Transmission of energy at a distance without wires. Transmission of current without wires by induction

Wireless transmission of electricity

Wireless transmission of electricity- a method of transmitting electrical energy without the use of conductive elements in an electrical circuit. By the year, there had been successful experiments with the transmission of energy with a power of the order of tens of kilowatts in the microwave range with an efficiency of about 40% - in 1975 in Goldstone, California and in 1997 in Grand Bassin on Reunion Island (range of the order of a kilometer, research in the field of power supply of the village without laying a cable power grids). The technological principles of such transmission include inductive (at short distances and relatively low powers), resonant (used in contactless smart cards and RFID chips) and directional electromagnetic for relatively long distances and powers (in the range from ultraviolet to microwaves).

History of wireless power transmission

1820 : André Marie Ampère discovered the law (later named after the discoverer, Ampère's law) showing that an electric current produces a magnetic field.
1831 Story: Michael Faraday discovered the law of induction, an important basic law of electromagnetism.
1862 : Carlo Matteuchi was the first to conduct experiments on the transmission and reception of electrical induction using flat helical coils.
1864 : James Maxwell systematized all previous observations, experiments and equations in electricity, magnetism and optics into a coherent theory and rigorous mathematical description of the behavior of the electromagnetic field.
1888 : Heinrich Hertz confirmed the existence of the electromagnetic field. " Apparatus for generating an electromagnetic field» Hertz was a microwave or UHF spark "radio wave" transmitter.
1891 : Nikola Tesla improved the RF power supply Hertzian wave transmitter in his patent no. 454.622, "Electric Lighting System."
1893 : Tesla demonstrates wireless fluorescent lighting in a project for the Columbian World's Fair in Chicago.
1894 : Tesla lights an incandescent lamp wirelessly at the Fifth Avenue Laboratory, and later at the Houston Street Laboratory in New York City, by "electrodynamic induction", i.e. by wireless resonant mutual induction.
1894 : Jagdish Chandra Bose remotely ignites gunpowder and strikes the bell using electromagnetic waves, showing that communication signals can be sent wirelessly.
1895 : A. S. Popov demonstrated the radio receiver he invented at a meeting of the Physics Department of the Russian Physico-Chemical Society on April 25 (May 7)
1895 : Bosche transmits a signal over a distance of about one mile.
1896 : Guglielmo Marconi applies for the invention of the radio on June 2, 1896.
1896 A: Tesla transmits a signal over a distance of about 48 kilometers.
1897 : Guglielmo Marconi transmits a text message in Morse code over a distance of about 6 km using a radio transmitter.
1897 : Tesla files the first of its wireless transmission patents.
1899 : In Colorado Springs, Tesla writes: “The failure of the method of induction seems enormous compared with earth and air charge excitation method».
1900 : Guglielmo Marconi was unable to obtain a patent for the invention of radio in the United States.
1901 : Marconi transmits a signal across the Atlantic Ocean using the Tesla apparatus.
1902 : Tesla v. Reginald Fessenden: Conflict of US Patent No. 21.701 "Signal transmission system (wireless). Selective switching on of incandescent lamps, electronic logic elements in general.
1904 : An award is offered at the St. Louis World's Fair for successfully attempting to control a 0.1 hp airship engine. (75 W) from power transmitted remotely over distances of less than 100 feet (30 m).
1917 : The Wardenclyffe Tower, built by Nikola Tesla to conduct experiments on wireless transmission of high power, is destroyed.
1926 : Shintaro Uda and Hidetsugu Yagi publish the first article " about high gain steered directional link”, well known as the “Yagi-Uda antenna” or the “wave channel” antenna.
1961 : William Brown publishes an article on the possibility of energy transfer through microwaves.
1964 : William Brown and Walter Cronict demonstrate on the channel CBS News model of a helicopter that receives all the energy it needs from a microwave beam.
1968 : Peter Glaser proposes wireless transmission of solar energy from space using "Power Beam" technology. This is considered the first description of an orbital power system.
1973 : World's first passive RFID system demonstrated at Los Alamos National Laboratory.
1975 : The Goldstone Deep Space Communications Complex is experimenting with power transmission of tens of kilowatts.
2007 : A research team led by Professor Marin Soljachich from the Massachusetts Institute of Technology wirelessly transmitted over a distance of 2 m the power sufficient to light a 60 W light bulb, with an efficiency of 60 W. 40%, using two coils with a diameter of 60 cm.
2008 : Bombardier offers a new wireless transmission product PRIMOVE, a powerful system for tram and light rail applications.
2008 : Intel reproduces the experiments of Nikola Tesla in 1894 and John Brown's group in 1988 on wireless power transmission to light efficient incandescent lamps. 75%.
2009 : A consortium of interested companies called the Wireless Power Consortium has announced the imminent completion of a new industry standard for low power induction chargers.
2009 : An industrial flashlight is introduced that can safely operate and recharge without contact in an atmosphere saturated with flammable gas. This product was developed by the Norwegian company Wireless Power & Communication .
2009 : Haier Group introduced the world's first fully wireless LCD TV based on the research of Professor Marin Soljacic on wireless power transmission and wireless home digital interface (WHDI).

Technology (ultrasonic method)

The invention of students of the University of Pennsylvania. For the first time, the installation was presented to the general public at The All Things Digital (D9) in 2011. As in other methods of wireless transmission of something, a receiver and a transmitter are used. The transmitter emits ultrasound, the receiver, in turn, converts what is heard into electricity. At the time of the presentation, the transmission distance reaches 7-10 meters, a direct line of sight of the receiver and transmitter is required. Of the known characteristics - the transmitted voltage reaches 8 volts, but the resulting current strength is not reported. The ultrasonic frequencies used have no effect on humans. There is also no evidence of negative effects on animals.

Electromagnetic induction method

The electromagnetic induction wireless transmission technique uses a near electromagnetic field at distances of about one-sixth of a wavelength. The near field energy itself is not radiative, but some radiative losses still occur. In addition, as a rule, there are also resistive losses. Due to electrodynamic induction, an alternating electric current flowing through the primary winding creates an alternating magnetic field that acts on the secondary winding, inducing an electric current in it. To achieve high efficiency, the interaction must be sufficiently close. As the secondary winding moves away from the primary, more and more of the magnetic field does not reach the secondary winding. Even over relatively short distances, inductive coupling becomes extremely inefficient, wasting much of the transmitted energy.

An electrical transformer is the simplest device for wireless power transmission. The primary and secondary windings of a transformer are not directly connected. The transfer of energy is carried out through a process known as mutual induction. The main function of a transformer is to increase or decrease the primary voltage. Contactless chargers for mobile phones and electric toothbrushes are examples of using the principle of electrodynamic induction. Induction cookers also use this method. The main disadvantage of the wireless transmission method is its extremely short range. The receiver must be in close proximity to the transmitter in order to communicate effectively with it.

The use of resonance slightly increases the transmission range. With resonant induction, the transmitter and receiver are tuned to the same frequency. Performance can be further improved by changing the drive current waveform from sinusoidal to non-sinusoidal transient waveforms. Pulsed energy transfer occurs over several cycles. Thus, significant power can be transferred between two mutually tuned LC circuits with a relatively low coupling factor. The transmitting and receiving coils, as a rule, are single-layer solenoids or a flat coil with a set of capacitors that allow you to tune the receiving element to the frequency of the transmitter.

A common application of resonant electrodynamic induction is to charge batteries in portable devices such as laptop computers and cell phones, medical implants, and electric vehicles. The localized charging technique uses the selection of an appropriate transmitting coil in a multilayer winding array structure. Resonance is used in both the wireless charging pad (transmitting loop) and the receiver module (built into the load) to ensure maximum power transfer efficiency. This transmission technique is suitable for universal wireless charging pads for charging portable electronics such as mobile phones. The technique has been adopted as part of the Qi wireless charging standard.

Resonant electrodynamic induction is also used to power batteryless devices such as RFID tags and contactless smart cards, as well as to transfer electrical energy from the primary inductor to the helical Tesla transformer resonator, which is also a wireless transmitter of electrical energy.

electrostatic induction

Alternating current can be transmitted through layers of the atmosphere having an atmospheric pressure of less than 135 mm Hg. Art. The current flows by electrostatic induction through the lower atmosphere at about 2-3 miles above sea level and by ion flux, that is, electrical conduction through an ionized region located at an altitude above 5 km. Intense vertical beams of ultraviolet radiation can be used to ionize atmospheric gases directly above the two elevated terminals, resulting in the formation of high-voltage plasma power lines leading directly to the conductive layers of the atmosphere. As a result, an electric current flow is formed between the two elevated terminals, passing to the troposphere, through it and back to the other terminal. Electrical conductivity through the layers of the atmosphere becomes possible due to the capacitive plasma discharge in an ionized atmosphere.

Nikola Tesla discovered that electricity can be transmitted both through the earth and through the atmosphere. In the course of his research, he achieved the ignition of a lamp at moderate distances and recorded the transmission of electricity over long distances. The Wardenclyffe Tower was conceived as a commercial project for transatlantic wireless telephony and became a real demonstration of the possibility of wireless transmission of electricity on a global scale. The installation was not completed due to insufficient funding.

The earth is a natural conductor and forms one conducting circuit. The return loop is realized through the upper troposphere and lower stratosphere at an altitude of about 4.5 miles (7.2 km).

A global system for transmitting electricity without wires, the so-called "World Wireless System", based on the high electrical conductivity of plasma and the high electrical conductivity of the earth, was proposed by Nikola Tesla in early 1904 and could well have caused the Tunguska meteorite, resulting from a "short circuit" between a charged atmosphere and earth.

Worldwide Wireless System

The early experiments of the famous Serbian inventor Nikola Tesla concerned the propagation of ordinary radio waves, that is, Hertzian waves, electromagnetic waves propagating through space.

In 1919, Nikola Tesla wrote: “I am supposed to have started work on wireless transmission in 1893, but in fact I spent the previous two years researching and designing apparatus. It was clear to me from the very beginning that success could be achieved through a series of radical decisions. High frequency generators and electrical oscillators were to be created first. Their energy had to be converted into efficient transmitters and received at a distance by proper receivers. Such a system would be effective if any outside interference is excluded and its full exclusivity is ensured. Over time, however, I realized that in order for devices of this kind to work effectively, they must be designed taking into account the physical properties of our planet.

One of the conditions for creating a worldwide wireless system is the construction of resonant receivers. A grounded Tesla coil helical resonator and an elevated terminal can be used as such. Tesla personally repeatedly demonstrated the wireless transmission of electrical energy from the transmitting to the receiving Tesla coil. This became part of his wireless transmission system (U.S. Patent No. 1,119,732, Apparatus for Transmitting Electrical Power, January 18, 1902). Tesla proposed to install more than thirty receiving and transmitting stations around the world. In this system, the pickup coil acts as a step-down transformer with a high output current. The parameters of the transmitting coil are identical to the receiving coil.

The goal of Tesla's Worldwide Wireless System was to combine power transmission with broadcasting and directional wireless communications, which would eliminate the many high-voltage power lines and facilitate the interconnection of electrical generating facilities on a global scale.

Notes

"Electricity at the Columbian Exposition", by John Patrick Barrett. 1894, pp. 168-169
Experiments with Alternating Currents of Very High Frequency and Their Application to Methods of Artificial Illumination, AIEE, Columbia College, N.Y., May 20, 1891
Experiments with Alternate Currents of High Potential and High Frequency, IEE Address, London, February 1892
On Light and Other High Frequency Phenomena, Franklin Institute, Philadelphia, February 1893 and National Electric Light Association, St. Louis, March 1893
The Work of Jagdish Chandra Bose: 100 years of mm-wave research
Jagadish Chandra Bose
Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 26-29. (English)
June 5, 1899, Nikola Tesla Colorado Spring Notes 1899-1900, Nolit, 1978 (English)
Nikola Tesla: Guided Weapons & Computer Technology
The Electrician(London), 1904 (English)
Scanning the Past: A History of Electrical Engineering from the Past, Hidetsugu Yagi
A survey of the elements of power transmission by microwave beam, in 1961 IRE Int. Conf. Rec., vol.9, part 3, pp.93-105
IEEE Microwave Theory and Techniques, Bill Brown's Distinguished Career
Power from the Sun: Its Future, Science Vol. 162, pp. 957-961 (1968)
Solar Power Satellite patent
History of RFID
Space Solar Energy Initiative
Wireless Power Transmission for Solar Power Satellite (SPS) (Second Draft by N. Shinohara), Space Solar Power Workshop, Georgia Institute of Technology
W. C. Brown: The History of Power Transmission by Radio Waves: Microwave Theory and Techniques, IEEE Transactions on September, 1984, v. 32 (9), pp. 1230-1242 (English)
Wireless Power Transfer via Strongly Coupled Magnetic Resonances. Science (7 June 2007). archived,
Earned a new method of wireless transmission of electricity (rus.). MEMBRANA.RU (June 8, 2007). Archived from the original on February 29, 2012. Retrieved September 6, 2010.
Bombardier PRIMOVE Technology
Intel imagines wireless power for your laptop
wireless electricity specification nearing completion
TX40 and CX40, Ex approved Torch and Charger
Haier's wireless HDTV lacks wires, svelte profile (video) (English) ,
Wireless electricity amazed its creators (Russian) . MEMBRANA.RU (February 16, 2010). Archived from the original on February 26, 2012. Retrieved September 6, 2010.
Eric Giler demos wireless electricity | Video on TED.com
"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, Ph.D. 1996
William Beaty, Yahoo Wireless Energy Transmission Tech Group Message #787 , reprinted in WIRELESS TRANSMISSION THEORY .
Wait, James R., The Ancient and Modern History of EM Ground-Wave Propagation," IEEE Antennas and Propagation Magazine, Vol. 40, no. 5, October 1998.
SYSTEM OF TRANSMISSION OF ELECTRICAL ENERGY, Sept. 2, 1897, U.S. Patent No. 645.576, Mar. 20, 1900.

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, but I never have, above my signature, anything announced that I did not prove first. That is the reason why no statement of mine was ever contradicted, and I do not think it will be, because whenever I publish something I go through it first by experiment, then from experiment I calculate, and when I have the theory and practice meet I announce the results.

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. That is simply an expression. . . .

Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power

According to history, the revolutionary technological project was frozen due to Tesla's lack of proper financial resources (this problem haunted the scientist almost all the time he worked in America). Generally speaking, the main pressure on him came from another inventor - Thomas Edison and his companies, who promoted DC technology, while Tesla was engaged in alternating current (the so-called "Current War"). History has put everything in its place: now alternating current is used almost everywhere in urban power networks, although echoes of the past reach our days (for example, one of the stated reasons for the breakdowns of the notorious Hyundai trains is the use of direct current power lines in some sections of the Ukrainian railway).

Wardenclyffe Tower, where Nikola Tesla conducted his experiments with electricity (photo from 1094)

As for the Wardenclyffe tower, according to legend, Tesla demonstrated to one of the main investors, J.P. Morgan, a shareholder in the world's first Niagara hydroelectric power plant and copper plants (copper is known to be used in wires), a working installation for wireless transmission of electricity, the cost to consumers of which would be (earn such installations on an industrial scale) an order of magnitude cheaper for consumers, after which he curtailed the financing of the project. Whatever it was, they started talking seriously about wireless transmission of electricity only 90 years later, in 2007. And while there is still a long way to go before power lines completely disappear from the urban landscape, pleasant little things like wireless charging of a mobile device are already available.

Progress crept up unnoticed

If we look through the archives of IT news at least two years ago, then in such collections we will find only rare reports that certain companies are developing wireless chargers, and not a word about finished products and solutions (except for the basic principles and general schemes ). Today, wireless charging is no longer something super original or conceptual. Such devices are sold with might and main (for example, LG demonstrated its chargers at MWC 2013), tested for electric vehicles (Qualcomm is doing this), and even used in public places (for example, at some European railway stations). Moreover, there are already several standards for such transmission of electricity and several alliances promoting and developing them.

Similar coils are responsible for wireless charging of mobile devices, one of which is in the phone, and the other is in the charger itself.

The best-known such standard is the Qi standard developed by the Wireless Power Consortium, which includes well-known companies such as HTC, Huawei, LG Electronics, Motorola Mobility, Nokia, Samsung, Sony, and about a hundred other organizations. This consortium was organized in 2008 with the aim of creating a universal charger for devices of various manufacturers and brands. In its work, the standard uses the principle of magnetic induction, when the base station consists of an induction coil that creates an electromagnetic field when AC is supplied from the network. In the device being charged, there is a similar coil that reacts to this field and is able to convert the energy received through it into direct current, which is used to charge the battery (you can learn more about the principle of operation on the consortium website http://www.wirelesspowerconsortium.com/what -we-do/how-it-works/). In addition, Qi supports a 2Kb/s communication protocol between chargers and devices to be charged, which is used to communicate the required amount of charge and the required operation.

Wireless charging according to the Qi standard is currently supported by many smartphones, and chargers are universal for all devices that support this standard.

Qi also has a serious competitor - the Power Matters Alliance, which includes AT&T, Duracell, Starbucks, PowerKiss and Powermat Technologies. These names are not at the forefront in the world of information technology (especially the Starbucks coffee chain, which is in an alliance due to the fact that it is going to introduce this technology everywhere in its establishments) - they specialize specifically in energy issues. This alliance was formed not so long ago, in March 2012, within the framework of one of the IEEE (Institute of Electrical and Electronics Engineers) programs. The PMA standard promoted by them works on the principle of mutual induction - a particular example of electromagnetic induction (which should not be confused with the magnetic induction used by Qi), when a change in current in one of the conductors or a change in the relative position of the conductors causes a change in the magnetic flux through the circuit of the second, created magnetic field generated by the current in the first conductor, which causes the occurrence of an electromotive force in the second conductor and (if the second conductor is closed) an induction current. Just as in the case of Qi, this current is then converted to direct current and fed into the battery.

Well, do not forget about the Alliance for Wireless Power, which includes Samsung, Qualcomm, Ever Win Industries, Gill Industries, Peiker Acustic, SK Telecom, SanDisk, etc. This organization has not yet presented ready-made solutions, but among its goals , including the development of chargers that would work through non-metal surfaces and that would not use coils.

One of the goals of the Alliance for Wireless Power is the ability to charge without being tied to a specific place and type of surface.

From all of the above, we can draw a simple conclusion: in a year or two, most modern devices will be able to recharge without using traditional chargers. In the meantime, wireless charging power is enough mainly for smartphones, however, such devices will also appear soon for tablets and laptops (Apple recently patented wireless charging for the iPad). This means that the problem of discharging devices will be solved almost completely - put or put the device in a certain place, and even during operation it charges (or, depending on the power, discharges much more slowly). Over time, there is no doubt that their range will expand (now you need to use a special mat or stand on which the device lies, or it must be very close), and they will be installed everywhere in cars, trains and even, possibly, airplanes.

Well, and one more conclusion - most likely, it will not be possible to avoid another war of formats between different standards and alliances that promote them.

Will we get rid of wires?

Wireless charging of devices is a good thing, of course. But the power that arises from it is sufficient only for the stated purposes. With the help of these technologies, it is not yet possible to even light up a house, not to mention the operation of large household appliances. Nevertheless, experiments on high-power wireless transmission of electricity are being conducted and they are based, among other things, on Tesla's materials. The scientist himself proposed to install around the world (here, most likely, developed countries at that time were meant, which were much smaller than now) more than 30 receiving and transmitting stations that would combine energy transmission with broadcasting and directional wireless communication, which would allow get rid of numerous high-voltage transmission lines and promoted the interconnection of electric generating facilities on a global scale.

Today there are several methods for solving the problem of wireless power transmission, however, all of them so far allow achieving globally insignificant results; It's not even about kilometers. Methods such as ultrasonic, laser and electromagnetic transmission have significant limitations (short distances, the need for direct visibility of transmitters, their size, and in the case of electromagnetic waves, very low efficiency and harm to health from a powerful field). Therefore, the most promising developments are associated with the use of a magnetic field, or rather, resonant magnetic interaction. One of them is WiTricity, developed by the WiTricity corporation, founded by MIT professor Marin Solyachich and a number of his colleagues.

So, in 2007, they managed to transmit a current of 60 W at a distance of 2 m. It was enough to light a light bulb, and the efficiency was 40%. But the indisputable advantage of the technology used was that it practically does not interact with living beings (the field strength, according to the authors, is 10 thousand times weaker than what reigns in the core of a magnetic resonance tomograph), or with medical equipment ( pacemakers, etc.), or with other radiation, which means it will not interfere, for example, with the operation of the same Wi-Fi.

What is most interesting, the efficiency of the WiTricity system is affected not only by the size, geometry and setting of the coils, as well as the distance between them, but also by the number of consumers, and in a positive way. Two receiving devices, placed at a distance of 1.6 to 2.7 m on either side of the transmitting "antenna", showed 10% better efficiency than separately - this solves the problem of connecting many devices to one power source.

In fact, in the 1970s, he technically realized the dreams of NATO and the United States of constant air patrols of Iraq (Libya, Syria, etc.) with drones with cameras, hunting (or fixing) "terrorists" on-line 24 hours.

In 1968, the American space research specialist Peter E. Glaser proposed placing large solar panels in geostationary orbit, and transmitting the energy they generate (5-10 GW level) to the Earth's surface with a well-focused beam of microwave radiation , then convert it into energy of direct or alternating current of technical frequency and distribute it to consumers.

Such a scheme made it possible to use the intense flux of solar radiation that exists in the geostationary orbit (~ 1.4 kW/sq.m.) and transmit the received energy to the Earth's surface continuously, regardless of the time of day and weather conditions. Due to the natural inclination of the equatorial plane to the ecliptic plane with an angle of 23.5 degrees, a satellite located in a geostationary orbit is illuminated by a flux of solar radiation almost continuously, except for short periods of time near the days of the spring and autumn equinoxes, when this satellite falls into the Earth's shadow. These periods of time can be accurately predicted, and in total they do not exceed 1% of the total length of the year.

The frequency of electromagnetic oscillations of the microwave beam must correspond to those ranges that are allocated for use in industry, scientific research and medicine. If this frequency is chosen to be 2.45 GHz, then meteorological conditions, including thick clouds and heavy precipitation, have little effect on the efficiency of power transmission. The 5.8 GHz band is tempting because it allows you to reduce the size of the transmitting and receiving antennas. However, the influence of meteorological conditions here already requires further study.

The current level of development of microwave electronics allows us to speak of a rather high efficiency of energy transfer by a microwave beam from a geostationary orbit to the Earth's surface - about 70% ÷ 75%. In this case, the diameter of the transmitting antenna is usually chosen to be 1 km, and the ground-based rectenna has dimensions of 10 km x 13 km for a latitude of 35 degrees. SCES with an output power level of 5 GW has a radiated power density in the center of the transmitting antenna of 23 kW/m², in the center of the receiving antenna - 230 W/m².

Various types of solid-state and vacuum microwave generators for the SCES transmitting antenna were investigated. William Brown showed, in particular, that magnetrons, which are well mastered by the industry, designed for microwave ovens, can also be used in transmitting antenna arrays of SCES, if each of them is provided with its own negative feedback circuit in phase with respect to an external synchronizing signal (so called Magnetron Directional Amplifier - MDA).

The most active and systematic research in the field of SCES was conducted by Japan. In 1981, under the guidance of Professors M. Nagatomo (Makoto Nagatomo) and S. Sasaki (Susumu Sasaki), research was started at the Space Research Institute of Japan to develop a prototype of SCES with a power level of 10 MW, which could be created using existing launch vehicles. The creation of such a prototype allows one to accumulate technological experience and prepare the basis for the formation of commercial systems.

The project was named SKES2000 (SPS2000) and received recognition in many countries of the world.

In 2008, Marin Soljačić, assistant professor of physics at the Massachusetts Institute of Technology (MIT), was awakened from a sweet sleep by the persistent beeping of a mobile phone. “The phone would not stop, demanding that I put it on charge,” Soljacic said. Tired and not going to get up, he began to dream that the phone, once at home, would start charging by itself.

In 2012-2015 University of Washington engineers have developed technology that allows Wi-Fi to be used as an energy source to power portable devices and charge gadgets. The technology has already been recognized by Popular Science magazine as one of the best innovations of 2015. The ubiquity of wireless data transmission technology itself has made a real revolution. And now it's the turn of wireless power transmission over the air, which the developers from the University of Washington called (from Power Over WiFi).

During the testing phase, the researchers were able to successfully charge low-capacity lithium-ion and nickel-metal hydride batteries. Using the Asus RT-AC68U router and several sensors located at a distance of 8.5 meters from it. These sensors just convert the energy of an electromagnetic wave into a direct current with a voltage of 1.8 to 2.4 volts, which is necessary to power microcontrollers and sensor systems. The peculiarity of the technology is that the quality of the working signal does not deteriorate. It is enough just to reflash the router, and you can use it as usual, plus supply power to low-power devices. One demonstration successfully powered a small, low-resolution covert surveillance camera located more than 5 meters away from a router. Then the Jawbone Up24 fitness tracker was charged to 41%, it took 2.5 hours.

To tricky questions about why these processes do not negatively affect the quality of the network communication channel, the developers replied that this becomes possible due to the fact that a flashed router sends out energy packets during its work on unoccupied information transfer channels. They came to this decision when they discovered that during periods of silence, energy simply flows out of the system, and in fact it can be directed to power low-power devices.

During the study, the PoWiFi system was placed in six houses, and the residents were invited to use the Internet as usual. Load web pages, watch streaming video, and then tell them what's changed. As a result, it turned out that network performance did not change in any way. That is, the Internet worked as usual, and the presence of the added option was not noticeable. And these were only the first tests, when a relatively small amount of energy was collected over Wi-Fi.

In the future, PoWiFi technology may well serve to power sensors built into household appliances and military equipment in order to control them wirelessly and carry out remote charging / recharging.

Relevant is the transfer of energy for UAVs (most likely, already by technology or from a carrier aircraft):

The idea looks quite tempting. Instead of today's 20-30 minutes of flight time:
→
→

→ Intel ran the drone show during Lady Gaga's US Super Bowl halftime performance-
get 40-80 minutes by wirelessly charging drones.

Let me explain:
-exchange of m / y drones is still necessary (swarm algorithm);
- the exchange of m / y drones and aircraft (womb) is also necessary (control center, correction of knowledge base, retargeting, command to eliminate, preventing "friendly fire", transfer of intelligence information and commands to use).

Who's next in line?

Note: A typical WiMAX base station radiates at approximately +43 dBm (20 W), while a mobile station typically transmits at +23 dBm (200 mW).

Permissible levels of radiation from mobile base stations (900 and 1800 MHz, the total level from all sources) in the sanitary-residential zone in some countries differ markedly:
Ukraine: 2.5 µW/cm². (the most stringent sanitary standard in Europe)
Russia, Hungary: 10 µW/cm².
Moscow: 2.0 µW/cm². (the norm existed until the end of 2009)
USA, Scandinavian countries: 100 µW/cm².

The temporary allowable level (TDU) from mobile radiotelephones (MRT) for users of radiotelephones in the Russian Federation is defined as 10 μW / cm² (Section IV - Hygienic requirements for mobile land radio stations SanPiN 2.1.8 / 2.2.4.1190-03).

In the USA, the Certificate is issued by the Federal Communications Commission (FCC) for cellular devices whose maximum SAR level does not exceed 1.6 W/kg (moreover, the absorbed radiation power is reduced to 1 gram of human tissue).

In Europe, according to the international directive of the Commission on Non-Ionizing Radiation Protection (ICNIRP), the SAR value of a mobile phone should not exceed 2 W / kg (with the absorbed radiation power given to 10 grams of human tissue).

More recently, in the UK, a level of 10 W/kg was considered a safe SAR level. A similar pattern was observed in other countries as well. The maximum SAR value accepted in the standard (1.6 W/kg) cannot even be safely attributed to “hard” or “soft” standards. The standards for determining the SAR value adopted both in the USA and in Europe (all the regulation of microwave radiation from cell phones in question is based only on the thermal effect, that is, associated with the heating of human tissues).

COMPLETE CHAOS.

Medicine has not yet given a clear answer to the question: is mobile / WiFi harmful and how much? And what about the wireless transmission of electricity by microwave technology?

Here the power is not watts and miles of watts, but already kW ...

Links, used documents, photos and videos:
"(JOURNAL OF RADIOELECTRONICS!" N 12, 2007 (ELECTRIC POWER FROM SPACE - SOLAR SPACE POWER PLANTS, V. A. Banke)
"Microwave electronics - prospects in space energy" V. Banke, Ph.D.
www.nasa.gov
www. whdi.org
www.defense.gov
www.witricity.com
www.ru.pinterest.com
www. raytheon.com
www. ausairpower.net
www. wikipedia.org
www.slideshare.net
www.homes.cs.washington.edu
www.dailywireless.org
www.digimedia.ru
www. powercoup.by
www.researchgate.net
www. proelectro.info
www.youtube.com

This is a simple circuit that can power a light bulb without any wires, at a distance of almost 2.5 cm! This circuit acts as both a boost converter and a wireless power transmitter and receiver. It is very easy to make and, if perfected, can be used in a variety of ways. So let's get started!

Step 1. Necessary materials and tools.

NPN transistor. I used 2N3904 but you can use any NPN transistor like BC337, BC547 etc. (Any PNP transistor will work, just be careful about the polarity of the connections.)
Winding or insulated wire. About 3-4 meters of wire should be enough (winding wires, just copper wires with very thin enamel insulation). Wires from most electronic devices will work, such as transformers, speakers, motors, relays, etc.
Resistor with a resistance of 1 kOhm. This resistor will be used to protect the transistor from burning out in case of overload or overheating. You can use higher resistance values up to 4-5 kΩ. It is possible not to use a resistor, but there is a risk of the battery draining faster.
Light-emitting diode. I used a 2mm ultra bright white LED. You can use any LED. In fact, the purpose of the LED here is only to show the health of the circuit.
AA size battery, 1.5 volts. (Do not use high voltage batteries unless you want to damage the transistor.)

Required tools:

1) Scissors or a knife.

2) Soldering iron (Optional). If you do not have a soldering iron, you can simply twist the wires. I did this when I didn't have a soldering iron. If you would like to try the circuit without soldering, you are most welcome.

3) Lighter (Optional). We will use a lighter to burn off the insulation on the wire and then use scissors or a knife to scrape off the remaining insulation.

Step 2: Watch the video to see how.

Step 3: Brief repetition of all steps.

So, first of all you have to take the wires, and make a coil by winding 30 turns around a round cylindrical object. Let's call this coil A. With the same round object, start making the second coil. After winding the 15th turn, create a branch in the form of a loop from the wire and then wind another 15 turns on the coil. So now you have a coil with two ends and one branch. Let's call this coil B. Tie knots at the ends of the wires so they don't unwind on their own. Burn the insulation on the ends of the wires and on the branch on both coils. You can also use scissors or a knife to strip the insulation. Make sure that the diameters and number of turns of both coils are equal!

Build the Transmitter: Take the transistor and place it with the flat side facing up and facing you. The pin on the left will be connected to the emitter, the middle pin will be the base pin, and the pin on the right will be connected to the collector. Take a resistor and connect one of its ends to the base terminal of the transistor. Take the other end of the resistor and connect it to one end (not the tap) of Coil B. Take the other end of Coil B and connect it to the collector of the transistor. If you like, you can connect a small piece of wire to the emitter of the transistor (This will work as an extension of the Emitter.)

Set up the receiver. To create a receiver, take Coil A and attach its ends to different pins on your LED.

You've got the blueprint!

Step 4: Schematic diagram.

Here we see the schematic diagram of our connection. If you don't know some symbols on the diagram, don't worry. The following pictures show everything.

Step 5. Drawing of circuit connections.

Here we see an explanatory drawing of the connections of our circuit.

Step 6. Using the scheme.

Simply take a branch of Coil B and connect it to the positive end of the battery. Connect the negative pole of the battery to the emitter of the transistor. Now if you bring the LED coil close to coil B, the LED lights up!

Step 7. How is this scientifically explained?

(I will just try to explain the science of this phenomenon in simple words and analogies, and I know that I can be wrong. In order to properly explain this phenomenon, I will have to go into all the details, which I am not able to do, so I just want to generalize analogies to explain the scheme).

The transmitter circuit we just created is the Oscillator circuit. You may have heard of the so-called Joule Thief circuit, and it bears a striking resemblance to the circuit we created. The Joule Thief circuit takes power from a 1.5 volt battery, outputs power at a higher voltage, but with thousands of intervals between them. The LED only needs 3 volts to light up, but in this circuit it may well light up with a 1.5 volt battery. So the Joule Thief circuit is known as a voltage boost converter and also as an emitter. The circuit we created is also an emitter and a voltage boost converter. But the question may arise: "How to light an LED from a distance?" This is due to induction. To do this, you can, for example, use a transformer. A standard transformer has a core on both sides. Assume that the wire on each side of the transformer is equal in size. When an electric current passes through one coil, the transformer coils become electromagnets. If an alternating current flows through the coil, then the voltage fluctuations occur along a sinusoid. Therefore, when an alternating current flows through the coil, the wire takes on the properties of an electromagnet, and then loses electromagnetism again when the voltage drops. The coil of wire becomes an electromagnet and then loses its electromagnetic characteristics at the same speed as the magnet moves out of the second coil. When the magnet moves quickly through the coil of wire, electricity is generated, so the oscillating voltage of one coil on the transformer induces electricity in the other coil of wire, and electricity is transferred from one coil to another without wires. In our circuit, the core of the coil is air, and an AC voltage passes through the first coil, thus causing voltage in the second coil and lighting the bulbs!!

Step 8. Benefits and tips for improvement.

So in our circuit, we just used an LED to show the effect of the circuit. But we could do more! The receiver circuit gets its electricity from AC, so we could use it to light up fluorescent lights! Also, with our scheme, you can do interesting magic tricks, funny gifts, etc. To maximize the results, you can experiment with the diameter of the coils and the number of revolutions on the coils. You can also try flattening the coils and see what happens! The possibilities are endless!!

Step 9. Reasons why the scheme may not work.

What problems you may encounter and how you can fix them:

The transistor gets too hot!

Solution: Did you use the right sized resistor? I didn't use the resistor the first time and the transistor started to smoke. If that doesn't help, try using heat shrink or use a higher grade transistor.

The LED is off!

Solution: There could be many reasons. First, check all connections. I accidentally changed the base and collector in my connection and it became a big problem for me. So, check all connections first. If you have a device such as a multimeter, you can use it to check all connections. Also make sure that both coils are the same diameter. Check if there is a short circuit in your network.

I am not aware of any other problems. But if you still encounter them, let me know! I'll try to help in any way I can. Also, I'm a grade 9 student and my scientific knowledge is extremely limited, so if you find any mistakes in me, please let me know. Suggestions for improvement are more than welcome. Good luck with your project!

Mankind strives for a complete rejection of wires, because, according to many, they limit the possibilities and do not allow to act completely freely. And what if it were possible to do so in the case of power transmission? You can find out the answer to this question in this review, which is devoted to a video on making a home-made design, which in small sizes represents the possibility of transmitting electricity without a direct connection of wires.

We will need:
- copper wire of small diameter, 7 m long;
- a cylinder with a diameter of 4 cm;
- finger battery;
- battery box
- 10 ohm resistor;
- transistor C2482;
- Light-emitting diode.

We take a wire 4 meters long and bend it in half so that two wires remain at one end, and the bent part is at the other end.

We take one wire, bend it in any direction and begin to wind it on the cylinder.

Having reached the middle, we also leave the double posting in any direction and continue to wind until a small piece remains, which must also be left.

The resulting ring with three ends must be removed from the cylinder and secured with insulating tape.

Now we take the second piece of wiring 3 m long and wind it in the usual way. That is, in this case, we need to get not three ends, as in the case of the last winding, but two.

The resulting ring is again fixed with electrical tape.

The ends of the wire must be cleaned, because it is covered with a protective layer of varnish.

To simplify the homemade assembly process, we present to your attention the author's connection diagram.

The diagram shows that the coil with three outputs is designed to connect the power supply of the resistor and transistor, and on the second coil, which has two ends, you need to attach the LED.

Thus, you can get a completely spectacular and interesting homemade product, which, if desired, can be upgraded and made more powerful by adding the number of turns and experimenting. We also draw your attention to the fact that the lighting of the LED bulb, which also serves as a tester, depends on the side of the coils being brought to each other. This means that if the light did not light up during the first presentation, then you should try to turn the coil over and do it again.