WiTricity - Wireless Transmission of Electricity

Pawan Kumar (Electronics Instrum

In this era of modernization, electricity has become the unavoidable partThe major source of conventional form of electricity is through wires. The continuous research and development has brought forward a major breakthrough, which provides electricity withoutwonder is called WiTricity. There are certain small but very useful discoveries made in history, which changed the world forever, Newton’s gravitational law, Watt’s steam engine, Thomson’s bulb and many more. But a renaissance occurred with the invention of Electromagnetic Waves by Maxwell. Sir Jagdish Chandra Bose successfully generated electromagnetic waves having wavelength in of 5mm to 25 mm. Thereafter an Italian scientist named Marconi succeeded in transmitting electromagnetic waves up to a distance of several miles.

And with this there started a new era called WIRELESS TECHNOLOGY. Today, as we can see the word ‘wireless’ is common in day Wireless communication has made the world smaller. Almost each and everything is wireless or cordless. Cordless mouse, cordless keyboard, satellite communication, mobiles, cordless microphones and headphones, wireless internet service i.e. WIFI, etc. And these have definitely increased the standard of living. In fact it dates back to the 19th century, when Nikola Tesla used conduction based systems instead of resonance magnetic fields to transfer wireless power. As it is in Radiative mode, most of the Power was wasted and has less efficiency.Further, in 2005, Dave Gerding coined the term WiTricity which is being used by the MIT researchers today. Moreover, we all are aware of the use of electromagnetic radiation (radio waves) which is quite well known for wireless transfer of information. In addition, lasers have also been used to transmit energy without wires.However, radio waves are not feasible for power transmissions because the nature of the radiation is such that it spreads across the place, resulting into a large amount of radiations being wasted. And in t

s Instrumentation & Control Engg.)

IINNTTRROODDUUCCTTIIOONN

n, electricity has become the unavoidable partThe major source of conventional form of electricity is through wires. The

research and development has brought forward a major breakthrough, which provides electricity without the medium of wires. This

There are certain small but very useful discoveries made in history, which r, Newton’s gravitational law, Watt’s steam engine,

Thomson’s bulb and many more. But a renaissance occurred with the invention of Electromagnetic Waves by Maxwell. Sir Jagdish Chandra Bose successfully generated electromagnetic waves having wavelength in of 5mm to 25 mm. Thereafter an Italian scientist named Marconi succeeded in transmitting electromagnetic waves up to a distance of several miles.

And with this there started a new era called WIRELESS TECHNOLOGY. Today, as we can see the

‘wireless’ is common in day – to – day life. Wireless communication has made the world smaller. Almost each and everything is wireless or cordless. Cordless mouse, cordless keyboard, satellite communication, mobiles, cordless microphones and

reless internet service i.e. WIFI, etc. And these have definitely increased the standard of

fact it dates back to the 19th century, when Nikola Tesla used conduction based systems instead of resonance magnetic fields to transfer wireless power. As it is in Radiative mode, most of the Power was wasted and has less efficiency.

e Gerding coined the term used by the MIT researchers

Moreover, we all are aware of the use of electromagnetic radiation (radio waves) which is quite well known for wireless transfer of information. In addition,

also been used to transmit energy without wires. However, radio waves are not feasible for power transmissions because the nature of the radiation is such that it spreads across the place, resulting into a large amount of radiations being wasted. And in the case of lasers, apart from

Nikola Tesla was the firstto experimentwireless electricity, butultimately failed afterlosing his key financialbacking in the late 1800's.

Page 1

n, electricity has become the unavoidable part of life. The major source of conventional form of electricity is through wires. The

research and development has brought forward a major the medium of wires. This

There are certain small but very useful discoveries made in history, which r, Newton’s gravitational law, Watt’s steam engine,

Thomson’s bulb and many more. But a renaissance occurred with the invention of Electromagnetic Waves by Maxwell. Sir Jagdish Chandra Bose successfully generated electromagnetic waves having wavelength in the range of 5mm to 25 mm. Thereafter an Italian scientist named Marconi succeeded in transmitting electromagnetic waves up to a distance of several miles.

Moreover, we all are aware of the use of electromagnetic radiation (radio waves) which is quite well known for wireless transfer of information. In addition,

However, radio waves are not feasible for power transmissions because the nature of the radiation is such that it spreads across the place, resulting into a

he case of lasers, apart from

Nikola Tesla was the first experiment with

wireless electricity, but ultimately failed after losing his key financial backing in the late

Pawan Kumar (Electronics Instrumentation & Control Engg.) Page 2

requirement of uninterrupted line of sight (obstacles hinder the transmission process). It is also very dangerous. WiTricity is nothing but wireless electricity. Transmission of electrical energy from one object to another without the use of wires is called as WiTricity. WiTricity ensures that the cell phones, laptops, iPods and other power hungry devices get charged on their own, eliminating the need of plugging them in. Even better, because of WiTricity some of the devices won't require batteries to operate.

WWiiTTrriicciittyy TTeecchhnnoollooggyy :: TThhee BBaassiiccss

WiTricity is a portmanteau for ‘wireless electricity’. Transmission of electrical

energy from one object to another without the use of wires is called as

WiTricity.

EElleeccttrriicciittyy: The flow of electrons (current)

through a conductor (like a wire), or charges through the atmosphere (like lightning). A convenient way for energy to get from one place to another!

MMaaggnneettiissmm: A fundamental force of nature, which

causes certain types of materials to attract or repel each other. Permanent magnets, like the ones on your refrigerator and the earth’s magnetic field, are examples of objects having constant magnetic fields. Oscillating magnetic fields vary with time, and can be generated by alternating current (AC) flowing on a wire. The strength, direction, and extent of magnetic fields are often represented and visualized by drawings of the magnetic field lines.

EElleeccttrroommaaggnneettiissmm: A term for the

interdependence of time-varying electric and magnetic fields. For example, it turns out that an oscillating magnetic field produces an electric field and an oscillating electric field produces a magnetic field.

An illustration representing

the earth's magnetic field.

As electric current, I, flows

in a wire, it gives rise to a magnetic field, B, which wraps around the wire. When the current reverses direction, the magnetic field also reverses its direction.


MMaaggnneettiicc IInndduuccttiioonn: A loop or coil of conductive

material like copper, carrying an alternating current (AC), is a very efficient structure for generating or capturing a magnetic field. If a conductive loop is connected to an AC power source, it will generate an oscillating magnetic field in the vicinity of the loop. A second conducting loop, brought close enough to the first, may “capture” some portion of that oscillating magnetic field, which in turn, generates or induces an electric current in the second coil. The current generated in the second coil may be used to power devices. This type of electrical power transfer from one loop or coil to another is well known and referred to as magnetic induction. Some common examples of devices based on magnetic induction are electric transformers and electric generators.

EEnneerrggyy//PPoowweerr CCoouupplliinngg: Energy

coupling occurs when an energy source has a means of transferring energy to another object. One simple example is a locomotive pulling a train car – the mechanical coupling between the two enables the locomotive to pull the train, and overcome the forces of friction and inertia that keep the train still – and, the train moves. Magnetic coupling occurs when the magnetic field of one object interacts with a second object and induces an electric current in or on that object. In this way, electric energy can be transferred from a power source to a powered device. In contrast to the example of mechanical coupling given for the train, magnetic coupling does not require any physical contact between the object generating the energy and the object receiving or capturing that energy.

The blue lines represent the

magnetic field that is created when current flows through a coil. When the current reverses direction, the magnetic field also reverses its direction.

An electric transformer is a device that uses magnetic induction to transfer energy from its primary winding to its secondary winding, without the windings being connected to each other. It is used to “transform” AC current at one voltage to AC current at a different voltage.


RReessoonnaannccee: Resonance is a property that exists in many different physical

systems. It can be thought of as the natural frequency at which energy can most efficiently be added to an oscillating system. A playground swing is an example of an oscillating system involving potential energy and kinetic energy. The child swings back and forth at a rate that is determined by the length of the swing. The child can make the swing go higher if she properly coordinates her arm and leg action with the motion of the swing. The swing is oscillating at its resonant frequency and the simple movements of the child efficiently transfer energy to the system. Another example of resonance is the way in which a singer can shatter a wine glass by singing a single loud, clear note. In this example, the wine glass is the resonant oscillating system. Sound waves traveling through the air are captured by the glass, and the sound energy is converted to mechanical vibrations of the glass itself. When the singer hits the note that matches the resonant frequency of the glass, the glass absorbs energy, begins vibrating, and can eventually even shatter. The resonant frequency of the glass depends on the size, shape, thickness of the glass, and how much wine is in it.

RReessoonnaanntt MMaaggnneettiicc CCoouupplliinngg: Magnetic coupling occurs when two objects exchange energy through their varying or oscillating magnetic fields. Resonant coupling occurs when the natural frequencies of the two objects are approximately the same.

WWiiTTrriicciittyy TTeecchhnnoollooggyy: WiTricity

power sources and capture devices are specially designed magnetic resonators that efficiently transfer power over large distances via the magnetic near-field. These proprietary source and device designs and the electronic systems that control them support efficient energy transfer over distances that are many times the size of the sources/devices themselves.

Two idealized resonant magnetic coils,

shown in yellow. The blue and red color bands illustrate their magnetic fields. The coupling of their respective magnetic fields is indicated by the connection of the color bands.

The WiTricity power source, left, is connected to AC power. The

blue lines represent the magnetic near field induced by the power source. The yellow lines represent the flow of energy from the source to the WiTricity capture coil, which is shown powering a light bulb. Note that this diagram also shows how the magnetic field (blue lines) can wrap around a conductive obstacle between the power source and the capture device.


EElleeccttrroo--mmaaggnneettiicc IInndduuccttiioonn: Christian Oersted’s discovery of magnetic field around a current carrying conductor was quite accidental. If a flow of electric current can produce a magnetic field then why can't a magnetic field produce an electric current? An attempt to find an answer to this lead Michel Faraday to the invention of generators. You know that the conversion between electrical and mechanical energy is the principle behind the working of generators and electric motors. They play an important role in reducing the work load and in enhancing the facilities in our life. Hence this chapter is important in familiarizing the parts and working principle of the devices such as generator, electric motor, transformer, microphone, loud speaker etc.

BBAASSIICC CCOONNCCEEPPTT

Make a solenoid having a large number of closely wound turns of insulated copper wire. Connect its ends to the terminals of a galvanometer. Bring the coil swiftly to one pole of a magnet. Observe the deflection in the galvanometer. What happens when the coil is suddenly taken off? Keeping the coil at rest bring one end of a magnet swiftly to the coil and then take it back at the same speed. Note down in your science diary the direction of deflections in the galvanometer. The needle deflects to opposite directions in the two different situations and suddenly comes back to the initial position.

We know that the magnetic flux lines have a basic property of magnetism. What happens to the magnetic flux lines when a magnet is moved into a solenoid or when a solenoid moves in the vicinity of a magnet?

In the above situations a temporary electric current was generated either because the flux lines were cut by the moving coil or the flux lines linked with the coil were changed. The process of inducing an emf in a conductor whenever the magnetic flux linked with it changes, is known as electromagnetic induction.

When a solenoid swiftly moves in a

strong magnetic field, the galvanometer needle deflects indicating the flow of a current.

A solenoid when brought in vicinity of

magnet (magnetic field), current flows.


The emf so developed is called induced emf and the current so obtained is called induced current.

If magnet is stationary, no current is produced.

If magnet is moving in, current is produced.

If magnet is moving out, current is produced in opposite direction.

If the poles of the magnet are reversed, current changes direction.

i.e. on summarizing..

When there is a changing magnetic field around a conductor (the coil of

wire), a current is induced in the conductor.

The amount of current induced is related to the strength of the

magnetic field and the rate at which the field changes.

SSOOMMEE MMOORREE FFAACCTTSS

While Oersted's surprising discovery of electromagnetism paved the way for more practical applications of electricity, it was Michael Faraday who gave us the key to the practical generation of electricity: electromagnetic induction. Faraday discovered that a voltage would be generated across a length of wire if that wire was exposed to a perpendicular magnetic field flux of changing intensity.

An easy way to create a magnetic field of changing intensity is to move a permanent magnet next to a wire or coil of wire. Remember: the magnetic field must increase or decrease in intensity perpendicular to the wire (so that the lines of flux "cut across" the conductor), or else no voltage will be induced:


Faraday was able to mathematically relate the rate of change of the magnetic field flux with induced voltage (note the use of a lowerThis refers to instantaneousrather than a steady, stable voltage.):

The "d" terms are standard calculus notation, representing rateflux over time. "N" stands for the number of turns, or wraps, in the wire coil (assuming that the wire is formed in the shape of a coil for maximelectromagnetic efficiency).

This phenomenon is put into obvious practical use in the construction of electrical generators, which use mechanical power to move a magnetic field past coils of wire to generate voltage. However, this is by no means the only practical use for this principle.

If we recall that the magnetic field produced by a currentalways perpendicular to that wire, and that the flux intensity of that magnetic field varied with the amount of current through it, we can see that capable of inducing a voltage current through it. This effect is called field produced by changes in current through a wire inducing voltage along the length of that same wire. If the magnetic field flux is enhanced by bending the wire into the shape of a coil, and/or wrapping that coil around a material of high permeability, this effect of selfdevice constructed to take adva

A magnetic field of changing intensity perpendicular to a wire will induce a voltage along the length of that wire. The amount of voltage induced depends on the rate of change of the magnetic field flux and the (if coiled) exposed to the change in flux.e = N(dΦ/dt)

A current-carrying wire will experience an induced voltage along its length if the current changes (thus changing the magnetic field flux perpendicular to the wire, thus inducing voltage according to Faraday's formula). A device built specifically to take advantage of this effect is called an


Faraday was able to mathematically relate the rate of change of the magnetic field flux with induced voltage (note the use of a lower-case letter "e" for voltage.

instantaneous voltage, or voltage at a specific point in time, teady, stable voltage.):

The "d" terms are standard calculus notation, representing rateflux over time. "N" stands for the number of turns, or wraps, in the wire coil (assuming that the wire is formed in the shape of a coil for maxim

ctromagnetic efficiency).

This phenomenon is put into obvious practical use in the construction of electrical generators, which use mechanical power to move a magnetic field past coils of wire to generate voltage. However, this is by no means the only

tical use for this principle.

If we recall that the magnetic field produced by a current-carrying wire was always perpendicular to that wire, and that the flux intensity of that magnetic field varied with the amount of current through it, we can see that capable of inducing a voltage along its own length simply due to a change in current through it. This effect is called self-induction: a changing magnetic field produced by changes in current through a wire inducing voltage along the

at same wire. If the magnetic field flux is enhanced by bending the wire into the shape of a coil, and/or wrapping that coil around a material of high permeability, this effect of self-induced voltage will be more intense. A device constructed to take advantage of this effect is called an inductor

A magnetic field of changing intensity perpendicular to a wire will induce a voltage along the length of that wire. The amount of voltage induced depends on the rate of change of the magnetic field flux and the number of turns of wire (if coiled) exposed to the change in flux. Faraday's equation for induced voltage:

carrying wire will experience an induced voltage along its length if the current changes (thus changing the magnetic field flux perpendicular to the wire, thus inducing voltage according to Faraday's formula). A device built

advantage of this effect is called an inductor

Page 7

Faraday was able to mathematically relate the rate of change of the magnetic case letter "e" for voltage.

voltage, or voltage at a specific point in time,

The "d" terms are standard calculus notation, representing rate-of-change of flux over time. "N" stands for the number of turns, or wraps, in the wire coil (assuming that the wire is formed in the shape of a coil for maximum

This phenomenon is put into obvious practical use in the construction of electrical generators, which use mechanical power to move a magnetic field past coils of wire to generate voltage. However, this is by no means the only

carrying wire was always perpendicular to that wire, and that the flux intensity of that magnetic field varied with the amount of current through it, we can see that a wire is

simply due to a change in a changing magnetic

field produced by changes in current through a wire inducing voltage along the at same wire. If the magnetic field flux is enhanced by bending the

wire into the shape of a coil, and/or wrapping that coil around a material of induced voltage will be more intense. A

inductor.

A magnetic field of changing intensity perpendicular to a wire will induce a voltage along the length of that wire. The amount of voltage induced depends

number of turns of wire Faraday's equation for induced voltage:

carrying wire will experience an induced voltage along its length if the current changes (thus changing the magnetic field flux perpendicular to the wire, thus inducing voltage according to Faraday's formula). A device built


RReessoonnaannccee:

In physics, resonance is the tendency of a system (usually a linear system) to oscillate at larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies (or resonance frequencies). At these frequencies, even small periodic driving forces can produce large amplitude oscillations.

Resonances occur when a system is able to store and easily transfer energy between two or more different storage modes (such as kinetic energy and potential energy in the case of a pendulum). However, there are some losses from cycle to cycle, called damping. When damping is small, the resonant frequency is approximately equal to a natural frequency of the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies.

Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, acoustic resonance, electromagnetic resonance, nuclear magnetic resonance (NMR), electron spin resonance (ESR) and resonance of quantum wave functions. Resonant systems can be used to generate vibrations of a specific frequency (e.g. musical instruments), or pick out specific frequencies from a complex vibration containing many frequencies.

Resonance was discovered by Galileo Galilei with his investigations of pendulums and musical strings beginning in 1602.

TThheeoorryy:

The exact response of a resonance, especially for frequencies far from the resonant frequency, depends on the details of the physical system, and is usually not exactly symmetric about the resonant frequency, as illustrated for the simple harmonic oscillator above. For a lightly damped linear oscillator with a resonant frequency Ω, the intensity of oscillations I when the system is driven with a driving frequency ω is typically approximated by a formula that is symmetric about the resonant frequency:

The intensity is defined as the square of the amplitude of the oscillations. This is a Lorentzian function, and this response is found in many physical situations involving resonant systems. Γ is a parameter dependent on the damping of the oscillator, and is known as the linewidth of the resonance.


Heavily damped oscillators tend to have broad linewidths, and respond to a wider range of driving frequencies around the resonant frequency. The linewidth is inversely proportional to the Q factor, which is a measure of the sharpness of the resonance.

In electrical engineering, this approximate symmetric response is known as the universal resonance curve, a concept introduced by Frederick E. Terman in 1932 to simplify the approximate analysis of radio circuits with a range of center frequencies and Q values.

RReessoonnaattoorrss:

A physical system can have as many resonance frequencies as it has degrees of freedom; each degree of freedom can vibrate as a harmonic oscillator. Systems with one degree of freedom, such as a mass on a spring, pendulums, balance wheels, and LC tuned circuits have one resonance frequency. Systems with two degrees of freedom, such as coupled pendulums and resonant transformers can have two resonance frequencies. As the number of coupled harmonic oscillators grows, the time it takes to transfer energy from one to the next becomes significant. The vibrations in them begin to travel through the coupled harmonic oscillators in waves, from one oscillator to the next.

Extended objects that experience resonance due to vibrations inside them are called resonators, such as organ pipes, vibrating strings, quartz crystals, microwave cavities, and laser rods. Since these can be viewed as being made of millions of coupled moving parts (such as atoms), they can have millions of resonance frequencies. The vibrations inside them travel as waves, at an approximately constant velocity, bouncing back and forth between the sides of the resonator. If the distance between the sides is , the length of a round trip is . In order to cause resonance, the phase of a sinusoidal wave after a round trip has to be equal to the initial phase, so the waves will reinforce. So the condition for resonance in a resonator is that the round trip distance, , be equal to an integer number of wavelengths of the wave:

If the velocity of a wave is , the frequency is so the resonance frequencies are:

So the resonance frequencies of resonators, called normal modes, are equally spaced multiples of a lowest frequency called the fundamental frequency. The multiples are often called overtones. There may be several such series of resonance frequencies, corresponding to different modes of vibration.


QQ--ffaaccttoorr:

The quality factor or Q factor is a dimensionless parameter that describes how damped an oscillator or resonator is, or equivalently, characterizes a resonator's bandwidth relative to its centre frequency. Higher Q indicates a lower rate of energy loss relative to the stored energy of the oscillator; the oscillations die out more slowly. A pendulum suspended from a high-quality bearing, oscillating in air, has a high Q, while a pendulum immersed in oil has a low one. Oscillators with high quality factors have low damping so that they ring longer.

Sinusoidally driven resonators having higher Q factors resonate with greater amplitudes (at the resonant frequency) but have a smaller range of frequencies around that frequency for which they resonate; the range of frequencies for which the oscillator resonates is called the bandwidth. Thus, a high Q tuned circuit in a radio receiver would be more difficult to tune, but would have more selectivity; it would do a better job of filtering out signals from other stations that lie nearby on the spectrum. High Q oscillators oscillate with a smaller range of frequencies and are more stable.

The quality factor of oscillators varies substantially from system to system. Systems for which damping is important (such as dampers keeping a door from slamming shut) have Q = ½. Clocks, lasers, and other resonating systems that need either strong resonance or high frequency stability need high quality factors. Tuning forks have quality factors around Q = 1000. The quality factor of atomic clocks and some high-Q lasers can reach as high as 1011 and higher.

There are many alternate quantities used by physicists and engineers to describe how damped an oscillator is and that are closely related to the quality factor. Important examples include: the damping ratio, relative bandwidth, linewidth and bandwidth measured in octaves.

Examples of resonance:

Mechanical and acoustic resonance Electrical resonance Optical resonance Orbital resonance Atomic, particle, and molecular resonance Failure of the original Tacoma Narrows Bridge Resonance causing a vibration on the International Space Station


EElleeccttrriiccaall RReessoonnaannccee:

Electrical resonance occurs in an electric circuit at a particular resonance frequency when the impedance between the input and output of the circuit is at a minimum (or when the transfer function is at a maximum). Often this happens when the impedance between the input and output of the circuit is almost zero and when the transfer function is close to one.

Resonant circuits exhibit ringing and can generate higher voltages and currents than are fed into them. They are widely used in wireless transmission for both transmission and reception.

RReessoonnaannccee wwiitthh CCaappaacciittoorrss aanndd IInndduuccttoorrss:

Resonance of a circuit involving capacitors and inductors occurs because the collapsing magnetic field of the inductor generates an electric current in its windings that charges the capacitor, and then the discharging capacitor provides an electric current that builds the magnetic field in the inductor, and the process is repeated continually. An analogy is a mechanical pendulum. In some cases, resonance occurs when the inductive reactance and the capacitive reactance of the circuit are of equal magnitude, causing electrical energy to oscillate between the magnetic field of the inductor and the electric field of the capacitor.

At resonance, the series impedance of the two elements is at a minimum and the parallel impedance is at maximum. Resonance is used for tuning and filtering, because it occurs at a particular frequency for given values of inductance and capacitance. It can be detrimental to the operation of communications circuits by causing unwanted sustained and transient oscillations that may cause noise, signal distortion, and damage to circuit elements.

Parallel resonance or near-to-resonance circuits can be used to prevent the waste of electrical energy, which would otherwise occur while the inductor built its field or the capacitor charged and discharged. As an example, asynchronous motors waste inductive current while synchronous ones waste capacitive current. The use of the two types in parallel makes the inductor feed the capacitor, and vice versa, maintaining the same resonant current in the circuit, and converting all the current into useful work.


Since the inductive reactance and the capacitive reactance are of equal magnitude, ωL = 1/ωC, so:

where ω = 2πf, in which f is the resonance frequency in hertz, L is the inductance in henries, and C is the capacitance in farads when standard SI units are used.

The quality of the resonance (how long it will ring when excited) is determined by its Q factor, which is a function of resistance

RReessoonnaanntt EEnneerrggyy TTrraannssffeerr:

Resonant energy transfer or resonant inductive coupling is the short-distance wireless transmission of energy between two coils that are highly resonant at the same frequency. The equipment to do this is sometimes called a resonant transformer. While many transformers employ resonance, this type has a high Q and is nearly always air-cored to avoid 'iron' losses. The coils may be present in a single piece of equipment or in separate pieces of equipment.

Resonant transfer works by making a coil ring with an oscillating current. This generates an oscillating magnetic field. Because the coil is highly resonant any energy placed in the coil dies away relatively slowly over very many cycles; but if a second coil is brought near to it, the coil can pick up most of the energy before it is lost, even if it is some distance away.

One of the applications of the resonant transformer is for the CCFL inverter. Another application of the resonant transformer is to couple between stages of a superheterodyne receiver, where the selectivity of the receiver is provided by tuned transformers in the intermediate-frequency amplifiers. Resonant transformers such as the Tesla coil can generate very high voltages without arcing, and are able to provide much higher current than electrostatic high-voltage generation machines such as the Van de Graaff generator.

Resonant energy transfer is the operating principle behind proposed short range wireless electricity systems such as WiTricity and similar systems. These types of systems generate magnetic fields that are unlikely to cause health issues in humans.


RReessoonnaanntt CCoouupplliinngg:

Non resonant coupled inductors, such as transformers, work on the principle of a primary coil generating a magnetic field and a secondary coil subtending as much as possible of that field so that the power passing though the secondary is as similar as possible to that of the primary. This requirement that the field be covered by the secondary results in very short range and usually requires a magnetic core. Over greater distances the non-resonant induction method is highly inefficient and wastes the vast majority of the energy in resistive losses of the primary coil.

Using resonance can help efficiency dramatically. If resonant coupling is used, each coil is capacitively loaded so as to form a tuned LC circuit. If the primary and secondary coils are resonant at a common frequency, it turns out that significant power may be transmitted between the coils over a range of a few times the coil diameters at reasonable efficiency.

EEnneerrggyy TTrraannssffeerr aanndd EEffffiicciieennccyy:

The general principle is that if a given amount of energy is placed into a primary coil which is capacitively loaded, the coil will 'ring', and form an oscillating magnetic field. The energy will transfer back and forth between the magnetic field in the inductor and the electric field across the capacitor at the resonant frequency. This oscillation will die away at a rate determined by the Q factor, mainly due to resistive and radiative losses. However, provided the secondary coil cuts enough of the field that it absorbs more energy than is lost in each cycle of the primary, then most of the energy can still be transferred.

The primary coil forms a series RLC circuit, and the Q factor for such a coil is:

Because the Q factor can be very high, (experimentally around a thousand has been demonstrated with air cored coils) only a small percentage of the field has to be coupled from one coil to the other to achieve high efficiency, even though the field dies quickly with distance from a coil, they can be several diameters apart.


CCoouupplliinngg CCooeeffffiicciieenntt:

The coupling coefficient is the fraction of flux of the primary that cuts the secondary coil, and is a function of geometry of the systemcoefficient is between 0 and 1.

Systems are said to be tightly coupled, loosely coupled, critically coupled or overcoupled. Tight coupling is when the coupling coefficient is around 1 as with conventional transformers. Overcoupling is when the secondary coil is close enough that it tends to collawhen the transfer in the passband is optimal. Loose coupling is when the coils are distant from each other, so that most of the flux misses the secondary, in Tesla coils around 0.2 is used, and at greater dwireless power transmission, it may be lower than 0.01.

PPoowweerr TTrraannssffeerr:

Because the Q can be very high, even when low power is fed into the transmitter coil, a relatively intense field builds up over multiple cycles, which increases the power that can be receivedthe oscillating field than is being fed inta percentage of that.

VVoollttaaggee GGaaiinn:

The voltage gain of resonantly coupled coils is proportional to the square root of the ratio of secondary and primary inductances.

TTrraannssmmiitttteerr CCooiillss aanndd

Unlike the multiple-layer secondary of a nonthis purpose are often single layer improved Q) in parallel with a suitable such as wave-wound.

Colpitts oscillator.


The coupling coefficient is the fraction of flux of the primary that cuts the secondary coil, and is a function of geometry of the system. coefficient is between 0 and 1.

re said to be tightly coupled, loosely coupled, critically coupled or overcoupled. Tight coupling is when the coupling coefficient is around 1 as with conventional transformers. Overcoupling is when the secondary coil is close enough that it tends to collapse the primary's field, and critical coupling is when the transfer in the passband is optimal. Loose coupling is when the coils are distant from each other, so that most of the flux misses the secondary, in Tesla coils around 0.2 is used, and at greater distances, for example for wireless power transmission, it may be lower than 0.01.

can be very high, even when low power is fed into the transmitter coil, a relatively intense field builds up over multiple cycles, which increases the power that can be received—at resonance far more power is in the oscillating field than is being fed into the coil, and the receiver coil receives

The voltage gain of resonantly coupled coils is proportional to the square root of the ratio of secondary and primary inductances.

dd CCiirrccuuiittrryy:

layer secondary of a non-resonant transformer, coils for this purpose are often single layer solenoids (to minimise skin effect

) in parallel with a suitable capacitor, or they may be other shapes

Colpitts oscillator.

Page 14

The coupling coefficient is the fraction of flux of the primary that cuts the . The coupling

re said to be tightly coupled, loosely coupled, critically coupled or overcoupled. Tight coupling is when the coupling coefficient is around 1 as with conventional transformers. Overcoupling is when the secondary coil is close

pse the primary's field, and critical coupling is when the transfer in the passband is optimal. Loose coupling is when the coils are distant from each other, so that most of the flux misses the secondary, in

istances, for example for

can be very high, even when low power is fed into the transmitter coil, a relatively intense field builds up over multiple cycles, which

at resonance far more power is in o the coil, and the receiver coil receives

The voltage gain of resonantly coupled coils is proportional to the square root of

resonant transformer, coils for skin effect and give

, or they may be other shapes


In resonant energy transfer the inductor would be the transmitter coil and

capacitors are used to tune the circuit to a suitable frequency.

To progressively feed energy/power into the primary coil with each cycle, different circuits can be used. One circuit employs a Colpitts oscillator.

In Tesla coils an intermittent breaker system is used to inject an impulsive signal into the coil; the coil then rings and decays.

RReecceeiivveerr CCooiillss aanndd CCiirrccuuiittrryy:

The secondary receiver coils are similar designs to the primary sending coils. Running the secondary at the same resonant frequency as the primary ensures that the secondary has a low impedance at the transmitter's frequency and that the energy is optimally absorbed.

To remove energy from the secondary coil, different methods can be used, the AC can be used directly or rectified and a regulator circuit can be used to generate DC voltage.


HHIISSTTOORRYY

In the late 1800’s and early 1900’s, at the dawn of the electrification of the modern world, some scientists and engineers believed that using wires to transfer electricity from every place it was generated to every place that it could be used would be too expensive to be practical. Nikola Tesla, one of the most well known of these scientists, had a vision for a wireless world in which wireless electric power and communications would reach around the world, delivering information and power to ships at sea, factories, and every home on the planet. Tesla contributed significantly to our understanding of electricity and electrical systems and is credited with inventing three-phase AC power systems, induction motors, fluorescent lamps, radio transmission, and various modes of wireless electric power transfer.

In 1902 Nikola Tesla patented a device, he called the device a "high-voltage, air-core, self-regenerative resonant transformer that generates very high voltages at high frequency"; it was a Tesla coil that transferred its energy using resonant transfer from the bottom coil a few feet through air to the top coil. This avoided arcing and permitted very high voltages to be created, and is one of the more common types built today.

In the early 1960s resonant inductive wireless energy transfer was used successfully in implantable medical devices including such devices as pacemakers and artificial hearts. While the early systems used a resonant receiver coil, later systems implemented resonant transmitter coils as well. These medical devices are designed for high efficiency using low power electronics while efficiently accommodating some misalignment and dynamic twisting of the coils. The separation between the coils in implantable applications is commonly less than 20 cm. Today resonant inductive energy transfer is regularly used for providing electric power in many commercially available medical implantable devices.

Wireless electric energy transfer for experimentally powering electric automobiles and buses is a higher power application (>10 kW) of resonant inductive energy transfer. High power levels are required for rapid recharging and high energy transfer efficiency is required both for operational economy and to avoid negative environmental impact of the system. An experimental electrified roadway test track built circa 1990 achieved 80% energy efficiency while recharging the battery of a prototype bus at a specially equipped bus stop. The bus could be outfitted with a retractable receiving coil for greater coil clearance when moving. The gap between the transmit and receive coils was designed to be less than 10 cm when powered. In addition to buses the use of wireless transfer has been investigated for recharging electric automobiles in parking spots and garages as well.


Some of these wireless resonant inductive devices operate at low milliwatt power levels and are battery powered. Others operate at higher kilowatt power levels. Current implantable medical and road electrification device designs achieve more than 75% transfer efficiency at an operating distance between the transmit and receive coils of less than 10 cm.

In 1995, Professor John Boys and Prof Grant Covic, of The University of Auckland in New Zealand, developed systems to transfer large amounts of energy across small air gaps

WiTricity technology for power transfer is different than the technologies proposed by Tesla, but his work is referenced and acknowledged in the scientific articles published by WiTricity founding technical team.

In November 2006, Marin Soljačić and other researchers at the Massachusetts Institute of Technology applied this near field behavior, well known in electromagnetic theory, the wireless power transmission concept based on strongly-coupled resonators. In a theoretical analysis, they demonstrate that, by designing electromagnetic resonators that suffer minimal loss due to

The 187-foot Nicolas Tesla’s Wardenclyffe Tower (Tesla Tower) built on Long Island, New York in 1903. This was to be the first broadcasting system in the world. Tesla wanted to transmit electricity from this Tower to the whole globe without wires using the Ionosphere. The source of the transmitted electricity was to be the Niagara Falls power plant. The tower was destroyed in 1917.


radiation and absorption and have a near field with mid-range extent (namely a few times the resonator size), mid-range efficient wireless energy-transfer is possible. The reason is that, if two such resonant circuits tuned to the same frequency are within a fraction of a wavelength, their near fields (consisting of 'evanescent waves') couple by means of evanescent wave coupling (which is related to quantum tunneling). Oscillating waves develop between the inductors, which can allow the energy to transfer from one object to the other within times much shorter than all loss times, which were designed to be long, and thus with the maximum possible energy-transfer efficiency. Since the resonant wavelength is much larger than the resonators, the field can circumvent extraneous objects in the vicinity and thus this mid-range energy-transfer scheme does not require line-of-sight. By utilizing in particular the magnetic field to achieve the coupling, this method can be safe, since magnetic fields interact weakly with living organisms.

CCoommppaarriissoonn wwiitthh OOtthheerr TTeecchhnnoollooggiieess:

Compared to inductive transfer in transformers, except when the coils are well within a diameter of each other, the efficiency is somewhat lower (around 80% at short range) whereas conventional transformers may achieve greater efficiency (around 90-95%), and for this reason, it's unlikely it will be used very much at larger distances where high energy is transferred.

However, compared to the costs associated with batteries, particularly non rechargeable batteries, the costs of the batteries are hundreds of times higher. In situations where a source of power is available nearby, it can be a cheaper solution. In addition, whereas batteries need periodic maintenance and replacement, resonant energy transfer could be used instead, which would not need this. Batteries additionally generate pollution during their construction and their disposal which largely would be avoided.

The WiTricity would reduce the cost of electrical energy used by the consumer and get rid of the landscape of wires, cables, and transmission towers. It has negligible demerits like reactive power which was found insignificant and biologically compatible.


WWiiTTrriicciittyy -- HHooww iitt ssttaarrtteedd?? The story started late one night a few years ago, with MIT Professor Marin Soljačić standing in his pyjamas, staring at his cell phone on the kitchen counter. It was probably the sixth time that month that he was awakened by his mobile phone beeping to let him know that he had forgotten to charge it. At that moment, it occurred to him: “There is electricity wired all through this house, all through my office – everywhere. This phone should take care of its own charging!” But to make this possible, one would have to find a way to transfer power from the existing wired infrastructure to the cell phone—without wires. Soljačić started thinking of physical phenomena that could make this dream a reality.

CCoouupplleedd RReessoonnaattoorrss wwaass FFiitt FFoorr TThhee SSiittuuaattiioonn: To achieve wireless power transfer in a way that is practical and safe, one needs to use a physical phenomenon that enables the power source and the device (in this case, the mobile phone) to exchange energy strongly, while interacting only weakly with living beings and other environmental objects, like furniture and walls. The phenomenon of coupled resonators precisely fits this description. Two resonant objects of the same resonant frequency tend to exchange energy efficiently, while interacting weakly with extraneous off-resonant objects. A child on a swing is a good example of a resonant system. A swing exhibits a type of mechanical resonance, so only when the child pumps her legs at the natural frequency of the swing is she able to impart substantial energy into the motion of the swing. Another example involves acoustic resonances: imagine a room with 100 identical wine glasses, but each filled with wine up to a different level, so that each resonates at a different frequency (that is, they each emit a different tone or note when tapped, by a utensil, for example). If an opera singer enters that room and sings a very loud single note, the glass having the corresponding resonant frequency can accumulate enough energy to shatter, while the other glasses are unaffected.

SSttrroonngg CCoouupplliinngg: Coupled resonators are said to operate in a strongly coupled regime if their energy transfer rate is substantially higher than the rate at which they lose energy due to factors such as material absorption and radiation. In the strongly coupled regime, energy transfer can be very efficient. These considerations are universal, applying to all kinds of resonances (e.g., acoustic, mechanical, electromagnetic, etc.). Soljačić and his colleagues at MIT (Karalis and Joannopoulos) set out to explore and develop the physical theory of how to


enable strongly coupled magnetic resonators to transfer power over distances that would enable the kind of wireless device charging that Soljačić first imagined. Their theoretical results were published first in 2006, and again in 2008 in the Annals of Physics. Once the physical theories were developed, Soljačić and his team (Kurs, Karalis, Moffatt, Joannopoulos, Fisher) set out to validate them experimentally. The theory was developed to cover a broad range of coupled resonator systems, but the experimental work focused on proving that magnetically coupled resonators could exchange energy in the manner predicted by the theory and required for the wireless charging or devices, such as cell phones. The team explored a system of two electro-magnetic resonators coupled through their magnetic fields. They were able to identify the strongly coupled regime in this system, and showed that strong coupling could be achieved over distances that greatly exceeded the size of the resonant objects themselves. The team had proven that in this strongly coupled regime, efficient wireless power transfer could be enabled. Their successful experiment was published in the journal, Science, in 2007.

WWiiTTrriicciittyy TTeecchhnnoollooggyy iiss BBoorrnn:

The experimental design consisted of two copper coils, each a self-resonant system. One of the coils, connected to an AC power supply, was the resonant source. The other coil, the resonant capture device, was connected to a 60 watt light bulb. The power source and capture device were suspended in mid-air with nylon thread, at distances that ranged from a few centimeters to over 2.5 meters (8.2 ft). Not only was the light bulb illuminated, but the theoretical predictions of high efficiency over distance were proven experimentally. By placing

various objects between the source and capture device, the team demonstrated how the magnetic near field can transfer power through certain materials and around metallic obstacles. Thus Prof. Soljačić’s dream of finding a method to wirelessly connect mobile electric devices to the existing electric grid was realized. WiTricity Corp. was soon launched to carry this technology forward from the MIT laboratories to commercial production.


WWiiTTrriicciittyy TTeecchhnnoollooggyy iiss MMoorree TThhaann……

WWiiTTrriicciittyy TTeecchhnnoollooggyy iiss ddiiffffeerreenntt tthhaann……

TTrraaddiittiioonnaall MMaaggnneettiicc IInndduuccttiioonn At first glance, WiTricity technology for power transfer appears to be traditional magnetic induction, such as is used in power transformers, where conductive coils transmit power to each other wirelessly, over very short distances. In a transformer, an electric current running in a sending coil (or “primary winding”) induces another current in a receiving coil (or “secondary winding”). The two coils must be very close together, and may even overlap, but the coils do not make direct electrical contact with each other. However, the efficiency of the power exchange in traditional magnetic induction systems drops by orders of magnitude when the distance between the coils becomes larger than their sizes. In addition to electric transformers, other devices based on traditional magnetic induction include rechargeable

electric toothbrushes, and inductive “charging pads” which require that the object being charged be placed directly on top of, or very close to, the base or pad supplying the power. The power exchange efficiency of some induction systems is improved by utilizing resonant circuits. These so-called resonantly enhanced induction techniques are used in certain medical implants and high-frequency RFIDs for example. However, to the best of our knowledge, WiTricity founding technical team was the first to discover that by specially designing the magnetic resonators, one could achieve strong coupling and highly efficient energy exchange over distances much larger than the size of the resonator coils, distances very large compared to traditional schemes.


RRaaddiiaattiivvee PPoowweerr TTrraannssffeerr

WiTricity technology for power transfer is non-radiative and relies on near-field magnetic coupling. Many other techniques for wireless power transfer rely on radiative techniques, either broadcasted or narrow beam (directed radiation) transmission of radio, or light waves. Broadcasted radiation of radio frequency energy is commonly used for wireless information transfer because information

An electric tooth brush uses traditional magnetic induction to recharge its batteries.


can be transmitted over a wide area to multiple users. The power received by each radio or wireless receiver is miniscule, and must be amplified in a receiving unit using an external power supply. Because the vast majority of radiated power is wasted into free space, radio transmission is considered to be an inefficient means of power transfer. Note that while more energy can be supplied to the receiver by “cranking up the power” of the transmitters in these systems, such high power levels may pose a safety hazard and may interfere with other radio frequency devices. “Directed radiation”, using highly directional antennas, is another means of using radio transmission to beam energy from a source to a receiver. However, directed radiation—in particular microwave radiation—may interact strongly with living organisms and certain metallic objects. Such energy transfer methods may pose safety hazards to people or objects that obstruct the line-of-sight between the transmitter and receiver. These limitations make directed radio transmission impractical for delivering substantial levels of wireless power in a typical consumer, commercial, or industrial application. In fact, defense researchers are exploring the use of directed energy systems to deliver lethal doses of power to targets in space and on the battlefield. In addition to radio waves, visible and invisible light waves can also be used to transfer energy. The sun is an excellent radiative source of light energy, and industry and academia are working hard to develop photovoltaic technologies to convert sunlight to electrical energy. A laser beam is a form of directed light radiation, in which visible or invisible light waves may be formed into a collimated beam, delivering energy in a targeted way. However, as in the case of directed radio waves, safe and efficient transmission of laser power requires a clear line of sight between the transmitter and receiver. As mentioned at the beginning of this section, WiTricity technology is based on non-radiative energy

A microwave oven utilizes microwave radiation to cook food.

The June 5, 1975 NASA JPL Goldstone

Demonstration of directed radiative microwave power transmission successfully transferred 34kw of electrical power over a distance of 1.5km.


transfer. It does not require a clear line of sight between the power sources and capture devices and it is safe for use in typical home, hospital, office, or industrial environments.


MMaaggnneettiicc RReessoonnaannccee IImmaaggiinngg ((MMRRII)) MRI machines use “magnetic resonance imaging” to produce diagnostic images of soft tissue. Many people assume that WiTricity “Resonant Magnetic Coupling” must be similar to magnetic resonance imaging (MRI) technology, however, the technologies are similar in name only. MRI is, as its name suggests, a technology for using magnetism as a basis for diagnostic imaging of soft tissue in the human body. It utilizes a strong DC magnet to orient the magnetic fields of atoms within tissues, and radio frequency fields to manipulate those atoms in a selective way, so that tissues and structures can be imaged clearly. The “resonance” referred to in “MRI” refers to the resonance of atomic structures. MRI is not considered to be a method for wireless power transfer.

MRI machines use “magnetic resonance

imaging” to produce diagnostic images of soft tissue.


FFEEAATT

1. Highly Resonant Strong Coupling Provides High Efficiency Over Distance:

WiTricity mode of wireless power transfer is highly ranging from centimeters toamount of usable electrical energy that is available to thedivided by the amount of energy that is drawn by the applications, efficiency can exceed 90%. And energy when it is needed. Whencapture additional energy, the its power consumption to a power saving “idle” state.


TTUURREESS AANNDD BBEENNEEFFIITTSS

Highly Resonant Strong Coupling Provides High Efficiency Over

WiTricity mode of wireless power transfer is highly efficient over distances ranging from centimeters to several meters. Efficiency may be defined as the amount of usable electrical energy that is available to the device being powered, divided by the amount of energy that is drawn by the WiTricity source. Iapplications, efficiency can exceed 90%. And WiTricity sources only transfer energy when it is needed. When a WiTricity powered device no longer needs to capture additional energy, the WiTricity power source will automatically reduce

mption to a power saving “idle” state.

Page 24

Highly Resonant Strong Coupling Provides High Efficiency Over

efficient over distances several meters. Efficiency may be defined as the

device being powered, source. In many

sources only transfer powered device no longer needs to

automatically reduce


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

The magnetic near field has several properties that make it an excellent means of transferring energy in a typical consumer, commercial, or industrial environment. Most common building and furnishing materials, such as wood, gypsum wall board, plastics, textiles, glass, brick, and concrete are essentially “transparent” to magnetic fields—enabling WiTricity technology to efficiently transfer power through them. In addition, the magnetic near field has the ability to “wrap around” many metallic obstacles that might otherwise block the magnetic fields. WiTricity applications engineering team will work with you to address the materials and environmental factors that may influence wireless energy transfer in your application.

3. Non-Radiative Energy Transfer is Safe for People and Animals: WiTricity technology is a non-radiative mode of energy transfer, relying instead on the magnetic near field. Magnetic fields interact very weakly with biological organisms—people and animals—and are scientifically regarded to be safe. Professor Sir John Pendry of Imperial College London, a world renowned physicist, explains: “The body really responds strongly to electric fields, which is why you can cook a chicken in a microwave. But it doesn't respond to magnetic fields. As far as we know the body has almost zero response to magnetic fields in terms of the amount of power it absorbs." Evidence of the safety of magnetic fields is illustrated by the widespread acceptance and safety of household magnetic induction cooktops. Through proprietary design of the WiTricity source, electric fields are almost completely contained within the source. This design results in levels of electric and magnetic fields which fall well within regulatory guidelines. Thus WiTricity technology doesn’t give rise to radio frequency emissions that interfere with other electronic devices, and is not a source of electric and magnetic field levels that pose a risk to people or animals. Limits for human exposure to magnetic fields are set by regulatory bodies such as the FCC, ICNIRP, and are based on broad scientific and medical consensus. WiTricity technology is being developed to be fully compliant with applicable regulations regarding magnetic fields and electromagnetic radiation.


4. Scalable Design Enables Solutions from milliwatts to Kilowatts:

WiTricity systems can be designed to handle a broad range of power levels. The benefits of highly efficient energy transfer over distance can be achieved at power levels ranging from milliwatts to several kilowatts. This enables WiTricity technology to be used in applications as diverse as powering a wireless mouse or keyboard (milliwatts) to recharging an electric passenger vehicle (kilowatts). WiTricity technology operates in a “load following” mode, transferring only as much energy as the powered device requires.

5. Flexible Geometry Allows WiTricity Devices to be Embedded Into OEM Products:

WiTricity technology is being designed so that it can be easily embedded into a wide variety of products and systems. The physics of resonant magnetic coupling enables WiTricity engineers to design power sources and devices of varying shapes and sizes, to match both the packaging requirements and the power transfer requirements in a given OEM application. WiTricity has designed power capture devices compact enough to fit into a cell phone.


WWiiTTrriicciittyy AAPPPPLLIICCAATTIIOONNSS WiTricity wireless power transfer technology can be applied in a wide variety of applications and environments. The ability of our technology to transfer power safely, efficiently, and over distance can improve products by making them more convenient, reliable, and environmentally friendly. WiTricity technology can be used to provide:

Direct Wireless Power—when all the power a device needs is provided wirelessly, and no batteries are required. This mode is for a device that is always used within range of its WiTricity power source.

Automatic Wireless Charging—when a device with rechargeable

batteries charges itself while still in use or at rest, without requiring a power cord or battery replacement. This mode is for a mobile device that may be used both in and out of range of its WiTricity power source.

WiTricity technology is designed for Original Equipment Manufacturers (OEM’s) to embed directly in their products and systems. WiTricity technology will make the products: More Convenient:

No manual recharging or changing batteries. Eliminate unsightly, unwieldy and costly power cords.

More Reliable:

Never run out of battery power. Reduce product failure rates by fixing the ‘weakest link’: flexing wiring

and mechanical interconnects. More Environmentally Friendly:

Reduce use of disposable batteries. Use efficient electric ‘grid power’ directly instead of inefficient battery

charging.


CCoonnssuummeerr EElleeccttrroonniiccss Automatic wireless charging of mobile electronics (phones, laptops, game controllers, etc.) in home, car, office, Widevices are in use and mobile. Direct wireless powering of stationary devices (flat screen TV’s, digital picture frames, home theater accessories, wireless loud … eliminating expensive custom wiring, unsightly cables and “wall-wart” power supplies. Direct wireless powering of desktop PC peripherals: wireless mouse, keyboard, printer, speakers, display, etc … eliminating disposable batteries and awkward cabling.


ss

Automatic wireless charging of mobile (phones, laptops, game controllers,

etc.) in home, car, office, Wi-Fi hotspots … while devices are in use and mobile.

Direct wireless powering of stationary devices (flat screen TV’s, digital picture frames, home theater accessories, wireless loud speakers, etc.) … eliminating expensive custom wiring, unsightly

wart” power supplies.

Direct wireless powering of desktop PC peripherals: wireless mouse, keyboard, printer, speakers, display, etc … eliminating disposable

awkward cabling.

Page 28


IInndduussttrriiaall Direct wireless power and communication interconnections across rotating and moving “joints” (robots, packaging machinery, assembly machinery, machine tools) … eliminating costly and failure-prone wiring. Direct wireless power and communication interconnections at points of use in harsh environments (drilling, mining, underwater, etc.) … where it is impractical or impossible to run wires. Direct wireless power for wireless sensors and actuators, eliminating the need fopower wiring or battery replacement and disposal.

TTrraannssppoorrttaattiioonn


Direct wireless power and communication interconnections across rotating and moving “joints” (robots, packaging machinery, assembly machinery, machine tools) … eliminating costly

power and communication interconnections at points of use in harsh environments (drilling, mining, underwater, etc.) … where it is impractical or impossible to run

Direct wireless power for wireless sensors and actuators, eliminating the need for expensive power wiring or battery replacement and

Automatic wireless charging for existing electric vehicle classes: golf carts, industrial vehicles. Automatic wireless charging for future hybrid and all-electric passenger and commercial vehicles, at home, in parking garages, at fleet depots, and at remote kiosks. Direct wireless power interconnections to replace costly vehicle wiring harnesses and slip rings.

Page 29

Automatic wireless charging for existing carts, industrial

Automatic wireless charging for future hybrid and commercial

vehicles, at home, in parking garages, at fleet

Direct wireless power interconnections to harnesses and slip


OOtthheerr AApppplliiccaattiioonnss Direct wireless power interconnections and automatic wirelessimplantable medical devices (ventricular assist devices, pacemaker, etc.). Automatic wireless charging and for high tech military systemspowered mobile devices, covert sunmanned mobile robots and aircraft, etc.). Direct wireless powering and automatic wireless charging of smart Direct wireless powering and automatic wireless charging of consumer appliances, mobile robots, etc.


power interconnections and automatic wireless charging for implantable medical devices (ventricular

pacemaker, defibrillator,

Automatic wireless charging and for high tech military systems (battery powered mobile devices, covert sensors,

robots and aircraft,

Direct wireless powering and automatic cards.

Direct wireless powering and automatic consumer appliances,

Page 30


CCOONNCCLLUUSSIIOONN The transmission of power without wires is not a theory or a mere possibility, it is now a reality. The electrical energy can be economically transmitted without wires to any terrestrial distance. Many researchers have established in numerous observations, experiments and measurements, qualitative and quantitative. Dr.N.Tesla is the pioneer of this invention. Wireless transmission of electricity have tremendous merits like high transmission integrity and Low Loss (90 – 97% efficient) and can be transmitted to anywhere in the globe and eliminate the need for an inefficient, costly, and capital intensive grid of cables, towers, and substations. The system would reduce the cost of electrical energy used by the consumer and get rid of the landscape of wires, cables, and transmission towers. It has negligible demerits like reactive power which was found insignificant and biologically compatible. It has a tremendous economic impact to human society.


RREEFFEERREENNCCEESS

i. IEEE Spectrum, May 2009

ii. http://www.WiTricity.com

iii. www.pcti.pctiltd.com/download/articals/WiTricity.pdf

iv. http://web.mit.edu/newsoffice/2007/wireless-0607.html

v. http://www.WiTricitypower.com

vi. http://www.tecfre.com/wi-tricity-technology-light-60-watt-bulb-from-7-feet/

vii. http://www.witricpower.com/

viii. http://www.powerbeaminc.com/

ix. http://en.wikipedia.org/wiki/WiTricity

x. http://www.sciencemag.org/cgi/data/1143254/DC1/1 xi. http://www.sciencemag.org/cgi/content/abstract/1143254

xii. http://www.breakingnewsenglish.com/0706/070613-WiTricity.html

xiii. http://www.witric.com/2007/06/10/WiTricity-impact/ xiv. An article published in the Science Magazine as “Wireless Power Transfer

via Strongly Coupled Magnetic Resonances” by Andre kurs, Science 317, 83(2007); Dol:10.1126/science.1143254.

xv. http://electron9.phys.utk.edu/optics507/modules/m6/coupled_resonat

ors.htm

xvi. http://www.ecoupled.com/technologyMain.html

Documents

WiTricity - Wireless Transmission of Electricity