50182295 wireless electricity

8/12/2019 50182295 Wireless Electricity

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A SEMINAR REPORT ON

WIRELESS ELECTRICITY (WiTricity)

Submitted for the requirement of award of Bachelors Degree in

Electrical Engineering

Submitted by:-

Mr. PRIYABRATA SAHOO

Electrical Engineering

Roll No.-26231

Regn No.-0701105103

7TH

SEMESTER,B.TECHUnder the guidance of :Prof. Pravat Ku. Ray

Professor, Department of Electrical Engineering,

INDIRA GANDHI INSTITUTE OF TECHNOLOGY, SARANG

DHENKANAL,ODISHA-759146


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CERTIFICATE

This is to certify that Mr. Priyabrata Sahoo of 4th

year,7th

semester, Bachelor in Technology ,ElectricalEngineering, Roll No.-26231,Registration No.-

0701105103 has completed the seminar entitled

WIRELESS ELECTRICITY or WiTricity for partial

fulfilment of requirement of B.Tech 4th

year 7th

semester of BPUT examination, Odisha for the academic

year 2010-2011.

Name of the guide- Prof. Pravat Ku.Ray

Signature of guide:

Date:

Signature:

Head of the Department

Prof. (Dr.) Bibhu Prasad Panigrahi

Date-


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ACKNOWLEDGEMENT

I express my sincere gratitude to my concerned teacher

and guideProf. Pravat Ku. Ray, Professor, Department

of Electrical Engineering, for his valuable and inspiring

guidance towards the progress on the topic WIRELESS

ELECTRICITY or WiTricity and providing valuable

information for the development of my report.

Last but not the least I express my sincere and hearty

thanks to all those who have directly or indirectly

helped me in completing this seminar presentation and

report successfully.

Date:

Place-IGIT,SARANG Priyabrata Sahoo


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CONTENTS1.INTRODUCTION

2. WHY DO WE GO FOR WIRELESS POWER

TRANSMISSION (WPT) SYSTEM

2.1-Losses in the wired system

2.2-Some advantages of WPT

3. HISTORY OF WPT

4. THEORIES ON WPT

4.1 Near field theory4.1.1-Electrical conduction principle

4.1.2-Electrostatic induction principle

4.1.3-Electro-dynamic induction resonant inductive

coupling method/Evanescent coupling method )

4.1.4-Experimental demonstration of evanescentcoupling at MIT

4.2 Far field theory4.2.1Microwave Power Transmission (MPT)

4.2.2-Applications

4.2.3- Safety issues

5. How WPT technology works

6. OVERVIEW OF FUTURE WITH WIRELESS

TRANSMISSION OF ELECTRICITY

7. CONCLUSION


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1. INTRODUCTION

Today we do live in the wireless age, in which the air that we breathe probablycontains more information than oxygen. However, this is also an age where mobilephones, MP3 players, laptop computers and domestic robots exist alongside old-fashioned power wires and bulky batteries. Unlike information, electrical energy is stillphysically confined to these borderline anachronistic appliances. Overcoming these lastobstacles would finally make this a truly wireless world. It all started a few years agowhen Marin Soljacìc, a physicist at the Massachusetts Institute of Technology(MIT) inthe US, was driving back home one cold winter night and he heard an unfriendly beepfrom his mobile phone. It was the annoying reminder that the battery was running out,once again. It then suddenly occurred to Soljacìchow great it would be if the mobilephone could take care of its own charging. The next morning, he returned to his office atthe MIT determined to find a solution to the problem. An exhaustive literature Today wedo live in the wireless age, in which the air that we breathe probably contains moreinformation than oxygen. However, this is also an age where mobile phones, MP3players, laptop computers and domestic robots exist alongside old-fashioned powerwires and bulky batteries. Unlike information, electrical energy is still physically confinedto these borderline anachronistic appliances. Overcoming these last obstacles wouldfinally make this a truly wireless world. It all started a few years ago when MarinSoljacìc, a physicist at the Massachusetts Institute of Technology(MIT) in the US, wasdriving back home one cold winter night and he heard an unfriendly beep from hismobile phone. It was the annoying reminder that the battery was running out, onceagain. It then suddenly occurred to Soljacìchow great it would be if the mobile phonecould take care of its own charging. The next morning, he returned to his office at theMIT determined to find a solution to the problem. An exhaustive literature Today we dolive in the wireless age, in which the air that we breathe probably contains moreinformation than oxygen. However, this is also an age where mobile phones, MP3players, laptop computers and domestic robots exist alongside old-fashioned powerwires and bulky batteries. Unlike information, electrical energy is still physically confinedto these borderline anachronistic appliances. Overcoming these last obstacles would


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finally make this a truly wireless world. It all started a few years ago when Marin In thenear future, wireless electricity could replace the ubiquitous power cable.2. WHY DO WE GO FOR WIRELESS POWER TRANSMISSION

(WPT)SYSTEM?

2.1-LOSSES IN THE WIRED SYSTEM

Professor Rauscher showed that the earths magnetosphere contains sufficientpotential energy (at least 3 billion kilowatts) so that the resonant excitation of the earth-ionosphere cavity can reasonably be expected to increase the amplitude of naturalSchumannfrequencies, facilitating the capture of useful electrical power. Tesla alsoknew that the earth could be treated as one big spherical conductor and the ionosphereas another bigger spherical conductor, so that together they have parallel plates andthus, comprise a spherical capacitor.Dr. Rauscher calculates the capacitance to beabout 15,000 microfarads for the complete earth-ionosphere cavity capacitor. W.O.Schumann is credited for predicting the self-oscillationsof the conducting sphere ofthe earth, surrounded by an air layer and an ionosphere in 1952, without knowing thatTesla had found the earths fundamental frequency fifty years earlier.In comparison tothe 3 billion kW available from the earth system, it is possible to calculatewhatProfessor Rauscher showed that the earths magnetosphere contains sufficientpotential energy (at least 3 billion kilowatts) so that the resonant excitation of the earth-ionosphere cavity can reasonably be expected to increase the amplitude of naturalSchumannfrequencies, facilitating the capture of useful electrical power. Tesla alsoknew that the earth could be treated as one big spherical conductor and the ionosphereas another bigger spherical conductor, so that together they have parallel plates andthu2/3 is totally wasted in conversion losses.(Ref.Electricity Flow Chart 1999, whichcontains US DOE/EIA data, updating the Toby Grotz article in this book.) No otherenergy production system of any kind in the world has so much wastefulness. Instead oftrying to build 2 power plants per week (at 300 MW each) for the next 20 years (only tohave a total of additional 6 trillion kWh available by 2020), as some U.S. governmentofficials want to do, we simply need to eliminate the 7trillion kWh of conversion lossesin our present electricity generation modality. Teslas wireless transmission of power


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accomplishes this goal, better than any distributed generation.

Fig-1(losses in the wired system)

2.2-Some advantages of WPT3. HISTORY OF WPT


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Fig-2 (wardencliffe tower)4. THEORIES ON WPT4.1-Near field theoryNear field is wireless transmission techniques over distances comparable to, or a fewtimes the diameter of the device(s), and up to around a quarter of the wavelengthsused. Near field energy itself is non radiative, but some radiative losses will occur. Inaddition there are usually resistive losses. Near field transfer is usually magnetic(inductive), but electric (capacitive) energy transfer can also occur.4.1.1-Electrical conduction principleElectrical energy can be transmitted by means of electrical currents made to flowthrough naturally existing conductors, specifically the earth, lakes and oceans, and


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through the upper atmosphere starting at approximately 35,000feet (11,000m)elevation a natural medium that can be made conducting if the is exceeded and theconstituent gas becomes . For example, when a high voltage is applied across a thegas becomes ionized and a current passes between the two internal . In a wirelessenergy transmission system using this principle, a high-power ultraviolet beam might beused to form vertical ionized channels in the air directly above the transmitter-receiverstations. The same concept is used in virtual , the and has been proposed for disablingvehicles. A global system for the transmission of electrical energy without wiresdependant upon the high electrical conductivity of the earth was proposed by as earlyas 1904.The earth is 4,000 miles radius. Around this conducting earth is an atmosphere. Theearth is a conductor; the atmosphere above is a conductor, only there is a little stratumbetween the conducting atmosphere and the conducting earth which is insulating. . . .Now, you realize right away that if you set up differences of potential at one point, say,you will create in the media corresponding fluctuations of potential. But, since thedistance from the earths surface to the conducting atmosphere is minute, as comparedwith the distance of the receiver at 4,000 miles, say, you can readily see that the energycannot travel along this curve and get there, but will be immediately transformed intoconduction currents, and these currents will travel like currents over a wire with a return.The energy will be recovered in the circuit, not by a beam that passes along this curveand is reflected and absorbed, . . . but it will travel by conduction and will be recoveredin this way.Researchers experimenting with Teslas wireless energy transmission system designhave made observations that may be inconsistent with a basic tenet of physics relatedto the scalar derivatives of the electromagnetic potentials, which are presentlyconsidered to be nonphysical. The intention of the Tesla world wireless energytransmission system is to combine electrical power transmission along withbroadcasting and point-to-point wireless telecommunications, and allow for theelimination of many existing high-tension power transmission lines, facilitating theinterconnection of electrical generation plants on a global scale. One of Teslas patents


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suggests he may have misinterpreted 2570km nodal structures associated with cloud-ground lightning observations made during the 1899 Colorado Springs experiments interms of circum globally propagating standing waves instead of a local interferencephenomenon of direct and reflected waves. Regarding the recent notion of powertransmission through the earth-ionosphere cavity, a consideration of the earth-ionosphere or concentric spherical shell waveguide propagation parameters as they areknown today shows that wireless energy transfer by directexcitation of a Schumanncavity resonance mode is not realizable. The conceptual difficulty with this model isthat, at the very low frequencies that Tesla said that he employed (1-50 kHz), earth-ionosphere waveguide excitation, now well understood, would seem to be impossiblewith the either the Colorado Springs or the Long Island apparatus (at least with theapparatus that is visible in the photographs of these facilities).

Fig-3 (Tesla coil transformer wound in the form of a flat spiral. This is the transmitter

form as described in )On the other hand, Teslas concept of a global wireless electrical power transmissiongrid and telecommunications network based upon energy transmission by means of a


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spherical conductor transmission line with an upper three-space model return circuit,while apparently not practical for power transmission, is feasible, defying no law ofphysics. Global wireless energy transmission by means of a spherical conductorsingle-wiresurface wave transmission line and a propagating TM00mode may also bepossible, a feasibility study using a sufficiently powerful and properly tuned Tesla coilearth-resonance transmitter being called for.

induction principle non resonant energy transfer)The action of an electrical is the simplest instance of wireless energy transfer. Theprimary and secondary circuits of a transformer are not directly connected. The transferof energy takes place by electromagnetic coupling through a process known as . (Anadded benefit is the capability to step the primary voltage either up or down.) The sof aor the on the street is examples of how this principle can be used. and many are alsopowered by this technique. The main drawback to induction, however, is the shortrange. The receiver must be very close to the transmitter or induction unit in order toinductively couple with it.4.1.2- Electrostatic induction principle

Fig-4(Tesla illuminating two exhausted tubes by means of a powerful, rapidly alternating

electrostatic field created between two vertical metal sheets suspended from the ceiling oninsulating cords.)The electrostatic induction effectorcapacitive couplingis an electric field gradientor between two elevated electrodes over a conducting ground plane for wirelessenergy transmission involving high frequency alternating current potential differencestransmitted between two plates or nodes. The electrostatic forces through natural media


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across a conductor situated in the changing magnetic flux can transfer energy to areceiving device (such as Teslas wireless bulbs).Sometimes called the Tesla effectitis the application of a type of electrical displacement, i.e., the passage of electricalenergy through space and matter, other than and in addition to the development of apotential across a conductor.Tesla stated,Instead of depending on [electrodynamic] induction at a distance to light the tube . . .[the] ideal way of lighting a hall or room would . . . be to produce such a condition in itthat an illuminating device could be moved and put anywhere, and that it is lighted, nomatter where it is put and without being electrically connected to anything. I have beenable to produce such a condition by creating in the room a powerful, rapidly alternatingelectrostatic field. For this purpose I suspend a sheet of metal a distance from theceiling on insulating cords and connect it to one terminal of the induction coil, the otherterminal being preferably connected to the ground. Or else I suspend two sheets . . .each sheet being connected with one of the terminals of the coil, and their size beingcarefully determined. An exhausted tube may then be carried in the hand anywherebetween the sheets or placed anywhere, even a certain distance beyond them; itremains always luminous.andIn some cases when small amounts of energy are required the high elevation of theterminals, and more particularly of the receiving-terminal D may not be necessary,since, especially when the frequency of the currents is very high, a sufficient amount ofenergy may be collected at that terminal by electrostatic induction from the upper airstrata, which are rendered conducting by the active terminal of the transmitter orthrough which the currents from the same are conveyed.4.1.3- Electro-dynamic induction Resonant inductive couplingmethod/Evanescent coupling method)An inductive transformer is a device commonly used in power circuits andelectromechanical motors (for example electrical toothbrushes and chargers). Atransformer typically operates up to mid-kHz frequencies. It essentially transferselectrical energy from one circuit to another via induction: the time-varying magnetic flux


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produced by a primary coil crosses a secondary coil and induces in it a voltage. Theprimary and the secondary coils are not physically connected, hence the method iswireless. Transformers can be very efficient but the distance between the coils must bevery small (typically a few millimetres). For distances a few times the size of the coils,the efficiency drops significantly. Part of the underlying physics for most of the existingmethods for the wireless transfer of electricity is the fundamental principle of resonance:the property of certain physical systems to oscillate with maximum amplitudes at certainfrequencies. It follows that, for any type of excitation (mechanical, acousticAn inductivetransformer is a device commonly used in power circuits and electromechanical motors(for example electrical toothbrushes and chargers). A transformer typically operates upto mid-kHz frequencies. It essentially transfers electrical energy from one circuit toanother via induction: the time-varying magnetic flux produced by a primary coil crossesa secondary coil and induces in it a voltage. The primary and the secondary coils arenot physically connected, hence the method is wireless. Transformers can be veryefficient but the distance between the coils must be very small (typically a fewmillimetres). For distances a few times the size of the coils, the efficiency dropssignificantly. Part of the underlying physics for most of the existing methods for thewireless transfer of electricity is the fundamental principle of resonance: the property ofcertain physical systems to oscillate with maximum amplitudes at certain frequencies. Itfollows that, f4.1.4-Experimental demonstration of evanescent coupling at MITRadiative modes of omni-directional antennas (which work very well for informationtransfer) are not suitable for such energy transfer, because a vast majority of energy iswasted into free space. Transmitting electricity within a room, namely over distances afew times greater than the size of the receiving devices themselves (what engineersdefine as mid-range distances), is a challenge for most modern applications. Achievingthis goal with satisfactory efficiency, safety and low cost remains an unsolved problem.That was the challenge for Soljac`ic and his collaborators at the MIT labs: JohnJoannopoulos, Peter Fisher, Andre Kurs, Robert Moffatt . The energy of any resonatornaturally decays due to intrinsic energy-loss mechanisms (friction for mechanicalresonances, radiation and resistive absorption for electromagnetic resonances,


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collisions with phonons and spontaneous emission for atomic resonances). Losses aretypically quantified by the number of oscillation periods that it takes for the energy todecay by a factor of 2.72. This number, represented by the quality factorQ, is anintrinsic property of resonators and depends on the strength of the loss mechanisms.(As a simple analogue, water inside a bucket with a hole will leak out at a rate thatdepends on the size of the hole.) If two equal resonators exchange energy, it also takesa characteristic number of oscillation periods to transfer the energy from resonator A toresonator B, which is proportional to a constant that quantifies the strength of thecoupling between the resonators, Qk. (If water is pumped from one bucket to anothervia a hose, then the transfer time depends on the strength of the pump.) Clearly, forenergy transfer to be efficient, Qneeds to be much larger than Qk, i.e. the rate at whichenergy is being transferred needs to far exceed the rate at which energy is being lost.(Water will be efficiently transferred between two leaking buckets if the pump is fasterthen the leaks from the holes.) The efficiency of the system can then be characterizedby Q/Qk. Thetransfer of energy is efficient only when this ratio is larger than one, the so-calledstrong-coupling regime. For our wireless method, they used one of the most basicelectric circuits as a resonator: the LC circuit. This circuit is an electromagnetic resonantcircuit that consists of an inductor (L), made by a wire coil, and a capacitor (C). Twosuch wire coils transfer energy via induction, like a transformer device, and the Qkclearly depends on the distance between the coils. For mid-range distances and longenough wavelengths, the spatial-decay rate of the magnetic field means that Qk isroughly proportional to the cube of the ratio of the distance between the coils, D, andthe size of each coil, d, while showing little dependency on the frequency and thegeometry of the coils. This means that, for mid-range distances, Qk will be large and thecoupling very weak. As a result, the best way to maximize the efficiency is to engineerthe resonators to have the highest possible value of Q(try to seal the holes in thebuckets). The resonance frequency of each coil (which has to be the same for bothcoils) can be tuned by varying the capacitance (and tuning a circuit element is exactlywhat the knob is tuning in a radio antenna). Qvaries with the tuneable frequency, and


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this variation is shown in the figure above for a coil with a diameter of 60 cm made ofcopper pipe with a radius of 2 cm. It can be seen that, for high-MHz frequencies, theresonator loses energy fast (low Q, often even less than 10) due to radiation. This isexactly how an antenna is designed to work. Similarly, for mid-kHz frequencies, it losesenergy fast (Q less than 100) via resistive absorption, which is typical of transformers.This explains why both omni-directional antennas and transformers fail to be efficientpower transmitters at mid-range distances: the transfer-time measure Qk is largebecause of D, and Q is small. On the other hand, in the intermediate, low-MHz regime,much longer loss-times are observed, with Q often larger than 1000. That was theirchosen regime.

Fig-5 ( ligtening a 60 watt bulb around 2m away from the source at MIT)Based on their theory, they started experiments in late 2006. The main challengesconsisted of designing a driving circuit that would operate in our desired low-MHzregime and constructing coils that would resonate with a high enough value of Q. Aftera trial-and-error phase, they realized that a simple coil design without a separatecapacitor, but using the coils self-capacitance to achieve resonance, was the bestoption in terms of Q. We made two copper-pipe coils with 60 cm diameters and with five

turns, such that they resonate at 10MHz and have Q=1000. A 60 W light bulb was thechosen device, since it operates at the tested frequencies (and what can be a clearersign of the functionality of a system than the switch on of a light bulb?). They


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suspended the coils from the ceiling with fishing wire, at a distance of 2m from eachother, tuned them up, turned them on andthere was light. At an efficiency of 45%, thiswas, to our knowledge, the first-ever demonstration of midrange efficient wirelessenergy transfer.4.2- Far field theorymethods achieve longer ranges, often multiple kilometer ranges, where the distance is

much greater than the diameter of the device(s). With radio wave and optical devicesthe main reason for longer ranges is the fact that electromagnetic radiation in the canbe made to match the shape of the receiving area (using high antennas or well-collimated Laser ) thereby delivering almost all emitted power at long ranges. Themaximum directivity for antennas is physically limited by .The Raytheon Company didthe first successful WPT experiment in 1963. In this experiment energy was transmittedwith a DC-to-DC efficiency of 13%. This company also demonstrated a microwave-powered helicopter in 1964 [2]. The Jet propulsion lab of NASA carried out anexperiment and demonstrated the transfer of 30 kW over a distance of 1 mile in 1975.They used an antenna array erected at the Goldstone facility. This test demonstratedthe possibilities of wireless power outside the laboratory. Rockwell International andDavid Sarnoff Lab methods achieve longer ranges, often multiple kilometer ranges,where the distance is much greater than the diameter of the device(s4.2.1Microwave Power Transmission MPT)In order to transport electricity is has to be transformed into a suitable energy form. Forwireless transmission, this has to be a form that can travel trough air. Microwavefrequencies hold this ability. The microwave spectrum is defined as electromagneticenergy ranging from approximately 1 GHz to 1000 GHz in frequency, but older usageincludes lower frequencies. Most common applications are within the 1 to 40 GHzrange. A complete microwave transmission system consists of three essential parts:


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Fig-6(Microwave transmit ter and rectenna)The components include a microwave source, a transmitting antenna and a receivingantenna. The microwave source consists of an electron tubes or solid-state devices withelectronics to control power output. The slotted waveguide antenna, parabolic dish andmicrostrip patch are the most popular types. Due to high efficiency (>95%) and highpower handling capacity, the slotted waveguide antenna seems to be the best option forpower transmission. The combination of receiving and converting unit is calledrectenna. The rectenna is a rectifying antenna that is used to directly convert microwaveenergy into DC electricity. It is an antenna includes a mesh of dipoles and diodes forabsorbing microwave energy from a transmitter and converting it into electric power. Itselements are usually arranged in a multi element phased array with a mesh patternreflector element to make it directional. One of the disadvantages is that microwaveshave long wavelengths that exhibit a moderate amount of diffraction over longdistances. The Rayleigh criterion dictates that any beam will spread (microwave orlaser), become weaker, and diffuse over distance. The larger the transmitter antenna orlaser aperture, the tighter the beam and the less it will spread as a function of distance(and vice versa). Therefore, the system requires large transmitters and receivers. Theused power density of the microwave beam is normally in de order of 100 W/m2. This isrelative low compared to the power density of solar radiation on earth (1000 W/m 2) andchosen this way for safety reasons.4.2.2-Applications


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The largest application for microwave power transmission is space solar powersatellites (SPS). In this application, solar power is captured in space and converted intoelectricity. The electricity is converted into microwaves and transmitted to the earth. Themicrowave power will be captured with antennas and converted into electricity. NASA isstill investigating the possibilities of SPS. One of the problems is the high investmentcost due to the space transport. The current rates on the Space Shuttle run between

7,000 and 11,000 per kilogram of transported material. Recently the idea of SpaceSolar Power caught again the public attention e.g. by the Obama transition team andThe Economist.

Fig-7 ( Space Solar Pow er satel l i te)Power transfer, bridging applications

Using a powerful focused beam in the microwave or laser range long distances can becovered. There are two methods of wireless power transmission for bridging application.First is the direct method, from transmitting array to rectenna. A line of sight is neededand is therefore limited to short (< 40 km) distances. Above 40 kilometers, hugestructures are needed to compensate for the curvature of the earth. The secondmethod is via a relay reflector between the transmitter and rectenna. This reflectorneeds to be at an altitude that is visible for both transmitter and rectenna. Next onebridging applications of WPT are discussed.

Alaska 21WPT can be an option for power supply to rural areas. In 1993 was a project presentedabout wireless power supply in Alaska. Because of limited infrastructure, hundreds of


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small rural communities in Alaska must provide their own electricity. These systems canbe expensive not standard or just not available. At the moment, the small communitiesproduce their own power with mainly diesel engines. These produce noise andpollution. Also the needed fuel has to be transported over long distances. All this resultsin an electricity price in excess of 40/kWh [14].Cable connections trough water is nooption because of ice. With the help of WPT, the needed power production of thecommunities can be combined. This can reduce noise, pollution and transportation offuel.WPT may be capable of transmitting electrical energy to Alaska s remote villages.To investigate these possibilities, a pilot project was conducted named Alaska21.The system used for the pilot project consisted of a2.45 GHz phased array design. Thedistances that should be bridged are between 1 and 15 miles. The status of the projectis unknown.

FIG-8(Alaska21)4.2.3- Safety issuesA general public perception that microwaves are harmful has been a major obstacle forthe acceptance of power transmission with microwaves. A major concern is that thelong-term exposure to low levels of microwaves might be unsafe and even could causecancer. Since 1950, there have been thousands of papers published about microwavebio-effects. The scientific research indicates that heating of humans exposed to the


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radiation is the only known effect. There are also many claims of low-level non thermaleffects, but most of these are difficult to replicate or show unsatisfying uncertainties.Large robust effects only occur well above exposure limits existing anywhere in theworld . The corresponding exposure limits listed in IEEE standards at 2.45 or 5.8 GHzare 81.6 W/m2 and 100 W/m2 averaged over 6 minutes, and 16.3 or 38.7 W/m2averaged over 30 minutes . This low compared to average solar radiation of 1000W/m2. A clearly relevant bio-effect is the effect of microwave radiation on birds, the so-called frieA general public perception that microwaves are harmful has been a majorobstacle for the acceptance of power transmission with microwaves. A major concern isthat the long-term exposure to low levels of microwaves might be unsafe and evencould cause cancer. Since 1950, there have been thousands of papers published aboutmicrowave bio-effects. The scientific research indicates that heating of humansexposed to the radiation is the only

Fig-9(graph showing safety level to different range of fre.)Further discussions about the maximum microwave power density are necessary. Arange of issues and safety-related factors should continue to receive considerationbecause of public concern about radio wave and micro wave exposure.

It is assumed that WPT systems working with microwaves use frequency bands around2.45 GHz or 5.8 GHz. These bands are already allocated in the ITU-R radio regulation


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to a number of radio services. They are also designated for industrial science andmedical (ISM applications). The ISM band is, as presently defined, for local use only.The 2.45 GHz is further more used for radio LAN and microwave ovens. The 5.8 GHz isalso used heavily for various applications like Radiolocation service and DSRC(Dedicated Short-Range Communications). More investigation is needed to get animage of the possible influencing between the systems .5. How WPT technology works

A copper coil attached to a power source is the sending unit. Another coil, attached tothe device to be induced is the receiver which makes it possible for energy to betransferred from one to the other. There are particular advantage on effective distance,maximum power transfer, control level and efficiency for each approach. We designedto make use of an advantageous position respectively and started to construct a simple,safe and efficient Wireless Charging Pad.

Fig-10(block diagram showing transmitter module and receiver module)Our design are the combination of both technologies which not only transfer powerthrough wireless by electromagnetic induction, but also contain self-resonance at theside of transmitter and receiver independently in order to achieve better efficiency andhence reduce the power loss.One Plug, One Pad, Various devices; whole system only consists of a transmitter anda receiver. The transmitter is a platform where powers by a one plug that is transmitted


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to the devices. It can simultaneously power wide variety of devices which their receivermodule is placed around the protuberance of the pads surface. The devices areelectrically charged as if they are plugged into a conventional adapter, irrespective oftheir position or orientation. The receiver, differently, is integrated into electronic devicessuch as mobile phones or PDA and allows an electronic device to receive charge fromthe transmitter. Consequently, electrical current creates magnetic fields and vice versa.This technology takes advantage of the fact that magnetic fields can travel through freespace. Electrical current in the base station creates a magnetic field that wirelesslycarries the power to the receiver where it is converted back to electrical current. Thiscoupling provides a secure charging condition because it One Plug, One Pad, Variousdevices; whole system only consist6. OVERVIEW OF FUTURE WITH WIRELESS

TRANSMISSION OF ELECTRICITY

As Tesla himself said,In the near future we shall see a great many uses of electricitywe shall be able todisperse fogs by electric force and powerful and penetrative rayswireless plants willbe installed for the purpose of illuminating the oceanspicture transmission by ordinarytelegraphic methods will soon be achievedanother valuable novelty will be atypewriter electrically operated by the human voicewe shall have smoke annihilators,dust absorbers, sterilizers of water, air, food and clothingit will become next toimpossible to contract disease germs and country folk will go to town to rest and getwell7. CONCLUSION

This technology is a big impediment to development in the retail sector right now. The wireless transfer of electricity has been a sci-fi dream up to this point ,and

truly, if electricity could simply be in the air, in the same way radio waves and wi-fi signals are, it would change the world.

8.REFERENCES


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1) Tesla, N. Apparatus for transmitting electrical energy. U.S. patent number1,119,732, issued in December 1914.2) Fernandez, J. M. and Borras, J. A. Contactless battery charger with wireless controllink.U.S. patent number 6,184,651, issued in February 2001.3) Ka-Lai, L., Hay, J. W. and Beart, P. G. W. Contact-less power transfer.U.S. patentnumber 7,042,196, issued in May 2006. (SplashPower Ltd., www.splashpower.com)4) Esser, A. and Skudelny, H.-C. A new approach to power supplies for robots.IEEETrans. on industry applications 27, 872 (1991).5) Hirai, J., Kim, T.-W. and Kawamura, A. Wireless transmission of power andinformation and information for cableless linear motor drive.IEEE Trans. on powerelectronics 15, 21 (2000).6) Scheible, G., Smailus, B., Klaus, M., Garrels, K. and Heinemann, L. System forwirelessly supplying a large number of actuators of a machine with electrical power.U.S. patent number 6,597,076, issued in July 2003. (ABB, )7) H. Feingold et al., Space Solar Power: A Fresh Look at the Feasibility of GeneratingSolar Power in Space for Use on Earth April 4, 1997, SAIC Report 97/1005 for contractNAS326565.8) Space Solar Power: Advanced Concepts Study Project, Technical InterchangeMeeting, Sept. 1920 1995 NASA Headquarters, Washington DC.9) G. Landis, A Supersynchronous Solar Power Satellite,SPS-97: Space and E lectricPower for Hum anity, Aug. 2428, 1997, Montreal, Canada, pp. 327328.10) G. Landis, An Evolutionary Path to SPS,Space Power Vol. 9 No. 4, pp. 365371(1990).11) G. Landis and R. Cull, Application of Thin Film Technology Toward a Low-MassSolar Power Satellite,Vision-21 Symposium Proceedings NASA CP10059, April1990, pp. 494500.12) G. Landis and R. Cull, Integrated Solar Power Satellites: An Approach to Low-Mass Space Power,Space Power Vol. 11 No. 34, 303218 (1992); presented atSPS-91: Power From Space , Aug. 2730, 1991, Paris France, pp. 22523213) www.witricity.com


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50182295 wireless electricity

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