Wireless power transfer

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Wireless power transfer ( WPT ), wireless power transmission , wireless energy transmission , or electromagnetic power transfer is energy transmission electricity without cables as a physical link. In a wireless power transmission system, the transmitting device, powered by electricity from a power source, produces a time-changing electromagnetic field, capable of transporting power across space to a receiving device, extracting power from the field and delivering it to the electrical load. Wireless power transfer is useful for powering electrical devices where interconnection cables are uncomfortable, dangerous, or impossible.

The wireless power technique is mainly divided into two categories, non-radiative and radiative. In a close field or non-radiative technique, power is transferred over short distances by magnetic fields using inductive coupling between wire reels, or by electric fields using capacitive coupling between metal electrodes. Inductive coupling is the most widely used wireless technology; its applications include the filling of handheld devices such as telephones and electric toothbrushes, RFID tags, and wireless transfer wirelessly or wirelessly or continuously on implantable medical devices such as artificial pacemakers, or electric vehicles.

In the far field or radiative techniques, also called radiant power , power is transferred by electromagnetic radiation beams, such as microwaves or laser light. These techniques can transport energy over longer distances but should be addressed to the receiver. The applications proposed for this type are solar powered satellites, and wireless powered drones.

An important issue related to all wireless power systems is to limit the exposure of people and other living beings to potentially harmful electromagnetic fields.

Video Wireless power transfer

Overview

Wireless power transfer is a generic term for a number of different technologies to transmit energy through an electromagnetic field. The technology, listed in the table below, differs in the distance at which they can efficiently transfer power, whether transmitters should be directed (directed) to the receiver, and in the type of electromagnetic energy they use: varying electric field time, magnetic fields, waves radio, microwaves, infrared or visible light waves.

Generally a wireless power system consists of a "transmitter" connected to a power source such as a main power line, which converts power to a time-changing electromagnetic field, and one or more "receivers" of devices receiving power and converting it back into DC electric current or AC used by the electrical load. At the transmitter the input power is converted to an oscillating electromagnetic field by some kind of "antenna" device. The word "antenna" is used loosely here; it may be a wire reel that produces a magnetic field, a metal plate that produces an electric field, a radio emitting antenna, or a light-emitting laser. An antenna or similar coupling device in the receiver changes the oscillating field to an electric current. The important parameter that determines the wave type is the frequency, which determines the wavelength.

Wireless uses the same fields and waves as wireless communication devices such as radio, other familiar technologies involving electrical energy transmitted wirelessly by electromagnetic fields, used in cell phones, radio and television broadcasts, and WiFi. In radio communication, the goal is the transmission of information, so the amount of power reaching the receiver is not so important, as long as it is enough so that the information can be received clearly. In wireless communication technology, only a small amount of power reaches the receiver. In contrast, with wireless power the amount of energy received is important, so that efficiency (the fraction of received energy received) is a more significant parameter. For this reason, wireless power technologies tend to be more limited by distance than wireless communication technologies.

The FCC approved the first wireless transmission charging system in December 2017.

This is a different wireless power technology:

Maps Wireless power transfer

Field region

The electric and magnetic fields are created by charged particles in matter such as electrons. A stationary charge creates an electrostatic field in the space around it. A stable charge current (direct current, DC) creates a static magnetic field around it. The above field contains energy, but can not carry power because it is static. But different fields of time can bring power. Speeding up the electrical charge, such as that found in alternating current (AC) electrons in a wire, creates an electric field and a time-changing magnet in the space around it. This field can exert an oscillating force on the electrons in the receiving "antenna", causing them to move back and forth. This is an alternating current that can be used to drive the load.

At a relatively large distance, the electric field and near field magnetic field components are quasi-static oscillating dipoles. These fields decrease with the cube distance: ( D _range / D _ant ) ^-3 Since power is proportional to the square of the field strength, the power transferred decreases as ( D _range / D _ant ) ^-6. or 60dB per decade. In other words, if it is far apart, doubling the distance between the two antennas causes the received power to decrease by a factor of 2 ⁶ = 64. As a result, inductive and capacitive coupling can only be used for short-range power transfers, diameter antenna device D _ant . Unlike in radiation systems where maximum radiation occurs when the dipole antenna is oriented transversely in the direction of propagation, with the maximum coupling dipole field occurring when the dipole is oriented longitudinally.

Inductive inductions

In inductive coupling ( electromagnetic induction or inductive power transfer , IPT), power is transferred between wire reels by magnetic field. The transmitter and receiver together form a transformer (see diagram) . The alternating current (AC) through the transmitter coil (L1) creates an oscillating magnetic field (B) by Ampere law. The magnetic field passes through the receiver coil (L2) , where it induces an alternating EMF (voltage) by the Faraday induction law, which creates alternating current at the receiver. Alternating current induction can drive the load directly, or fixed to the direct current (DC) by the rectifier in the receiver, which drives the load. Some systems, such as an electric toothbrush replacement booth, work on 50/60 Hz so that AC power is applied directly to the transmitter coil, but in most electronic oscillator systems produce higher frequency AC currents that drive the coil, as transmission efficiency increases with frequency.

Inductive coupling is the oldest and most widely used wireless power technology, and is almost the only one that has been used in commercial products. It is used in inductive charging for wireless equipment used in wet environments such as electric toothbrushes and shavers, to reduce the risk of electric shock. Another application area is "transcutaneous" filling of biomedical prosthetic devices implanted in the human body, such as pacemakers and insulin pumps, to avoid wires through the skin. It is also used to charge electric vehicles such as cars and either to charge or transit vehicles such as buses and trains.

But the fastest growing usage is the wireless charging pad to recharge mobile and handheld devices such as laptops and tablet computers, mobile phones, digital media players and video game controllers.

The usual inductive coupling can only achieve high efficiency when the coil is very close together, usually adjacent. In most modern inductive systems, inductive coupling coupling (described below) is used, where efficiency is enhanced by using resonance circuits. It can achieve high efficiency at longer distances than nonresonance inductive coupling.

Resonant inductive coupling

The resistive inductive coupling ( electrodynamic coupling , highly coupled magnetic resonance ) is an inductive coupling form in which power is transferred by the magnetic field (B, green) (see diagram, right) . Each resonant circuit consists of a wire coil connected to a capacitor, or self resonance coil or other resonator with internal capacitance. Both are tuned to resonate at the same resonance frequency. The resonance between the coils can greatly improve coupling and power transfer, analogous to the way a vibrating tuning fork can cause sympathetic vibrations in a remote fork that are tuned to the same tone.

Nikola Tesla first discovered resonance echoes during his pioneering experiments in wireless power transfers around the turn of the 20th century, but the possibility of using resonance coupling to increase the transmission range has recently been explored. In 2007 a team led by Marin Solja? I? at MIT using two coupled tuned circuits each made of 25Ãƒ,Ã‚Â® wire self-resonance wire at 10 MHz to achieve 60 W transmission of power over a distance of 2 meters (6.6Ãƒ, ft) (8 times the diameter of the coil) at about 40% efficiency. Solja? I? founded the WiTricity company (the same name as the team used for technology) that seeks to commercialize the technology.

The concept behind resonance inductive coupling systems is that high Q factor resonators exchange energy at a much higher rate than energy loss due to internal damping. Therefore, by using resonance, the same amount of power can be transferred over a longer distance, using a much weaker magnetic field in the peripheral region (the "tail") of the near plane (this is sometimes called an evanescent field). The resonant inductive clutch can achieve high efficiency in the range of 4 to 10 times the diameter of the coil ( _ant ). This is called "mid-range" transfer, in contrast to "short distances" of inductive nonresonance transfers, which can achieve similar efficiency only when the coil is close together. Another advantage is that resonant circuits interacting with each other are much more powerful than they do with nonresonant objects that lose power because the absorption of nearby scattered objects is negligible.

A weakness of the resonance coupling theory is that at close range when two resonant circuits are tightly coupled, the resonant frequency of the system is no longer constant but is "divided" into two peaks of resonance, so the maximum power transfer no longer occurs in the original. The resonant frequency and oscillator frequency must be set to the new resonance peak. The case of using a peak shift is called a "single resonance". The "Single Reson" system has also been used, where only the secondary is the tuned circuit. The principle of this phenomenon is also called "(Magnetic) phase synchronization" and has begun practical applications for AGV in Japan from around 1993. And now, the high resonance concept presented by MIT researchers is only applied to secondary side resonators, and high efficiency high power width slits the wireless power transfer system is realized and used for collecting SCMaglev inductor currents.

Current resonance technology is widely incorporated in modern inductive wireless power systems. One of the possibilities envisioned for this technology is the coverage of wireless area power. A coil on a wall or ceiling might be able to turn on lights and mobile devices wirelessly anywhere in the room, with reasonable efficiency. The environmental and economic benefits of small wireless devices such as clocks, radios, music players, and remote controls are that it can drastically reduce 6 billion disposable batteries annually, a large source of toxic waste and groundwater contamination.

Capacitive coupling

In capacitive coupling (electrostatic induction), inductive coupling conjugates, energy is transmitted by an electric field between electrodes such as metal plates. The transmitter and receiver electrodes form a capacitor, with an intervening space as dielectric. An alternating voltage generated by the transmitter is applied to the transmission plate, and the oscillating electric field induces the alternating potential on the receiving plate by electrostatic induction, causing an alternating current to flow in the load circuit. The amount of power transferred increases with the quadratic frequency of the voltage, and the capacitance between the plates, which is proportional to the smaller plate area and (for short distances) is inversely proportional to the separation.

Capacitive coupling is only used practically in some low power applications, because the very high voltage on the electrode required to transmit significant power can be harmful, and can cause unpleasant side effects such as the production of harmful ozone. In addition, in contrast to magnetic fields, electric fields interact strongly with most materials, including the human body, due to dielectric polarization. Intervention of materials between or near the electrode can absorb energy, in the case of humans may cause exposure to excessive electromagnetic fields. However, capacitive coupling has several advantages over inductive coupling. This field is largely confined between the capacitor plates, reducing the disturbance, which in inductive coupling requires a heavy "confinement flux" ferrite core. Also, the alignment requirements between transmitter and receiver are less critical. Capacitive coupling has recently been applied to charging battery-powered portable devices as well as continuously charging or transferring wireless power in biomedical implants, and is being considered as a means of transferring power between substrate layers in integrated circuits.

Two types of series have been used:

Bipolar design: In this type of circuit, there are two transmitting plates and two receiver plates. Each transmitting plate is coupled to the receiver plate. The transmitter oscillator moves the transmitting plate on the opposite phase (180 Ã‚ Â° phase difference) with alternating high voltage, and the load is connected between two receiving plates. The alternating electric field induces alternating phase alternating potentials in the receiving plate, and this "push-pull" action causes the current to flow back and forth between the plates through the load. The disadvantage of this configuration for wireless charging is that both plates on the receiving device must be parallel to the charger plate for the device to work.

Capacitive resonant coupling

Resonance can also be used with capacitive coupling to extend the range. At the turn of the 20th century, Nikola Tesla conducted the first experiment with inductive and capacitive resonant coupling.

Magnetodynamic coupling

In this method, power is transmitted between two rotating armatures, one in the transmitter and one at the receiver, which rotates simultaneously, coupled together by the magnetic field generated by a permanent magnet on armatures. The transmitter fleet is altered by or as an electric motor rotor, and its magnetic field provides torque to the receiving armature, changing it. The magnetic field acts like a mechanical coupling between armatures. The armature receiver produces power to drive the load, either by turning a separate electric generator or by using the receiver armature itself as the rotor in the generator.

This device has been proposed as an alternative to inductive power transfer for charging nonkontak electric vehicles. A rotating armature embedded in the garage or sidewalk floor will alter the receiving armature at the bottom of the vehicle to charge the battery. It is claimed that this technique can transfer power from a distance of 10 to 15 cm (4 to 6 inches) with high efficiency, more than 90%. Also, the low frequency magnetic field generated by a rotating magnet produces less electromagnetic interference to nearby electronic devices than the high frequency magnetic field generated by the inductive coupling system. A prototype electric vehicle charging system has been operating at the University of British Columbia since 2012. Other researchers, however, claim that two energy conversions (electricity to mechanics for electricity anymore) make the system less efficient than electrical systems such as inductive coupling.

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Teknik far-field (radiative)

The far-field method reaches a longer range, often a span of several kilometers, where the distance is much greater than the diameter of the device. High-directivity antennas or well-collaborated laser light produce a beam of energy that can be made to match the shape of the receiving area. The maximum directivity for the antenna is physically limited by diffraction.

In general, visible light (from lasers) and microwaves (from specially designed antennas) are the most appropriate forms of electromagnetic radiation for energy transfer.

The dimensions of a component can be determined by the distance from transmitter to receiver, wavelength and Rayleigh criteria or diffraction limits, used in standard radio frequency antenna design, which also applies to lasers. Airy diffraction limits are also often used to determine the approximate place size at an arbitrary distance from the aperture. Electromagnetic radiation undergoes less diffraction at shorter wavelengths (higher frequencies); so, for example, the blue laser diffracts less than the red color.

Rayleigh's criterion states that any radio waves, microwaves or laser beams will spread and become weaker and spaced out; the larger the transmitting antenna or the laser opening compared to the wavelength of the radiation, the tighter the ray and the less it will spread as a function of distance (and vice versa). The smaller antenna also suffers from excessive losses due to the side lobe. However, the concept of laser aperture is very different from the antenna. Typically, laser openings far greater than the wavelength induce multi-moded radiation and most collimators are used before the radiation pair is emitted into the fiber or into space.

Ultimately, the beamwidth is physically determined by diffraction due to the size of the disk in relation to the wavelength of the electromagnetic radiation used to make the beam.

The power of microwaves can be more efficient than lasers, and less susceptible to atmospheric attenuation caused by dust or moisture.

Here, the power level is calculated by combining the above parameters together, and adding advantages and disadvantages due to antenna characteristics and transparency and media dispersion through passing radiation. The process is known as link budget calculation.

Microwaves

Transmission of power through radio waves can be made more direct, allowing for further power extension, with shorter wavelengths of electromagnetic radiation, usually in microwave range. Rectenna can be used to convert microwave energy into electricity. Rectenna conversion efficiency exceeding 95% has been realized. The radiant power using microwaves has been proposed for the transmission of energy from solar satellites orbiting to the Earth and the emission of power to the spacecraft leaving the orbit has been considered.

The radiant power by microwaves has the difficulty that, for most space applications, the required aperture size is great because of the diffraction that limits the antenna direction. For example, NASA's 1978 study of solar satellites requires transmitter antennas 1 kilometer (0.62 miles) in diameter and a 10 km-diameter (6.2 mi) receiving rectenna for microwave emission at 2.45 GHz. This measure may slightly decrease by using shorter wavelengths, although short wavelengths may have difficulty with atmospheric absorption and clogging of rays by rain or water droplets. Due to "thinned array curse", it is not possible to make the beam narrower by combining the beams of some of the smaller satellites.

For grounded applications, a large-diameter receiver array of 10 km enables a large total power level to be used when operating at the recommended low power density for the safety of human electromagnetic exposure. The safe human power density of 1 mW/cm ² is distributed in a 10 km diameter area corresponding to 750 megawatts of total power level. This is the level of power found in many modern power stations.

After World War II, which saw the development of high power microwave transmitters known as magnetron cavities, the idea of â€‹â€‹using microwaves to transfer power has been investigated. In 1964, a miniature helicopter that was driven by microwave power has been shown.

Japanese researcher Hidetsugu Yagi also investigated the wireless energy transmission using the directional array antenna he designed. In February 1926, Yagi and his partner Shintaro Uda published their first paper on a high-directional directional gain array now known as the Yagi antenna. Although not proven to be particularly useful for power transmission, this radiant antenna has been widely adopted throughout the broadcasting and wireless telecommunications industry due to its excellent performance characteristics.

High power wireless transmission using well proven microwave waves. Experiments in dozens of kilowatts were performed at Goldstone in California in 1975 and more recently (1997) at the Grand Bassin on Reunion Island. This method reaches a distance on the order of one kilometer.

Under experimental conditions, the microwave conversion efficiency is measured to about 54%.

Changes to 24 GHz have been suggested as microwave transmitters similar to LEDs have been made with very high quantum efficiency using negative resistance, ie, Gunn or IMPATT diodes, and this would be feasible for close-range links.

In 2013, inventor Hatem Zeine demonstrated how wireless power transmission using a phased array antenna can generate up to 30 feet of electrical power. It uses the same radio frequency as WiFi.

By 2015, researchers at the University of Washington are introducing power over Wi-Fi, which drips battery and battery-resistant cameras and temperature sensors using transmissions from Wi-Fi routers. Wi-Fi signal is shown to power battery and camera sensor temperatures up to 20 feet. It also shows that Wi-Fi can be used to charge nickel-metal hydride batteries wirelessly and lithium-ion coin cell battery at a distance of up to 28 feet.

In 2017, the Federal Communications Commission (FCC) certifies the first wireless medium frequency (RF) frequency transmitter in the wireless field.

Laser

In the case of electromagnetic radiation closer to the visible region of the spectrum (tens of micrometers up to tens of nanometers), power can be transmitted by converting electricity into a laser beam which then points to a photovoltaic cell. This mechanism is commonly known as 'radiant power' because its power is emitted on a receiver that can convert it into electrical energy. At the receiver, a special laser photovoltaic power converter optimized for monochromatic light conversion is applied.

Advantages compared to other wireless methods are:

Monochromatic propagation wave propagation enables a narrow beam section area for large distance transmission.
Compact size: solid state laser goes into small product.
There is no radio frequency interruption to existing radio communications such as Wi-Fi and cell phones.
Access control: only laser-affected recipients receive power.

Disadvantages include:

Harmful laser radiation. Low power levels can blind humans and other animals. High power levels can kill through local spot heating.
Conversion between electricity and light is limited. Photovoltaic cells achieve 40% -50% efficiency. (The conversion efficiency of laser light into electricity is much higher than sunlight to electricity).
Absorption of the atmosphere, and absorption and dispersion by clouds, fogs, rain, etc., cause up to 100% loss.
Needs a direct line of sight with the target. (Instead of being transmitted directly to the receiver, the laser beam can also be guided by an optical fiber.Then one talks about the power-over-fiber technology.)

Laser technology 'powerbeaming' is explored in military weapons and aerospace applications. Also, it is applied to power various types of sensors in industrial environments. Lately it was developed to power commercial and consumer electronics. The wireless energy transfer system using lasers for the consumer space must meet the standard laser safety requirements under IEC 60825.

The first wireless power system that uses lasers for consumer applications is shown in 2018. This tool can send power to stationary and moving devices throughout the room. This wireless power system complies with safety regulations under IEC 60825 standards. It is also approved by the US Food and Drug Administration (FDA).

Other details include propagation, and coherence and range boundary issues.

Geoffrey Landis is one of the pioneers of solar powered satellites and laser-based energy transfers primarily for space and lunar missions. The demand for space missions that are safe and often has resulted in proposals for laser-powered space lifts.

NASA Dryden Flight Research Center shows a lightweight unmanned model aircraft powered by a laser beam. These concepts demonstrate the feasibility of periodic replenishment using a laser beam system.

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Clutch of atmospheric plasma channels

In the clutch of atmospheric plasma channels, energy is transferred between two electrodes by electrical conduction through ionized air. When an electric field gradient exists between two electrodes, exceeding 34 kilovolts per centimeter at atmospheric sea level pressures, an electric arc occurs. This atmospheric dielectric division produces an electric current flow along a random path through an ionized plasma channel between two electrodes. An example of this is natural lightning, where one electrode is a virtual point in the cloud and the other is a point on Earth. The Induced Plasma Channel Laser Research (LIPC) is currently underway using ultracellular lasers to artificially promote the development of airborne plasma channels, direct the arc, and guide the flow across certain paths in a controllable manner. The laser energy reduces the atmospheric dielectric breakdown voltage and the air is made less insulated by superheating, which lowers the density ( ${\ displaystyle p}$ ) of the air filament.

The new process is being explored for use as a laser lightning rod and as a means to trigger lightning from clouds for natural lightning channel studies, for artificial atmospheric propagation studies, in lieu of conventional radio antennas, for applications related to electrical and machining welding, to divert power from the discharge of high voltage capacitors, for the application of directed energy weapons using electrical conduction via backlinks, and electronic noise.

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Energy harvesters

In the context of wireless power, energy harvesting, also called energy harvesting or energy scavengers, is the conversion of environmental energy from the environment to power, a small, autonomous wireless electronic device. Environmental energy can come from an electric or magnetic field or radio wave from nearby electrical equipment, light, heat energy (heat), or kinetic energy such as vibration or movement of the device. Although the conversion efficiency is usually low and the power collected is often very small (milliwatts or microwatts), it is sufficient to run or recharge a small wireless device such as a remote sensor, which multiplies in many areas. This new technology is being developed to eliminate the need for battery replacement or charging of such wireless devices, allowing them to operate entirely independently.

Wireless power transfer technology for high capacity transit

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History

19th century development and deadlock

The 19th century saw many theoretical developments, and counter-theories about how electrical energy can be transmitted. In 1826 AndrÃƒ Â© Â© -Marie AmpÃƒÆ'Ã‚Â¨re discovered Ampezre's circus laws which show that electric currents produce magnetic fields. Michael Faraday described in 1831 with his law induced an electromotive force that moves the current in a conductor loop by a time-varying magnetic flux. The transmission of elecrical energy without cables is observed by many inventors and researchers, but the lack of coherent theory connects this phenomenon vaguely with electromagnetic induction. A brief description of this phenomenon will come from Maxwell's equation in the 1860s by James Clerk Maxwell, setting a theory that unites electricity and magnetism to electromagnetism, predicting the existence of electromagnetic waves as carriers of "wireless" electromagnetic energy. Around 1884 John Henry Poynting defined the Poynting vector and provided the Poynting theorem, which describes the flow of electricity in an area in electromagnetic radiation and allows a correct analysis of the wireless power transfer system. This was followed by the validation of Heinrich Rudolf Hertz in 1888 theory, which included evidence for radio waves.

During the same period two wireless signal schemes were proposed by William Henry Ward (1871) and Mahlon Loomis (1872) based on a false belief that there is an accessible low-energy atmospheric stratum. Both inventor patents note that this layer connected to the return path using "Earth currents" will allow wireless telegraphs and power supplies for telegraphs, disposing of artificial batteries, and can also be used for lighting, heat, and motives. power. A more practical wireless transmission demonstration through conduction came on the Amos Dolbear magneto electric telephone in 1879 which used ground conduction to transmit over a quarter of a mile.

Tesla

After the inventor of 1890, Nikola Tesla experimented with power transmission with inductive and capacitive coupling using a vibrant radio frequency resonance transformer, now called Tesla, which produces a high AC voltage. Initially he tried to develop a wireless lighting system based on inductive and capacitive near-field coupling and conducted a series of public demonstrations in which he lit the Geissler tube and even an incandescent bulb from across the stage. He finds he can increase the distance where he can turn on the light by using an LC circuit that receives tuned for resonance with the LC circuit transmitter. using resonance inductive coupling. Tesla failed to make commercial products out of its findings but resonant inductive coupling methods are now widely used in electronics and are currently being applied to short-range wireless power systems.

Tesla went on to develop a wireless power distribution system that he hoped would be capable of transmitting long-distance power directly to homes and factories. Originally he apparently borrowed from the ideas of Mahlon Loomis, proposed a system consisting of balloons to suspend transmission and received electrodes in the air above 30,000 feet (9,100 m) at altitude, where he thought the pressure would allow him to send high voltages (millions volts) remotely. To learn more about the conductive properties of low-pressure air he set up a high-altitude test facility in Colorado Springs during 1899. His experiments were there with a large coil operating in the megavolts range, as well as the observations he made from the electronic noise of lightning strikes, wrongly concluded that he could use the whole globe to conduct electrical energy. This theory includes moving an alternating current to Earth at the resonant frequency of the Tesla-driven coil working against the increased capacitance to make the Earth's potential oscillate. Tesla thinks this will allow alternating current to be received with similar capacitive antennas tuned to resonance with it at any point on Earth with very little power loss. His observations also led him to believe that the high voltage used in the coils at a height of several hundred feet would "break the air layer down," eliminating the need for miles of wires that depend on the balloon to create the atmospheric circuit. Tesla will leave next year to propose a "World Wireless System" that will broadcast information and power around the world. In 1901, in Shoreham, New York he attempted to build a large high-voltage power plant, now called the Wardenclyffe Tower, but in 1904 the investment dried up and the facility was never completed.

Near-field and non-radiation technology

Inductive power transfer between the nearest wire coil is the earliest wireless power technology to be developed, existing since the transformer was developed in the 1800s. Induction heating has been in use since the early 1900s. With the advent of cordless devices, induction filling booths have been developed for equipment used in wet environments, such as electric toothbrushes and electric razors, to eliminate electrical shock hazards. One of the earliest inductive diverting applications is to drive an electric locomotive. In 1892, Maurice Hutin and Maurice Leblanc patented a wireless method for running a railway train using a resonant coil which is inductively coupled to a wire path at 3 kHz. The first passive RFID (Radio Frequency Identification) technology was invented by Mario Cardullo (1973) and Koelle et al. (1975) and in 1990 used in proximity cards and contactless smart cards.

The development of portable wireless communications devices such as mobile phones, tablets and laptop computers in recent decades has led to the development of medium range wireless power and charging technology to eliminate the need for this device to be tethered to wall plugs during charging. The Wireless Power Consortium was established in 2008 to develop interoperable standards across manufacturers. Qi's inductive power standards issued in August 2009 allow high charging and power from portable devices up to 5 watts at a distance of 4 cm (1.6 inches). The wireless device is placed on a flat charger plate (which can be embedded at table tops in the cafe, for example) and the power is transferred from a flat coil on a charger to a similar device.

In 2007, the team led by Marin Solja? I? at MIT using a dual resonance transmitter with a diameter of 25,, a secondary cm is set to 10 MHz to transfer 60 W of power to the same dual resonance receiver over a distance of 2 meters (6.6Ãƒ, ft) (approximately eight diameters of the transmitter coil) around 40%. In 2008 Greg Leyh and Mike Kennan's team from Nevada Lightning Lab used a 57 cm diameter resonance transmitter tuned to 60 kHz and the same dual resonance receiver to transfer electricity through an electric field coupled with an earth turning circuit over a distance of 12 meters (39 feet).

Microwaves and lasers

Before World War 2, little progress was made in the wireless power transmission. Radio is developed for communication usage, but can not be used for power transmission because relatively low frequency radio waves spread in all directions and less energy reaches the receiver. In radio communications, at the receiver, amplifiers intensify weak signals using energy from other sources. For power transmission, efficient transmission requires a transmitter that can produce higher frequency microwave frequencies, which can be focused on the narrow beam to the receiver.

The development of microwave technology during World War 2, such as klystron and magnetron tubes and parabolic antennas, made the first practical (radiation far) radiation method, and the first long-distance wireless transmission achieved in the 1960s by William. C. Brown. In 1964 Brown discovered a rectenna that could efficiently convert microwaves into DC power, and in 1964 demonstrated it with the first wireless-powered aircraft, a helicopter model powered by microwaves emitted from the ground. The primary motivation for microwave research in the 1970s and 80s was to develop solar satellites. Invented in 1968 by Peter Glaser, it will harvest energy from sunlight using solar cells and channel it to Earth as microwaves to large rectennas, which will convert it into electrical energy in electric grids. In a 1975 landmark experiment as technical director of the JPL/Raytheon program, Brown demonstrated a long-distance transmission by emitting 475 W of microwave power to a rectenna a mile away, with a 54% microwave efficiency to DC conversion. At NASA's Jet Propulsion Laboratory he and Robert Dickinson deliver a 30 kW DC output power of 1.5 km with 2.38 GHz microwaves from a 26 m dish to an array of 7.3 x 3.5 m rectifiers. Incident-RF to DC conversion efficiency of rectenna is 80%. In 1983 Japan launched MINIX (Microwave Ionosphere Nonlinear Interaction Experiment), a rocket experiment to test high-power microwave transmissions through the ionosphere.

In recent years the focus of the research is the development of wireless powered drones, which began in 1959 with the RAMP project (Raytheon Airborne Microwave Platform) Dept. The defense that sponsored Brown's research. In 1987 the Canadian Communications Research Center developed a small prototype aircraft called the High Altitude Relay Platform Stationary (SHARP) to deliver telecommunications data between points on earth similar to communications satellites. Powered by rectenna, it can fly at an altitude of 13 miles (21 km) and stay high for months. In 1992 a team at Kyoto University built a more sophisticated craft called MILAX (MIcrowave Lifted Airplane eXperiment).

In 2003 NASA flew the first laser-powered aircraft. The small plane model aircraft is powered by photocurrants from infrared light beam from ground-based lasers, while the control system keeps the laser on the plane.

Wireless power transmission safely charges devices anywhere within ...

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References

Wireless Power Transfer DIY Electronics Kit Introduction Video ...

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External links

Howstuffworks "How Wireless Power Works" - describes the short and medium range wireless power transmission using induction and radiation techniques.
Microwave Power Transmission, - its history before 1980.
High Stationary Height Relay Platform (SHARP), - Powerful microwave beam.
Marin Solja? i? MIT WiTricity - page of wireless power transmission.
Rezence - the official site of the wireless power standards promoted by Alliance for Wireless Power
Qi - the official site of the wireless power standards promoted by Wireless Power Consortium
PMA - the official site of the wireless power standards promoted by the Power Matters Alliance
WiPow - the official WiPow Coalition website, promoting standard wireless power for medical, mobility and wheeled devices

Source of the article : Wikipedia

Wireless power transfer

Minggu, 03 Juni 2018