A Seminar Report

OnWireless power transmission

SUBMITTED BY

Kusum lata vermaRoll No.: - 1143131902

B.Tech. IIIrd Year VIth Semester

SEMINAR INCHARGE HEAD OF DEPARTMENT

Mr. Awill Anurag Mishra Mrs. Monica Mehrotra

Department of

Electronics & Communication Engineering

B. N. COLLEGE OF ENGINEERING & TECHNOLOGY, LUCKNOW-227202

2012-2013

ACKNOWLEDGEMENT

I would like to acknowledge our indebtedness to all those who willingly helped me in

completion of this seminar work. Without their help the completion of seminar would have been

move like groping in the dark for a way-out. First of all I owe my thanks to Mrs. Monica

Mehrotra (Head of Department, Electronics & Communication Engineering) for her

guidance.

I would like to extend my thanks to Mr. Awill Anurag Misra (Lecturer, Electronics &

Communication Engineering Department) for his proper guidance, valuable suggestions and

constructive approach to clear all my doubts during the course of this seminar. Without his

valuable suggestion and advice, completion of this seminar would have been a mammoth task.

Kusum lata verma

B. Tech- 3rd year (EC)

Roll no.- 1143131902

B.N.C.E.T.

ABSTRACT

The aim of this paper is to introduce a new system of transmitting the power which is called

wireless electricity or witricity. Witricity is based upon coupled resonant objects to transfer

electrical energy between objects without wires. The system consists of a Witricity transmitter

(power source), and devices which act as receivers (electrical load). It is based on the principle of

resonant coupling and microwave energy transfers. The action of an electrical transformer is the

simplest instance of wireless energy transfer. There are mainly two types of transfer i.e. short

range and long range transmission short range are of 2-3 meters where as the long range are of

few kilometers.

Wireless transmission is ideal in cases where instantaneous or continuous energy transfer is

needed, but interconnecting wires are inconvenient, hazardous, or impossible. The tangle of

cables and plugs needed to recharge today's electronic gadgets could soon be a thing of the past.

The concept exploits century-old physics and could work over distances of many metres.

Consumers desire a simple universal solution that frees them from the hassles of plug-in chargers

and adaptors. "Wireless power technology has the potential to deliver on all of these needs."

However, transferring the power is the important part of the solution.

Witricity, standing for wireless electricity, is a term coined by MIT researchers, to describe the

ability to provide electricity to remote objects without wires. Using self-resonant coils in a

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

times the radius of the coils can be done.

Unlike the conduction-based systems, Witricity uses resonant magnetic fields to reduce wastage

of power. Currently the project is looking for power transmissions in the range of 100 watts.

With wireless energy transfer, the efficiency is a more critical parameter and this creates

important differences from the wireless data transmission technologies. To avoid the conflicts

like recharging and carrying its appliances of electrical and electronic devices, wireless power

transmission is desirable. Wireless power transmission was originally proposed to avoid long

distance electrical distribution based mainly on copper cables. This can be achieved by using

microwave beams and the rectifying antenna, or rectenna, which can receive electromagnetic

radiation and convert it efficiently to DC electricity. Researchers have developed several

techniques for moving electricity over long distances without wires. Some exist only as theories

or prototypes, but others are already in use.

Magnetic resonance was 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

frequencies, on living beings and hence is a leading technology for developing witricity.

CONTENTS

1. INTRODUCTION

2. HISTORY OF WIRELESS POWER TRANSMISSION

2.1. WIRELESS ELECTRICITY OF NOKIA TESLA

2.2. BASIC DESIGN AND IMPLETION OF WPT SYSTEM

3. METHODS USED FOR WPT

3.1. INDUCTION METHOD

3.2. RESONANT INDUCTION

4. MAIN CHELLENGES FOR WPT

4.1. INDUCTION METHOD

4.2. DIRECTED RADIO WAVES

4.3. MICROWAVE METHODS

5. EXISTING WPT SYSTEM

6. HOW IT WORKS?

6.1. HOW WIRELESS ENERGY COULD WORK?

6.2. SHORT RANGE POWER TRANSMISSION AND RECEPTION

7. HOW SAFE IS WPT?

8. FUTURE OF WPT

9. NEED OF WPT

10. DEVELOPMENT MADE SO FAR

11. EXPERIMENTAL RESULT

12. ADVANTAGES

13. DISADVANTAGES

14. APPLICATION

15. CONCLUSION

16. REFERENCES

INTRODUCTION

It encompasses various types of fixed, mobile, and portable two-way radios, cellular telephones, personal digital assistance (PDAs), and wireless networking. Wireless operations permits services, such as long-range communications, that are impossible and impractical in conventional methods. A. Conventional Power System One of the major issue in power system is that the loss occurring during the transmission and allocation of electrical power. As the demand drastically increases day by day, the power generation increases and the power loss is also increased.

The percentage of loss of power during transmission and distribution is approximated as 26%. The main reason for power loss during transmission and distribution is the resistance of wires used for grid. The efficiency of power transmission can be improved to certain level by using high strength composite over head conductors and underground cables that use high temperature super conductor. But, the transmission is still inefficient. According to the World Resources Institute (WRI), India’s electricity grid has the highest transmission and distribution losses in the world i.e. around 27%. Numbers published by various Indian government agencies put that number at 30%, 40% and greater than 40%. This is attributed to technical losses (grid’s inefficiencies) and theft [2]. It is indeed alarming to know the level of losses in Indian electricity and transmission business. These losses not only eat the revenues of the companies but also hinder the financing of future projects, which require huge capital, because of increased risk.

However, it would be worth knowing the categorization of technical and commercial losses that add up to the total losses. The theft comes in the latter category. Majority of theft is happening because the line is open to theft. The pole and the wires are bare and the voltage is at lower level than transmission and thus useful to run the 240 V equipment only. The theft always occurs at 400V and 240V level and not on transmission levels. Not much of energy auditing is done in most of the state utility.

Long low tension (LT) line are being pulled to reach villages under much publicized government schemes. Low tension lines are many times over the High tension lines causing more technical I2R losses. Transformer are running at less than optimal efficiency when infact they should have the efficiency rate close to 99% since they do not have any moving part . After generating power at any power plant, it is necessary to transport the power to the places where it will be used. Currently, this is achieved largely through thick transmission lines, which require a lot of material and tall towers. However, there is an interesting possibility of transmitting electrical energy without these cumbersome structures, by implementing wireless power transmission.

Various methods of wireless energy transfer are being studied that may allow us to transmit large amounts of power over long distances without the need for a conducting connection. Additionally, wireless transmission presents the possibility of sending and receiving power from space, which can have useful applications.

2. HISTORY OF WIRELESS POWER TRANSMISSION

Nikola Tesla he is who invented radio and is referred to as “Father of Wireless”. Nikola Tesla is the one who first conceived the idea Wireless Power Transmission and demonstrated “the transmission of electrical energy without wires" that depends upon electrical conductivity as early as 1891.

In 1893, Tesla demonstrated the illumination of vacuum bulbs without using wires for power transmission at the World Columbian Exposition in Chicago.

The Wardenclyffe tower was designed and constructed by Tesla mainly for wireless transmission of electrical power rather than telegraphy . Warden clyffe Tower, including the partially-complete cupola

The world’s first fuel free airplane powered by microwave energy from ground was reported in 1987 at Canada. This system is called SHARP (Stationary High – Altitude Relay Platform).

A physics research group, led by Prof. Marin Soljacic, at the Massachusetts Institute of technology (MIT) demonstrated wireless powering of a 60W light bulb with 40% efficiency at a 2m (7ft) distance using two 60cm-diameter coils in 2007 .

In 2008, Intel reproduced the MIT group's experiment by wirelessly powering a light bulb with 75% efficiency at a shorter distance.

Imagine a future in which wireless power transfer is feasible: cell phones, household robots, mp3 players, laptop computers and other portable electronics capable of charging themselves without ever being plugged in, freeing us from that final, ubiquitous power wire. Some of these devices might not even need their bulky batteries to operate. A team from MIT's Department of Physics, Department of Electrical Engineering and Computer Science, and Institute for Soldier Nanotechnologies (ISN) has experimentally demonstrated an important step toward accomplishing this vision of the future.

Realizing their recent theoretical prediction, they were able to light a 60W light bulb from a power source seven feet (more than two meters) away; there was no physical connection between the source and the appliance. refers to its concept as "WiTricity" (as in wireless electricity). Sony Corporation in 2009 announced the development of a highly efficient wireless power transfer system that eliminates the use of power cables from electronic products such as television sets. Using this system, up to 60 Watts of electrical energy can be transferred over a distance of 50cm (at an efficiency of approximately 80%, approximately 60% including rectifier) .

This new wireless power transfer system incorporates a form of contactless electrical energy transmission technology based on magnetic resonance. With magnetic resonance, electromagnetic energy is only transferred to recipient devices that share the identical resonant frequencies as the energy source, so energy transfer efficiency is maintained, even when misalignment occurs. Furthermore, even if there are metal objects located between the transmitter and receiver, no heat induction occurs. With the growth in networked products, the number of cables used to connect these products has also increased. While data cables are rapidly being replaced with wireless communication systems such as Wi-Fi, the demand for wireless power transfer systems is also continuing to grow. Sony will proceed with its efforts to develop further technologies that meet customer needs for the wireless transfer of power across a wide range of products, distances and energy levels.

2.1 The Wireless Electricity Of Nikola Tesla

If a single one-megaton nuclear warhead were exploded 300 miles over the center of the country, a high-voltage electromagnetic pulse would in theory disrupt communication and electrical systems all over the continental U.S. Gamma rays emitted by such an explosion would instantly strip away the electrons from air molecules in the upper atmosphere in roughly a circular, pancake-shaped zone. The free electrons would then accelerate radially with the earth's magnetic field, separating from the heavier, positively charged ions and creating a downward directed high-voltage electromagnetic pulse. This in turn results in electrical surges in all exposed conductors on the ground.

When Nikola Tesla discovered alternating current (AC) electricity, he had great difficulty convincing men of his time to believe in it. Thomas Edison was in favor of direct current (DC) electricity and opposed AC electricity strenuously. Tesla eventually sold his rights to his alternating current patents to George Westinghouse for $1,000,000. After paying off his investors, Tesla spent his remaining funds on his other inventions and culminated his efforts in a major breakthrough in 1899 at Colorado Springs by transmitting 100 million volts of high-frequency electric power wirelessly over a distance of 26 miles at which he lit up a bank of 200 light bulbs and ran one electric motor! With this souped up version of his Tesla coil, Tesla claimed that only 5% of the transmitted energy was lost in the process. But broke of funds again, he looked for investors to back his project of broadcasting electric power in almost unlimited amounts to any point on the globe.

The method he would use to produce this wireless power was to employ the earth's own resonance with its specific vibrational frequency to conduct AC electricity via a large electric oscillator. When J.P. Morgan agreed to underwrite Tesla's project, a strange structure was begun and almost completed near Wardenclyffe in Long Island, N.Y. Looking like a huge lattice-like, wooden oil derrick with a mushroom cap, it had a total height of 200 feet. Then suddenly, Morgan withdrew his support to the project in 1906, and eventually the structure was dynamited and brought down in 1917.

A Tesla coil is a special transformer that takes a small amount of power and boosts it rapidly to a great deal of power. The high-frequency output of even a small Tesla coil can light up fluorescent tubes held several feet away without any wire connections. Even a large number of spent or discarded fluorescent tubes (their burned out cathodes are irrelevant) will light up if hung near a long wire running from a Tesla coil while using less than 100 watts drawn by the coil itself when plugged into an electrical outlet! Since the Tesla coil steps up the voltage to such a high degree, the alternating oscillations achieve sufficient excitations within the tubes of gases to produce lighting at a minimal expense of original power! Fluorescent tubes can be held under high-tension wires to produce the same lighting up effect. Remember the farmer a few years ago who was caught with an adaptive transformer under a set of high tension lines that ran over his property? Through the air, he pulled down all the power he needed to run his farm without using any connecting apparatus to the lines overhead! Any electrical engineer with the proper materials can do the same thing.

Incandescent bulbs burn high resistance filaments that gobble up energy. Fluorescent tubes burn filaments (cathodes) to create an electrical flow that sets their internal phosphorus coatings aglow. Using a Tesla coil, high voltage AC can light up glass-enclosed vacuum bulbs coolly without any gases inside them at all! Any number of cold light bulbs can be lit using only one Tesla coil, and since there is nothing inside them to burn out, they can last indefinitely. It seems like a low cost form of street lighting, doesn't it?

When Tesla was determining the resonant frequencies of the earth to potentially transmit unlimited electric power, he also recognized frequencies that acted as a damping field to nullify electric power. With the advent of the wireless and Tesla's unique investigations into broadcasting electricity, a dozen or more inventors thereafter announced their own means for transmitting electrical energy without wires. One British inventor, H. Grindell-Matthews, actually demonstrated his "mystery ray" apparatus in 1924 to a Popular Science Monthly writer in London (See: Pop. Sci. Monthly, Aug. 1924, P. 33). When his beam was directed toward the magneto system of a gasoline engine, it stopped the system. Afterwards, it ignited gun powder, lit an electric lamp bulb from a distance and killed a mouse in seconds! Grindell-Matthews said the secret was involved with the "carrier beam" he used to conduct a high-voltage, low-frequency electrical current.

During 1936, Guglielmo Marconi experimented with extremely low frequency (ELF) waves and displayed their exceptional ability to penetrate metallic shielding. These waves could affect electrical devices, overload circuits and cause machines like generators, electric motors and automobiles to stall. Diesel engines, which do not rely on electrical ignition, were not affected. Mysteriously, Marconi's research on the subject was never found after the war.

Fig.1 Tesla tower

2.2 BASIC DESIGN AND IMPLEMENTATION OF WIRELESS TRANSMISSION SYSTEM William C. Brown, the pioneer in wireless power transmission technology, has designed, developed a unit and demonstrated to show how power can be transferred through free space by microwaves. The concept of Wireless Power Transmission System is explained with functional block diagram as shown in figure 3. In the transmission side, the microwave power source generates microwave power and the output power is controlled by electronic control circuits. The wave guide ferrite circulator which protects the microwave source from reflected power is connected with the microwave power source through the Coax – Waveguide Adaptor. The tuner matches the impedance between the transmitting antenna and the microwave source. The attenuated signals will be then separated based on the direction of signal propagation by Directional Coupler. The transmitting antenna radiates the power uniformly through free space to the rectenna. In the receiving side, a rectenna receives the transmitted power and converts the microwave power into DC power. The impedance matching circuit and filter is provided to setting the output impedance of a signal source equal to the rectifying circuit. The rectifying

circuit consists of Schottky barrier diodes converts the received microwave power into DC power. The Primary components of Wireless Power Transmission are Microwave Generator, Transmitting antenna and Receiving antenna (Rectenna). Flow and components of Wireless power System The key for the present world is to save energy and related recourses in the organizations and as well as at home. Energy costs account for a huge portion of most companies operating expenses, so monitoring, controlling and conserving a building's lighting, heating and cooling, and other energy-hungry systems can lead to substantial savings. Several energy management vendors report that customers have shrunk their power bills by at least 30 percent. Saving energy also means lowering your carbon footprint, which could help reduce carbon taxes and promote a green image, another plus for business. The figure shows a typical energy wireless light controller device.

Fig:1.2 Basic components of Witricity system

As shown in Fig. 1.2, the witricity system consists of two resonators (labelled as “Source” and

“Device”), a driving loop, and an output loop. The source resonator is coupled inductively with

the driving loop which is linked to an oscillator to obtain the energy for the system. Similarly,

the device resonator is coupled inductively with the output loop to supply power to an external

load. As discussed in over a greater distance, the conventional non-resonant magnetic induction

method (such as those used in transformers) is inefficient to transmit energy because of the rapid

decrease in magnetic coupling between the primary and secondary coil.

In the witricity design, strongly coupled magnetic resonance is utilized, which increases the

transfer efficiency dramatically by "tunnelling" the magnetic fields from the source resonator to

the device resonator, provided that both resonators have the same resonant frequency. Due to this

tunnelling effect, the distance of transmission can be extended significantly The physical

principle of operation is that, if two resonators are in the midrange as defined previously, their

near fields (evanescent waves) will strongly couple each other, allowing the total energy to

concentrate on a specific resonant frequency.

This “tuned” form of energy travels between the two resonators in an oscillatory fashion, rather

than mono directional as observed in traditional systems. The respond time of the oscillatory

energy transfer is designed to be much shorter than the time constant of system losses. Since the

resonant wavelength is much larger than the diameter of the resonators, the coupling magnetic

fields can effectively circumvent extraneous non-resonant objects in the path of energy transfer.

Therefore, this midrange energy-transfer scheme does not impose the “line of- sight” condition,

which is highly desirable in many practical applications. Under the same energy transmitted from

a distance, the witricity system can be more safely implemented than electromagnetic energy

transfer systems because the witricity system can be designed to use the magnetic field in energy

transfer and this type of field interacts weakly with living organisms.

3. METHODS USED FOR WIRELESS POWER TRANSMISSION

3.1. INDUCTION (INDUCTIVE COUPLING)

This is the first method used for wireless power transfer. The simplest example for wireless

energy transfer using this method is the electrical transformer. in this electrically isolated from

each other. The transfer of energy takes place by electromagnetic coupling through mutual

induction. The main draw back of this method is the short range. For efficient working of a

system which uses this method, the receiver must be in very close proximity to the transmitter.

A larger, stronger field can be used for energy transfer over low distance, but this process is

extremely inefficient. Since magnetic field spreads in all direction, making a large wastage of

energy.

Fig.1.3 Two idealized resonant magnetic coil

3.2. RESONANT INDUCTION

In this a curved coils of wire uses as an inductor. A capacitance plate which can hold a charge

attaches to each end of the coil. As electricity travels through this coil the coil begins to resonate.

Its resonant frequency is a product of the inductance of the coil and the capacitance of the plate.

Unlike multiple layer secondary of non resonant transformer single layer solenoids with closely

spaced capacitor plates on each end as shown in figure 1 is used as transmitter and receiver.

Fig.1.4 Curved coil and capacitive plate

Non-radiative energy transfer, introduces a concept called “resonance” to

the wireless energy equation. Similar to mutual induction, wherein electricity

traveling along an electromagnetic wave moves between coils on the same frequency, EWC

functions on the concept that if you make both coils resonate at the same frequency, electricity

can be passed between them at farther distances and without health dangers. According to this

theory, one can even send electricity to multiple devices at once, as long as they all share the

same resonance frequency. While this technology is yet to come to market, in 2007, researchers

at MIT published a detailed report describing a working prototype they had built which powered

a light bulb from two meters away.

Fig.1.5 resonant induction recharging

4. Main Challenges For Wireless Electricity

4.1 Induction methods: The electrodynamic induction wireless transmission technique is near

field over distances up to about one-sixth of the wavelength used. Near field energy itself is non-

radiative but some radiative losses do occur. In addition there are usually resistive losses. With

electrodynamic induction, electric current flowing through a primary coil creates a magnetic

field that acts on a secondary coil producing a current within it. Coupling must be tight in order

to achieve high efficiency. As the distance from the primary is increased, more and more of the

magnetic field misses the secondary. Even over a relatively short range the inductive coupling is

grossly inefficient, wasting much of the transmitted energy.

4.2 Directed radio waves: Power transmission via radio waves can be made more directional,

allowing longer distance power beaming, with shorter wavelengths of electromagnetic radiation,

typically in the microwave range. A rectenna may be used efficiencies exceeding 95% have been

realized. Power beaming using microwaves has been proposed for the transmission of energy

from orbiting solar power satellites to Earth and the beaming of power to spacecraft leaving orbit

has been considered.

4.3 Microwave methods: In the case of electromagnetic radiation closer to visible region of

spectrum (10s of microns (um) to 10s of nm), power can be transmitted by converting electricity

into a laser beam that is then pointed at a solar cell receiver. This mechanism is generally known

as "power beaming" because the power is beamed at a receiver that can convert it to usable

electrical energy.

5. Existing Wireless Electricity System

5.1 First Experiment of Witricity

The first experiment of historicity, the concept of wireless electricity, was conducted in the year

2006, by researchers from Massachusetts Institute of Technology. The Assistant Professor of this

team of researchers was Marin Soljacic.

This experiment was done using two copper coils of diameter two feet, a transmitter that was

attached to a power source and a receiver that was placed about seven feet from the transmitter.

This receiver was attached to a light bulb and once power was switched on at the transmitter, the

bulb lit up despite there being no physical connection between the transmitter and receiver.

The MIT researchers have been able to power a 60 watt light bulb from a power source that is

located about seven feet away, while providing forty percent efficiency. This was made possible

using two copper coils that were twenty inches in diameter which were designed so that they

resonated together in the MHz range. One of these coils were connected to a power source while

the other, to a bulb. With this witricity setup, the bulb got powered even when the coils were not

in sight.

Data collected through measurements showed that there was transference of 40% of electricity

through witricity. The interesting part of the electricity was that the bulb glowed despite the fact

that wood, metal and other devices were placed in between the two coils.

This concept of witricity was made possible using resonance where an object vibrates with the

application of a certain frequency of energy. So two objects having similar resonance tend to

exchange energy without causing any effects on the surrounding objects. Just like in acoustic

resonance, where there is a chance of a glass breaking if you strike the right tone, witricity is

made possible with the resonance of low frequency electromagnetic waves.

In this experiment, the coils were resonated at 10 MHz where the cols coupled and energy made

to flow between them. With each cycle, more pressure and voltage built up in the coil till the

accumulation of voltage provided enough pressure and energy to flow to the light bulb. These

low frequency electromagnetic waves are rather safe as though the body responds strongly to

electric fields; it has almost zero response to absorbing power from a magnetic field.

Fig1.6 power a 60 watt light bulb from a power source

The main objective of this research is to achieve resilience by adding two new, real time data

mining-based layers to complement the two existing non-data mining layers. These new layers

will improve detection of fraudulent applications because the detection system can detect more

types of attacks, better account for changing legal behaviour, and remove the redundant

attributes.

These new layers are not human resource intensive. They represent patterns in a score where the

higher the score for an application, the higher the suspicion of fraud (or anomaly). In this way,

only the highest scores require human intervention. These two new layers do not use external

databases, but only the credit application database. And crucially, these two layers are

unsupervised algorithms which are not completely dependent on known frauds but use them only

for evaluation.

The main contribution of this paper is the demonstration of resilience, with adaptivity and quality

data in real-time data mining-based detection algorithms. The second contribution is the

significant extension of knowledge in credit application fraud detection because publications in

this area are rare. In addition, this research uses the key ideas from other related domains to

design the credit application fraud detection algorithms. Finally, the last contribution is the

recommendation of credit application fraud detection as one of the many solutions to identity

crime. Being at the first stage of the credit life cycle, credit application fraud detection also

prevents some credit transactional fraud.

6.HOW IT WORKS-

Wireless light: Researchers used magnetic resonance coupling to power a 60-watt light bulb. Tuned to the same frequency, two 60-centimeter copper coils can transmit electricity over 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 meters apart.When they plugged one coil into the wall, alternating current flowed through it, Creating a magnetic field. The second coil, tuned to the same frequency and hooked to a light bulb, resonated with the magnetic field, generating an electric current that lit up the bulb--even with a thin wall between the coils.

6.1 How wireless energy could work-

"Resonance", a phenomenon that causes an object to vibrate when energy of a certain frequency is applied. Two resonant objects of the same frequency tend to couple very strongly." Resonance can be seen in musical instruments for example. "When you play a tune on one, then another instrument with the same acoustic resonance will pick up that tune, it will visibly vibrate," Instead of using acoustic vibrations, system exploits the resonance of electromagnetic waves. Electromagnetic radiation includes radio waves, infrared and X-rays. Typically, systems that use electromagnetic radiation, such as radio antennas, are not suitable for the efficient transfer of energy because they scatter energy in all directions, wasting large amounts of it into free space.

To overcome this problem, the team investigated a special class of "non-radiative" objects with so-called "long-lived resonances". When energy is applied to these objects it remains bound to them, rather than escaping to space. "Tails" of energy, which can be many metres long, flicker over the surface. If another resonant object is brought with the same frequency close enough to these tails then it turns out that the energy can tunnel from one object to another.

Fig.1.7 witricity power source

Hence, 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. Any energy not diverted into a gadget or appliance is simply reabsorbed. The systems that are described would be able to transfer energy over three to five metres. This would work in a room let's say but can be adapted to work in a factory. It could also be scaled down to the microscopic or nanoscopic world.

HOW WIRELESS POWER COULD WORK

Power from mains to antenna, which is made of copper Antenna resonates at a frequency of 6.4MHz, emitting electromagnetic waves. 'Tails' of energy from antenna 'tunnel' up to 5m (16.4ft) Electricity picked up by laptop's antenna, which must also be resonating at 6.4MHz. Energy used to re-charge device.

6.2 Short range power transmission and reception –

Power supply for portable electronic devices is considered, which receives ambient radio frequency radiation (typically in an urban environment) and converts it to DC electricity that is stored in a battery for use by the portable device.

Fig.1.7 Transmission and receiving coil

A Power transmission unit (PTU) is connected 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 take the form of visible light, microwave radiation, near infrared radiation or any appropriate frequency or frequencies, depending on the technology chosen. The beam can be focused and shaped using a focusing mechanism: for example, a parabola shape may be chosen to focus light waves at a certain distance from the PTU.

A Power reception unit (PRU) receives power from one or several PTU's, and converts the total power received to electricity, which is used to trickle charge a storage unit such as a battery or transferred directly to the appliance for use, or both. If transferred to the storage unit, the output of the storage unit can power the appliance. Similarly to the focusing of the transmitted power, it is possible to concentrate the received power for conversion, using receiving arrays, antennas, reflectors or similar means.

Fig .1.8 transmitter and receiver

It is possible to construct power "relay units", consisting of PRU's powering PTU's, whose function is to make the transmitted power available at further distances than would normally be possible. Long-distance Wireless Power-Some plans for wireless power involve moving electricity over a span of miles. A few proposals even involve sending power to the Earth from space. The Stationary High Altitude Relay Platform (SHARP) unmanned plane could run off power beamed from the Earth. The secret to the SHARP's long flight time was a large, ground-based microwave transmitter. A large, disc-shaped rectifying antenna, or rectenna, near the system changed the microwave energy from the transmitter into direct-current (DC) electricity. Because 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 have positive and negative poles. These antennae connect to semiconductor diodes. Here's what happens: 1. Microwaves, which are part of the electromagnetic spectrum, reach the dipole antennae. 2. The antennae collect the microwave energy and transmit it to the diodes. 3. The diodes act like switches that are open or closed as well as turnstiles that let electrons flow in only one direction. They direct the electrons to the rectenna's circuitry. 4. The circuitry routes the electrons to the parts and systems that need them. .

5. How Safe is WiTricity?

Human beings or other objects placed between the transmitter and receiver do not hinder

the transmission of power. However, does magnetic coupling or resonance coupling have any

harmful effects on humans?

MIT's researchers are quite confident that WiTricity's 'coupling resonance' is safe for

humans. They say that the 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.

6. The Future of WiTricity

MIT's WiTricity is only 40 to 45% efficient and according to Soljacic, 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 of a laptop working, charging devices placed anywhere in the room and even

robots on factory floors. The researchers are also currently working on the health issues

related to this concept and have said that in another three to five years time, they will

come up with a WiTricity system for commercial use.

WiTricity, if successful will definitely change the way we live. Imagine cellphones, 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!

7. NEED OF WITRICITY

Now a days there is a Rapid development of autonomous electronics like Laptops, Cell-phones,

House-hold robots and all those 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.

Fig 1.9 No need of plug in

10. Developments Made So Far

As witricity is in the developmental stage, lots of work is still to be done in improving it as it is

disclosed that witricity power applications operate at only 40% efficiency. However, Intel

reproduced the MIT group's experiment by wirelessly powering a light bulb with 75% efficiency

at a shorter distance.

Just as beneficial witricity may be, there are some contraindications to the concept, with debates

if it is risky living next to power lines and having a low power witricity network running in the

home. They wonder what happens if a glass of water is spilt in a witricity room. This has also

been achieved.It is realized that instead of irradiating the environment with electromagnetic

waves, a power transmitter could fill the space around it with a "non-radiative" electromagnetic

field. Essentially, energy would only be picked up by gadgets specified to "resonate" with the

frequency.

However despite these contraindications, witricity has a bright future with the many advantages

it provides in terms of weight, convenience and portability of electrical appliances.

11.EXPERIMENTAL RESULT

Fig.1.10 shows an experimental 7 MHz witricity system on a workbench. Wireless energy fully

illuminated the LED. When we misaligned the axes of source and device resonators, the power

was still be transmitted efficiently as shown in Fig.4b. This phenomenon differs from that of the

conventional magnetic induction methods. In order to evaluate system performance

quantitatively, we replaced the LED with a resistor whose resistance approximates the

impedance of the output terminals at resonance. Utilizing a diode-based RF detector, we

measured the RF energy at the input terminals of the driving loop and the energy at the load

terminals of the output loop.

Fig 1.10 (a) Measured transmission efficiency vs. distances of separation

Fig 1.11 witricity system at 7 MHz (a) alignment setup (b) inalignment setup

Then the power transfer efficiencies with and without misalignment are measured and plotted in

Fig. It can be seen that, the efficiency without misalignment can reach approximately 80 % at a

15- cm separation between the transmitter and receiver. It can also be seen that certain

misalignments (e.g. 5 cm) between transmitter and receiver cause only a slight drop in

efficiency. This tolerance in misalignment is highly desirable in practical applications since, for

example, it allows energy to be transmitted to a moving target or multiple locations . As [2, 3],

we also arrived at the same conclusion that the uninterruptible line of- sight between the

transmitter and receiver is unnecessary in the witricity system. Also in [9], we reported a relay

effect of witricity, which allows a much longer effective transmission distance with one or more

relay resonator between source and device resonators.

12. ADVANTAGES OF WITRICITY

No need of line of sight — In witricity power transmission there is any need of line of sight

between transmitter and receiver. That is power transmission can be possible if there is any

obstructions like wood, metal, or other devices were placed in between the transmitter and

receiver.

No need of power cables and batteries — Witricity replaces the use of power cables and

batteries.

Does not interfere with radio waves.

Wastage of power is small - Electromagnetic waves would tunnel, they would riot propagate

through air to be absorbed or dissipated. So the wastage is small.

Negative health implications — By the use of resonant coupling wave lengths produced are far

lower and thus make it harmless.

.Highly efficient than electromagnetic induction - Electro magnetic induction system can be

used for wireless energy transfer only if the primary and secondary are in very close proximity.

Resonant induction system is one million times as efficient as electro magnetic induction system.

Less costly - The components of transmitter and receivers are cheaper. So this system is less

costly

13. DISADVANAGES

1. Wireless power transmission can be possible only in few meters.

2. Efficiency is only about 40 %, as witricity is in development stage; lot of work is done

for improving the efficiency and distance between transmitter and receiver.

3. Capital Cost for practical implementation of WPT to be very high.

4. The other disadvantage of the concept is interference of microwave with present communication systems.

5. Common belief fears the effect of microwave radiation.

6. Need for standardization and adaptation. So no overheating occurs because of different

voltages. Retrofitting old equipment or purchasing new equipment could become a very

expensive and behaviour possibility of “energy theft”. Wi Fi, someone can be using your

internet or your power.

14. APPLICATIONS

1. Witricity has a bright future in providing wireless electricity. There are no limitations in

witiricity power applications. Some of the potential applications are powering of cell phones,

laptops and other devices that normally run with the help of batteries or plugging in wires.

Witricity applications are expected to work on the gadgets that are in close proximity to a source

of wireless power, where in the gadgets charges automatically without necessarily having to get

plugged in.

2. By the use of witricity there is no need of batteries or remembering recharge batteries

periodically. If a source is placed in each room to provide power supply to the whole house,

Witricity has many medical applications. It is used for providing electric power in many

commercially available medical implantable devices. Another application of this technology

includes transmission of information. It would not interfere with radio waves and it is cheap and

efficient.

3. It provides magnetic induction charging of car.

Fig.1.12 Magnetic induction charging of car

4. for charging of mobile without using wires.

5. Generating power by placing satellites with giant solar arrays in Geosynchronous Earth Orbit and transmitting the power as microwaves to the earth known as Solar Power Satellites (SPS) is the largest application of WPT.

6. Less cost for cabling infrastructure and device

7. Moving targets such as fuel free airplanes, fuel free electric vehicles, moving robots and fuel free rockets. The other applications of WPT are Ubiquitous Power Source (or) Wireless Power Source, Wireless sensors and RF Power Adaptive Rectifying Circuits (PARC).

8. Mobility - user device can be moved easily within the wireless range. 4. Neat and easy Installation - since no cable running here and there, just start up the wireless device and you're ready to rumble.

9. More user supported - cable device have limited slots Whereas wireless does not.

15. CONCLUSION

The concepts of Microwave Power transmission (MPT), Wireless Power Transmission history

and basic implementation of Power System are discussed elaborately. Technological

developments in Wireless Power Transmission (WPT), the merits, demerits, applications of WPT

are also discussed in this paper. By this we are able to know the greater possibilities for

transmitting power with negligible losses and ease of transmission in the years to come. It is

envisaged that wireless energy would be really accomplished with an advantage of easy

implementation and cost effective i.e., cost of transmission and distribution overhead would

become less and moreover it is important that the cost of electrical energy to the consumer would

also be reduced compared to existing systems.

 Witricity is in development stage, lots of work is to be done to use it for wireless power

applications. Currently the project is looking for power transmission in the range of 100w.

Before the establishment of this technology the detailed study must be done to check whether it

cause any harm on any living beings

16. REFERENCES

[1] http://en.wikipedia.org/wiki/Microwave_transmission.

[2] Nikola Tesla, My Inventions, Ben Johnston, Ed., Austin, Hart Brothers, p. 91,1982.

[3] Nikola Tesla, “The Transmission of Electrical Energy Without Wires as a Means for

Furthering Peace,” Electrical World and Engineer. Jan. 7, p. 21, 1905

[4] HISTORY OF WIRELESS Tapan K. Sarkar Robert J. Mailloux Arthur A. Oliner Magdalena

Salazar-Palma Dipak L. Sengupta.

[5] J.J. Schelesak, A. Alden and T. Ohno, A microwave powered high altitude platform, IEEE

MTT-S Int. Symp. Digest, pp - 283- 286, 1988