Misplaced Pages

Wireless power transfer: Difference between revisions

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
Browse history interactively← Previous editNext edit →Content deleted Content addedVisualWikitext
Revision as of 04:16, 28 April 2012 editWtshymanski (talk | contribs)Extended confirmed users76,122 edits see main article for lengthy Tesla quotes; undue emphasis here disproportionate to results← Previous edit Revision as of 13:06, 29 July 2012 edit undoGLPeterson (talk | contribs)Extended confirmed users4,915 editsm →Timeline of wireless powerNext edit →
(39 intermediate revisions by 14 users not shown)
Line 1: Line 1:
'''Wireless energy transfer''' or '''wireless power''' is the transmission of electrical energy from a ] to an ] without a ] physical connection. Wireless transmission is useful in cases where interconnecting wires are inconvenient, hazardous, or impossible. The problem of wireless ] differs from that of wireless telecommunications, such as radio. In the latter, the proportion of ] received becomes critical only if it is too low for the signal to be distinguished from the background ].<ref>A radio transmitter can produce waves having a power of several kilowatts or even megawatts but this energy scatters in all directions. Only a small fraction, less than a millionth part, of the transmitted energy is received. However, this is sufficient to yield the intelligence.</ref> With wireless power, efficiency is the more significant parameter.&nbsp; A large part of the energy sent out by the generating plant must arrive at the receiver or receivers to make the system economical. '''Wireless energy transfer''' or '''wireless power''' is the transmission of electrical energy from a ] to an ] without interconnecting manmade ]s.&nbsp; Wireless transmission is useful in cases where interconnecting wires are inconvenient, hazardous, or impossible.&nbsp; The problem of wireless ] differs from that of wireless telecommunications, such as radio.&nbsp; In the latter, the proportion of ] received becomes critical only if it is too low for the signal to be distinguished from the background ].<ref>A radio transmitter can produce waves having a power of several kilowatts or even megawatts but this energy scatters in all directions.&nbsp; Only a small fraction, less than a millionth part, of the transmitted energy is received.&nbsp; However, this is sufficient to yield the intelligence.</ref>&nbsp; With wireless power, efficiency is the more significant parameter.&nbsp; A large part of the energy sent out by the generating plant must arrive at the receiver or receivers to make the system economical.


The most common form of wireless power transmission is carried out using ] followed by ]. Other methods under consideration include ] in the form of ] or ].<ref name=space/> The most common form of wireless power transmission is carried out using ] followed by ]. Other methods under consideration include ] in the form of ] or ].<ref name=space/>
Line 6: Line 6:
{{Main|Coupling (electronics)}} {{Main|Coupling (electronics)}}


An electric current flowing through a conductor carries electrical energy.&nbsp; When an electric current passes through a circuit there is an electric field in the ] surrounding the conductor; magnetic field lines around the conductor and lines of electric force radially about the conductor.<ref name="SteinmetzGE15VPEF"/> An electric current flowing through a conductor, such as a ], carries electrical energy.&nbsp; When an electric current passes through a circuit there is an electric field in the ] surrounding the conductor; magnetic field lines around the conductor and lines of electric force radially about the conductor.<ref name="SteinmetzGE15VPEF"/>


In a ] circuit, if the current is continuous, the fields are constant; there is a condition of stress in the space surrounding the conductor, which represents stored electric and magnetic energy, just as a compressed spring or a moving mass represents stored energy. In an ] circuit, the fields also alternate; that is, with every half wave of current and of voltage, the magnetic and the electric field start at the conductor and run outwards into space with the speed of light.<ref>188,000 miles per second</ref> Where these alternating fields impinge on another conductor a voltage and a current are induced.<ref name="SteinmetzGE15VPEF" /> In a ] circuit, if the current is continuous, the fields are constant; there is a condition of stress in the space surrounding the conductor, which represents stored electric and magnetic energy, just as a compressed spring or a moving mass represents stored energy.&nbsp; In an ] circuit, the fields also alternate; that is, with every half wave of current and of voltage, the magnetic and the electric field start at the conductor and run outwards into space with the speed of light.<ref>188,000 miles per second</ref> Where these alternating fields impinge on another conductor a voltage and a current are induced.<ref name="SteinmetzGE15VPEF" />


Any change in the electrical conditions of the circuit, whether internal<ref>Such as an internal change of load, starting and switching operations, and short circuits.</ref> or external<ref>Such as the external change due to lightning.</ref> involves a readjustment of the stored magnetic and electric field energy of the circuit, that is, a so-called ]. A transient is of the general character of a condenser discharge through an inductive circuit. The phenomenon of the condenser discharge through an inductive circuit therefore is of the greatest importance to the engineer, as the foremost cause of ] and ] troubles in electric circuits.<ref name="Steinmetz">] (Fellow, A. I. E. E. Chief Consulting Engineer, General Electric Company, Schenectady, N. Y.). "''''". American Institute of Electrical Engineers., 1922. Transactions of the American Institute of Electrical Engineers. New York: American Institute of Electrical Engineers. Presented at the 10th Midwinter Convention of the A. I. E. E., New York, N. Y., 15–17 February 1922.</ref> Any change in the electrical conditions of the circuit, whether internal<ref>Such as an internal change of load, starting and switching operations, and short circuits.</ref> or external<ref>Such as the external change due to lightning.</ref> involves a readjustment of the stored magnetic and electric field energy of the circuit, that is, a so-called ].&nbsp; A transient is of the general character of a condenser discharge through an inductive circuit. The phenomenon of the condenser discharge through an inductive circuit therefore is of the greatest importance to the engineer, as the foremost cause of ] and ] troubles in electric circuits.<ref name="Steinmetz">] (Fellow, A. I. E. E. Chief Consulting Engineer, General Electric Company, Schenectady, N. Y.). "''''". American Institute of Electrical Engineers., 1922. Transactions of the American Institute of Electrical Engineers. New York: American Institute of Electrical Engineers. Presented at the 10th Midwinter Convention of the A. I. E. E., New York, N. Y., 15–17 February 1922.</ref>


Electromagnetic induction is proportional to the intensity of the current and voltage in the conductor which produces the fields and to the ]. The higher the frequency the more intense the induction effect. Energy is transferred from a conductor that produces the fields (the primary) to any conductor on which the fields impinge (the secondary). Part of the energy of the primary conductor passes inductively across space into secondary conductor and the energy decreases rapidly along the primary conductor. A high frequency current does not pass for long distances along a conductor but rapidly transfers its energy by induction to adjacent conductors. Higher induction resulting from the higher frequency is the explanation of the apparent difference in the propagation of high frequency disturbances from the propagation of the low frequency power of alternating current systems. The higher the frequency the more preponderant become the inductive effects that transfer energy from circuit to circuit across space. The more rapidly the energy decreases and the current dies out along the circuit, the more local is the phenomenon.<ref name="SteinmetzGE15VPEF" /> Electromagnetic induction is proportional to the intensity of the current and voltage in the conductor which produces the fields and to the ].&nbsp; The higher the frequency the more intense the induction effect.&nbsp; Energy is transferred from a conductor that produces the fields (the primary) to any conductor on which the fields impinge (the secondary).&nbsp; Part of the energy of the primary conductor passes inductively across space into secondary conductor and the energy decreases rapidly along the primary conductor.&nbsp; A high frequency current does not pass for long distances along a conductor but rapidly transfers its energy by induction to adjacent conductors.&nbsp; Higher induction resulting from the higher frequency is the explanation of the apparent difference in the propagation of high frequency disturbances from the propagation of the low frequency power of alternating current systems.&nbsp; The higher the frequency the more preponderant become the inductive effects that transfer energy from circuit to circuit across space. The more rapidly the energy decreases and the current dies out along the circuit, the more local is the phenomenon.<ref name="SteinmetzGE15VPEF" />


The flow of electric energy thus comprises phenomena inside of the conductor<ref>], the dissipation of electric energy by the resistance of the conductor through its conversion into heat;</ref> and phenomena in the space outside of the conductor—the electric field—which, in a continuous current circuit, is a condition of steady magnetic and dielectric stress, and in an alternating current circuit is alternating, that is, an electric wave launched by the conductor<ref name="SteinmetzGE15VPEF" /> to become far-field electromagnetic radiation traveling through space with the speed of light. The flow of electric energy thus comprises phenomena inside of the conductor<ref>], the dissipation of electric energy by the resistance of the conductor through its conversion into heat;</ref> and phenomena in the space outside of the conductor—the electric field—which, in a continuous current circuit, is a condition of steady magnetic and dielectric stress, and in an alternating current circuit is alternating, that is, an electric wave launched by the conductor<ref name="SteinmetzGE15VPEF" /> to become far-field electromagnetic radiation traveling through space with the speed of light.


In electric power transmission and distribution, the phenomena inside of the conductor are of main importance, and the electric field of the conductor is usually observed only incidentally.<ref>Such as when it gives trouble by induction in telephone circuits or when it reaches such high intensities as to puncture insulation, cause mechanical motion, etc.</ref> Inversely, in the use of electric power for ''radio'' telecommunications it is only the electric and magnetic fields outside of the conductor, that is electromagnetic radiation, which is of importance in transmitting the message. The phenomenon in the conductor, the current in the launching structure, is not used.<ref name="SteinmetzGE15VPEF" /> In electric power transmission and distribution, the phenomena inside of the conductor are of main importance, and the electric field of the conductor is usually observed only incidentally.<ref>Such as when it gives trouble by induction in telephone circuits or when it reaches such high intensities as to puncture insulation, cause mechanical motion, etc.</ref>&nbsp; Inversely, in the use of electric power for ''radio'' telecommunications it is only the electric and magnetic fields outside of the conductor, that is electromagnetic radiation, which is of importance in transmitting the message.&nbsp; The phenomenon in the conductor, the current in the launching structure, is not used.<ref name="SteinmetzGE15VPEF" />


The electric charge displacement in the conductor produces a magnetic field and resultant lines of electric force. The magnetic field is a maximum in the direction concentric, or approximately so, to the conductor. That is, a ferromagnetic body<ref>such as an iron needle.</ref> tends to set itself in a direction at right angles to the conductor. The electric field has a maximum in a direction radial, or approximately so, to the conductor. The electric field component tends in a direction radial to the conductor and dielectric bodies may be attracted or repelled radially to the conductor.<ref name="TheoryandcalculationSteinmetz"> By Charles Proteus Steinmetz</ref> The electric charge displacement in the conductor produces a magnetic field and resultant lines of electric force.&nbsp; The magnetic field is a maximum in the direction concentric, or approximately so, to the conductor.&nbsp; That is, a ferromagnetic body<ref>such as an iron needle.</ref> tends to set itself in a direction at right angles to the conductor.&nbsp; The electric field has a maximum in a direction radial, or approximately so, to the conductor.&nbsp; The electric field component tends in a direction radial to the conductor and dielectric bodies may be attracted or repelled radially to the conductor.<ref name="TheoryandcalculationSteinmetz"> By Charles Proteus Steinmetz</ref>


The electric field of a circuit over which energy flows has three main axes at right angles with each other: The electric field of a circuit over which energy flows has three main axes at right angles with each other:
Line 25: Line 25:
# The ''power gradient'', ] to the conductor. # The ''power gradient'', ] to the conductor.


Where the electric circuit consists of several conductors, the electric fields of the conductors superimpose upon each other, and the resultant magnetic field lines and lines of electric force are not concentric and radial respectively, except ''approximately in the immediate neighborhood'' of the conductor. Between parallel conductors they are ] of circles. Neither the power consumption in the conductor, nor the magnetic field, nor the electric field, are proportional to the flow of energy through the circuit. However, the product of the intensity of the magnetic field and the intensity of the electric field is proportional to the flow of energy or the power, and the power is therefore resolved into a product of the two components '''i''' and '''e''', which are chosen proportional respectively to the intensity of the magnetic field and of the electric field. The component called the current is defined as that factor of the electric power which is proportional to the magnetic field, and the other component, called the voltage, is defined as that factor of the electric power which is proportional to the electric field.<ref name="TheoryandcalculationSteinmetz" /> Where the electric circuit consists of several conductors, the electric fields of the conductors superimpose upon each other, and the resultant magnetic field lines and lines of electric force are not concentric and radial respectively, except ''approximately in the immediate neighborhood'' of the conductor.&nbsp; Between parallel conductors they are ] of circles.&nbsp; Neither the power consumption in the conductor, nor the magnetic field, nor the electric field, are proportional to the flow of energy through the circuit.&nbsp; However, the product of the intensity of the magnetic field and the intensity of the electric field is proportional to the flow of energy or the power, and the power is therefore resolved into a product of the two components '''i''' and '''e''', which are chosen proportional respectively to the intensity of the magnetic field and of the electric field.&nbsp; The component called the current is defined as that factor of the electric power which is proportional to the magnetic field, and the other component, called the voltage, is defined as that factor of the electric power which is proportional to the electric field.<ref name="TheoryandcalculationSteinmetz" />


In ''radio'' telecommunications the electric field of the transmit antenna propagates through space as a ] and impinges upon the receive antenna where it is observed by its magnetic and electric effect.<ref name="TheoryandcalculationSteinmetz" /> Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X rays and gamma rays are shown to be the same ] phenomenon, differing one from the other only in frequency of vibration.<ref name="SteinmetzGE15VPEF">General Electric review, Volume 15 By General Electric. "Velocity of Propagation of Electric Field", ]</ref><ref>Speculation was made as to what the electric wave was, leading to the contradictory deductions that for certain reasons space is considered as a gas of infinitely low density, and for certain others as a solid.</ref><!--At frequencies of many thousand cycles per second, the ordinary measuring instruments, the oscillograph, etc., fail to record the wave; but such very high frequency waves can still be observed and measured through their inductive effects by bringing a conductor near them: the electric wave, impinging on this exploring conductor ("resonator" or "receiving antenna") then induces a current in it, and this is observed by a sufficiently delicate apparatus.<ref>In this manner, the telephone disturbances caused by alternating electric railway circuits have been studied by exploring antennae. </ref><ref name="SteinmetzGE15VPEF"/>--><!--A very intense wave, at short distance from its origin, may be observed by the spark across a small gap in the exploring antenna. Inversely, at hundreds of miles distance from the wireless sending station, the extremely weak wave is still observed in the receiving antenna by a sensitive detector.--><!--By exploring antenna, electric waves have been studied and observed up to frequencies of hundreds of millions of cycles per second—so-called "Hertz waves"—as they occur in industrial circuits between the end cylinders of high voltage multi-gap lightning arresters. There, they are the cause of the high sensitivity of the arrester for high frequency disturbances.<ref name="SteinmetzGE15VPEF"/><ref>Steinmetz here went on to point out that for frequencies of hundreds of thousands of millions, or millions of millions of cycles per second, the above method of observing the electric waves fails- however, they may be detected by placing a conducting body in their path, when they manifest themselves as "radiant heat." Frequencies of several hundred millions of millions are apparent to the eye as light, while frequencies of ten thousand millions of millions probably constitute the X-rays. For the full discussion of this subject, see Steinmetz's paper on "Arc Lighting" in the December, 1911.</ref>--> In ''radio'' telecommunications the electric field of the transmit antenna propagates through space as a ] and impinges upon the receive antenna where it is observed by its magnetic and electric effect.<ref name="TheoryandcalculationSteinmetz" /> Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X rays and gamma rays are shown to be the same ] phenomenon, differing one from the other only in frequency of vibration.<ref name="SteinmetzGE15VPEF">General Electric review, Volume 15 By General Electric.&nbsp; "Velocity of Propagation of Electric Field", ]</ref><ref>Speculation was made as to what the electric wave was, leading to the contradictory deductions that for certain reasons space is considered as a gas of infinitely low density, and for certain others as a solid.</ref><!--At frequencies of many thousand cycles per second, the ordinary measuring instruments, the oscillograph, etc., fail to record the wave; but such very high frequency waves can still be observed and measured through their inductive effects by bringing a conductor near them: the electric wave, impinging on this exploring conductor ("resonator" or "receiving antenna") then induces a current in it, and this is observed by a sufficiently delicate apparatus.<ref>In this manner, the telephone disturbances caused by alternating electric railway circuits have been studied by exploring antennae.&nbsp; </ref><ref name="SteinmetzGE15VPEF"/>--><!--A very intense wave, at short distance from its origin, may be observed by the spark across a small gap in the exploring antenna.&nbsp; Inversely, at hundreds of miles distance from the wireless sending station, the extremely weak wave is still observed in the receiving antenna by a sensitive detector.--><!--By exploring antenna, electric waves have been studied and observed up to frequencies of hundreds of millions of cycles per second—so-called "Hertz waves"—as they occur in industrial circuits between the end cylinders of high voltage multi-gap lightning arresters.&nbsp; There, they are the cause of the high sensitivity of the arrester for high frequency disturbances.<ref name="SteinmetzGE15VPEF"/><ref>Steinmetz here went on to point out that for frequencies of hundreds of thousands of millions, or millions of millions of cycles per second, the above method of observing the electric waves fails- however, they may be detected by placing a conducting body in their path, when they manifest themselves as "radiant heat." Frequencies of several hundred millions of millions are apparent to the eye as light, while frequencies of ten thousand millions of millions probably constitute the X-rays.&nbsp; For the full discussion of this subject, see Steinmetz's paper on "Arc Lighting" in the December, 1911.</ref>-->


===Electromagnetic induction=== ===Electromagnetic induction===
Line 34: Line 34:
====Electrodynamic induction method==== ====Electrodynamic induction method====
{{Main|Inductive coupling|Electrodynamic induction|Resonant inductive coupling}} {{Main|Inductive coupling|Electrodynamic induction|Resonant inductive coupling}}
The ] wireless transmission technique is ] over distances up to about one-sixth of the wavelength used. Near field energy itself is non-radiative but some radiative losses do occur. In addition there are usually resistive losses. With electrodynamic induction, electric current flowing through a ] creates a ] that acts on a secondary coil producing a current within it. Coupling must be tight in order to achieve high efficiency. As the distance from the primary is increased, more and more of the magnetic field misses the secondary. Even over a relatively short range the inductive coupling is grossly inefficient, wasting much of the transmitted energy.<ref>{{cite web|url=http://ecoupled.com/pdf/eCoupled_Understanding_Wireless_Power.pdf |title=Understanding Wireless Power |author=Dave Baarman and Joshua Schwannecke |date=2009-12-00}}</ref> The ] wireless transmission technique is ] over distances up to about one-sixth of the wavelength used.&nbsp; Near field energy itself is non-radiative but some radiative losses do occur.&nbsp; In addition there are usually resistive losses.&nbsp; With electrodynamic induction, electric current flowing through a ] creates a ] that acts on a secondary coil producing a current within it.&nbsp; Coupling must be tight in order to achieve high efficiency.&nbsp; As the distance from the primary is increased, more and more of the magnetic field misses the secondary.&nbsp; Even over a relatively short range the inductive coupling is grossly inefficient, wasting much of the transmitted energy.<ref>{{cite web|url=http://ecoupled.com/pdf/eCoupled_Understanding_Wireless_Power.pdf |title=Understanding Wireless Power |author=Dave Baarman and Joshua Schwannecke |date=2009-12-00}}</ref>


This action of an electrical ] is the simplest form of wireless power transmission. The primary and secondary circuits of a transformer are not directly connected. Energy transfer takes place through a process known as ]. Principal functions are stepping the primary voltage either up or down and electrical isolation. Mobile phone and ] ]s, and electrical power distribution ]s are examples of how this principle is used. ]s use this method. The main drawback to this basic form of wireless transmission is short range. The receiver must be directly adjacent to the transmitter or induction unit in order to efficiently couple with it. This action of an electrical ] is the simplest form of wireless power transmission.&nbsp; The primary and secondary circuits of a transformer are not directly connected.&nbsp; Energy transfer takes place through a process known as ].&nbsp; Principal functions are stepping the primary voltage either up or down and electrical isolation.&nbsp; Mobile phone and ] ]s, and electrical power distribution ]s are examples of how this principle is used.&nbsp; ]s use this method.&nbsp; The main drawback to this basic form of wireless transmission is short range.&nbsp; The receiver must be directly adjacent to the transmitter or induction unit in order to efficiently couple with it.


The application of resonance increases the transmission range somewhat. When resonant coupling is used, the transmitter and receiver inductors are tuned to the same natural frequency. Performance can be further improved by modifying the drive current from a sinusoidal to a nonsinusoidal transient waveform.<ref>{{cite book|url=http://books.google.com/?id=Q_ltAAAAMAAJ&dq=%22Elementary+Lectures+on+Electric+Discharges,+Waves,+and+Impulses%22&printsec=frontcover |title=Steinmetz, Dr. Charles Proteus, Elementary Lectures on Electric Discharges, Waves, and Impulses, and Other Transients, 2nd Edition, McGraw-Hill Book Company, Inc., 1914 |publisher=Google Books |date=29 August 2008 |accessdate=4 June 2009|author1=Steinmetz, Charles Proteus}}</ref> Pulse power transfer occurs over multiple cycles. In this way significant power may be transmitted between two mutually-attuned LC circuits having a relatively low coefficient of coupling. Transmitting and receiving coils are usually single layer ] or flat spirals with series ]s, which, in combination, allow the receiving element to be tuned to the transmitter frequency. The application of resonance increases the transmission range somewhat.&nbsp; When resonant coupling is used, the transmitter and receiver inductors are tuned to the same natural frequency.&nbsp; Performance can be further improved by modifying the drive current from a sinusoidal to a nonsinusoidal transient waveform.<ref>{{cite book|url=http://books.google.com/?id=Q_ltAAAAMAAJ&dq=%22Elementary+Lectures+on+Electric+Discharges,+Waves,+and+Impulses%22&printsec=frontcover |title=Steinmetz, Dr. Charles Proteus, Elementary Lectures on Electric Discharges, Waves, and Impulses, and Other Transients, 2nd Edition, McGraw-Hill Book Company, Inc., 1914 |publisher=Google Books |date=29 August 2008 |accessdate=4 June 2009|author1=Steinmetz, Charles Proteus}}</ref> Pulse power transfer occurs over multiple cycles.&nbsp; In this way significant power may be transmitted between two mutually-attuned LC circuits having a relatively low coefficient of coupling.&nbsp; Transmitting and receiving coils are usually single layer ] or flat spirals with series ]s, which, in combination, allow the receiving element to be tuned to the transmitter frequency.


Common uses of resonance-enhanced electrodynamic induction are charging the batteries of portable devices such as laptop computers and cell phones, ] and ].<ref>{{cite news|url=http://www.economist.com/science/tq/displayStory.cfm?story_id=13174387 |title=Wireless charging, Adaptor die, Mar 5th 2009 |work=The Economist |date=7 November 2008 |accessdate=4 June 2009}}</ref><ref>{{cite news|url=http://www.forbes.com/2009/01/09/ces-wireless-power-tech-sciences-cx_tb_0109power.html |title=Wireless technologies are starting to power devices, 01.09.09, 06:25&nbsp;pm EST |work=Forbes |date= 9 January 2009|accessdate=4 June 2009 |first=Taylor |last=Buley}}</ref><ref>{{cite news|url=http://www.nxtbook.com/nxtbooks/cmp/eetimes_altenergy_20100621/ |title=Alternative Energy, From the unsustainable...to the unlimited |publisher=EETimes.com| date= 21 June 2010}}</ref> A localized charging technique<ref>Patent Application PCT/CN2008/0728855</ref> selects the appropriate transmitting coil in a multilayer winding array structure.<ref>Patent US7164255</ref> Resonance is used in both the wireless charging pad (the transmitter circuit) and the receiver module (embedded in the load) to maximize energy transfer efficiency. This approach is suitable for universal wireless charging pads for portable electronics such as mobile phones. It has been adopted as part of the ] wireless charging standard. Common uses of resonance-enhanced electrodynamic induction are charging the batteries of portable devices such as laptop computers and cell phones, ] and ].<ref>{{cite news|url=http://www.economist.com/science/tq/displayStory.cfm?story_id=13174387 |title=Wireless charging, Adaptor die, Mar 5th 2009 |work=The Economist |date=7 November 2008 |accessdate=4 June 2009}}</ref><ref>{{cite news|url=http://www.forbes.com/2009/01/09/ces-wireless-power-tech-sciences-cx_tb_0109power.html |title=Wireless technologies are starting to power devices, 01.09.09, 06:25&nbsp;pm EST |work=Forbes |date= 9 January 2009|accessdate=4 June 2009 |first=Taylor |last=Buley}}</ref><ref>{{cite news|url=http://www.nxtbook.com/nxtbooks/cmp/eetimes_altenergy_20100621/ |title=Alternative Energy, From the unsustainable...to the unlimited |publisher=EETimes.com| date= 21 June 2010}}</ref> A localized charging technique<ref>Patent Application PCT/CN2008/0728855</ref> selects the appropriate transmitting coil in a multilayer winding array structure.<ref>Patent US7164255</ref> Resonance is used in both the wireless charging pad (the transmitter circuit) and the receiver module (embedded in the load) to maximize energy transfer efficiency.&nbsp; This approach is suitable for universal wireless charging pads for portable electronics such as mobile phones.&nbsp; It has been adopted as part of the ] wireless charging standard.


It is also used for powering devices having no batteries, such as RFID patches and ]s, and to couple electrical energy from the primary inductor to the helical resonator of ] wireless power transmitters. It is also used for powering devices having no batteries, such as RFID patches and ]s, and to couple electrical energy from the primary inductor to the helical resonator of ] wireless power transmitters.
Line 46: Line 46:
====Electrostatic induction method==== ====Electrostatic induction method====
{{Main|Capacitive coupling}} {{Main|Capacitive coupling}}
] ]


Electrostatic or ] is the passage of electrical energy through a ]. In practice it is an electric field gradient or ] between two or more insulated terminals, plates, electrodes, or nodes that are elevated over a conducting ground plane. The electric field is created by charging the plates with a high potential, high frequency alternating current power supply. The capacitance between two elevated terminals and a powered device form a voltage divider. Electrostatic or ] is the passage of electrical energy through a ].&nbsp; In practice it is an electric field gradient or ] between two or more insulated terminals, plates, electrodes, or nodes that are elevated over a conducting ground plane.&nbsp; The electric field is created by charging the plates with a high potential, high frequency alternating current power supply.&nbsp; The capacitance between two elevated terminals and a powered device form a voltage divider.


The electric energy transmitted by means of electrostatic induction can be utilized by a receiving device, such as a wireless lamp.<ref>, AIEE, Columbia College, N.Y., 20 May 1891</ref><ref>, IEE Address, London, February 1892</ref><ref name="tfcbooks.com">, Franklin Institute, Philadelphia, February 1893, and National Electric Light Association, St. Louis, March 1893</ref> ] demonstrated the illumination of wireless lamps by energy that was coupled to them through an alternating electric field.<ref>Gernsback, Hugo. "Nikola Tesla and His Achievements," Electrical Experimenter, January 1919. p. 615</ref><ref>Cheney, Margaret. Tesla: Man Out of Time, p. 174</ref><ref name="induction1907">Norrie, H. S., "Induction Coils: How to make, use, and repair them". Norman H. Schneider, 1907, New York. 4th edition.</ref> The electric energy transmitted by means of electrostatic induction can be utilized by a receiving device, such as a wireless lamp.<ref>, AIEE, Columbia College, N.Y., 20 May 1891</ref><ref>, IEE Address, London, February 1892</ref><ref name="tfcbooks.com">, Franklin Institute, Philadelphia, February 1893, and National Electric Light Association, St. Louis, March 1893</ref> ] demonstrated the illumination of wireless lamps by energy that was coupled to them through an alternating electric field.<ref>Gernsback, Hugo.&nbsp; "Nikola Tesla and His Achievements," Electrical Experimenter, January 1919. p. 615</ref><ref>Cheney, Margaret. Tesla: Man Out of Time, p. 174</ref><ref name="induction1907">Norrie, H. S., "Induction Coils: How to make, use, and repair them". Norman H. Schneider, 1907, New York. 4th edition.</ref>


{{quote|"Instead of depending on ''electrodynamic induction'' at a distance to light the tube . . . ideal way of lighting a hall or room would . . . be to produce such a condition in it that an illuminating device could be moved and put anywhere, and that it is lighted, no matter where it is put and without being electrically connected to anything. I have been able to produce such a condition by creating in the room a powerful, ''] ]''. For this purpose I suspend a sheet of metal a distance from the ceiling on insulating cords and connect it to one terminal of the induction coil, the other terminal 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 being carefully determined. An exhausted tube may then be carried in the hand anywhere between the sheets or placed anywhere, even a certain distance beyond them; it remains always luminous."<ref>Martin, T. C., & Tesla, N. (1894). Inventions, Researches and Writings of Nikola Tesla, with special reference to his work in polyphase currents and high potential lighting. New York: The Electrical Engineer. Page 188.</ref>}} {{quote|"Instead of depending on ''electrodynamic induction'' at a distance to light the tube . . . ideal way of lighting a hall or room would . . . be to produce such a condition in it that an illuminating device could be moved and put anywhere, and that it is lighted, no matter where it is put and without being electrically connected to anything.&nbsp; I have been able to produce such a condition by creating in the room a powerful, ''] ].''&nbsp; For this purpose I suspend a sheet of metal a distance from the ceiling on insulating cords and connect it to one terminal of the induction coil, the other terminal being preferably connected to the ground.&nbsp; Or else I suspend two sheets . . . each sheet being connected with one of the terminals of the coil, and their size being carefully determined.&nbsp; An exhausted tube may then be carried in the hand anywhere between the sheets or placed anywhere, even a certain distance beyond them; it remains always luminous."<ref>Martin, T. C., & Tesla, N. (1894). Inventions, Researches and Writings of Nikola Tesla, with special reference to his work in polyphase currents and high potential lighting. New York: The Electrical Engineer. Page 188.</ref>}}


The principle of electrostatic induction is applicable to the electrical conduction wireless transmission method. The principle of electrostatic induction is applicable to the electrical conduction wireless transmission method.
Line 62: Line 62:


====Beamed power, size, distance, and efficiency==== ====Beamed power, size, distance, and efficiency====
The size of the components may be dictated by the distance from ] to ], the ] and the ] or ] limit, used in standard ] ] design, which also applies to lasers. In addition to the Rayleigh criterion ] is also frequently used to determine an approximate spot size at an arbitrary distance from the ]. The dimensions of the components may be dictated by the distance from ] to ], the ] and the ] or ] limit, used in standard ] ] design, which also applies to lasers. In addition to the Rayleigh criterion ] is also frequently used to determine an approximate spot size at an arbitrary distance from the ].


The ] dictates that any radio wave, microwave or laser beam will spread and become weaker and ] over distance; the larger the transmitter antenna or laser aperture compared to the ] of radiation, the tighter the beam and the less it will spread as a function of distance (and vice versa). Smaller antennae also suffer from excessive losses due to ]s. However, the concept of ] considerably differs from an antenna. Typically, a laser aperture much larger than the wavelength induces ] radiation and mostly ] are used before emitted radiation couples into a fiber or into space. The ] dictates that any radio wave, microwave or laser beam will spread and become weaker and ] over distance; the larger the transmitter antenna or laser aperture compared to the ] of radiation, the tighter the beam and the less it will spread as a function of distance (and vice versa). Smaller antennae also suffer from excessive losses due to ]s. However, the concept of ] considerably differs from an antenna. Typically, a laser aperture much larger than the wavelength induces ] radiation and mostly ] are used before emitted radiation couples into a fiber or into space.
Line 72: Line 72:
====Microwave method==== ====Microwave method====
{{Main|Microwave power transmission}} {{Main|Microwave power transmission}}
] that could send electric energy by microwaves to a space vessel or planetary surface.]] ] that could send electric energy by microwaves to a space vessel or planetary surface.]]
Power transmission via radio waves can be made more directional, allowing longer distance power beaming, with shorter wavelengths of electromagnetic radiation, typically in the ] range. A ] may be used to convert the microwave energy back into electricity. Rectenna conversion efficiencies exceeding 95% have been realized. Power beaming using microwaves has been proposed for the transmission of energy from orbiting ]s to Earth and the ] leaving orbit has been considered.<ref name=space>G. A. Landis, "Applications for Space Power by Laser Transmission," SPIE Optics, Electro-optics & Laser Conference, Los Angeles CA, 24–28 January 1994; ''Laser Power Beaming, SPIE Proceedings Vol. 2121,'' 252–255.</ref><ref>G. Landis, M. Stavnes, S. Oleson and J. Bozek, "Space Transfer With Ground-Based Laser/Electric Propulsion" (AIAA-92-3213) ''NASA Technical Memorandum TM-106060'' (1992).</ref> Power transmission via radio waves can be made more directional, allowing longer distance power beaming, with shorter wavelengths of electromagnetic radiation, typically in the ] range.&nbsp; A ] may be used to convert the microwave energy back into electricity. Rectenna conversion efficiencies exceeding 95% have been realized. Power beaming using microwaves has been proposed for the transmission of energy from orbiting ]s to Earth and the ] leaving orbit has been considered.<ref name=space>G. A. Landis, "Applications for Space Power by Laser Transmission," SPIE Optics, Electro-optics & Laser Conference, Los Angeles CA, 24–28 January 1994; ''Laser Power Beaming, SPIE Proceedings Vol. 2121,'' 252–255.</ref><ref>G. Landis, M. Stavnes, S. Oleson and J. Bozek, "Space Transfer With Ground-Based Laser/Electric Propulsion" (AIAA-92-3213) ''NASA Technical Memorandum TM-106060'' (1992).</ref>


Power beaming by microwaves has the difficulty that for most space applications the required aperture sizes are very large due to ] limiting antenna directionality. For example, the 1978 ] Study of solar power satellites required a 1-km diameter transmitting antenna, and a 10&nbsp;km diameter receiving rectenna, for a microwave beam at 2.45&nbsp;GHz{{Citation needed|date=April 2009}}. These sizes can be somewhat decreased by using shorter wavelengths, although short wavelengths may have difficulties with atmospheric absorption and beam blockage by rain or water droplets. Because of the "]," it is not possible to make a narrower beam by combining the beams of several smaller satellites. Power beaming by microwaves has the difficulty that for most space applications the required aperture sizes are very large due to ] limiting antenna directionality.&nbsp; For example, the 1978 ] Study of solar power satellites required a 1-km diameter transmitting antenna, and a 10&nbsp;km diameter receiving rectenna, for a microwave beam at 2.45&nbsp;GHz.<ref>
{{cite conference|url=http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070005136_2007004947.pdf|title=Reevaluating Satellite Solar Power Systems for Earth|first=Geoffrey A.|last=Landis|date=May 7-12, 2006|accessdate=May 11, 2012|page=2|publisher=IEEE 4th World Conference on Photovoltaic Energy Conversion
}}
</ref> These sizes can be somewhat decreased by using shorter wavelengths, although short wavelengths may have difficulties with atmospheric absorption and beam blockage by rain or water droplets. Because of the "]," it is not possible to make a narrower beam by combining the beams of several smaller satellites.


For earthbound applications a large area 10&nbsp;km diameter receiving array allows large total power levels to be used while operating at the low power density suggested for human electromagnetic exposure safety. A human safe power density of 1&nbsp;mW/cm<sup>2</sup> distributed across a 10&nbsp;km diameter area corresponds to 750 megawatts total power level. This is the power level found in many modern electric power plants. For earthbound applications a large area 10&nbsp;km diameter receiving array allows large total power levels to be used while operating at the low power density suggested for human electromagnetic exposure safety. A human safe power density of 1&nbsp;mW/cm<sup>2</sup> distributed across a 10&nbsp;km diameter area corresponds to 750 megawatts total power level. This is the power level found in many modern electric power plants.
Line 86: Line 89:


====Laser method==== ====Laser method====
] ]


In the case of electromagnetic radiation closer to visible region of spectrum (10s of ] to 10s of ]), power can be transmitted by converting electricity into a ] beam that is then pointed at a ] receiver. In the case of electromagnetic radiation closer to visible region of spectrum (10s of ] to 10s of ]), power can be transmitted by converting electricity into a ] beam that is then pointed at a ] receiver.
Line 103: Line 106:
# As with microwave beaming, this method requires a direct line of sight with the target. # As with microwave beaming, this method requires a direct line of sight with the target.


The laser "powerbeaming" technology has been mostly explored in ]<ref>{{cite web|last=Skillings |first=Jonathan |url=http://news.cnet.com/8301-11386_3-10024153-76.html |title=Laser weapons: A distant target, CNET news August 23, 2008 1:41&nbsp;pm PDT |publisher=News.cnet.com |date=23 August 2008 |accessdate=4 June 2009}}</ref><ref>{{cite web|url=http://www.defensetech.org/archives/002078.html |title=Laser Weapons "Almost Ready?" Not! |publisher=Defensetech.org |accessdate=4 June 2009}}</ref><ref>{{cite web|url=http://www.army.mil/-news/2009/01/30/16279-white-sands-testing-new-laser-weapon-system/ |title=White Sands testing new laser weapon system, US Army.mil, 30 Jan 2009 |publisher=Army.mil |date=30 January 2009 |accessdate=4 June 2009}}</ref> and ]<ref>{{cite web|url=http://www.defensetech.org/archives/000658.html |title=Lasers Power Planes, Drones |publisher=Defensetech.org |accessdate=4 June 2009}}</ref><ref>{{cite web|url=http://www.space.com/businesstechnology/051024_spaceelevator_challenge.html |title=Riding a Beam of Light |publisher=Space.com |date=24 October 2005 |accessdate=4 June 2009}}</ref> applications and is now being developed for commercial and ] Low-Power applications. Wireless energy transfer system using laser for consumer space has to satisfy ] requirements standardized under IEC 60825. The laser "powerbeaming" technology has been mostly explored in ]<ref>{{cite web|last=Skillings |first=Jonathan |url=http://news.cnet.com/8301-11386_3-10024153-76.html |title=Laser weapons: A distant target, CNET news August 23, 2008 1:41&nbsp;pm PDT |publisher=News.cnet.com |date=23 August 2008 |accessdate=4 June 2009}}</ref><ref>{{cite web|url=http://www.defensetech.org/archives/002078.html |title=Laser Weapons "Almost Ready?" Not! |publisher=Defensetech.org |accessdate=4 June 2009}}</ref><ref>{{cite web|url=http://www.army.mil/-news/2009/01/30/16279-white-sands-testing-new-laser-weapon-system/ |title=White Sands testing new laser weapon system, US Army.mil, 30 Jan 2009 |publisher=Army.mil |date=30 January 2009 |accessdate=4 June 2009}}</ref> and ]<ref>{{cite web|url=http://www.defensetech.org/archives/000658.html |title=Lasers Power Planes, Drones |publisher=Defensetech.org |accessdate=4 June 2009}}</ref><ref>{{cite web|url=http://www.space.com/businesstechnology/051024_spaceelevator_challenge.html |title=Riding a Beam of Light |publisher=Space.com |date=24 October 2005 |accessdate=4 June 2009}}</ref> applications and is now being developed for commercial and ] Low-Power applications.&nbsp; Wireless energy transfer system using laser for consumer space has to satisfy ] requirements standardized under IEC 60825.


To develop an understanding of the trade-offs of Laser ("a special type of light wave"-based system):<ref>{{Dead link|date=June 2009}}</ref><ref>{{cite web|url=http://nobelprize.org/educational_games/physics/laser/facts/history.html |title=Nobelprize.org, Laser facts, Laser history and Nobel Prizes in Physics |publisher=Nobelprize.org |date=19 December 2002 |accessdate=4 June 2009}}</ref><ref>{{Dead link|date=June 2009}}</ref><ref>{{cite web|url=http://nobelprize.org/educational_games/physics/laser/facts/use.html |title=Nobelprize.org, Laser facts, Everyday Use of Laser |publisher=Nobelprize.org |date=19 December 2002 |accessdate=4 June 2009}}</ref> To develop an understanding of the trade-offs of Laser ("a special type of light wave"-based system):<ref>{{Dead link|date=June 2009}}</ref><ref>{{cite web|url=http://nobelprize.org/educational_games/physics/laser/facts/history.html |title=Nobelprize.org, Laser facts, Laser history and Nobel Prizes in Physics |publisher=Nobelprize.org |date=19 December 2002 |accessdate=4 June 2009}}</ref><ref>{{Dead link|date=June 2009}}</ref><ref>{{cite web|url=http://nobelprize.org/educational_games/physics/laser/facts/use.html |title=Nobelprize.org, Laser facts, Everyday Use of Laser |publisher=Nobelprize.org |date=19 December 2002 |accessdate=4 June 2009}}</ref>
#]<ref>{{cite web|url=http://www.ieee.org/organizations/pubs/newsletters/leos/oct05/free_space.html |title=Free-Space Laser Propagation: Atmospheric Effects |publisher=Ieee.org |accessdate=4 June 2009}}</ref><ref></ref><ref>{{cite book|url=http://books.google.com/?id=4NXHYg70qqIC&dq=Laser+propagation&printsec=frontcover |title=L. C. Andrews and R. L. Phillips, Laser Beam Propagation through Random Media, 2nd ed. (SPIE Press, 2005) |publisher=Google Books |accessdate=4 June 2009 | isbn=9780819459480|year=2005}}</ref> (on how Laser beam propagation is much less affected by diffraction limits) #]<ref>{{cite web|url=http://www.ieee.org/organizations/pubs/newsletters/leos/oct05/free_space.html |title=Free-Space Laser Propagation: Atmospheric Effects |publisher=Ieee.org |accessdate=4 June 2009}}</ref><ref></ref><ref>{{cite book|url=http://books.google.com/?id=4NXHYg70qqIC&dq=Laser+propagation&printsec=frontcover |title=L. C. Andrews and R. L. Phillips, Laser Beam Propagation through Random Media, 2nd ed. (SPIE Press, 2005) |publisher=Google Books |accessdate=4 June 2009 | isbn=978-0-8194-5948-0|year=2005}}</ref> (on how Laser beam propagation is much less affected by diffraction limits)
#] (on how spatial and spectral coherence characteristics of Lasers allows better distance-to-power capabilities<ref>{{cite web|author=Dr. Rüdiger Paschotta |url=http://www.rp-photonics.com/coherence.html |title=An explanation of Coherence |publisher=Rp-photonics.com |accessdate=4 June 2009}}</ref>) #] (on how spatial and spectral coherence characteristics of Lasers allows better distance-to-power capabilities<ref>{{cite web|author=Dr. Rüdiger Paschotta |url=http://www.rp-photonics.com/coherence.html |title=An explanation of Coherence |publisher=Rp-photonics.com |accessdate=4 June 2009}}</ref>)
#] (on how wavelength fundamentally dictates the size of a disk with distance) #] (on how wavelength fundamentally dictates the size of a disk with distance)
Line 119: Line 122:
===Electrical conduction=== ===Electrical conduction===


] ]
] ]


⚫ ====Disturbed charge of ground and air method====
{{main|World Wireless System}} {{main|World Wireless System}}
⚫ ====Disturbed charge of ground and air method====
⚫ Nikola Tesla proposed transmission of high-potential, high-frequency alternating current through the earth with an atmospheric return circuit for transmission of power and signals. Tesla's method relied on alternating current to be transmitted through atmospheric strata having a barometric pressure even greater than 130 millimeters of mercury.<ref>, 2 Sept. 1897, U.S. Patent No. 645,576, 20 Mar. 1900.</ref> Tesla proposed to induce current flows by means of electrostatic induction through the lower atmosphere up to about two or three miles above the Earth's surface. <ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power</ref> <ref>Henry Bradford, </ref>&nbsp; Electrical conduction through atmospheric strata is made possible by the creation of capacitively coupled discharge plasma through the process of atmospheric ionization.<ref>], Electromagnetic Phenomena in Complex Geometries and Nonlinear Phenomena, Non-Hertzian Waves and Magnetic Monopoles, Tesla Book Company.</ref><ref>APPARATUS FOR TRANSMISSION OF ELECTRICAL ENERGY, 2 September 1897, U.S. Patent No. 649,621, 15 May 1900</ref><ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 126, 127.</ref>
The wireless transmission of alternating current electricity through the earth with an equivalent electrical displacement through the air above it achieves long ranges that are superior to the resonant electrical induction methods and favorably comparable to the electromagnetic radiation methods.&nbsp; Electrical energy can be transmitted through inhomogeneous Earth with low loss because the net resistance between earth antipodes is considerably less than 1 ohm.<ref>"Nikola Tesla and the Diameter of the Earth: A Discussion of One of the Many Modes of Operation of the Wardenclyffe Tower," K. L. Corum and J. F. Corum, PhD 1996</ref> The electrical displacement takes place predominantly by electrical conduction through the oceans, and metallic ore bodies and similar subsurface structures. The electrical displacement is also by means of electrostatic induction through the more dielectric regions such as quartz deposits and other non-conducting minerals.<ref>William Beaty, , reprinted in .</ref><ref>Wait, James R., The Ancient and Modern History of EM Ground-Wave Propagation," ''IEEE Antennas and Propagation Magazine'', Vol. 40, No. 5, October 1998.</ref>

⚫ This energy transfer technique is suitable for transmission of electrical power in industrial quantities and also for wireless broadband telecommunications. <!--&nbsp; The method depends upon an electrical current flowing through the earth between a Tesla coil transmitter and a Tesla coil receiver.&nbsp; Both the transmitter and receiver are built the same way, with a powerful Tesla coil located inside each of the tower structures.-->&nbsp; The ] project was an early commercial venture for trans-Atlantic wireless telephony and proof-of-concept demonstrations of global wireless power transmission using this method.<ref>"The Future of the Wireless Art," Wireless Telegraphy and Telephony, Walter W. Massie & Charles R. Underhill, 1908, pp. 67–71.
{{quote|It is intended to give practical demonstrations of these principles with the plant illustrated. . . . An inexpensive instrument, not bigger than a watch, will enable its bearer to hear anywhere, on sea or land, music or song, the speech of a political leader . . . delivered in some other place, however distant. . . . Millions of such instruments can be operated from but one plant of this kind.&nbsp; More important than all of this, however, will be the transmission of power, without wires, which will be shown on a scale large enough to carry conviction.}}</ref>&nbsp; The facility was not completed due to insufficient funding.

=====Terrestrial transmission line with atmospheric return=====
] electrical power transmission systems rely on current flowing through the earth plus a single wire insulated from the earth to complete the circuit. In emergencies ] power transmission systems can also operate in the 'single wire with earth return' mode. Elimination of the raised insulated wire, and transmission of high-potential alternating current through the earth with an atmospheric return circuit is the basis of this method of wireless electrical power transmission.

The atmospheric conduction method depends upon the passage of electrical current through the earth, and through the upper ] and the ].<ref>, 2 Sept. 1897, U.S. Patent No. 645,576, 20 Mar. 1900.</ref>&nbsp; Current flow is induced by electrostatic induction up to an elevation of approximately {{convert|3|miles|km}} above Earth's surface.<ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power
{{quote|I have to say here that when I filed the applications of September 2, 1897, for the transmission of energy in which this method was disclosed, it was already clear to me that I did not need to have terminals at such high elevation. . . .}}

⚫ {{quote|At that time I was absolutely sure that I could put up a commercial plant, if I could do nothing else but what I had done in my laboratory on Houston Street; but I had already calculated and found that I did not need great heights to apply this method.&nbsp; My patent says that I break down the atmosphere "at or near" the terminal.&nbsp; If my conducting atmosphere is 2 or 3 miles above the plant, I consider this very near the terminal as compared to the distance of my receiving terminal, which may be across the Pacific. . . .}}</ref><ref>Henry Bradford, </ref>&nbsp; Electrical conduction and the flow of current through the upper atmospheric strata starting at a barometric pressure of approximately 130 millimeters of mercury is made possible by the creation of capacitively coupled discharge plasma through the process of atmospheric ionization.<ref>], Electromagnetic Phenomena in Complex Geometries and Nonlinear Phenomena, Non-Hertzian Waves and Magnetic Monopoles, Tesla Book Company.</ref><ref>APPARATUS FOR TRANSMISSION OF ELECTRICAL ENERGY, 2 September 1897, U.S. Patent No. 649,621, 15 May 1900</ref><ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 126, 127.</ref>&nbsp; In this way electric lamps can be lit and electric motors turned at moderate distances. The transmitted energy can be detected at much greater distances.<ref>Boksan, Slavko, <u>Nikola Tesla und sein Werk</u>, Deutscher Verlag für Jugend und Volk, 1932, pp. 237-238.</ref>


A global system for "the transmission of electrical energy without wires" called the ], dependent upon the high electrical conductivity of ] and the high electrical conductivity of the earth, was proposed as early as 1904.<ref name="Tesla Electrical world">{{cite web|url=http://www.tfcbooks.com/tesla/1904-03-05.htm |title=The Transmission of Electrical Energy Without Wires," Electrical World, March 5, 1904 |publisher=21st Century Books |date=5 March 1904 |accessdate=4 June 2009}}."</ref><ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 128–130.
⚫ Tesla theorized that electrical energy can be transmitted through the earth and the atmosphere. In the course of his research he successfully lit lamps at moderate distances and was able to detect the transmitted energy at much greater distances. The ] project was a commercial venture for trans-Atlantic wireless telephony and proof-of-concept demonstrations of global wireless power transmission. The facility was not completed because of insufficient funding.<ref>"The Future of the Wireless Art," Wireless Telegraphy and Telephony, Walter W. Massie & Charles R. Underhill, 1908, pp. 67–71</ref>
{{quote|"The earth is 4,000 miles radius.&nbsp; Around this conducting earth is an atmosphere.&nbsp; The earth is a conductor; the atmosphere above is a conductor, only there is a little stratum between 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.&nbsp; But, since the distance from the earth's surface to the conducting atmosphere is minute, as compared with the distance of the receiver at 4,000 miles, say, you can readily see that the energy cannot travel along this curve and get there, but will be immediately transformed into conduction currents, and these currents will travel like currents over a wire with a return.&nbsp; The energy will be recovered in the circuit, not by a beam that passes along this curve and is reflected and absorbed, . . . but it will travel by conduction and will be recovered in this way}}</ref>


{{main|Single-wire transmission line}} =====Terrestrial single-conductor surface wave transmission line=====
The same transmitter used for the atmospheric conduction method is used for the terrestrial single-conductor earth resonance method.<ref>, 18 Jan. 1902, U.S. Patent 1,119,732, 1 Dec. 1914.</ref><ref> {{main|Single-wire transmission line}}The basic transmitter used for the terrestrial single-conductor earth resonance method is identical to that used for the atmospheric conduction method.<ref>, 18 Jan. 1902, U.S. Patent 1,119,732, 1 Dec. 1914.</ref><ref></ref>
</ref>


Observations have been made that may be ] with a basic tenet of physics related to the scalar derivatives of the electromagnetic potentials<ref>Meyl, Konstantin, Furtwangen University, Germany</ref><ref>Meyl, Konstantin, </ref><ref>van Vlaenderen, Koen J., Institute for Basic Research, 2008</ref><ref>C. Monstein and J.P Wesley, ''Observation of scalar longitudinal electrodynamic waves'', Europhysics Letters '''59''' (2002), no. 4, 514–520.</ref><ref>{{cite journal | last1 = Chubykalo | first1 = Andrew E. | last2 = Tzontchev | first2 = Rumen I. | last3 = Rivera-Juárez | first3 = Juan M. | year = 2000 | title = Coulomb interaction does not spread instantaniously | url = | journal = Hadrionic Journal | volume = 23 | pages = 401–424 }}</ref><ref>Dea, Jack Y., "Scalar Fields: Their Prediction from Classical Electromagnetism and Interpretation from Quantum Mechanics, 1985.</ref><ref>Bearden, T. E., Solutions to Tesla's Secrets and the Soviet Tesla Weapons, 1981; John T. Ratzlaff, Reference Articles for Solutions to Tesla's Secrets.</ref> that are presently considered to be ''].<ref>Electromagnetic fields, waves and numerical methods By Zijad Haznadar, Željko Štih. Page 61.</ref>


==Timeline of wireless power== ==Timeline of wireless power==
Line 139: Line 154:
* '''1836''': ] invents the electrical transformer. * '''1836''': ] invents the electrical transformer.
* '''1864''': ] synthesizes the previous observations, experiments and equations of electricity, magnetism and optics into a consistent theory and ] the behavior of ]. * '''1864''': ] synthesizes the previous observations, experiments and equations of electricity, magnetism and optics into a consistent theory and ] the behavior of ].
* '''1888''': ] confirms the existence of electromagnetic radiation. Hertz’s "''apparatus for generating electromagnetic waves''" was a ] or ] "radio wave" ]. * '''1888''': ] confirms the existence of electromagnetic radiation.&nbsp; Hertz’s "''apparatus for generating electromagnetic waves''" was a ] or ] "radio wave" ].
* '''1891''': Tesla patents a practical method for the efficient production of high-power radio frequency electric current, {{US patent|447920}}, "Method of Operating Arc-Lamps."
* '''1893''': Tesla demonstrates the wireless illumination of phosphorescent lamps of his design at the ] in Chicago.<ref>"Electricity at the Columbian Exposition" By John Patrick Barrett. 1894. Page 168&nbsp;– 169.</ref> * '''1893''': Tesla demonstrates the wireless illumination of phosphorescent lamps of his design at the ] in Chicago.<ref>"Electricity at the Columbian Exposition" By John Patrick Barrett. 1894. Page 168&nbsp;– 169.</ref>
* '''1893''': Tesla publicly demonstrates wireless power before a meeting of the ] in St. Louis.<ref name="tfcbooks.com"/><ref>"Nikola Tesla, 1856 – 1943". IEEE History Center, IEEE, 2003. lecture-demonstration St. Louis.</ref><ref>Cheney, Margaret, Tesla Man Out of Time</ref> * '''1893''': Tesla publicly demonstrates wireless power and proposes the wireless transmission of signals before a meeting of the ] in St. Louis.<ref name="tfcbooks.com"/><ref>"Nikola Tesla, 1856 – 1943". IEEE History Center, IEEE, 2003. lecture-demonstration St. Louis.</ref><ref>Cheney, Margaret, Tesla Man Out of Time</ref><ref>{{cite web|url=http://supreme.justia.com/us/320/1/case.html|title=MARCONI WIRELESS TEL. CO. V. UNITED STATES, 320 U. S. 1 (1943)}}</ref>
* '''1894''': Tesla lights incandescent lamps wirelessly at the 35 South ] laboratory in New York City by means of "electro-dynamic induction" or resonant inductive coupling.<ref name="INVENTIONS, RESEARCHES AND WRITINGS OF NIKOLA TESLA-1">{{cite web|url=http://www.tfcbooks.com/tesla/1891-05-20.htm |title=Experiments with Alternating Currents of Very High Frequency and Their Application to Methods of Artificial Illumination, AIEE, Columbia College, N.Y., May 20, 1891 |date=20 June 1891}}</ref><ref name="INVENTIONS, RESEARCHES AND WRITINGS OF NIKOLA TESLA-2">{{cite web|url=http://www.tfcbooks.com/tesla/1892-02-03.htm |title=Experiments with Alternate Currents of High Potential and High Frequency, IEE Address,' London, February 1892 |date=1892-02-00}}</ref><ref name="INVENTIONS, RESEARCHES AND WRITINGS OF NIKOLA TESLA-3">{{cite web|url=http://www.tfcbooks.com/tesla/1893-02-24.htm |title=On Light and Other High Frequency Phenomena, 'Franklin Institute,' Philadelphia, February 1893, and National Electric Light Association, St. Louis, March 1893 |date=1893-03-00}}</ref> * '''1894''': Tesla lights incandescent lamps wirelessly at the 35 South ] laboratory in New York City by means of "electro-dynamic induction" or resonant inductive coupling.<ref name="INVENTIONS, RESEARCHES AND WRITINGS OF NIKOLA TESLA-1">{{cite web|url=http://www.tfcbooks.com/tesla/1891-05-20.htm |title=Experiments with Alternating Currents of Very High Frequency and Their Application to Methods of Artificial Illumination, AIEE, Columbia College, N.Y., May 20, 1891 |date=20 June 1891}}</ref><ref name="INVENTIONS, RESEARCHES AND WRITINGS OF NIKOLA TESLA-2">{{cite web|url=http://www.tfcbooks.com/tesla/1892-02-03.htm |title=Experiments with Alternate Currents of High Potential and High Frequency, IEE Address,' London, February 1892 |date=1892-02-00}}</ref><ref name="INVENTIONS, RESEARCHES AND WRITINGS OF NIKOLA TESLA-3">{{cite web|url=http://www.tfcbooks.com/tesla/1893-02-24.htm |title=On Light and Other High Frequency Phenomena, 'Franklin Institute,' Philadelphia, February 1893, and National Electric Light Association, St. Louis, March 1893 |date=1893-03-00}}</ref>
* '''1894''': Hutin & LeBlanc, espouse long held view that inductive energy transfer should be possible, they received U.S. Patent # 527,857 describing a system for power transmission at 3&nbsp;kHz.<ref>{{cite web|url=http://www.google.com/patents?id=XpRGAAAAEBAJ|title=Transformer System for Electric Railways|last=Hutin|first=Maurice|coauthors=Maurice LeBlanc|date=23 October 1894|publisher=United States Patent Office|accessdate=14 April 2010}}</ref> * '''1894''': Hutin & LeBlanc, espouse long held view that inductive energy transfer should be possible, they received U.S. Patent # 527,857 describing a system for power transmission at 3&nbsp;kHz.<ref>{{cite web|url=http://www.google.com/patents?id=XpRGAAAAEBAJ|title=Transformer System for Electric Railways|last=Hutin|first=Maurice|coauthors=Maurice LeBlanc|date=23 October 1894|publisher=United States Patent Office|accessdate=14 April 2010}}</ref>
* '''1894''': ] rings a bell at a distance using ] waves and also ignites ], showing that communications signals can be sent without using wires.<ref name=Bose-1>"''''". tuc.nrao.edu.</ref><ref name=Bose-2>"''''", ieeeghn.org.</ref> * '''1894''': ] rings a bell at a distance using ] waves and also ignites ], showing that communications signals can be sent without using wires.<ref name=Bose-1>"''''". tuc.nrao.edu.</ref><ref name=Bose-2>"''''", ieeeghn.org.</ref>
* '''1895''': Marconi was the first scientist to achieve successful radio transmission.<ref>{{cite web|url=http://supreme.justia.com/us/320/1/case.html|title=MARCONI WIRELESS TEL. CO. V. UNITED STATES, 320 U. S. 1 (1943)}}</ref> In summer 1895, Marconi sent signals 1.5&nbsp;miles.<ref name="Guglielmo Marconi"> -- Britannica Online Encyclopedia</ref> Developed ]. * '''1895''': Marconi demonstrates radio transmission over a distance of 1.5 miles.<ref>{{cite web|url=http://supreme.justia.com/us/320/1/case.html|title=MARCONI WIRELESS TEL. CO. V. UNITED STATES, 320 U. S. 1 (1943)}}</ref><ref name="Guglielmo Marconi"> -- Britannica Online Encyclopedia</ref> Developed ].
* '''1896''': Tesla demonstrates wireless transmission over a distance of about {{convert|48|km|mi}}.<ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 26–29.</ref> * '''1896''': Tesla demonstrates wireless transmission over a distance of about {{convert|48|km|mi}}.<ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 26–29.</ref>
* '''1897''': Tesla files his first patent application dealing specifically with ]. * '''1897''': Tesla files his first patent application dealing specifically with ].
* '''1899''': Tesla continues his wireless power transmission research in Colorado Springs and writes, "the inferiority of the induction method would appear immense as compared with the ''disturbed charge of ground and air method''."<ref>5 June 1899, </ref> * '''1899''': Tesla continues wireless power transmission research in Colorado Springs and writes, "the inferiority of the induction method would appear immense as compared with the ''disturbed charge of ground and air method''."<ref>5 June 1899, </ref>
* '''1902''': Nikola Tesla vs. Reginald Fessenden – U.S. Patent Interference No. 21,701, System of Signaling (wireless); wireless power transmission, time and frequency domain ] telecommunications, electronic ]s in general.<ref>Nikola Tesla: Guided Weapons & Computer Technology.</ref> * '''1902''': Nikola Tesla vs. Reginald Fessenden – U.S. Patent Interference No. 21,701, System of Signaling (wireless); wireless power transmission, time and frequency domain ] telecommunications, electronic ]s in general.<ref>Nikola Tesla: Guided Weapons & Computer Technology.</ref>
* '''1904''': At the St. Louis World's Fair, a prize is offered for a successful attempt to drive a 0.1 ] (75 W) ] ] by energy transmitted through space at a distance of at least {{convert|100|ft|m}}.<ref>''The Electrician'' (London), 1904).</ref> * '''1904''': At the St. Louis World's Fair, a prize is offered for a successful attempt to drive a 0.1 ] (75 W) ] ] by energy transmitted through space at a distance of at least {{convert|100|ft|m}}.<ref>''The Electrician'' (London), 1904).</ref>
* '''1916''': Tesla states, "In my system, you should free yourself of the idea that there is radiation, that energy is radiated. It is not radiated; it is conserved."<ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, p. 133.</ref> * '''1916''': Tesla states, "In my system, you should free yourself of the idea that there is radiation, that energy is radiated. It is not radiated; it is conserved."<ref>Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, p. 133.</ref>
* '''1917''': Tesla's ] is demolished. . . . * '''1917''': The ] is demolished.


* '''1926''': ] and ] publish their first paper on Uda's ''"tuned high-gain directional array"''<ref name=autogenerated2>{{cite web|url=http://ieee.cincinnati.fuse.net/reiman/05_2004.htm |title=Scanning the Past: A History of Electrical Engineering from the Past, Hidetsugu Yagi |publisher=Ieee.cincinnati.fuse.net |accessdate=4 June 2009}}</ref> better known as the ]. * '''1926''': ] and ] publish their first paper on Uda's ''"tuned high-gain directional array"''<ref name=autogenerated2>{{cite web|url=http://ieee.cincinnati.fuse.net/reiman/05_2004.htm |title=Scanning the Past: A History of Electrical Engineering from the Past, Hidetsugu Yagi |publisher=Ieee.cincinnati.fuse.net |accessdate=4 June 2009}}</ref> better known as the ].
Line 182: Line 198:
* '''2008''': Bombardier offers a new wireless power transmission product ], a system for use on trams and light-rail vehicles.<ref>{{cite web|url=http://www.bombardier.com/en/transportation/sustainability/technology/primove-catenary-free-operation?docID=0901260d800486ab |title=Bombardier PRIMOVE Technology |publisher=Bombardier.com |accessdate=4 June 2009}}</ref> * '''2008''': Bombardier offers a new wireless power transmission product ], a system for use on trams and light-rail vehicles.<ref>{{cite web|url=http://www.bombardier.com/en/transportation/sustainability/technology/primove-catenary-free-operation?docID=0901260d800486ab |title=Bombardier PRIMOVE Technology |publisher=Bombardier.com |accessdate=4 June 2009}}</ref>
* '''2008''': Industrial designer Thanh Tran, at Brunel University make a wireless lamp incorporating a high efficiency 3W LED.{{Citation needed|date=December 2009}} * '''2008''': Industrial designer Thanh Tran, at Brunel University make a wireless lamp incorporating a high efficiency 3W LED.{{Citation needed|date=December 2009}}
* '''2008''': ] reproduces Tesla's original 1894 implementation of electrodynamic induction and Prof. John Boys group's 1988 follow-up experiments by wirelessly powering a nearby light bulb with 75% efficiency.<ref>{{cite web|url=http://www.tgdaily.com/content/view/39008/113/ |title=Intel imagines wireless power for your laptop |publisher=TG Daily |date=22 August 2008 |accessdate=4 June 2009}}</ref> * '''2008''': ] reproduces the original 1894 implementation of electrodynamic induction and Prof. John Boys group's 1988 follow-up experiments by wirelessly powering a nearby light bulb with 75% efficiency.<ref>{{cite web|url=http://www.tgdaily.com/content/view/39008/113/ |title=Intel imagines wireless power for your laptop |publisher=TG Daily |date=22 August 2008 |accessdate=4 June 2009}}</ref>
* '''2008''': Greg Leyh and Mike Kennan of the ] publish a paper on Tesla's ''disturbed charge of ground and air method'' of wireless power transmission with circuit simulations and test results showing an efficiency greater than can be obtained using the electrodynamic induction method.<ref>Leyh, G. E. and M. D. Kennan, </ref> * '''2008''': Greg Leyh and Mike Kennan of the ] publish a paper on the ''disturbed charge of ground and air method'' of wireless power transmission with circuit simulations and test results showing an efficiency greater than can be obtained using the electrodynamic induction method.<ref>Leyh, G. E. and M. D. Kennan, </ref>
* '''2009''': Palm (now a division of ]) launches the ] smartphone with the ] wireless charger. * '''2009''': Palm (now a division of ]) launches the ] smartphone with the ] wireless charger.
* '''2009''': A Consortium of interested companies called the ] announce they are nearing completion for a new industry standard for low-power (which is eventually published in August 2010) ].<ref>{{cite web|url=http://www.pcworld.com/article/170360/wireless_electricity_specification_nearing_completion.html?loomia_ow=t0:s0:a41:g2:r18:c0.016236:b27254916:z0 |title=wireless electricity specification nearing completion |publisher=PCWorld |date=18 August 2009 |accessdate=21 August 2009}}</ref> * '''2009''': A Consortium of interested companies called the ] announce they are nearing completion for a new industry standard for low-power (which is eventually published in August 2010) ].<ref>{{cite web|url=http://www.pcworld.com/article/170360/wireless_electricity_specification_nearing_completion.html?loomia_ow=t0:s0:a41:g2:r18:c0.016236:b27254916:z0 |title=wireless electricity specification nearing completion |publisher=PCWorld |date=18 August 2009 |accessdate=21 August 2009}}</ref>
Line 192: Line 208:
* '''2009''': ] uses diode laser to win $900k NASA prize in power beaming, breaking several world records in power and distance, by transmitting over a kilowatt more than several hundred meters.<ref>{{cite web |url=http://www.nasa.gov/offices/ipp/innovation_incubator/centennial_challenges/cc_pb_feature_11_10_09.html |title=LaserMotive LLC Wins Prize in Power Beaming Challenge}}</ref> * '''2009''': ] uses diode laser to win $900k NASA prize in power beaming, breaking several world records in power and distance, by transmitting over a kilowatt more than several hundred meters.<ref>{{cite web |url=http://www.nasa.gov/offices/ipp/innovation_incubator/centennial_challenges/cc_pb_feature_11_10_09.html |title=LaserMotive LLC Wins Prize in Power Beaming Challenge}}</ref>
* '''2009''': Sony shows a wireless electrodynamic-induction powered TV set, 60 W over 50&nbsp;cm<ref>http://presscentre.sony.eu/content/detail.aspx?NewsAreaId=2&ReleaseID=4993</ref> * '''2009''': Sony shows a wireless electrodynamic-induction powered TV set, 60 W over 50&nbsp;cm<ref>http://presscentre.sony.eu/content/detail.aspx?NewsAreaId=2&ReleaseID=4993</ref>
* '''2010''': Haier Group debuts “the world's first” completely wireless LCD television at CES 2010 based on Prof. ]'s follow-up research on Tesla's electrodynamic induction wireless energy transmission method and the ] (WHDI).<ref>{{cite web|url=http://www.engadget.com/2010/01/07/haiers-wireless-hdtv-lacks-wires-svelte-profile-video/ |title=Haier's wireless HDTV lacks wires, svelte profile (video) |publisher=Engadget |date=7 January 2010 |accessdate=7 January 2009}}</ref> * '''2010''': Haier Group debuts “the world's first” completely wireless LCD television at CES 2010 based on Prof. ]'s follow-up research on the 1894 electrodynamic induction wireless energy transmission method and the ] (WHDI).<ref>{{cite web|url=http://www.engadget.com/2010/01/07/haiers-wireless-hdtv-lacks-wires-svelte-profile-video/ |title=Haier's wireless HDTV lacks wires, svelte profile (video) |publisher=Engadget |date=7 January 2010 |accessdate=7 January 2009}}</ref>
* '''2010''': System On Chip (SoC) group in University of British Columbia develops an optimization tool for the design of highly efficient wireless power transmission systems using multiple coils. The design is optimized for implantable applications and power transfer efficiency of 82% is achieved.<ref>{{cite web|url=http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5595028&isnumber=4358093 |title= Anil Kumar RamRakhyani; Shahriar Mirabbasi; Mu Chiao; , "Design and Optimization of Resonance-Based Efficient Wireless Power Delivery Systems for Biomedical Implants," IEEE Transactions on Biomedical Circuits and Systems}}</ref> * '''2010''': System On Chip (SoC) group in University of British Columbia develops a highly efficient wireless power transmission systems using 4-coils. The design is optimized for implantable applications and power transfer efficiency of 82% is achieved.<ref>{{cite web|url=http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5595028&isnumber=4358093 |title= Anil Kumar RamRakhyani; Shahriar Mirabbasi; Mu Chiao; , "Design and Optimization of Resonance-Based Efficient Wireless Power Delivery Systems for Biomedical Implants," IEEE Transactions on Biomedical Circuits and Systems}}</ref>
* '''2012''': "Bioelectromagnetics and Implantable Devices" group in University of Utah, USA develops an efficient multi-Coil telemetry system for power and data transfer in biomedical Implants. Design approach is extendable to other industrial "smart" wireless power transfer system. Proposed multi-coil based telemetry system achieves more than twice power transfer efficiency and higher tunable frequency bandwidth as compared to its equivalent two-coil design. Based on circuit theory, analytical formulation is proposed to optimize the design for maximum power transfer, frequency bandwidth and power transfer efficiency. <ref>{{cite web|url=http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6192334 |title= Anil Kumar RamRakhyani; Gianluca Lazzi;, "On the Design of Efficient Multi-Coil Telemetry System for Biomedical Implants," IEEE Transactions on Biomedical Circuits and Systems}}</ref>


==See also== ==See also==
Line 242: Line 259:
* , – microwave beam powered. * , – microwave beam powered.
* – wireless power transmission pages. * – wireless power transmission pages.
* – Tesla demonstrated resonant magnetic induction over 110 years ago. * – The resonant magnetic induction method was demonstrated in 1894.


{{Emerging technologies}}


{{DEFAULTSORT:Wireless Energy Transfer}} {{DEFAULTSORT:Wireless Energy Transfer}}

Revision as of 13:06, 29 July 2012

Wireless energy transfer or wireless power is the transmission of electrical energy from a power source to an electrical load without interconnecting manmade conductors.  Wireless transmission is useful in cases where interconnecting wires are inconvenient, hazardous, or impossible.  The problem of wireless power transmission differs from that of wireless telecommunications, such as radio.  In the latter, the proportion of energy received becomes critical only if it is too low for the signal to be distinguished from the background noise.  With wireless power, efficiency is the more significant parameter.  A large part of the energy sent out by the generating plant must arrive at the receiver or receivers to make the system economical.

The most common form of wireless power transmission is carried out using direct induction followed by resonant magnetic induction. Other methods under consideration include electromagnetic radiation in the form of microwaves or lasers.

Electric energy transfer

Main article: Coupling (electronics)

An electric current flowing through a conductor, such as a wire, carries electrical energy.  When an electric current passes through a circuit there is an electric field in the dielectric surrounding the conductor; magnetic field lines around the conductor and lines of electric force radially about the conductor.

In a direct current circuit, if the current is continuous, the fields are constant; there is a condition of stress in the space surrounding the conductor, which represents stored electric and magnetic energy, just as a compressed spring or a moving mass represents stored energy.  In an alternating current circuit, the fields also alternate; that is, with every half wave of current and of voltage, the magnetic and the electric field start at the conductor and run outwards into space with the speed of light. Where these alternating fields impinge on another conductor a voltage and a current are induced.

Any change in the electrical conditions of the circuit, whether internal or external involves a readjustment of the stored magnetic and electric field energy of the circuit, that is, a so-called transient.  A transient is of the general character of a condenser discharge through an inductive circuit. The phenomenon of the condenser discharge through an inductive circuit therefore is of the greatest importance to the engineer, as the foremost cause of high-voltage and high-frequency troubles in electric circuits.

Electromagnetic induction is proportional to the intensity of the current and voltage in the conductor which produces the fields and to the frequency.  The higher the frequency the more intense the induction effect.  Energy is transferred from a conductor that produces the fields (the primary) to any conductor on which the fields impinge (the secondary).  Part of the energy of the primary conductor passes inductively across space into secondary conductor and the energy decreases rapidly along the primary conductor.  A high frequency current does not pass for long distances along a conductor but rapidly transfers its energy by induction to adjacent conductors.  Higher induction resulting from the higher frequency is the explanation of the apparent difference in the propagation of high frequency disturbances from the propagation of the low frequency power of alternating current systems.  The higher the frequency the more preponderant become the inductive effects that transfer energy from circuit to circuit across space. The more rapidly the energy decreases and the current dies out along the circuit, the more local is the phenomenon.

The flow of electric energy thus comprises phenomena inside of the conductor and phenomena in the space outside of the conductor—the electric field—which, in a continuous current circuit, is a condition of steady magnetic and dielectric stress, and in an alternating current circuit is alternating, that is, an electric wave launched by the conductor to become far-field electromagnetic radiation traveling through space with the speed of light.

In electric power transmission and distribution, the phenomena inside of the conductor are of main importance, and the electric field of the conductor is usually observed only incidentally.  Inversely, in the use of electric power for radio telecommunications it is only the electric and magnetic fields outside of the conductor, that is electromagnetic radiation, which is of importance in transmitting the message.  The phenomenon in the conductor, the current in the launching structure, is not used.

The electric charge displacement in the conductor produces a magnetic field and resultant lines of electric force.  The magnetic field is a maximum in the direction concentric, or approximately so, to the conductor.  That is, a ferromagnetic body tends to set itself in a direction at right angles to the conductor.  The electric field has a maximum in a direction radial, or approximately so, to the conductor.  The electric field component tends in a direction radial to the conductor and dielectric bodies may be attracted or repelled radially to the conductor.

The electric field of a circuit over which energy flows has three main axes at right angles with each other:

  1. The magnetic field, concentric with the conductor.
  2. The lines of electric force, radial to the conductor.
  3. The power gradient, parallel to the conductor.

Where the electric circuit consists of several conductors, the electric fields of the conductors superimpose upon each other, and the resultant magnetic field lines and lines of electric force are not concentric and radial respectively, except approximately in the immediate neighborhood of the conductor.  Between parallel conductors they are conjugate of circles.  Neither the power consumption in the conductor, nor the magnetic field, nor the electric field, are proportional to the flow of energy through the circuit.  However, the product of the intensity of the magnetic field and the intensity of the electric field is proportional to the flow of energy or the power, and the power is therefore resolved into a product of the two components i and e, which are chosen proportional respectively to the intensity of the magnetic field and of the electric field.  The component called the current is defined as that factor of the electric power which is proportional to the magnetic field, and the other component, called the voltage, is defined as that factor of the electric power which is proportional to the electric field.

In radio telecommunications the electric field of the transmit antenna propagates through space as a radio wave and impinges upon the receive antenna where it is observed by its magnetic and electric effect. Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X rays and gamma rays are shown to be the same electromagnetic radiation phenomenon, differing one from the other only in frequency of vibration.

Electromagnetic induction

Energy transfer by electromagnetic induction is typically magnetic but capacitive coupling can also be achieved.

Electrodynamic induction method

Main articles: Inductive coupling, Electrodynamic induction, and Resonant inductive coupling

The electrodynamic induction wireless transmission technique is near field over distances up to about one-sixth of the wavelength used.  Near field energy itself is non-radiative but some radiative losses do occur.  In addition there are usually resistive losses.  With electrodynamic induction, electric current flowing through a primary coil creates a magnetic field that acts on a secondary coil producing a current within it.  Coupling must be tight in order to achieve high efficiency.  As the distance from the primary is increased, more and more of the magnetic field misses the secondary.  Even over a relatively short range the inductive coupling is grossly inefficient, wasting much of the transmitted energy.

This action of an electrical transformer is the simplest form of wireless power transmission.  The primary and secondary circuits of a transformer are not directly connected.  Energy transfer takes place through a process known as mutual induction.  Principal functions are stepping the primary voltage either up or down and electrical isolation.  Mobile phone and electric toothbrush battery chargers, and electrical power distribution transformers are examples of how this principle is used.  Induction cookers use this method.  The main drawback to this basic form of wireless transmission is short range.  The receiver must be directly adjacent to the transmitter or induction unit in order to efficiently couple with it.

The application of resonance increases the transmission range somewhat.  When resonant coupling is used, the transmitter and receiver inductors are tuned to the same natural frequency.  Performance can be further improved by modifying the drive current from a sinusoidal to a nonsinusoidal transient waveform. Pulse power transfer occurs over multiple cycles.  In this way significant power may be transmitted between two mutually-attuned LC circuits having a relatively low coefficient of coupling.  Transmitting and receiving coils are usually single layer solenoids or flat spirals with series capacitors, which, in combination, allow the receiving element to be tuned to the transmitter frequency.

Common uses of resonance-enhanced electrodynamic induction are charging the batteries of portable devices such as laptop computers and cell phones, medical implants and electric vehicles. A localized charging technique selects the appropriate transmitting coil in a multilayer winding array structure. Resonance is used in both the wireless charging pad (the transmitter circuit) and the receiver module (embedded in the load) to maximize energy transfer efficiency.  This approach is suitable for universal wireless charging pads for portable electronics such as mobile phones.  It has been adopted as part of the Qi wireless charging standard.

It is also used for powering devices having no batteries, such as RFID patches and contactless smartcards, and to couple electrical energy from the primary inductor to the helical resonator of Tesla coil wireless power transmitters.

Electrostatic induction method

Main article: Capacitive coupling
The illumination of two exhausted tubes by means of a powerful, rapidly alternating electrostatic field created between two vertical metal sheets suspended from the ceiling on insulating cords.  This involves the physics of electrostatic induction.

Electrostatic or capacitive coupling is the passage of electrical energy through a dielectric.  In practice it is an electric field gradient or differential capacitance between two or more insulated terminals, plates, electrodes, or nodes that are elevated over a conducting ground plane.  The electric field is created by charging the plates with a high potential, high frequency alternating current power supply.  The capacitance between two elevated terminals and a powered device form a voltage divider.

The electric energy transmitted by means of electrostatic induction can be utilized by a receiving device, such as a wireless lamp. Tesla demonstrated the illumination of wireless lamps by energy that was coupled to them through an alternating electric field.

"Instead of depending on electrodynamic induction at a distance to light the tube . . . ideal way of lighting a hall or room would . . . be to produce such a condition in it that an illuminating device could be moved and put anywhere, and that it is lighted, no matter where it is put and without being electrically connected to anything.  I have been able to produce such a condition by creating in the room a powerful, rapidly alternating electrostatic field.  For this purpose I suspend a sheet of metal a distance from the ceiling on insulating cords and connect it to one terminal of the induction coil, the other terminal 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 being carefully determined.  An exhausted tube may then be carried in the hand anywhere between the sheets or placed anywhere, even a certain distance beyond them; it remains always luminous."

The principle of electrostatic induction is applicable to the electrical conduction wireless transmission method.

“In some cases when small amounts of energy are required the high elevation of the terminals, 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 of energy may be collected at that terminal by electrostatic induction from the upper air strata, which are rendered conducting by the active terminal of the transmitter or through which the currents from the same are conveyed."

Electromagnetic radiation

Far field methods achieve longer ranges, often multiple kilometer ranges, where the distance is much greater than the diameter of the device(s). The main reason for longer ranges with radio wave and optical devices is the fact that electromagnetic radiation in the far-field can be made to match the shape of the receiving area (using high directivity antennas or well-collimated Laser Beam) thereby delivering almost all emitted power at long ranges. The maximum directivity for antennas is physically limited by diffraction.

Beamed power, size, distance, and efficiency

The dimensions of the components may be dictated by the distance from transmitter to receiver, the wavelength and the Rayleigh criterion or diffraction limit, used in standard radio frequency antenna design, which also applies to lasers. In addition to the Rayleigh criterion Airy's diffraction limit is also frequently used to determine an approximate spot size at an arbitrary distance from the aperture.

The Rayleigh criterion dictates that any radio wave, microwave or laser beam will spread and become weaker and diffuse over distance; the larger the transmitter antenna or laser aperture compared to the wavelength of radiation, the tighter the beam and the less it will spread as a function of distance (and vice versa). Smaller antennae also suffer from excessive losses due to side lobes. However, the concept of laser aperture considerably differs from an antenna. Typically, a laser aperture much larger than the wavelength induces multi-moded radiation and mostly collimators are used before emitted radiation couples into a fiber or into space.

Ultimately, beamwidth is physically determined by diffraction due to the dish size in relation to the wavelength of the electromagnetic radiation used to make the beam. Microwave power beaming can be more efficient than lasers, and is less prone to atmospheric attenuation caused by dust or water vapor losing atmosphere to vaporize the water in contact.

Then the power levels are calculated by combining the above parameters together, and adding in the gains and losses due to the antenna characteristics and the transparency and dispersion of the medium through which the radiation passes. That process is known as calculating a link budget.

Microwave method

Main article: Microwave power transmission
An artist's depiction of a solar satellite that could send electric energy by microwaves to a space vessel or planetary surface.

Power transmission via radio waves can be made more directional, allowing longer distance power beaming, with shorter wavelengths of electromagnetic radiation, typically in the microwave range.  A rectenna may be used to convert the microwave energy back into electricity. Rectenna conversion efficiencies exceeding 95% have been realized. Power beaming using microwaves has been proposed for the transmission of energy from orbiting solar power satellites to Earth and the beaming of power to spacecraft leaving orbit has been considered.

Power beaming by microwaves has the difficulty that for most space applications the required aperture sizes are very large due to diffraction limiting antenna directionality.  For example, the 1978 NASA Study of solar power satellites required a 1-km diameter transmitting antenna, and a 10 km diameter receiving rectenna, for a microwave beam at 2.45 GHz. These sizes can be somewhat decreased by using shorter wavelengths, although short wavelengths may have difficulties with atmospheric absorption and beam blockage by rain or water droplets. Because of the "thinned array curse," it is not possible to make a narrower beam by combining the beams of several smaller satellites.

For earthbound applications a large area 10 km diameter receiving array allows large total power levels to be used while operating at the low power density suggested for human electromagnetic exposure safety. A human safe power density of 1 mW/cm distributed across a 10 km diameter area corresponds to 750 megawatts total power level. This is the power level found in many modern electric power plants.

Following World War II, which saw the development of high-power microwave emitters known as cavity magnetrons, the idea of using microwaves to transmit power was researched. By 1964 a miniature helicopter propelled by microwave power had been demonstrated.

Japanese researcher Hidetsugu Yagi also investigated wireless energy transmission using a directional array antenna that he designed. In February 1926, Yagi and Uda published their first paper on the tuned high-gain directional array now known as the Yagi antenna. While it did not prove to be particularly useful for power transmission, this beam antenna has been widely adopted throughout the broadcasting and wireless telecommunications industries due to its excellent performance characteristics.

Wireless high power transmission using microwaves is well proven. Experiments in the tens of kilowatts have been performed at Goldstone in California in 1975 and more recently (1997) at Grand Bassin on Reunion Island. These methods achieve distances on the order of a kilometer.

Laser method

With a laser beam centered on its panel of photovoltaic cells, a lightweight model plane makes the first flight of an aircraft powered by a laser beam inside a building at NASA Marshall Space Flight Center.

In the case of electromagnetic radiation closer to visible region of spectrum (10s of microns (um) to 10s of nm), power can be transmitted by converting electricity into a laser beam that is then pointed at a solar cell receiver. This mechanism is generally known as "powerbeaming" because the power is beamed at a receiver that can convert it to usable electrical energy.

Advantages of laser based energy transfer compared with other wireless methods are:

  1. collimated monochromatic wavefront propagation allows narrow beam cross-section area for energy transmission over large ranges.
  2. compact size of solid state lasers-photovoltaics semiconductor diodes fit into small products.
  3. no radio-frequency interference to existing radio communication such as Wi-fi and cell phones.
  4. control of access; only receivers illuminated by the laser receive power.

Its drawbacks are:

  1. Conversion to light, such as with a laser, is inefficient
  2. Conversion back into electricity is inefficient, with photovoltaic cells achieving 40%–50% efficiency. (Note that conversion efficiency is rather higher with monochromatic light than with insolation of solar panels).
  3. Atmospheric absorption causes losses.
  4. As with microwave beaming, this method requires a direct line of sight with the target.

The laser "powerbeaming" technology has been mostly explored in military weapons and aerospace applications and is now being developed for commercial and consumer electronics Low-Power applications.  Wireless energy transfer system using laser for consumer space has to satisfy Laser safety requirements standardized under IEC 60825.

To develop an understanding of the trade-offs of Laser ("a special type of light wave"-based system):

  1. Propagation of a laser beam (on how Laser beam propagation is much less affected by diffraction limits)
  2. Coherence and the range limitation problem (on how spatial and spectral coherence characteristics of Lasers allows better distance-to-power capabilities)
  3. Airy disk (on how wavelength fundamentally dictates the size of a disk with distance)
  4. Applications of laser diodes (on how the laser sources are utilized in various industries and their sizes are reducing for better integration)

Geoffrey Landis is one of the pioneers of solar power satellite and laser-based transfer of energy especially for space and lunar missions. The continuously increasing demand for safe and frequent space missions has resulted in serious thoughts on a futuristic space elevator that would be powered by lasers. NASA's space elevator would need wireless power to be beamed to it for it to climb a tether.

NASA's Dryden Flight Research Center has demonstrated flight of a lightweight unmanned model plane powered by a laser beam. This proof-of-concept demonstrates the feasibility of periodic recharging using the laser beam system and the lack of need to return to ground.

Electrical conduction

The Tesla coil wireless transmitter
U.S. patent 1,119,732
Means for long conductors of electricity forming part of an electric circuit and electrically connecting said ionized beam to an electric circuit. Hettinger 1917 -(U.S. patent 1,309,031)
Main article: World Wireless System

Disturbed charge of ground and air method

The wireless transmission of alternating current electricity through the earth with an equivalent electrical displacement through the air above it achieves long ranges that are superior to the resonant electrical induction methods and favorably comparable to the electromagnetic radiation methods.  Electrical energy can be transmitted through inhomogeneous Earth with low loss because the net resistance between earth antipodes is considerably less than 1 ohm. The electrical displacement takes place predominantly by electrical conduction through the oceans, and metallic ore bodies and similar subsurface structures. The electrical displacement is also by means of electrostatic induction through the more dielectric regions such as quartz deposits and other non-conducting minerals.

This energy transfer technique is suitable for transmission of electrical power in industrial quantities and also for wireless broadband telecommunications.   The Wardenclyffe Tower project was an early commercial venture for trans-Atlantic wireless telephony and proof-of-concept demonstrations of global wireless power transmission using this method.  The facility was not completed due to insufficient funding.

Terrestrial transmission line with atmospheric return

Single wire with Earth return electrical power transmission systems rely on current flowing through the earth plus a single wire insulated from the earth to complete the circuit. In emergencies high-voltage direct current power transmission systems can also operate in the 'single wire with earth return' mode. Elimination of the raised insulated wire, and transmission of high-potential alternating current through the earth with an atmospheric return circuit is the basis of this method of wireless electrical power transmission.

The atmospheric conduction method depends upon the passage of electrical current through the earth, and through the upper troposphere and the stratosphere.  Current flow is induced by electrostatic induction up to an elevation of approximately 3 miles (4.8 km) above Earth's surface.  Electrical conduction and the flow of current through the upper atmospheric strata starting at a barometric pressure of approximately 130 millimeters of mercury is made possible by the creation of capacitively coupled discharge plasma through the process of atmospheric ionization.  In this way electric lamps can be lit and electric motors turned at moderate distances. The transmitted energy can be detected at much greater distances.

A global system for "the transmission of electrical energy without wires" called the World Wireless System, dependent upon the high electrical conductivity of plasma and the high electrical conductivity of the earth, was proposed as early as 1904.

Terrestrial single-conductor surface wave transmission line
Main article: Single-wire transmission line

The basic transmitter used for the terrestrial single-conductor earth resonance method is identical to that used for the atmospheric conduction method.

Observations have been made that may be inconsistent with a basic tenet of physics related to the scalar derivatives of the electromagnetic potentials that are presently considered to be nonphysical.

Timeline of wireless power

  • 1820: André-Marie Ampère develops Ampere’s law showing that electric current produces a magnetic field.
  • 1831: Michael Faraday develops Faraday’s law of induction describing the electromagnetic force induced in a conductor by a time-varying magnetic flux.
  • 1836: Nicholas Callan invents the electrical transformer.
  • 1864: James Clerk Maxwell synthesizes the previous observations, experiments and equations of electricity, magnetism and optics into a consistent theory and mathematically models the behavior of electromagnetic radiation.
  • 1888: Heinrich Rudolf Hertz confirms the existence of electromagnetic radiation.  Hertz’s "apparatus for generating electromagnetic waves" was a VHF or UHF "radio wave" spark gap transmitter.
  • 1891: Tesla patents a practical method for the efficient production of high-power radio frequency electric current, U.S. patent 447,920, "Method of Operating Arc-Lamps."
  • 1893: Tesla demonstrates the wireless illumination of phosphorescent lamps of his design at the World's Columbian Exposition in Chicago.
  • 1893: Tesla publicly demonstrates wireless power and proposes the wireless transmission of signals before a meeting of the National Electric Light Association in St. Louis.
  • 1894: Tesla lights incandescent lamps wirelessly at the 35 South Fifth Avenue laboratory in New York City by means of "electro-dynamic induction" or resonant inductive coupling.
  • 1894: Hutin & LeBlanc, espouse long held view that inductive energy transfer should be possible, they received U.S. Patent # 527,857 describing a system for power transmission at 3 kHz.
  • 1894: Jagdish Chandra Bose rings a bell at a distance using electromagnetic waves and also ignites gunpowder, showing that communications signals can be sent without using wires.
  • 1895: Marconi demonstrates radio transmission over a distance of 1.5 miles. Developed Marconi's Law.
  • 1896: Tesla demonstrates wireless transmission over a distance of about 48 kilometres (30 mi).
  • 1897: Tesla files his first patent application dealing specifically with wireless transmission.
  • 1899: Tesla continues wireless power transmission research in Colorado Springs and writes, "the inferiority of the induction method would appear immense as compared with the disturbed charge of ground and air method."
  • 1902: Nikola Tesla vs. Reginald Fessenden – U.S. Patent Interference No. 21,701, System of Signaling (wireless); wireless power transmission, time and frequency domain spread spectrum telecommunications, electronic logic gates in general.
  • 1904: At the St. Louis World's Fair, a prize is offered for a successful attempt to drive a 0.1 horsepower (75 W) airship motor by energy transmitted through space at a distance of at least 100 feet (30 m).
  • 1916: Tesla states, "In my system, you should free yourself of the idea that there is radiation, that energy is radiated. It is not radiated; it is conserved."
  • 1917: The Wardenclyffe tower is demolished.
  • 1961: William C. Brown publishes an article exploring possibilities of microwave power transmission.
  • 1964: Brown demonstrates on CBS News with Walter Cronkite a model helicopter that receives all of the power needed for flight from a microwave beam. Between 1969 and 1975, Brown is technical director of a JPL Raytheon program that beams 30 kW over a distance of 1600 meters (1 mile) at 84% efficiency.
  • 1968: Peter Glaser proposes wirelessly transmitting solar energy captured in space using "Powerbeaming" technology. This is usually recognized as the first description of a solar power satellite.
  • 1971: Prof. Don Otto develops a small trolley powered by induction at The University of Auckland, in New Zealand.
  • 1973: The world's first passive RFID system is demonstrated at Los-Alamos National Lab.
  • 1975: Goldstone Deep Space Communications Complex does experiments in the tens of kilowatts.
  • 1988: A power electronics group led by Prof. John Boys at The University of Auckland in New Zealand, develops an inverter using novel engineering materials and power electronics and conclude that power transmission by means of electrodynamic induction should be achievable. A first prototype for a contact-less power supply is built. Auckland Uniservices, the commercial company of The University of Auckland, patents the technology.
  • 1989: Daifuku, a Japanese company, engages Auckland Uniservices Ltd. to develop technology for car assembly plants and materials handling providing challenging technical requirements including multiplicity of vehicles.
  • 1990: Prof. John Boys team develops novel technology enabling multiple vehicles to run on the same inductive power loop and provide independent control of each vehicle. Auckland UniServices Patents the technology.
  • 1996: Auckland Uniservices develops an Electric Bus power system using electrodynamic induction to charge (30–60 kW) opportunistically commencing implementation in New Zealand. Prof John Boys Team commission 1st commercial IPT Bus in the world at Whakarewarewa, in New Zealand.
  • 1998: RFID tags are powered by electrodynamic induction over a few feet.
  • 1999: Dr. Herbert L. Becker powers a lamp and a hand held fan from a distance of 30 feet.
  • 1999: Prof. Shu Yuen (Ron) Hui and Mr. S.C. Tang file a patent on "Coreless Printed-Circuit-Board (PCB) transformers and operating techniques", which form the basis for future planar charging surface with "vertical flux" leaving the planar surface. The circuit uses resonant circuits for wireless power transfer. EP(GB)0935263B
  • 2000: Prof. Shu Yuen (Ron) Hui invent a planar wireless charging pad using the "vertical flux" approach and resonant power transfer for charging portable consumer electronic products. A patent is filed on "Apparatus and method of an inductive battery charger,” PCT Patent PCT/AU03/00 721, 2000.
  • 2000: Based on the coreless PCB transformer developed by Prof. Ron Hui, Prof. B. Choi and his team at Kyungpook National University publish a paper on “A new contactless battery charger for portable telecommunication/computing electronics,” in Proc. ICCE’00 Int. Conf. Consumer Electron., 2000, pp. 58–59. The coreless PCB transformer is used to wirelessly charge a mobile phone.
  • 2001 Prof. Shu Yuen (Ron) Hui and Dr. S.C. Tang file a patent on "Planar Printed-Circuit-Board Transformers with Effective Electromagnetic Interference (EMI) Shielding". The EM shield consists of a thin layer of ferrite and a thin layer of copper sheet. It enables the underneath of the future wireless charging pads to be shielded with a thin EM shield structure with thickness of typically 0.7mm or less. Patent: US6,501,364.
  • 2001: Prof. Ron Hui's team demonstrate that the coreless PCB transformer can transmit power close to 100W in ‘A low-profile low-power converter with coreless PCB isolation transformer, IEEE Transactions on Power Electronics, Volume: 16 Issue: 3 , May 2001. A team of Philips Research Center Aachen, led by Dr. Eberhard Waffenschmidt, use it to power an 100W lighting device in their paper "Size advantage of coreless transformers in the MHz range" in the European Power Electronics Conference in Graz.
  • 2001: Splashpower formed in the UK. Uses coupled resonant coils in a flat "pad" style to transfer tens of watts into a variety of consumer devices, including lamp, phone, PDA, iPod etc.
  • 2002: Prof. Shu Yuen (Ron) Hui extends the planar wireless charging pad concept using the vertical flux approach to incorporate free-positioning feature for multiple loads. This is achieved by using a multilayer planar winding array structure. Patent were granted as "Planar Inductive Battery Charger", GB2389720 and GB 2389767.
  • 2004: Electrodynamic induction used by 90 percent of the US$1 billion clean room industry for materials handling equipment in semiconductor, LCD and plasma screen manufacture.
  • 2005: Prof. Shu Yuen (Ron) Hui and Dr. W.C. Ho publish their work in the IEEE Transactions on a planar wireless charging platform with free-positioning feature. The planar wireless charging pad is able to charge several loads simultaneously on a flat surface.
  • 2005: Prof Boys' team at The University of Auckland, refines 3-phase IPT Highway and pick-up systems allowing transmission of power to moving vehicles in the lab.
  • 2007: A localized charging technique is reported by Dr. Xun Liu and Prof. Ron Hui for the wireless charging pad with free-positioning feature. With the aid of the double-layer EM shields enclosing the transmitter and receiver coils, the localized charging selects the right transmitter coil so as to minimize flux leakage and human exposure to radiation.
  • 2007: Using electrodynamic induction a physics research group, led by Prof. Marin Soljacic, at MIT, wirelessly power a 60W light bulb with 40% efficiency at a 2 metres (6.6 ft) distance with two 60 cm-diameter coils.
  • 2008: Bombardier offers a new wireless power transmission product PRIMOVE, a system for use on trams and light-rail vehicles.
  • 2008: Industrial designer Thanh Tran, at Brunel University make a wireless lamp incorporating a high efficiency 3W LED.
  • 2008: Intel reproduces the original 1894 implementation of electrodynamic induction and Prof. John Boys group's 1988 follow-up experiments by wirelessly powering a nearby light bulb with 75% efficiency.
  • 2008: Greg Leyh and Mike Kennan of the Nevada Lightning Laboratory publish a paper on the disturbed charge of ground and air method of wireless power transmission with circuit simulations and test results showing an efficiency greater than can be obtained using the electrodynamic induction method.
  • 2009: Palm (now a division of HP) launches the Palm Pre smartphone with the Palm Touchstone wireless charger.
  • 2009: A Consortium of interested companies called the Wireless Power Consortium announce they are nearing completion for a new industry standard for low-power (which is eventually published in August 2010) inductive charging.
  • 2009: An Ex approved Torch and Charger aimed at the offshore market is introduced. This product is developed by Wireless Power & Communication, a Norway based company.
  • 2009: A simple analytical electrical model of electrodynamic induction power transmission is proposed and applied to a wireless power transfer system for implantable devices.
  • 2009: Lasermotive uses diode laser to win $900k NASA prize in power beaming, breaking several world records in power and distance, by transmitting over a kilowatt more than several hundred meters.
  • 2009: Sony shows a wireless electrodynamic-induction powered TV set, 60 W over 50 cm
  • 2010: Haier Group debuts “the world's first” completely wireless LCD television at CES 2010 based on Prof. Marin Soljacic's follow-up research on the 1894 electrodynamic induction wireless energy transmission method and the Wireless Home Digital Interface (WHDI).
  • 2010: System On Chip (SoC) group in University of British Columbia develops a highly efficient wireless power transmission systems using 4-coils. The design is optimized for implantable applications and power transfer efficiency of 82% is achieved.
  • 2012: "Bioelectromagnetics and Implantable Devices" group in University of Utah, USA develops an efficient multi-Coil telemetry system for power and data transfer in biomedical Implants. Design approach is extendable to other industrial "smart" wireless power transfer system. Proposed multi-coil based telemetry system achieves more than twice power transfer efficiency and higher tunable frequency bandwidth as compared to its equivalent two-coil design. Based on circuit theory, analytical formulation is proposed to optimize the design for maximum power transfer, frequency bandwidth and power transfer efficiency.

See also

Further reading

Books
  • Walker, J., Halliday, D., & Resnick, R. (2011). Fundamentals of physics. Hoboken, NJ: Wiley.
  • Hu, A. P. (2009). Wireless/Contactless power supply: Inductively coupled resonant converter solutions. Saarbrücken, Germany: VDM Verlag Dr. Müller.
  • Valone, T. (2002). Harnessing the wheelwork of nature: Tesla's science of energy. Kempton, Ill: Adventure Unlimited Press.
  • General Electric Co. (1915). General Electric review, Volume 18. "Wireless Transmission of Energy" By Elihu Thomson. General Electric Company, Lynn. (ed. Lecture by Professor Thomson, National Electric Light Association, New York.)
  • Steinmetz, C. P. (1914). Elementary lectures on electric discharges, waves and impulses, and other transients. New York: McGraw-Hill book co., inc.
  • Louis Cohen (1913). Formulae and tables for the calculation of alternating current problems. McGraw-Hill.
  • Kennelly, A. E. (1912). The application of hyperbolic functions to electrical engineering problems: Being the subject of a course of lectures delivered before the University of London in May and June 1911. London: University of London Press.
  • Orlich, E. M. (1912). Die Theorie der Wechselströme.
  • Fleming, J. A. (1916) The principles of electric wave telegraphy and telephony. London: Longmans, Green and Co.
  • Fleming, J. A. (1911). Propagation of electric currents in telephone & telegraph conductors. New York: Van Nostrand.
  • Franklin, W. S. (1909). Electric waves: An advanced treatise on alternating-current theory. New York: Macmillan Co.
Patents

References

  1. A radio transmitter can produce waves having a power of several kilowatts or even megawatts but this energy scatters in all directions.  Only a small fraction, less than a millionth part, of the transmitted energy is received.  However, this is sufficient to yield the intelligence.
  2. ^ G. A. Landis, "Applications for Space Power by Laser Transmission," SPIE Optics, Electro-optics & Laser Conference, Los Angeles CA, 24–28 January 1994; Laser Power Beaming, SPIE Proceedings Vol. 2121, 252–255.
  3. ^ General Electric review, Volume 15 By General Electric.  "Velocity of Propagation of Electric Field", Charles Proteus Steinmetz
  4. 188,000 miles per second
  5. Such as an internal change of load, starting and switching operations, and short circuits.
  6. Such as the external change due to lightning.
  7. Charles Steinmetz (Fellow, A. I. E. E. Chief Consulting Engineer, General Electric Company, Schenectady, N. Y.). "Condenser Discharge Through a General Gas Circuit". American Institute of Electrical Engineers., 1922. Transactions of the American Institute of Electrical Engineers. New York: American Institute of Electrical Engineers. Presented at the 10th Midwinter Convention of the A. I. E. E., New York, N. Y., 15–17 February 1922.
  8. viz., the dissipation of electric energy by the resistance of the conductor through its conversion into heat;
  9. Such as when it gives trouble by induction in telephone circuits or when it reaches such high intensities as to puncture insulation, cause mechanical motion, etc.
  10. such as an iron needle.
  11. ^ Theory and calculation of transient electric phenomena and oscillations By Charles Proteus Steinmetz
  12. Speculation was made as to what the electric wave was, leading to the contradictory deductions that for certain reasons space is considered as a gas of infinitely low density, and for certain others as a solid.
  13. Dave Baarman and Joshua Schwannecke (2009-12-00). "Understanding Wireless Power" (PDF). {{cite web}}: Check date values in: |date= (help)
  14. Steinmetz, Charles Proteus (29 August 2008). Steinmetz, Dr. Charles Proteus, Elementary Lectures on Electric Discharges, Waves, and Impulses, and Other Transients, 2nd Edition, McGraw-Hill Book Company, Inc., 1914. Google Books. Retrieved 4 June 2009.
  15. "Wireless charging, Adaptor die, Mar 5th 2009". The Economist. 7 November 2008. Retrieved 4 June 2009.
  16. Buley, Taylor (9 January 2009). "Wireless technologies are starting to power devices, 01.09.09, 06:25 pm EST". Forbes. Retrieved 4 June 2009.
  17. "Alternative Energy, From the unsustainable...to the unlimited". EETimes.com. 21 June 2010.
  18. Patent Application PCT/CN2008/0728855
  19. Patent US7164255
  20. ^ Norrie, H. S., "Induction Coils: How to make, use, and repair them". Norman H. Schneider, 1907, New York. 4th edition.
  21. Electrical experimenter, January 1919. pg. 615
  22. Tesla: Man Out of Time, Margaret Cheney., p. 174
  23. Experiments with Alternate Currents of Very High Frequency and Their Application to Methods of Artificial Illumination, AIEE, Columbia College, N.Y., 20 May 1891
  24. Experiments with Alternate Currents of High Potential and High Frequency, IEE Address, London, February 1892
  25. ^ "On Light and Other High Frequency Phenomena, Franklin Institute, Philadelphia, February 1893, and National Electric Light Association, St. Louis, March 1893
  26. Gernsback, Hugo.  "Nikola Tesla and His Achievements," Electrical Experimenter, January 1919. p. 615
  27. Cheney, Margaret. Tesla: Man Out of Time, p. 174
  28. Martin, T. C., & Tesla, N. (1894). Inventions, Researches and Writings of Nikola Tesla, with special reference to his work in polyphase currents and high potential lighting. New York: The Electrical Engineer. Page 188.
  29. Systems of Transmission of Electrical Energy, U.S. Patent No. 645,576, March 20, 1900.
  30. G. Landis, M. Stavnes, S. Oleson and J. Bozek, "Space Transfer With Ground-Based Laser/Electric Propulsion" (AIAA-92-3213) NASA Technical Memorandum TM-106060 (1992).
  31. Landis, Geoffrey A. (May 7–12, 2006). Reevaluating Satellite Solar Power Systems for Earth (PDF). IEEE 4th World Conference on Photovoltaic Energy Conversion. p. 2. Retrieved May 11, 2012.{{cite conference}}: CS1 maint: date format (link)
  32. Experimental Airborne Microwave Supported Platform Descriptive Note : Final rept. Jun 64 – Apr 65
  33. ^ "Scanning the Past: A History of Electrical Engineering from the Past, Hidetsugu Yagi". Ieee.cincinnati.fuse.net. Retrieved 4 June 2009.
  34. ^ "Space Solar Energy Initiative". Space Island Group. Retrieved 4 June 2009.
  35. ^ Wireless Power Transmission for Solar Power Satellite (SPS) (Second Draft by N. Shinohara), Space Solar Power Workshop, Georgia Institute of Technology
  36. ^ Brown., W. C. (1984). "The History of Power Transmission by Radio Waves". Microwave Theory and Techniques, IEEE Transactions on. 32 (Volume: 32, Issue: 9 On page(s): 1230-1242+ ISSN: 0018-9480): 1230. Bibcode:1984ITMTT..32.1230B. doi:10.1109/TMTT.1984.1132833. {{cite journal}}: |issue= has extra text (help); Unknown parameter |month= ignored (help)
  37. POINT-TO-POINT WIRELESS POWER TRANSPORTATION IN REUNION ISLAND 48th International Astronautical Congress, Turin, Italy, 6–10 October 1997 – IAF-97-R.4.08 J. D. Lan Sun Luk, A. Celeste, P. Romanacce, L. Chane Kuang Sang, J. C. Gatina – University of La Réunion – Faculty of Science and Technology.
  38. Smith, David (Sunday 4 January 2009). "Wireless power spells end for cables". The Observer. London. {{cite news}}: Check date values in: |date= (help)
  39. "power transmission via lasers". Laserfocusworld.com. Retrieved 4 June 2009.
  40. Skillings, Jonathan (23 August 2008). "Laser weapons: A distant target, CNET news August 23, 2008 1:41 pm PDT". News.cnet.com. Retrieved 4 June 2009.
  41. "Laser Weapons "Almost Ready?" Not!". Defensetech.org. Retrieved 4 June 2009.
  42. "White Sands testing new laser weapon system, US Army.mil, 30 Jan 2009". Army.mil. 30 January 2009. Retrieved 4 June 2009.
  43. "Lasers Power Planes, Drones". Defensetech.org. Retrieved 4 June 2009.
  44. "Riding a Beam of Light". Space.com. 24 October 2005. Retrieved 4 June 2009.
  45. Nobelprize.org, Laser facts, What is a Laser?
  46. "Nobelprize.org, Laser facts, Laser history and Nobel Prizes in Physics". Nobelprize.org. 19 December 2002. Retrieved 4 June 2009.
  47. Nobelprize.org, Laser facts, Applications of Laser
  48. "Nobelprize.org, Laser facts, Everyday Use of Laser". Nobelprize.org. 19 December 2002. Retrieved 4 June 2009.
  49. "Free-Space Laser Propagation: Atmospheric Effects". Ieee.org. Retrieved 4 June 2009.
  50. Propagation Characteristics of Laser Beams – Melles Griot catalog
  51. L. C. Andrews and R. L. Phillips, Laser Beam Propagation through Random Media, 2nd ed. (SPIE Press, 2005). Google Books. 2005. ISBN 978-0-8194-5948-0. Retrieved 4 June 2009.
  52. Dr. Rüdiger Paschotta. "An explanation of Coherence". Rp-photonics.com. Retrieved 4 June 2009.
  53. "An Evolutionary Path to SPS". Islandone.org. Retrieved 4 June 2009.
  54. "A Supersynchronous SPS". Geoffreylandis.com. 28 August 1997. Retrieved 4 June 2009.
  55. "Papers Relating to Space Photovoltaic Power, Power beaming, and Solar Power Satellites". Sff.net. doi:10.1089/153110701753198927. Retrieved 4 June 2009. {{cite web}}: Check |doi= value (help)
  56. "Limitless clean energy from space". Nss.org. Retrieved 4 June 2009.
  57. "Power Beaming (Climber) Competition". Spaceward.org. Retrieved 4 June 2009.
  58. "From Concept to Reality". The Space Elevator. Retrieved 4 June 2009.
  59. "Space Elevator Tethers Coming Closer". Crnano.typepad.com. 31 January 2009. Retrieved 4 June 2009.
  60. "Dryden Flight Research Center, Beamed Laser Power For UAVs". Nasa.gov. 7 May 2008. Retrieved 4 June 2009.
  61. "Nikola Tesla and the Diameter of the Earth: A Discussion of One of the Many Modes of Operation of the Wardenclyffe Tower," K. L. Corum and J. F. Corum, PhD 1996
  62. William Beaty, Yahoo Wireless Energy Transmission Tech Group Message #787, reprinted in WIRELESS TRANSMISSION THEORY.
  63. Wait, James R., The Ancient and Modern History of EM Ground-Wave Propagation," IEEE Antennas and Propagation Magazine, Vol. 40, No. 5, October 1998.
  64. "The Future of the Wireless Art," Wireless Telegraphy and Telephony, Walter W. Massie & Charles R. Underhill, 1908, pp. 67–71.

    It is intended to give practical demonstrations of these principles with the plant illustrated. . . . An inexpensive instrument, not bigger than a watch, will enable its bearer to hear anywhere, on sea or land, music or song, the speech of a political leader . . . delivered in some other place, however distant. . . . Millions of such instruments can be operated from but one plant of this kind.  More important than all of this, however, will be the transmission of power, without wires, which will be shown on a scale large enough to carry conviction.

  65. SYSTEM OF TRANSMISSION OF ELECTRICAL ENERGY, 2 Sept. 1897, U.S. Patent No. 645,576, 20 Mar. 1900.
  66. Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power

    I have to say here that when I filed the applications of September 2, 1897, for the transmission of energy in which this method was disclosed, it was already clear to me that I did not need to have terminals at such high elevation. . . .

    At that time I was absolutely sure that I could put up a commercial plant, if I could do nothing else but what I had done in my laboratory on Houston Street; but I had already calculated and found that I did not need great heights to apply this method.  My patent says that I break down the atmosphere "at or near" the terminal.  If my conducting atmosphere is 2 or 3 miles above the plant, I consider this very near the terminal as compared to the distance of my receiving terminal, which may be across the Pacific. . . .

  67. Henry Bradford, "Tesla on Global Wireless Energy Transmission for Telecommunications and Other Purposes"
  68. Rauscher, Elizabeth A., Electromagnetic Phenomena in Complex Geometries and Nonlinear Phenomena, Non-Hertzian Waves and Magnetic Monopoles, Tesla Book Company.
  69. APPARATUS FOR TRANSMISSION OF ELECTRICAL ENERGY, 2 September 1897, U.S. Patent No. 649,621, 15 May 1900
  70. Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 126, 127.
  71. Boksan, Slavko, Nikola Tesla und sein Werk, Deutscher Verlag für Jugend und Volk, 1932, pp. 237-238.
  72. "The Transmission of Electrical Energy Without Wires," Electrical World, March 5, 1904". 21st Century Books. 5 March 1904. Retrieved 4 June 2009.."
  73. Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 128–130.

    "The earth is 4,000 miles radius.  Around this conducting earth is an atmosphere.  The earth is a conductor; the atmosphere above is a conductor, only there is a little stratum between 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 the distance from the earth's surface to the conducting atmosphere is minute, as compared with the distance of the receiver at 4,000 miles, say, you can readily see that the energy cannot travel along this curve and get there, but will be immediately transformed into conduction 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 curve and is reflected and absorbed, . . . but it will travel by conduction and will be recovered in this way

  74. Apparatus for Transmitting Electrical Energy, 18 Jan. 1902, U.S. Patent 1,119,732, 1 Dec. 1914.
  75. One wireless system – Two methods
  76. Meyl, Konstantin, "Wireless Tesla Transponder : Field-physical basis for electrically coupled bidirectional far range transponders according to the invention of Nikola Tesla," Furtwangen University, Germany
  77. Meyl, Konstantin, Scalar Waves : Theory and Experiments
  78. van Vlaenderen, Koen J., "A Generalization of Classical Electrodynamics for the Prediction of Scalar Field Effects," Institute for Basic Research, 2008
  79. C. Monstein and J.P Wesley, Observation of scalar longitudinal electrodynamic waves, Europhysics Letters 59 (2002), no. 4, 514–520.
  80. Chubykalo, Andrew E.; Tzontchev, Rumen I.; Rivera-Juárez, Juan M. (2000). "Coulomb interaction does not spread instantaniously". Hadrionic Journal. 23: 401–424.
  81. Dea, Jack Y., "Scalar Fields: Their Prediction from Classical Electromagnetism and Interpretation from Quantum Mechanics, 1985.
  82. Bearden, T. E., Solutions to Tesla's Secrets and the Soviet Tesla Weapons, 1981; John T. Ratzlaff, Reference Articles for Solutions to Tesla's Secrets.
  83. Electromagnetic fields, waves and numerical methods By Zijad Haznadar, Željko Štih. Page 61.
  84. "Electricity at the Columbian Exposition" By John Patrick Barrett. 1894. Page 168 – 169.
  85. "Nikola Tesla, 1856 – 1943". IEEE History Center, IEEE, 2003. lecture-demonstration St. Louis.
  86. Cheney, Margaret, Tesla Man Out of Time
  87. "MARCONI WIRELESS TEL. CO. V. UNITED STATES, 320 U. S. 1 (1943)".
  88. "Experiments with Alternating Currents of Very High Frequency and Their Application to Methods of Artificial Illumination, AIEE, Columbia College, N.Y., May 20, 1891". 20 June 1891.
  89. "Experiments with Alternate Currents of High Potential and High Frequency, IEE Address,' London, February 1892". 1892-02-00. {{cite web}}: Check date values in: |date= (help)
  90. "On Light and Other High Frequency Phenomena, 'Franklin Institute,' Philadelphia, February 1893, and National Electric Light Association, St. Louis, March 1893". 1893-03-00. {{cite web}}: Check date values in: |date= (help)
  91. Hutin, Maurice (23 October 1894). "Transformer System for Electric Railways". United States Patent Office. Retrieved 14 April 2010. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  92. "The Work of Jagdish Chandra Bose: 100 years of mm-wave research". tuc.nrao.edu.
  93. "Jagadish Chandra Bose", ieeeghn.org.
  94. "MARCONI WIRELESS TEL. CO. V. UNITED STATES, 320 U. S. 1 (1943)".
  95. Guglielmo Marconi -- Britannica Online Encyclopedia
  96. Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 26–29.
  97. 5 June 1899, NIKOLA TESLA COLORADO SPRINGS NOTES 1899–1900, Nolit, 1978
  98. Nikola Tesla: Guided Weapons & Computer Technology.
  99. The Electrician (London), 1904).
  100. Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, p. 133.
  101. A survey of the elements of power Transmission by microwave beam, in 1961 IRE Int. Conf. Rec., vol.9, part 3, pp.93–105
  102. "IEEE Microwave Theory and Techniques, Bill Brown's Distinguished Career". Mtt.org. Retrieved 4 June 2009.
  103. "Power from the Sun: Its Future," Science Vol. 162, pp. 957–961 (1968)
  104. "Solar Power Satellite patent". Patft.uspto.gov. Retrieved 4 June 2009.
  105. History of RFID
  106. "MIT lights 60W light bulb by wireless power transmission". EetIndia.co.in. Retrieved 3 May 2010.
  107. "Bombardier PRIMOVE Technology". Bombardier.com. Retrieved 4 June 2009.
  108. "Intel imagines wireless power for your laptop". TG Daily. 22 August 2008. Retrieved 4 June 2009.
  109. Leyh, G. E. and M. D. Kennan, "Efficient Wireless Transmission of Power Using Resonators with Coupled Electric Fields," 2008 North American Power Symposium.
  110. "wireless electricity specification nearing completion". PCWorld. 18 August 2009. Retrieved 21 August 2009.
  111. "TX40 and CX40, Ex approved Torch and Charger".
  112. "A. Kumar, S. Mirabbasi, and M. Chiao, "Resonance-Based Wireless Power Delivery for Implantable Devices," IEEE Biomedical Circuits and Systems Conference (BioCAS), pp. 25–28, November 2009".
  113. "LaserMotive LLC Wins Prize in Power Beaming Challenge".
  114. http://presscentre.sony.eu/content/detail.aspx?NewsAreaId=2&ReleaseID=4993
  115. "Haier's wireless HDTV lacks wires, svelte profile (video)". Engadget. 7 January 2010. Retrieved 7 January 2009.
  116. "Anil Kumar RamRakhyani; Shahriar Mirabbasi; Mu Chiao; , "Design and Optimization of Resonance-Based Efficient Wireless Power Delivery Systems for Biomedical Implants," IEEE Transactions on Biomedical Circuits and Systems".
  117. "Anil Kumar RamRakhyani; Gianluca Lazzi;, "On the Design of Efficient Multi-Coil Telemetry System for Biomedical Implants," IEEE Transactions on Biomedical Circuits and Systems".

External links

Categories: