A PAPER PRESENTATION ON

UNWIRED CHARGING TRULY WIRELESS WORLD

(AUTONOMOUS)

Presented By

V.ASHWINI D.MALLESWARAMMAIII-B-Tech, EEE III-B-Tech, EEEJNTU COLLEGE OF Engg, JNTU COLLEGE OF Engg Anantapur, AnantapurAndhra Pradesh Andhra PradeshE-mail: Ashwinivanam@gmail.com E-mail: malliswari212@gmail.comPh.no-8099858086 ph.no-9640261495

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ABSTRACT:

Yes, now we can forget wires

even for charging. My mobile have been

switched off, my Laptop computer have

no charging …….no such questions!

Can we imagine the life without

electrical wires? from now, answer to

this question is yes. The methods

proposed in the present paper though

utilizes contrasting technologies for wire

less transmission of power namely

‘power cast technology’ and ‘eCoupled

technology’ are presented in the name of

“unwired charging”, Which will

facilitate to Transfer power without

using wires.

The efficient low-range power can be

transmitted to any device which uses that

range of power by the technique used in

this concept called “power casting”. This

technology uses radio frequency waves

for carrying power.

The efficient mid-range power can be

transmitted to any device which uses that

range of power by the technique used in

this concept called “eCoupling”. This

technology uses electro magnetic

coupling for carrying power.

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,

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Wireless energy transfer would be useful

for many applications as above and they

need low-range and mid-range energy.

This is the main reason to prepare this

concept.

INTRODUCTION:

In our day-to-day life we use laptop

computers, cell phones, digital cameras,

voice recorder, portable printer,

MP3players all plays a significant role.

But the major limitation is that they have

to be charged regularly which is possible

only by connecting the device to the

supply through electrical Wires. More

often it looks like snakes ……cables,

cables…..and more cables… as shown

But this dream of wire less charging

might be possible very soon, by means

of technology explained below. Unless

this concept is not implemented we can’t

really call the world as really wire free

world. This is because although wireless

mantra is a old concept over the world

we still need electric wires and chemical

batteries for purpose of charging and

transmitting power.

TECHNOLOGY:

Power casting technology :

The Basic Idea:

If we walk a few meters from

where we are standing now we will

probably be cutting across at least a

dozen radio waves zipping invisibly

across our room that is how common

they are…. So common that we barely

spare time to even think about them

seriously!

Radio frequencies are foundational for

most devices we use today right from

TVs and radios to mobile phones. But

we ever think of how powerful the radio

frequencies are?

The simple example that makes radio

frequency identification (RFID) superior

to barcodes is that they can store more

data, they can be read and written to,

they can be re-used etc., but what makes

all this possible? How is RFID chip able

to survive on its own, woven into some

product or person, isolated from the rest

of civilization? It is because the chip is

able to charge itself through the radio

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waves transmitted by the transceiver

when reading or writing. Basically this is

a simple example of the energy carrying

property of radio waves

Then why cannot RF (Radio

Frequency) be used to power devices?

If we have a Base station that

draws power from a power line and

keeps transmitting it as radio waves and

all our mobile devices have receivers

that can receive these radio waves and

convert them into DC current, that’s

pretty much a wire less powering

system. That is one base station can

charge quite number of devices-provided

they all have the receivers built into

them this is precisely how the power cast

system works

TECHNOLOGY BEHIND THE

POWER:

The mess of wires, those power strips

overloaded with transformers and

maddening gadget connectors half a

nanometer from perfection may all soon

be a thing of the past.

The power cast wireless power platform

consists of a transmitter called ‘power

caster’ and a receiver called ‘power

harvester’. The ‘power caster’ can

double the effective range, compared to

normal RF transmitters and a power

harvester can harvest up to 70% of the

theoretical maximum power with in the

range and convert it into dc current for

the device to use. The power harvester is

a chip about half the size of an ordinary

battery used for charging and must be

accompanied by a small antenna whose

size varies according to the frequency of

transmitted power. It can fit quite

comfortably into the battery

compartment of most devices, and many

devices could use the case itself as the

antenna. Of course small tweaks in the

circuitry of the device will be needed to

connect the power harvester to it.

The power harvester is available in

various models for multiple frequency

ranges, voltage requirements sizes and

so on. The design can fully customized

according to the requirements. Any

device fitted with a power harvester gets

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charged automatically whenever it is

with in the range of power caster and

any number of ‘power harvesting

devices’ can be placed within the range

of single power caster. This does not

give rise to problems like cancellation

and interference because power caster

neither causes nor is affected by such

problems. In-fact, the power harvesters

actually outwit noises by making use of

them.

POTENTIAL POWER

HARVESTERS:

All the devices cannot be powered

using power cast system only devices

that work on AA, AAA batteries or cell

batteries can make use of this wire less

power system. Power cast is designed to

power devices with very low power.

Sensor networks, hearing aids, headsets

etc., are ideally suited for this

technology basically any device which

requires small battery (to be recharged)

are requires very little power for direct

powering (such as Light Emitting Diode

LED) is suitable for taking advantage of

power cast technology. Power cast

technology is designed to provide milli

watts of power to devices with in an

effective range of the transmitter.

Radio waves are in fact energy. They

are already used to send and receive cell

phone, television, radio, and ‘Wi-Fi’

signals every day. Those waves spread

out in all directions until they reach an

antenna that is tuned to the appropriate

frequency. Power cast's wireless power

platform uses a "Power caster"

transmitter circuit running on

conventional current to broadcast a low-

power radio signal at a predetermined

frequency. The smaller "Power

harvester" receiver circuit which can be

embedded in any low-power device then

uses that energy to recharge or can even

replace the device's battery.

The Power cast solution is able to

maximize power transfer by using a

much broader area of the RF spectrum,

the 900-MHz band. While not

necessarily a replacement for a

conventional charger, the technology

will be able to "trickle charge" a variety

of electronics over a period of time so

that their energy is never fully depleted.

As with a traditional AM/FM radio,

the closer one is to the tower

transmitting the signal, the better the

reception. Power cast's wireless platform

operates using a similar principle. The

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wireless power platform can harvest a

few milli watts of energy within a meter

of the source, in this case the transmitter.

That is enough energy to charge a single

depleted cell phone battery about half

way overnight. The solution will also be

ideal for devices with small batteries

such as watches, hearing aids, wireless

keyboards and mice, and game

controllers, all of which could be

continuously charged. But there are

limits to the charging capabilities the

Power cast platform. Larger devices

will not be able to make use of this

‘power cast’ technology solution simply

because they require too much power. In

fact, the size limit for now seems to be at

the cell phone level for effective

charging.

eCoupled technology:

The Basic Idea:

The basic concept behind this is

Magnetic Resonance. Two resonant

objects of the same resonant frequency

tend to exchange energy efficiently,

while dissipating relatively little energy

in extraneous off-resonant objects. In

systems of coupled resonances, there is

often a general “Strongly Coupled”

regime of operation. If one can operate

in that regime in a given system, the

energy transfer is expected to be very

efficient. Midrange power transfer

implemented in this way can be nearly

omni directional and efficient,

irrespective of the geometry of the

surrounding space, with low interference

and losses into environmental objects.

The above considerations apply

irrespective of the physical nature of the

resonances.

Magnetic resonances are

particularly suitable for everyday

applications because most of the

common materials do not interact with

Magnetic Fields, so interactions with

Environmental objects are suppressed

even further. We were able to identify

the strongly coupled regime in the

system of two coupled magnetic

resonances by exploring Non-radiative

(near-field) magnetic resonant induction

at Megahertz frequencies.

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Experimental Design:

Our experimental scheme

consists of two Self-resonant coils. One

coil (source coil) is coupled inductively

to an oscillating circuit; the other (device

coil) is coupled inductively to a resistive

load. Self-resonant coils rely on the

interplay between distributed inductance

and distributed capacitance to achieve

resonance.

The coils are made of an

electrically conducting wire of total

length ‘l’ and cross-sectional radius ‘a’,

wound into a helix of ‘n’ turns, radius

‘r’, and height ‘h’. There is no exact

solution for a finite helix in the

literature, and even in the case of

infinitely long coils, the solutions rely on

assumptions that are inadequate for this

system. So here the method implemented

is simple Quasi-static model to find the

parameters. Those are in Electro

Magnetic equations.

Efficiency of the System:

The efficiency of the system is

nothing but the ratio of output power to

input power. The output power is

nothing but the device power rating and

input power is sum of the power

dissipated by source, power loss due to

decay and output power.

Efficiency=Pw / (Ps+Pd+Pw)

The experiment done in 7th June,

2007 by the Massachusetts Institute of

Technology, Cambridge gives the result

that in order to get 60W approximate

power is the output useful power with

40% efficiency. They resonated the

circuit at ≈9.9 MHz so that they

developed the power is transmitted up to

8 times greater than the radius of the coil

used.

ADVANTAGES OF ABOVE

TECHNOLOGIES:

The need for batteries and

numerous redundant adaptors

which consists of toxic

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substances like nickel, cadmium,

mercury are reduced. This

reduces the electronic waste.

There is no need for alkaline

batteries which are to be

recharged regularly.

Complexity and risk of electric

shorts reduces as we are not

using any electrical wires.

Unaffected by the day night

cycle, weather or seasons.

This is an eco friendly and the

system poses no health hazards

what so ever as the power limits.

It is a boon for the devices which

use low-range and mid-range

power

COMPARISON BETWEEN ABOVE

TECHNOLOGIES:

Power cast technology is suitable

for only low range power, while

eCoupled technology is suitable

for both low-range and mid-

range powers

Power cast technology is

effective even though the

distance between transmitter and

receiver is high but major

limitation of eCoupled

technology is air gap should be

low.

As eCoupled technology is based

on magnetic resonance it could

be easily effected by presence of

Ferro magnetic materials in its

path.

In eCoupled technology as the

device is close to the charging

source it is able to provide more

power than while charging using

RF.

Inductive method gives higher

power at shorter distances but

power cast system though gives

low range power it transmits

even at longer distances.

In eCoupled technology the

resonance condition should be

satisfied, if any medium error is

there possibility of power

transfer is affected, while as

power cast system uses radio

waves it is independent of

medium around it.

In power cast technology any

number of power harvesting

devices can be placed with in the

range of single power caster. It

is not possible in case of

eCoupled technology

CONCLUSION:

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From the above discussion we can

conclude that no technology can be

perfectly ideal by making use of best

ideas in the technologies and

working in conjunction with them

we can achieve wireless power

transmission very sooner. This

reduces the risk of using electrical

cables and redundant adaptors. Each

of the above system has its own pros

and cons and one needs to decide

based on one’s needs.

This is the Christmas tree which is

lighted based on power transmission

by radio frequency waves using

power cast technology. It can be

placed anywhere in the range of

transmitter.

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