beam of electromagnetic

radiation. This beam can ta!e the form of visiblelight, microwave radiation, near infrared

radiation or any appropriate frequency or

frequencies, depending on the technologychosen. The beam can be focused and shaped

using a focusing mechanism: for e$ample, a

parabola shape may be chosen to focus lightwaves at a certain distance from the T/.

) ower reception unit R/8 receives power

from one or several T/*s, and converts the total

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power received to electricity, which is used to

tric!le charge a storage unit such as a battery or

transferred directly to the appliance for use, orboth. %f transferred to the storage unit, the output

of the storage unit can power the appliance.

imilarly to the focusing of the transmittedpower, it is possible to concentrate the received

power for conversion, using receiving arrays,

antennas, reflectors or similar means.

%t is possible to construct power "relay units",

consisting of R/*s powering T/*s, whose

function is to ma!e the transmitted poweravailable at further distances than would

normally be possible.

L&n+/i$an% Wir%*% P&%r/

ome plans for wireless power involve

moving electricity over a span of miles. ) fewproposals even involve sending power to the

&arth from space. The tationary (igh )ltitude

Relay latform ()R8 unmanned plane could

run off power beamed from the &arth. The secretto the ()R*s long flight time was a large,

ground-based microwave transmitter. ) large,

disc-shaped r%$i'in+ an$%nna, or r%$%nna,near the system changed the microwave energy

from the transmitter into direct-current 8

electricity. ;ecause of the microwaves*interaction with the rectenna, the system had a

constant power supply as long as it was in range

of a functioning microwave array.

Rectifying antennae are central to many wireless

power transmission theories. They are usually

made of an array of dipole antennae, which havepositive and negative poles. These antennae

connect to semiconductor diodes. (ere*s what

happens:

7. 3icrowaves, which are part of the

electromagnetic spectrum, reach the

dipole antennae

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can be used. The main drawbac! to induction,

however, is the short range. The receiver must

be very close to the transmitter or induction unitin order to inductively couple with it.

R%&nan$ in"$i&n

A $r"!5%$8 i%, a5% an !a$%ria* &!5&i$i&n %$%r!in% i$ r%&nan$

'r%:"%n;

;y designing electromagnetic resonators that

suffer minimal loss due to radiation andabsorption and have a nearfield with mid-range

e$tentnamely a few times the resonator si4e8,

mid-range efficient wireless energy- transfer is

possible. The reasonment is that, if two suchresonant ob#ects are brought in mid- range

pro$imity, their near fields consisting ofso-called *evanescent waves*8 couple evanescent

wave coupling8 and can allow the energy to

transfer from one ob#ect to the other within timesmuch shorter than all loss times, which were

designed to be long, and thus with the ma$imum

possible energy-transfer efficiency. ince the

resonant wavelength is much larger than theresonators, the field can circumvent e$traneous

ob#ects in the vicinity and thus this mid-range

energy-transfer scheme does not require line-of-sight. ;y utili4ing in particular the magnetic

field to achieve the coupling, this method can be

safe, since magnetic fields interact wea!ly withliving organisms.

"Resonant inductive coupling" has !ey

implications in solving the two main problemsassociated with non-resonant inductive coupling

and electromagnetic radiation, one of which is

caused by the other> distance and efficiency.&lectromagnetic induction wor!s on the

principle of a primary coil generating a

predominantly magnetic field and a secondarycoil being within that field so a current is

induced within its coils. This causes the

relatively short range due to the amount of

power required to produce an

electromagnetic field. +ver greater distances the

non-resonant induction method is inefficient and

wastes much of the transmitted energy #ust toincrease range. This is where the resonance

comes in and helps efficiency dramatically by

"tunneling" the magnetic field to a receiver coilthat resonates at the same frequency. /nli!e the

multiple-layer secondary of a non-resonant

transformer, such receiving coils are single layersolenoids with closely spaced capacitor plates on

each end, which in combination allow the coil to

be tuned to the transmitter frequency thereby

eliminating the wide energy wasting "waveproblem" and allowing the energy used to focus

in on a specific frequency increasing the range.

ome of these wireless resonant inductivedevices operate at low milliwatt power levels

and are battery powered. +thers operate athigher !ilowatt power levels. urrent

implantable medical and road electrification

device designs achieve more than ?5@ transferefficiency at an operating distance between the

transmit and receive coils of less than 70 cm.

R%&nan% an Wir%*% P&%r/

(ousehold devices produce relatively small

magnetic fields. Aor this reason, chargers holddevices at the distance necessary to induce a

current, which can only happen if the coils are

close together. ) larger, stronger field couldinduce current from farther away, but the

process would be e$tremely inefficient. ince a

magnetic field spreads in all directions, ma!ing a

larger one would waste a lot of energy.

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The distance between the coils can be e$tended

by adding resonance to the equation.

) good way to understand resonance is to thin!

of it in terms of sound. )n ob#ect*s physicalstructure -- li!e the si4e and shape of a trumpet

-- determines the frequency at which it naturally

vibrates. This is its resonant frequency. %t*s easyto get ob#ects to vibrate at their resonant

frequency and difficult to get them to vibrate at

other frequencies. This is why playing a trumpet

can cause a nearby trumpet to begin to vibrate.;oth trumpets have the same resonant

frequency.

%nduction can ta!e place a little differently if theelectromagnetic fields around the coils resonate

at the same frequency. The theory uses a curvedcoil of wire as an inductor. )a5ai$an% 5*a$%,

which can hold a charge, attaches to each end of

the coil. )s electricity travels through this coil,the coil begins to resonate. %ts resonant

frequency is a product of the inductance of the

coil and the capacitance of the plates.

)s with an electric toothbrush, this system relies

on two coils. &lectricity, traveling along an

electromagnetic wave, can$"nn%*from one coil to the other as long as they both

have the same resonant frequency. The effect is

similar to the way one vibrating trumpet cancause another to vibrate.

)s long as both coils are out of range of one

another, nothing will happen, since the fields

around the coils

T% MIT ir%*% 5&%r 5r&%$ "%

a "rv% &i* an a5ai$iv% 5*a$%;

aren*t strong enough to affect much around them.

imilarly, if the two coils resonate at different

frequencies, nothing will happen. ;ut if two

resonating coils with the same frequency getwithin a few meters of each other, streams of

energy move from the transmitting coil to the

receiving coil. )ccording to the theory, one coilcan even send electricity to several receivingcoils, as long as they all resonate at the same

frequency. The researchers have named this

raia$iv% %n%r+ $ran'%r since it involvesstationary fields around the coils rather than

fields that spread in all directions. This !ind of

setup could power or rechar ge all the devices inone room. ome modifications would be

necessary to send power over long distances,

li!e the length of a building or a city.

7ar 'i%*/

3eans for long conductors of electricityforming part of an electric circuit and electrically

connecting said ioni4ed beam to an electric

circuit.

These methods achieve longer ranges,

often multiple !ilometre ranges, where thedistance is much greater than the diameter of the

devices8.

Rai& an !ir&av%/

icrowave power transmission

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ower transmission via radio waves can be mademore directional, allowing longer distance power

beaming, with shorter wavelengths of

electromagnetic radiation, typically in themicrowave range. ) rectenna may be used to

convert the microwave energy bac! into

electricity. Rectenna conversion efficiencies

e$ceeding B5@ have been reali4ed. ower

beaming using microwaves has been proposedfor the transmission of energy from orbiting

solar power satellites to &arth and the beamingof power to spacecraft leaving orbit has been

considered.

ower beaming by microwaves has the difficulty

that for most space applications the required

aperture si4es are very large. These si4es can be

somewhat decreased by using shorterwavelengths, although short wavelengths may

have difficulties with atmospheric absorptionand beam bloc!age by rain or water droplets.

Aor earthbound applications a large area 70 !m

diameter receiving array allows large total powerlevels to be used while operating at the low

power density suggested for human

electromagnetic e$posure safety. ) human safepower density of 7 mW9cm distributed across a

70 !m diameter area corresponds to ?50

megawatts total power level. This is the power

level found in many modern electric powerplants.

igh power- Wireless ower Transmission

using microwaves8 is well proven. &$periments

in the tens of !ilowatts have been performed,achieving distances on the order of a !ilometer.

1ow power- ) new company, owercast

introduced wireless power transfer technology

using RA energy> this system is applicable for anumber of devices with low power requirements.

This could include &s, computer peripherals,

wireless sensors, and medical implants.urrently, it achieves a ma$imum output of 6

volts for a little over one meter.

La%r/

With a laser beam centered on its panel of

photovoltaic cells, a lightweight model plane

ma!es the first flight of an aircraft powered by alaser beam inside a building at C)) 3arshall

pace Alight enter.

%n the case of light, power can be transmitted

by converting electricity into a laser beam that

is then fired at a solar cell receiver. This isgenerally !nown as "power beaming".

%ts drawbac!s are:7. onversion to light, such as with a laser,

is moderately inefficient although

quantum cascade lasers improve this8

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through naturally e$isting conductors,specifically the earth, la!es and oceans, and

through the atmosphere D a natural medium

that can be made conducting if the brea!downvoltage is e$ceeded and the gas becomes

ioni4ed. Aor e$ample, when a high voltage is

applied across a neon tube the gas becomesioni4ed and a current passes between the two

internal electrodes. %n a practical wireless energy

transmission system using this principle, a high-power ultraviolet beam might be used to form a

vertical ioni4ed channel in the air directly above

the transmitter-receiver stations. The same

concept is used in virtual lightning rods, theelectrolaser electroshoc! weapon and has been

proposed for disabling vehicles.

The Tesla effect-

) "world system" for "the transmission ofelectrical energy without wires" that depends

upon electrical conductivity was proposed by

Tesla. Through longitudinal waves, an operator

uses the Tesla effect in the wireless transfer ofenergy to a receiving device. The Tesla effectis

the application of a type of electrical conduction

that is, the movement of energy through spaceand matter> not #ust the production of voltage

across a conductor8.

Tesla stated, E%nstead of depending on induction

at a distance to light the tube F... theG ideal wayof lighting a hall or room wouldF...G be to

produce such a condition in it that an

illuminating device could be moved and put

anywhere, and that it is lighted, no matter where

it is put and without being electrically connected

to anything. % have been able to produce such acondition by creating in the room a powerful,

rapidly alternating electrostatic field. Aor this

purpose % suspend a sheet of metal a distancefrom the ceiling on insulating cords and connect

it to one terminal of the induction coil, the other

terminal being preferably connected to theground. )n e$hausted tube may then be carried

in the hand anywhere between the sheets or

placed anywhere, even a certain distance beyond

them> it remains always luminous.H

The Tesla effect is a type of high field gradient

between electrode plates for wireless energy

transfer.

A

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AC.S/

I The wireless transmission of energy iscommon in much of the world. Radio waves are

energy, and people use them to send and receive

cell phone, TK, radio and Wi-Ai signals everyday. The radio waves spread in all directions

until they reach an$%nna%that are tuned to the

right frequency. This method for transferringelectrical power would be both inefficient and

dangerous.

I The main drawbac! to induction, however, is

the short range. The receiver must be very closeto the transmitter or induction unit in order to

inductively couple with it.

I 3any people would resist the idea of being

constantly bathed in microwaves from space,even if the ris! were relatively low.

APPLICATIONS/

7. Researchers have outlined a relatively simplesystem that could deliver power to devices such

as laptop computers or 3= players without

wires. The concept e$ploits century-old physics

and could wor! over distances of many metres,the researchers said.

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Lou can use the same principle to recharge

several devices at once. Aor e$ample, theplashpower recharging mat and &dison

&lectric*s owerdes! both use coils to create a

magnetic field. &lectronic devices use

corresponding built-in or plug-in receivers torecharge while resting on the mat. These

receivers contain compatible coils and the

circuitry necessary to deliver electricity to

devices* batteries.

&liminating the power cord would ma!e todayMs

ubiquitous portable electronics truly wireless.

S5*a5&%r !a$ "% in"$i&n $&

r%ar+% !"*$i5*% %vi% i!"*$an%&"*;

+C/%+C -

Arom these researches and discoveries it can be

said that wireless power transmission is going tobe a ma#or field of interest for scientists and for

people. The facts that the power can be

transmitted from space to earth willrevolutioni4e the field of satellites. ince the

uses of wireless power transmission are many,from easy installation, neatness, easymaintenance to multi-equipment wor!ing are

ama4ing, the area for researchers on this field

seems very interesting.

Rather concentrating on the false beliefs, the

concentration should be put on advantages of

witricity for further increasing the efficiency of

wireless power transmission with more safety

measures. %t is a roc!ing technology providedthe researches continue to move in same

speeding direction.