An artist's depiction of a solar satellite, which could send energy wirelessly to a space vessel or planetary surface.

Wireless energy transfer or wireless power transmission is the process that takes place in any system where electrical energy is transmitted from a power source to an electrical load, without interconnecting wires. Wireless transmission is employed in cases where instantaneous or continuous energy transfer is needed, but interconnecting wires are inconvenient, hazardous, or impossible. Image File history File links Download high resolution version (1024x768, 191 KB)The Sun Tower in Vancouver, British Columbia. ... Image File history File links Download high resolution version (1024x768, 191 KB)The Sun Tower in Vancouver, British Columbia. ... Electrical energy can refer to several closely related things. ... A wall wart style variable DC power supply with its cover removed. ... If an electric circuit has a well-defined output terminal, the circuit connected to this terminal (or its input impedance) is the load. ...

Though the physics are related, this is distinct from wireless transmission for the purpose of transferring information (such as radio), where the percentage of the power that is received is only important if it becomes too low to successfully recover the signal. With wireless energy transfer, the efficiency is a more critical parameter and this creates important differences in these technologies. The ASCII codes for the word Wikipedia represented in binary, the numeral system most commonly used for encoding computer information. ... In physics, power (symbol: P) is the rate at which work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time. ... By the mid 20th century humans had achieved a mastery of technology sufficient to leave the surface of the Earth for the first time and explore space. ...

History

In 1825 William Sturgeon invented the electromagnet, a conducting wire wrapped around an iron core. The principle of electromagnetic induction — that a changing magnetic field can induce an electrical current in an adjacent wire — was discovered by Michael Faraday in 1831. Combining these two discoveries, Nicholas Joseph Callan was the first to demonstrate the transmission and reception of electrical energy without wires. Callan’s 1836 induction coil apparatus consisted of two insulated coils — called the primary and secondary windings — both placed around a common iron core. A battery intermittently connected to the primary would ‘induce’ a voltage in the longer secondary causing a spark to jump across its free terminals.^[1][2] William Sturgeon (May 22, 1783 - December 4, 1850) was an English physicist and inventor who made the first electromagnets. ... An electromagnet is a type of magnet in which the magnetic field is produced by a flow of electric current. ... For magnetic induction, see Magnetic field. ... Michael Faraday, FRS (September 22, 1791 – August 25, 1867) was an English chemist and physicist (or natural philosopher, in the terminology of that time) who contributed to the fields of electromagnetism and electrochemistry. ... Nicholas Callan (1799 – 1864) Irish physicist, invented the induction coil in 1836. ... An induction coil or spark coil (archaically known as a Ruhmkorff coil) is a type of disruptive discharge coil. ...

In an induction coil or electrical transformer, which can have either an iron core or an air core, the transmission of energy takes place by simple electromagnetic coupling through a process known as mutual induction. With this method it is possible to transmit and receive energy over a considerable distance. However, to draw significant power in that way, the two inductors must be placed fairly close together. Inductance (or electric inductance) is a measure of the amount of magnetic flux produced for a given electric current. ...

If resonant coupling is used, where inductors are tuned to a mutual frequency, significant power may be transmitted over a range of many meters.

In 1864 James Clerk Maxwell mathematically modeled the behavior of electromagnetic radiation. Some early work in the area of wireless transmission via radio waves was done in 1888 by Heinrich Hertz who performed experiments that validated Maxwell’s mathematical model. Hertz’s apparatus for generating electromagnetic waves is generally acknowledged as the first radio transmitter. A few years later Guglielmo Marconi worked with a modified form of the Hertz-wave transmitter, the main improvement being the addition of an elevated conductor and a ground connection. Both of these elements can be traced back to the 1749 work of Benjamin Franklin and that of Mahlon Loomas in 1864. James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist from Edinburgh, Scotland, UK. His most significant achievement was aggregating a set of equations in electricity, magnetism and inductance — eponymously named Maxwells equations — including an important modification (extension) of the Ampères... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894) was the German physicist and mechanician for whom the hertz, an SI unit, is named. ... For the inventor of radio,Marconi see the competing claims in history of radio and the invention of radio. ... Benjamin Franklin (January 17 [O.S. January 6] 1706 – April 17, 1790) was one of the most well known Founding Fathers of the United States. ...

Nikola Tesla also investigated radio transmission and reception but unlike Marconi, Tesla designed his own transmitter — one with power-processing capability some five orders-of-magnitude greater than those of its predecessors.^[3] He would use this same coupled-tuned-circuit oscillator to implement his conduction-based wireless energy transmission method as well. Both of these wireless methods employ a minimum of four tuned circuits, two at the transmitter and two at the receiver. Nikola Tesla (1856-1943)[1] was a world-renowned Serbian inventor, physicist, mechanical engineer and electrical engineer. ...

As wireless technologies were being developed during the early 1900s, researchers further investigated these different wireless transmission methods. The goal was simply to generate an effect locally and detect it at a distance. Around the same time, efforts began to power more significant loads than the high-resistance sensitive devices that were being used to simply detect the received energy. At the St. Louis World's Fair (1904), a prize was offered for a successful attempt to drive a 0.1 horsepower (75 W) air-ship motor by energy transmitted through space at a distance of least 100 feet (30 m).^[4] It has been suggested that this article or section be merged with wireless communication. ... This article is about a unit of measurement. ... For other uses, see Watt (disambiguation). ... For other kinds of motors, see motor. ... This article is about the unit of length. ...

William C. Brown demonstrated in 1964 on the CBS Walter Cronkite news a microwave-powered model helicopter that received all the power needed for flight from a microwave beam. Between 1969 and 1975 Bill Brown was technical director of a JPL Raytheon program that beamed 30 kW over a distance of 1 mile at 84% efficiency. William C Brown pioneered microwave power transmission in the 1960s. ... Walter Leland Cronkite, Jr. ... The JPL complex in Pasadena, Ca. ... Raytheon Company (NYSE: RTN) is a major American defense contractor and industrial corporation with core manufacturing concentrations in defense systems and defense and commercial electronics. ... The kilowatt (symbol: kW) is a unit for measuring power, equal to one thousand watts. ...

Modern day usage

Except for RFID tags, wireless power transmission over room-sized or community-sized distances has not been widely implemented. Rightly or not, it has been assumed by some that any system for broadcasting energy to power electrical devices will have negative health implications. With focused beams of microwave radiation there are definite health and safety risks. Considering the hazards associated with powerful radiation, the physical alignment and targeting of devices to receive the energy beam is of particular concern. However with the use of resonant coupling, wavelengths produced are longer, making it no more dangerous than being exposed to radio waves. Radio frequency identification (RFID) is a method of remotely storing and retrieving data using devices called RFID tags. ...

Size and power level

The size of the components is dictated by:

• distance from transmitter to receiver
• the wavelength of the radiation
• the laws of physics, specifically the Rayleigh Criterion or Diffraction limit, used in standard RF (Radio Frequency) antenna design, which also applies to lasers. These laws dictate that any beam will spread (microwave or laser) and become weaker and diffuse over distance. The larger the transmitter antenna or laser aperture, the tighter the beam and the less it will spread as a function of distance (and vice versa). Smaller antennas also suffer from excessive losses due to sidelobes.

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 of the medium through which the radiation passes. That process is known as calculating a Link Budget. Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ... The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ... RF may mean: RF, the IATA code for Florida West International Airways RF, NYSE ticker symbol for Regions Financial Corporation Royalty free Rf or RF may stand for: Radio frequency Volumetric flow rate/rate of flow (Rf) RF connectors, electrical connectors designed to work at radio frequencies Red Faction, a... It has been suggested that this article or section be merged with Radio waves. ... A Yagi-Uda beam antenna Short Wave Curtain Antenna (Moosbrunn, Austria) A building rooftop supporting numerous dish and sectored mobile telecommunications antennas (Doncaster, Victoria, Australia) An antenna is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves. ... In antenna engineering, the parts of the radiation pattern that are not the main lobe. ... In electronics, gain is usually taken as the mean ratio of the signal output of a system to the signal input of the system. ... Look up loss, lose in Wiktionary, the free dictionary. ... A Yagi-Uda beam antenna Short Wave Curtain Antenna (Moosbrunn, Austria) A building rooftop supporting numerous dish and sectored mobile telecommunications antennas (Doncaster, Victoria, Australia) An antenna is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves. ... Transparent glass ball In optics, transparency is the property of allowing light to pass. ... A link budget is the accounting of all of the gains and losses from the transmitter, through the medium (free space, cable, waveguide, fiber, etc. ...

Efficiency

Parts of this article may be confusing or unclear. Please help clarify the article. Suggestions may be on the talk page. (March 2007)

The efficiency of wireless power is the ratio between power that reaches the receiver and the power supplied to the transmitter. Generally wirelessly transmitted energy is dispersed as the energy radiates into the environment or is lost as heat at the transmitter or receiver. Wired transmission techniques on the other hand lose less power, as wires confine and guide the energy to where it is needed. Generally, wireless energy transfer works best at short range; although long distances are possible if the transmitters and receivers are physically large, or the energy can be formed into a tight beam, such as with lasers or large microwave dishes. The ultimate beamwidth is limited by diffraction. Image File history File links Broom_icon. ... The word receiver has a number of different meanings: In communications and information processing, a receiver is the recipient (observer) of a message (information), which is sent from a source (object). ... Antenna tower of Crystal Palace transmitter, London A transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications. ... In telecommunication, the term beamwidth has the following meanings: 1. ... The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ...

When phased arrays are used for wireless transmission, the phased array normally needs to be contiguous due to a phenomenon called the thinned array curse; gaps in the array act as a diffraction grating and cause side lobes that lose energy. The thinned array curse (sometimes, sparse array curse) is a theorem in electromagnetic theory of transmitters. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In antenna engineering, the parts of the radiation pattern that are not the main lobe. ...

Microwave power beaming often achieves higher conversion efficiency than lasers, and is less prone to atmospheric attenuation. However microwaves have far longer wavelengths than visible light, and require proportionately larger transmitters and receivers to deal with diffraction over long distances. The most efficient laser power beaming system today has photovoltaic panels optimized to the wavelength of the laser. Losses due to atmospheric spreading can be reduced by the use of adaptive optics, and losses due to absorption can be reduced by a properly chosen laser wavelength. Laser power beaming does not work well through clouds. This article is about the type of Electromagnetic radiation. ... This article is about Physics. ... A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ...

Although laser and photovoltaic technologies have been rapidly advancing, it is unknown what transmission efficiency improvement is possible. The most efficient lasers — laser diode arrays, can surpass 50% efficiency, but such lasers do not have mutual coherence. Other options include standard chemical lasers with efficiencies of a few percent or less. High-coherence diode laser arrays or a similar technology would allow for notably improved power usage efficiency, as laser inefficiency comprises most of the energy loss. A packaged laser diode with penny for scale. ... Two sinusoidal oscillations of the same frequency are said to be mutually coherent if they exhibit a constant phase relationship during the course of time. ... A chemical laser is a laser that obtains its energy from a chemical reaction. ...

Taking the theoretical example of transferring 50 MJ of energy from one place to another (see space elevator and space elevator economics): The base cost of payload transfer, given the current power grid rate of about US$0.11/kW·h = about US$0.03/MJ,^[5] is around US$1.74/kg. Factoring for transmission losses, assuming current laser efficiencies of 2%, solar cell efficiencies of 30%, and atmospheric losses of about 20%, this works out to about 0.5% overall efficiency, or $350/kg. The joule (IPA: or ) (symbol: J) is the SI unit of energy. ... A space elevator would consist of a cable anchored to the Earths surface, reaching into space. ... Space elevator economics compared and contrasted with the economics of alternatives, like rockets. ... The watt hour (symbol W·h) is a unit of energy. ... Kg redirects here. ... For other uses, see Laser (disambiguation). ... A solar cell, made from a monocrystalline silicon wafer A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. ... Air redirects here. ...

Short distance induction

These methods can reach at most a few centimetres.

Main article: Electromagnetic induction

The action of an electrical transformer is the simplest instance of wireless energy transfer. The primary and secondary circuits of a transformer are electrically isolated from each other. The transfer of energy takes place by electromagnetic coupling through a process known as mutual induction. (An added benefit is the capability to step the primary voltage either up or down.) The electric toothbrush charger is an example of how this principle can be used. The main drawback to induction, however, is the short range. The receiver must be in very close proximity to the transmitter or induction unit in order to inductively couple with it. For magnetic induction, see Magnetic field. ... For other uses, see Transformer (disambiguation). ... Inductance (or electric inductance) is a measure of the amount of magnetic flux produced for a given electric current. ...

Applications

• The electric toothbrush battery charger
• The induction cooker stovetop

It can be argued the cookware part of an induction cooker is not a secondary in the strictest sense of the term. It is more accurately described as the non-laminated core of an alternating-current electromagnet, in which eddy currents are induced resulting in the heating effect.

• The electromagnetic card reader The act of swiping the card induces eddy currents in the reader which are measured.
• Transcutaneous energy transfer (TET) systems in artificial hearts and other surgically implanted devices.
• Devices using induction to charge portable consumer electronics such as cell phones.^[6][7]

Electric toothbrush, made by Braun. ... Induction Hob (Top View) An induction cooker uses induction heating for cooking. ... An eddy current is a phenomenon caused by a moving magnetic field intersecting a conductor or vice-versa. ... An artificial heart is a device that is implanted into the body to replace the original biological heart. ...

Moderate distance

These methods achieve distances of a few meters

Low power

A new company, Powercast introduced wireless power transfer technology using RF energy at the 2007 Consumer Electronics Show, winning best Emerging Technology.^[8] The Powercast system is applicable for a number of devices with low power requirements. This could include LEDs, computer peripherals, wireless sensors, and medical implants. Currently, it achieves a maximum output of 6 volts for a little over one meter. It is expected for arrival late 2007.^[9]. The International Consumer Electronics Show (CES) is a trade show held each January in Las Vegas, Nevada, and is sponsored by the Consumer Electronics Association. ...

A different low-power wireless power technology has been proposed by Landis^[10]. Geoffrey A. Landis emerged in the late 1980s as one of the foremost scientist-writers in the science fiction genre. ...

Evanescent wave coupling

Main article: Evanescent wave coupling

In 2006, Marin Soljačić and other researchers at the Massachusetts Institute of Technology applied the near field behaviour well known in electromagnetic theory to a wireless power transfer concept based on coupled resonators. ^[11][12][13] In a short theoretical analysis they demonstrate that by sending electromagnetic waves around in a highly angular waveguide, evanescent waves are produced which carry no energy. If a proper resonant waveguide is brought near the transmitter, the evanescent waves can allow the energy to tunnel (specifically evanescent wave coupling, the electromagnetic equivalent of tunneling ^{[citation needed]}) to the power drawing waveguide, where they can be rectified into DC power. Since the electromagnetic waves would tunnel, they would not propagate through the air to be absorbed or dissipated, and would not disrupt electronic devices or cause physical injury like microwave or radio wave transmission might. Researchers anticipate up to 5 meters of range for the initial device, and are currently working on a functional prototype.^[11] Evanescent Wave Coupling is a process by which electromagnetic waves are transmitted from one medium to another by means of the evanescent (or decaying) electromagnetic field(s). ... Marin Soljačić (born February 7, 1974) is a Croatian physicist and electrical engineer known for wireless non-radiative energy transfer. ... Mapúa Institute of Technology (MIT, MapúaTech or simply Mapúa) is a private, non-sectarian, Filipino tertiary institute located in Intramuros, Manila. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... Look up waveguide in Wiktionary, the free dictionary. ... An evanescent wave is an electromagnetic wave that decays exponentially with distance. ... This article is about resonance in physics. ... Quantum tunneling is the quantum-mechanical effect of transitioning through a classically-forbidden energy state. ... Evanescent Wave Coupling is a process by which electromagnetic waves are transmitted from one medium to another by means of the evanescent (or decaying) electromagnetic field(s). ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ...

On June 7, 2007, it was reported that a prototype system had been implemented. The MIT researchers successfully demonstrated the ability to power a 60 watt light bulb from a power source that was seven feet (2 meters) away at roughly 40% efficiency.

"Resonant inductive coupling" has key implications in solving the two main problems associated with non-resonant inductive coupling and electromagnetic radiation, one of which is caused by the other; distance and efficiency. Electromagnetic induction works on the principle of a primary coil generating a predominantly magnetic field and a secondary coil being within that field so a current is induced within its coils. This causes the relatively short range due to the amount of power required to produce an electromagnetic field. Over greater distances the non-resonant induction method is inefficient and wastes much of the transmitted energy just to increase range. This is where the resonance comes in and helps efficiency dramatically by "tunneling" the magnetic field to a receiver coil that resonates at the same frequency. Unlike the multiple-layer secondary of a non-resonant transformer, such receiving coils are single layer solenoids with closely spaced capacitor plates on each end, which in combination allow the coil to be tuned to the transmitter frequency thereby eliminating the wide energy wasting "wave problem" and allowing the energy used to focus in on a specific frequency increasing the range. In electronics, inductive coupling refers to the transfer of energy from one circuit component to another through a shared magnetic field. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... For magnetic induction, see Magnetic field. ... The Transformers toys, and the related comics and animated television series which have run from the 1980s onwards. ... Magnetic field lines shown by iron filings Magnetostatics Electrodynamics Electrical Network Tensors in Relativity This box:      In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. ... In engineering, a solenoid is a mechanical device that converts energy into linear motion. ... See Capacitor (component) for a discussion of specific types. ...

Tesla

Nikola Tesla had two patents that he claimed would enable long distance power transmission. Nikola Tesla (1856-1943)[1] was a world-renowned Serbian inventor, physicist, mechanical engineer and electrical engineer. ...

Tesla coil transformer wound in the form of a flat spiral. This is the transmitter form as described in U.S. Patent 645,576 .

Tesla, in U.S. Patent 0,645,576  System of Transmission of Electrical Energy and U.S. Patent 0,649,621  Apparatus for Transmission of Electrical Energy, described new and useful combinations of transformer coils. The transmitting coil or conductor arranged and excited to cause currents or oscillation to propagate through conduction through the natural medium from one point to another remote point therefrom and a receiver coil or conductor of the transmitted signals. ^[14] The production of currents of very high potential could be attained in these coils. Image File history File links Download high resolution version (273x908, 4 KB)See also Image:TeslaCoil0645576. ... Image File history File links Download high resolution version (273x908, 4 KB)See also Image:TeslaCoil0645576. ...

Long distance

These methods achieve multiple kilometre ranges.

Radio and microwave

Main article: Microwave power transmission

The earliest work in the area of wireless transmission via radio waves was performed by Heinrich Rudolf Hertz in 1888. A few years later Guglielmo Marconi worked with a modified form of Hertz's transmitter. Nikola Tesla also investigated radio transmission and reception. This article does not cite any references or sources. ... Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894) was the German physicist and mechanician for whom the hertz, an SI unit, is named. ... For the inventor of radio,Marconi see the competing claims in history of radio and the invention of radio. ... Nikola Tesla (1856-1943)[1] was a world-renowned Serbian inventor, physicist, mechanical engineer and electrical engineer. ...

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^[15]. Hidetsugu Yagi (八木 秀次 Yagi Hidetsugu, January 28, 1886 - January 19, 1976) was a Japanese electrical scientist who wrote several important articles that led to the development of the Yagi antenna, which allows directional communication with electromagnetic waves. ... A Yagi-Uda antenna. ...

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 ^[16],^[17]. This article does not cite any references or sources. ... A rectenna is a rectifying antenna, a special type of antenna that is used to directly convert microwave energy into DC electricity. ... An artists depiction of a solar satellite, which could send energy wirelessly to a space vessel or planetary surface. ... Beam-powered propulsion is a class of spacecraft propulsion mechanisms that use energy beamed to the spacecraft from a remote power plant. ...

Power beaming by microwaves has the difficulty that for most space applications the required aperture sizes are very large. 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. The National Aeronautics and Space Administration (NASA) (IPA [ˈnæsÉ™]) is an agency of the United States government, responsible for the nations public space program. ... The thinned array curse (sometimes, sparse array curse) is a theorem in electromagnetic theory of transmitters. ...

High power

Wireless Power Transmission (using microwaves) is well proven. Experiments in the tens of kilowatts have been performed at Goldstone in California in 1975^{[18] [19][20]} and more recently (1997) at Grand Bassin on Reunion Island^[21]. The Goldstone Deep Space Communications Complex (GDSCC) —commonly called the Goldstone Observatory— is located in Californias Mojave Desert (USA). ... Réunion is an island and overseas département (département doutre-mer, or DOM) of France, located in the Indian Ocean east of Madagascar, about 200 km southwest of Mauritius. ...

Light

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 light, power can be transmitted by converting electricity into a laser beam that is then fired at a solar cell receiver. This is generally known as "power beaming". Its drawbacks are: Image File history File links Size of this preview: 662 × 599 pixelsFull resolution‎ (1,131 × 1,024 pixels, file size: 586 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 662 × 599 pixelsFull resolution‎ (1,131 × 1,024 pixels, file size: 586 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... For other uses, see Laser (disambiguation). ... A solar cell, made from a monocrystalline silicon wafer A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. ...

1. Conversion to light, such as with a laser, is moderately inefficient (although quantum cascade lasers improve this)
2. Conversion back into electricity is moderately inefficient, with photovoltaic cells achieving 40%-50% efficiency^[22]. (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.

NASA has demonstrated flight of a lightweight model plane powered by a laser beam. The quantum cascade laser or QC laser is a unipolar laser which uses electrons as its only charge carrier. ...

Electrical conduction

Main article: Electrical conduction

Electrical energy can also be transmitted by means of electrical currents made to flow through naturally existing conductors, specifically the earth, lakes and oceans, and through the atmosphere — a natural medium that can be made conducting if the breakdown voltage is exceeded and the gas becomes ionized. For example, when a high voltage is applied across a neon tube the gas becomes ionized and a current passes between the two internal electrodes. In a practical wireless energy transmission system using this principle, a high-power ultraviolet beam might be used to form a vertical ionized channel in the air directly above the transmitter-receiver stations. The same concept is used in virtual lightning rods, the electrolaser electroshock weapon^[23] and has been proposed for disabling vehicles.^[24][25][26] Conduction is the movement of electrically charged particles through a transmission medium (electrical conductor). ... Breakdown Voltage (Insulator) = The minimum voltage that makes an insulator react as a conductor. ... ... Neon signs are often used to advertise for hotels, bars and entertainment venues. ... Alternative meanings: There is also an Electric-type Pokémon named Electrode. ... An example of a standard, pointed-tip air terminal The term lightning rod is also used as a metaphorical term to describe those who attract controversy. ... // An electrolaser is a type of electroshock weapon which is also a directed-energy weapon. ... TASER and Taser redirect here. ...

The Tesla effect.

A "world system" for "the transmission of electrical energy without wires" that depends upon the electrical conductivity was proposed by Nikola Tesla as late as 1904.^[27] The Tesla effect (named in honor of Tesla) is an archaic term for an application of a type of electrical conduction (that is, the movement of energy through space and matter; not just the production of voltage across a conductor).^[28][29][30] Tesla stated, Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Nikola Tesla (1856-1943)[1] was a world-renowned Serbian inventor, physicist, mechanical engineer and electrical engineer. ...

Instead of depending on induction at a distance to light the tube [... the] ideal way of lighting a hall or room would [...] be to produce such a condition in 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 as [...] 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.^[31][32]

Through longitudinal waves, an operator uses the Tesla effect in the wireless transfer of energy to a receiving device. The Tesla effect is a type of high field gradient between electrode plates for wireless energy transfer. Longitudinal waves are waves that have vibrations along or parallel to their direction of travel. ...

Wireless transmission of power and energy demonstration during his high frequency and potential lecture of 1891.

The Tesla effect uses high frequency alternating current potential differences transmitted between two plates or nodes. The electrostatic forces through natural media across a conductor situated in the changing magnetic flux can transfer power to the conducting receiving device (such as Tesla's wireless bulbs). Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...

Currently, the effect has been appropriated by some in the fringe scientific community as an effect which purportedly causes man-made earthquakes from electromagnetic standing waves, for example Tesla's teleforce via mechanical earth-resonance concepts.^[33][34] A number of modern writers have "reinterpreted" and expanded upon Tesla's original writings. In the process, they have invoked behavior and phenomena that are often inconsistent with experimental observation and mainstream science. The wireless system would combine electrical power transmission along with broadcasting and wireless telecommunications, allowing for the elimination of many existing high-tension power transmission lines and facilitate the interconnection of electrical generation plants on a global scale.

See also

energy Portal

• Electric power transmission
• Distributed generation
• Electricity distribution
• Electric power transmission
• HV-AC, High voltage alternating current
• Microwave power transmission
• Rectenna
• Solar power satellite
• Thinned array curse
• Transmission medium
• WiTricity

Image File history File links Portal. ... Power line redirects here. ... Distributed generation generates electricity from many small energy sources. ... 11kV/400V-230V transformer in an older suburb of Wellington, New Zealand Electricity distribution is the penultimate stage in the delivery (before retail) of electricity to end users. ... Power line redirects here. ... In electrical engineering High voltage refers to a voltage which is high. ... City lights viewed in a motion blurred exposure. ... This article does not cite any references or sources. ... A rectenna is a rectifying antenna, a special type of antenna that is used to directly convert microwave energy into DC electricity. ... An artists depiction of a solar satellite, which could send energy wirelessly to a space vessel or planetary surface. ... The thinned array curse (sometimes, sparse array curse) is a theorem in electromagnetic theory of transmitters. ... A transmission medium is any material substance, such as fiber-optic cable, twisted-wire pair, coaxial cable, dielectric-slab waveguide, water, or air, that can be used for the propagation of signals, usually in the form of modulated radio, light, or acoustic waves, from one point to another. ... WiTricity, a portmanteau for wireless electricity, is a term coined initially by Dave Gerding in 2005 and used by a MIT research team led by prof. ...

Notes

// Within the timeline of radio, many people were involved in the invention of radio transmission of information as we know it today. ... arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 55th day of the year in the Gregorian calendar. ... Mapúa Institute of Technology (MIT, MapúaTech or simply Mapúa) is a private, non-sectarian, Filipino tertiary institute located in Intramuros, Manila. ...

References

General information

Not to be confused with Public Broadcasting Services in Malta. ... Distinguish from Tesla Roadster. ...

Transmission and efficiency readings

• Oliver Nichelson, A Special Case of Voltage Gain, Utah 84003-1948
• Shokalo, V.M., D.V. Gretskih, A.M. Rybalko, "Efficiency of wireless power transmission system with non-axial arrangement of transmitting and receiving apertures".
• Akademii︠a︡nauk SSSR. (1939). Journal of physics. Moscow: Pub. House of the Academy of Sciences of the USSR. Pg Page 505.
• Seth Potter, "A Few Things You Occasionally Wanted To Know About Wireless Power Transmission". The Boeing Company, Seal Beach, California, USA.
• Yoshihiro Ishizawa, "Efficiency estimation of microwave power transmission antenna system". Electronics and Communications in Japan (Part I: Communications), Volume 83, Issue 8 , Pages 94 - 104
• Cutting the Last Wire, True wireless devices require untethered power distribution. 14 April 2007
• "Voltage and Efficiency". Ask A Scientist, Environmental Earth Science Archive. Sunday, May 05, 2002

Related patents

• U.S. Patent 649,621 , "Apparatus for Transmission of Electrical Energy".
• U.S. Patent 685,953 , "Apparatus for Utilizing Effects Transmitted from a Distance to a Receiving Device through Natural Media".
• U.S. Patent 685,954 , "Method of Utilizing Effects Transmitted through Natural Media".
• U.S. Patent 514,168 , "Means for Generating Electric Currents".
• U.S. Patent 593,138 , "Electrical Transformer".
• U.S. Patent 685,955 , "Apparatus for Utilizing Effects Transmitted From A Distance To A Receiving Device Through Natural Media".
• U.S. Patent 685,956 , "Apparatus for Utilizing Effects Transmitted through Natural Media".
• U.S. Patent 685,957 , "Apparatus for the Utilization of Radiant Energy".
• U.S. Patent 685,958 , "Method of Utilizing of Radiant Energy".
• U.S. Patent 787,412 , "Art of Transmitting Electrical Energy through the Natural Mediums".
• U.S. Patent 1,119,732 , "Apparatus for Transmitting Electrical Energy".
• U.S. Patent 1,990,977 , "Energy transmission system".
• U.S. Patent 2,415,688 , "Induction device".
• U.S. Patent 3,781,647 , "Method And Apparatus For Converting Solar Radiation To Electrical Power".
• U.S. Patent 6,798,716 , "System and method for wireless electrical power transmission".
• U.S. Patent 6,906,495 , "Contact-less power transfer".
• U.S. Patent 7,027,311 , "Method and apparatus for a wireless power supply".

External links

• Powercast Technology
• Project Tesla
• History of Microwave Power Transmission before 1980
• The SHARP's Stationary High Altitude Relay Platform, microwave beam powered
• MIT project
• MIT at Wireless Power
• Wireless Power Transfer, [1]
• Wireless energy could power consumer, industrial electronics
• Powercast
• Howstuffworks "How Wireless Power Works" Describes wireless power transmission over short, medium, and very long distances.
• The Model 'F' Wireless Power Transmitter
• ConvenientPower