Contactless electricity. Wireless transmission of electricity: history, technology, equipment

Since the discovery of electricity by man, many scientists have been trying to study the amazing phenomenon of currents and increase the useful coefficient of action by conducting numerous experiments and inventing more modern materials that have improved properties for transmitting energy with zero resistance. The most promising direction in such scientific work is the wireless transmission of electricity over long distances and with minimal transportation costs. This article discusses ways to transfer energy over a distance, as well as types of devices for such actions.

Wireless power transmission is a method of transportation that does not use any conductors or networks of cables, and the current is transmitted over a considerable distance to the consumer with the maximum effective power factor over the air. To do this, devices are used to generate electricity, as well as a transmitter that accumulates current in itself and dissipates it in all directions, as well as a receiver with a consumer device. The receiver captures electromagnetic waves and fields and, by concentrating them on a short section of the conductor, transmits energy to a lamp or any other device of a certain power.

There are many ways for the wireless transmission of electricity, which were invented in the process of studying currents by many scientists, but Nikola Tesla achieved the greatest results in practical terms. He managed to make a transmitter and receiver, which were separated from each other by a distance equal to 48 kilometers. But at that time there were no technologies that could transmit electricity over such a distance with a coefficient higher than 50%. In this regard, the scientist expressed a great prospect not for the transfer of ready generated energy, but for generating current from the earth's magnetic field and using it for domestic needs. The transportation of such electricity had to be carried out wirelessly, by transmission through magnetic fields.

Methods for wireless transmission of electricity

Most theorists and practitioners who study the operation of electric current have proposed their own methods for transmitting it over a distance without the use of conductors. At the beginning of such studies, many scientists tried to borrow practice from the principle of operation of radio receivers, which are used to transmit Morse code or shortwave radio. But such technologies did not justify themselves, since the current dissipation was too small and could not cover long distances, moreover, the transportation of electricity via radio waves was possible only when working with low powers that could not drive even the simplest mechanism.

As a result of the experiments, it was found that microwave waves are most suitable for transmitting electricity without a wire, which have a more stable configuration and voltage, and also lose much less energy during dissipation than any other method.

For the first time, this method was successfully applied by the inventor and designer William Brown, who modeled a flying platform consisting of a metal platform with an engine with a power of about 0.1 horsepower. The platform was made in the form of a receiving antenna with a grid that captures microwave waves that were transmitted by a specially designed generator. After only fourteen years, the same designer presented a low-power aircraft that received energy from a transmitter at a distance of 1.6 kilometers, the current was transmitted in a concentrated beam through microwave waves. Unfortunately, this work was not widely used, since at that time there were no technologies that could ensure the transportation of high voltage current by this method, although the efficiency of the receiver and generator was more than 80%.

In 1968, American scientists developed a project, supported by scientific work, which proposed the placement of large solar arrays in low Earth orbit. Energy receivers had to be directed at the sun, and current storage devices were placed at their base. After absorbing solar radiation and transforming it into microwave or magnetic waves, the current was directed to the ground through a special device. Reception had to be carried out by a special large-area antenna, tuned to a certain wave and converting the waves into direct or alternating current. Such a system has been highly appreciated in many countries as a promising alternative to modern sources of electricity.

Powering an electric car wirelessly

Many manufacturers of cars running on electric current are developing alternative recharging of a car without connecting it to the network. Great success in this area has been achieved by the technology of charging vehicles from a special roadbed, when the car received energy from a coating charged with a magnetic field or microwave waves. But such recharge was possible only if the distance between the road and the receiving device was no more than 15 centimeters, which is not always feasible in modern conditions.

This system is under development, so it can be assumed that this type of power transmission without a conductor will still be developed and, possibly, will be introduced into the modern transport industry.

State-of-the-art power transmission developments

In modern realities, wireless electricity is once again becoming an important direction in the study and design of devices. There are the most promising ways to develop wireless power transmission, which include:

1. The use of electricity in mountainous areas, in cases where it is not possible to lay carrier cables to the consumer. Despite the study of the issue of electricity, there are places on earth where there is no electricity, and the people living there cannot enjoy such a blessing of civilization. Of course, autonomous power sources are often used there, such as solar panels or generators, but this resource is limited and cannot fully meet the needs;
2. Some manufacturers of modern household appliances are already introducing devices for transmitting energy without wires into their products. For example, a special unit is offered on the market, which is connected to the mains supply and, by converting direct current into microwave waves, transmits them to surrounding devices. The only condition for using this device is that household appliances have a receiving device that converts these waves into direct current. There are televisions on the market that are completely powered by wireless energy received from the transmitter;
3. For military purposes, in most cases in the defense sector, there are developments of communication devices and other auxiliary devices.

A big breakthrough in this field of technology occurred in 2014, when a group of scientists developed a device for generating and receiving energy over a distance without wires, using a lens system placed between the transmitting and receiving coils. Previously, it was believed that the transmission of current without a conductor is possible at a distance not exceeding the size of the devices, so a huge structure was required to transport electricity over a long distance. But modern designers have changed the principle of operation of this device and created a transmitter that directs not microwave waves, but magnetic fields with low frequencies. In this case, electrons do not lose power and are transmitted over a distance in a concentrated beam, moreover, energy consumption is possible not only by connecting to the receiving part, but also simply by being in the area of ​​the fields.

1. Charging mobile devices without connecting to a cable;
2. The implementation of power for unmanned aerial vehicles is a direction that will be in great demand in both the civil and military industries, since such devices have recently become often used for various purposes.

The very procedure for transmitting data over a distance without the use of wires some time ago was considered a breakthrough in the research of physics and energy, now it no longer surprises anyone and has become accessible to any person. Thanks to the modern development of technologies and developments, the transportation of electricity by this method is becoming a reality and may well be implemented.

Video

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 somewhat 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.

see also

• energy beam

Notes

1. "Electricity at the Columbian Exposition", by John Patrick Barrett. 1894, pp. 168-169
2. Experiments with Alternating Currents of Very High Frequency and Their Application to Methods of Artificial Illumination, AIEE, Columbia College, N.Y., May 20, 1891
3. Experiments with Alternate Currents of High Potential and High Frequency, IEE Address, London, February 1892
4. On Light and Other High Frequency Phenomena, Franklin Institute, Philadelphia, February 1893 and National Electric Light Association, St. Louis, March 1893
5. The Work of Jagdish Chandra Bose: 100 years of mm-wave research
6. Jagadish Chandra Bose
7. Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power, pp. 26-29. (English)
8. June 5, 1899, Nikola Tesla Colorado Spring Notes 1899-1900, Nolit, 1978 (English)
9. Nikola Tesla: Guided Weapons & Computer Technology
10. The Electrician(London), 1904 (English)
11. Scanning the Past: A History of Electrical Engineering from the Past, Hidetsugu Yagi
12. A survey of the elements of power transmission by microwave beam, in 1961 IRE Int. Conf. Rec., vol.9, part 3, pp.93-105
13. IEEE Microwave Theory and Techniques, Bill Brown's Distinguished Career
14. Power from the Sun: Its Future, Science Vol. 162, pp. 957-961 (1968)
15. Solar Power Satellite patent
16. History of RFID
17. Space Solar Energy Initiative
18. Wireless Power Transmission for Solar Power Satellite (SPS) (Second Draft by N. Shinohara), Space Solar Power Workshop, Georgia Institute of Technology
19. 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)
20. 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.
21. Bombardier PRIMOVE Technology
22. Intel imagines wireless power for your laptop
23. wireless electricity specification nearing completion
24. TX40 and CX40, Ex approved Torch and Charger
25. 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.
26. Eric Giler demos wireless electricity | Video on TED.com
27. "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
28. William Beaty, Yahoo Wireless Energy Transmission Tech Group Message #787 , reprinted in WIRELESS TRANSMISSION THEORY .
29. Wait, James R., The Ancient and Modern History of EM Ground-Wave Propagation," IEEE Antennas and Propagation Magazine, Vol. 40, no. 5, October 1998.
30. SYSTEM OF TRANSMISSION OF ELECTRICAL ENERGY, Sept. 2, 1897, U.S. Patent No. 645.576, Mar. 20, 1900.

31. 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. . . .

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

Scientists have been studying the issue of transmitting electricity without wires for the third century. Recently, the issue has not lost its relevance, but, on the contrary, has taken a step forward, which is only pleasing. We decided to tell the readers of the site in detail how wireless transmission of electricity has developed over distances from the beginning to the present day, as well as what technologies are already being practiced.

History of development

The development of transmission of electricity without wires over a distance is associated with progress in the field of radio engineering, since both processes are of the same nature. Inventions in both areas are related to the study of the method of electromagnetic induction and its effect on the generation of electric current.

In 1820 A.M. Ampère discovered the law of interaction of currents, which was that if two closely spaced conductors current flows in the same direction, then they are attracted to each other, and if they are in different directions, they repel each other.

M. Faraday in 1831 established in the process of conducting experiments that a variable (changing in magnitude and direction in time) magnetic field generated by the flow of electric current induces (induces) currents in nearby conductors. Those. transmission of electricity without wires. We discussed it in detail in an earlier article.

Well, J.K. Maxwell 33 years later, in 1864, translated Faraday's experimental data into a mathematical form, Maxwell's own equations are fundamental in electrodynamics. They describe how an electric current and an electromagnetic field are related.

The existence of electromagnetic waves was confirmed in 1888 by G. Hertz, in the course of his experiments with a spark transmitter with a chopper on a Ruhmkorff coil. In this way, EM waves were produced with frequencies up to half a gigahertz. It is worth noting that these waves could be received by several receivers, but they must be tuned to resonance with the transmitter. The range of the installation was in the region of 3 meters. When a spark appeared in the transmitter, the same spark appeared on the receivers. In fact, these are the first experiments in the transmission of electricity without wires.

Deep research was conducted by the famous scientist Nikola Tesla. In 1891 he studied alternating current of high voltage and frequency. As a result, the following conclusions were drawn:

For each specific purpose, you need to adjust the installation to the appropriate frequency and voltage. In this case, a high frequency is not a prerequisite. The best results were achieved at a frequency of 15-20 kHz and a transmitter voltage of 20 kV. To obtain a high frequency current and voltage, an oscillatory discharge of a capacitor was used. Thus, it is possible to transmit both electricity and produce light.

The scientist in his speeches and lectures demonstrated the glow of lamps (vacuum tubes) under the influence of a high-frequency electrostatic field. Actually, Tesla's main conclusions were that even in the case of using resonant systems, a lot of energy cannot be transmitted using an electromagnetic wave.

In parallel, a number of scientists were engaged in similar studies until 1897: Jagdish Bose in India, Alexander Popov in Russia and Guglielmo Marconi in Italy.

Each of them contributed to the development of wireless power transmission:

1. J. Bose in 1894, ignited gunpowder, transmitting electricity over a distance without wires. He did this at a demonstration in Calcutta.
2. A. Popov on April 25 (May 7), 1895, using Morse code, transmitted the first message. In Russia, this day, May 7, is still Radio Day.
3. In 1896, G. Marconi in the UK also transmitted a radio signal (Morse code) over a distance of 1.5 km, later 3 km on Salisbury Plain.

It is worth noting that Tesla's works, underestimated in their time and lost for centuries, surpassed the work of his contemporaries in terms of parameters and capabilities. At the same time, namely in 1896, his devices transmitted a signal over long distances (48 km), unfortunately this was a small amount of electricity.

And by 1899, Tesla comes to the conclusion:

The inconsistency of the method of induction seems to be enormous in comparison with the method of excitation of the charge of the earth and air.

These conclusions will lead to other research, in 1900 he managed to power a lamp from a coil in the field, and in 1903 the Wondercliff tower on Long Island was launched. It consisted of a transformer with a grounded secondary, and on top of it stood a copper spherical dome. With its help, it turned out to light 200 50-watt lamps. At the same time, the transmitter was located 40 km from it. Unfortunately, these studies were interrupted, funding was cut off, and free transmission of electricity without wires was not economically beneficial for businessmen. The tower was destroyed in 1917.

Nowadays

Wireless power transmission technologies have made great strides forward, mainly in the field of data transmission. So significant success has been achieved by radio communication, wireless technologies such as Bluetooth and Wi-fi. There were no special innovations, the frequencies, the methods of signal encryption were mainly changed, the signal representation switched from analog to digital form.

When it comes to the transmission of electricity without wires to power electrical equipment, it is worth mentioning that in 2007, researchers from the Massachusetts Institute transmitted energy over 2 meters and lit a 60-watt light bulb in this way. This technology is called WiTricity, it is based on the electromagnetic resonance of the receiver and transmitter. It is worth noting that the receiver receives about 40-45% of the electricity. A generalized diagram of a device for transmitting energy through a magnetic field is shown in the figure below:

The video shows an example of using this technology to charge an electric car. The bottom line is that a receiver is attached to the bottom of the electric car, and a transmitter is installed on the floor in a garage or other place.

You must position the car so that the receiver is above the transmitter. The device transmits a lot of electricity without wires - from 3.6 to 11 kW per hour.

In the future, the company is considering providing electricity with such technology and household appliances, as well as the entire apartment as a whole. In 2010, Haier introduced a wireless TV that receives power using a similar technology, as well as a video signal without wires. Similar developments are being carried out by other leading companies such as Intel and Sony.

In everyday life, wireless power transmission technologies are widespread, for example, for charging a smartphone. The principle is similar - there is a transmitter, there is a receiver, the efficiency is about 50%, i.e. to charge with a current of 1A, the transmitter will consume 2A. The transmitter is usually called the base in such kits, and the part that connects to the phone is called the receiver or antenna.

Another niche is the wireless transmission of electricity using microwaves or lasers. This provides a greater range than the parameters provided by magnetic induction. In the microwave method, a rectenna (a non-linear antenna for converting an electromagnetic wave into direct current) is installed on the receiving device, and the transmitter directs its radiation in this direction. In this version of the wireless transmission of electricity, there is no need for a direct line of sight of objects. The downside is that microwave radiation is unsafe for the environment.

In conclusion, I would like to note that wireless transmission of electricity is certainly convenient for use in everyday life, but it has its pros and cons. If we talk about using such technologies to charge gadgets, then the advantage is that you do not have to constantly insert and remove the plug from the connector of your smartphone, respectively, the connector will not fail. The downside is low efficiency, if energy losses are not significant for a smartphone (several watts), then for wireless charging of an electric car this is a very big problem. The main goal of development in this technology is to increase the efficiency of the installation, because against the background of the widespread race for energy saving, the use of technologies with low efficiency is very doubtful.

Related content:

When Apple introduced its first wireless charger for cell phones and gadgets, many considered it a revolution and a huge leap forward in wireless power delivery.

But were they pioneers or even before them, did someone manage to do something similar, though without proper marketing and PR? It turns out there were, moreover, a very long time ago and there were many such inventors.

So back in 1893, the famous Nikola Tesla demonstrated to the astonished public the glow of fluorescent lamps. Despite the fact that they were all without wires.

Now any student can repeat such a trick by going out into an open field and standing with a fluorescent lamp under a high voltage line of 220 kV and above.

A little later, Tesla already managed to light a phosphor incandescent bulb in the same wireless way.

In Russia in 1895 A. Popov showed the world's first radio receiver in operation. But by and large, this is also a wireless transmission of energy.

The most important question and at the same time the problem of the whole technology of wireless charging and similar methods lies in two points:

• how far can electricity be transmitted in this way

• and how many

To begin with, let's figure out how much power devices and household appliances around us have. For example, a phone, smartwatch or tablet requires a maximum of 10-12W.

The laptop has more requests - 60-80W. This can be compared to an average incandescent light bulb. But household appliances, especially kitchen appliances, already consume several thousand watts.

Therefore, it is very important not to save on the number of outlets in the kitchen.

So what are the methods and methods for the transmission of electrical energy without the use of cables or any other conductors that humanity has come up with over the years. And most importantly, why they have not yet been introduced as actively into our lives as we would like.

Take the same kitchen appliances. Let's understand in more detail.

Power transfer through coils

The most easily implemented way is to use inductors.

Here the principle is very simple. 2 coils are taken and placed close to each other. One of them is catering. The other plays the role of a receiver.

When the current is adjusted or changed in the power supply, the magnetic flux on the second coil automatically also changes. As the laws of physics say, in this case, an EMF will arise and it will directly depend on the rate of change of this flux.

It would seem that everything is simple. But the flaws spoil the whole rosy picture. Three cons:

• little power

In this way, you will not transfer large volumes and will not be able to connect powerful devices. And if you try to do this, then just melt all the windings.

• short distance

Don't even think about transferring electricity to tens or hundreds of meters here. This method has limited effect.

To physically understand how bad things are, take two magnets and figure out how far they need to be separated so that they stop attracting or repelling each other. That's about the same efficiency for coils.

Of course, you can contrive and ensure that these two elements are always close to each other. For example, an electric car and a special recharging road.

But how much will the construction of such highways cost?

• low efficiency

Another problem is low efficiency. It does not exceed 40%. It turns out that you will not be able to transmit a lot of electricity over long distances in this way.

The same N. Tesla pointed out this back in 1899. Later, he switched to experiments with atmospheric electricity, hoping to find a clue and a solution to the problem in it.

However, no matter how useless all these things may seem, they can still be used to arrange beautiful light and music performances.

Or recharge equipment much larger than phones. For example, electric bicycles.

Laser energy transfer

But how to transfer more energy over a greater distance? Think about the films in which we see this technology very often.

The first thing that comes to mind even to a schoolboy is Star Wars, lasers and lightsabers.

Of course, with their help, you can transfer a large amount of electricity over very decent distances. But again, a small problem spoils everything.

Fortunately for us, but unfortunately for the laser, Earth has an atmosphere. And it just dampens well and eats most of the entire energy of laser radiation. Therefore, with this technology, you need to go into space.

On Earth, there were also attempts and experiments to test the performance of the method. Nasa even hosted laser wireless power transmission competitions with a prize pool of just under $1 million.

In the end, Laser Motive won. Their winning result is 1km and 0.5kW of transmitted continuous power. True, in the process of transmission, scientists lost 90% of all original energy.

But still, even with an efficiency of ten percent, the result was considered successful.

Recall that a simple light bulb has useful energy that goes directly to the light, and even less. Therefore, it is advantageous to make infrared heaters from them.

Microwave

Is there really no other really working way to transmit electricity without wires. There is, and it was invented before attempts and children's games in star wars.

It turns out that special microwaves with a length of 12 cm (frequency 2.45 GHz) are, as it were, transparent to the atmosphere and it does not interfere with their propagation.

No matter how bad the weather, when transmitting using microwaves, you will lose only five percent! But for this, you must first convert the electric current into microwaves, then catch them and return them to their original state again.

Scientists solved the first problem a very long time ago. They invented a special device for this and called it the magnetron.

Moreover, it was done so professionally and safely that today each of you has such a device at home. Go into the kitchen and take a look at your microwave.

She has the same magnetron inside with an efficiency of 95%.

But here's how to do the reverse transformation? And here two approaches have been developed:

• American

• Soviet

Back in the sixties, the scientist W. Brown invented an antenna in the USA, which performed the required task. That is, it converted the radiation falling on it back into an electric current.

He even gave her his name - rectenna.

After the invention, experiments followed. And in 1975, with the help of a rectenna, as many as 30 kW of power were transmitted and received at a distance of more than one kilometer. The transmission loss was only 18%.

Almost half a century later, no one has been able to surpass this experience so far. It would seem that a method has been found, so why weren't these rectennas launched into the masses?

And here again the shortcomings emerge. Rectennas were assembled on the basis of miniature semiconductors. Their normal job is to transmit only a few watts of power.

And if you want to transfer tens or hundreds of kilowatts, then get ready to assemble giant panels.

And this is where the unsolvable difficulties appear. First, it is re-emission.

Not only will you lose some of your energy because of it, but you won’t be able to get close to the panels without losing your health.

The second headache is the instability of the semiconductors in the panels. It is enough to burn out one due to a small overload, and the rest fail like an avalanche, like matches.

In the USSR, things were somewhat different. It was not in vain that our military were sure that even with a nuclear explosion, all foreign equipment would immediately fail, but the Soviet one would not. The whole secret is in the lamps.

At Moscow State University, two of our scientists, V. Savin and V. Vanke, designed the so-called cyclotron energy converter. It has a decent size, as it is assembled on the basis of lamp technology.

Outwardly, this is something like a tube 40 cm long and 15 cm in diameter. The efficiency of this lamp unit is slightly less than that of the American semiconductor thing - up to 85%.

But unlike semiconductor detectors, the cyclotron energy converter has a number of significant advantages:

• reliability

• big power

• overload resistance

• no reemission

• low manufacturing cost

However, despite all of the above, all over the world, it is semiconductor methods for implementing projects that are considered advanced. There is also an element of fashion here.

After the first appearance of semiconductors, everyone abruptly began to abandon tube technology. But practical experience suggests that this is often the wrong approach.

Of course, tube cell phones of 20 kg each or computers occupying entire rooms are of no interest to anyone.

But sometimes only proven old methods can help us out in hopeless situations.

As a result, today we have three possibilities to transfer energy without wires. The very first of those considered is limited by both distance and power.

But this is quite enough to charge the battery of a smartphone, tablet or something bigger. Although the efficiency is small, the method is still working.

The first one started out very promising. In the 2000s, on the island of Reunion, there was a need for a constant transmission of 10 kW of power over a distance of 1 km.

The mountainous terrain and local vegetation did not allow laying either overhead power lines or cable lines there.

All movements on the island to this point were carried out exclusively by helicopters.

To solve the problem, the best minds from different countries were gathered into one team. Including those previously mentioned in the article, our scientists from Moscow State University V. Vanke and V. Savin.

However, at the moment when they were supposed to start the practical implementation and construction of energy transmitters and receivers, the project was frozen and stopped. And with the onset of the crisis in 2008, they completely abandoned it.

In fact, this is very disappointing, since the theoretical work done there was colossal and worthy of implementation.

The second project looks crazier than the first. However, real funds are allocated for it. The idea itself was expressed as early as 1968 by a physicist from the USA, P. Glazer.

He proposed at that time not quite a normal idea - to put a huge satellite into a geostationary orbit 36,000 km above the earth. On it, place solar panels that will collect free energy from the sun.

Then all this should be converted into a beam of microwave waves and transmitted to the ground.

A sort of "death star" in our earthly realities.

On the ground, the beam must be caught by giant antennas and converted into electricity.

How big do these antennas need to be? Imagine that if the satellite is 1 km in diameter, then on the ground the receiver should be 5 times larger - 5 km (the size of the Garden Ring).

But size is only a small part of the problem. After all the calculations, it turned out that such a satellite would generate electricity with a capacity of 5 GW. Upon reaching the ground, only 2 GW would remain. For example, the Krasnoyarsk HPP provides 6GW.

Therefore, his idea was considered, counted and put aside, since everything initially rested on the price. The cost of the space project in those days climbed over $ 1 trillion.

But science, fortunately, does not stand still. Technology is getting better and cheaper. Several countries are already developing such a solar space station. Although at the beginning of the twentieth century, only one brilliant person was enough for the wireless transmission of electricity.

The total cost of the project has fallen from the original to $25 billion. The question remains - will we see its implementation in the near future?

Unfortunately no one can give you a clear answer. Bets are made only on the second half of this century. Therefore, for now, let's be content with wireless chargers for smartphones and hope that scientists will be able to increase their efficiency. Well, or in the end, the second Nikola Tesla will be born on Earth.

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.