How to wirelessly determine the presence of electrical power. Methods for wirelessly transmitting electricity over a distance

If history is to be believed, the revolutionary technological project was frozen due to Tesla’s lack of adequate 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 were promoting direct current technology while Tesla was working on alternating current (the so-called “War of the Currents”). History has put everything in its place: now alternating current is used in city power grids almost everywhere, although echoes of the past continue to this day (for example, one of the stated reasons for 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 Wardenclyffe Tower, according to legend, Tesla demonstrated to one of the main investors J.P. Morgan, a shareholder of the world's first Niagara hydroelectric power station and copper plants (copper, as you know, is used in wires), a working installation for wireless current transmission, the cost of which for consumers would be (if such installations were built on an industrial scale) an order of magnitude cheaper for consumers, after why he curtailed funding for the project. Be that as it may, they started talking seriously about wireless power transmission only 90 years later, in 2007. And although it's still a long way until power lines completely disappear from the cityscape, nice little things like wireless charging mobile device available now.

Progress has crept up unnoticed

If we look through the archives of IT news from 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 basic principles And general schemes). Today, wireless charging is no longer something super-original or conceptual. Similar devices are widely sold (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, several standards for such power transmission already exist and several alliances promote and develop them.

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

The most famous such standard is the Qi standard, developed by the Wireless Power Consortium, which includes such well-known companies 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 from various manufacturers and brands. In its work, the standard uses the principle of magnetic induction, when base station consists of an induction coil that creates an electromagnetic field when it enters AC from the network. The device being charged contains 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 operating principle on the consortium website http://www.wirelesspowerconsortium.com/what -we-do/how-it-works/). In addition, Qi supports a data transfer protocol between chargers and charging devices at a speed of 2 kbps, which is used to transmit data about the required charging amount and the required operation.

Today, many smartphones support wireless charging using the Qi standard, 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 far from being at the forefront in the world of information technology (especially the Starbucks coffee chain, which is in an alliance because it is going to introduce this technology), - they specialize specifically in energy issues. This alliance was formed not so long ago, in March 2012, as part of one of the IEEE (Institute of Electrical and Electronics Engineers) programs. The PMA standard they promote 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 when the current in one of the conductors changes or when the relative position of the conductors changes, the magnetic flux through the circuit of the second one changes. magnetic field generated by the current in the first conductor, which causes the occurrence electromotive force in the second conductor and (if the second conductor is closed) the induced current. Just as with Qi, this current is then converted to direct current and fed into the battery.

Well, don’t 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, among other things, is the development of charges that would work through non-metallic 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 location or 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. For now, the wireless charging power is sufficient mainly for smartphones, but 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 place 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 of action will expand (now it is necessary to use a special mat or stand on which the device rests, or it must be very close), and they will be universally installed in cars, trains and even, possibly, airplanes.

Well, one more conclusion - most likely, it will not be possible to avoid another format war between different standards and the alliances promoting them.

Will we get rid of wires?

Wireless charging devices are, of course, a good thing. But the powers that arise with it are sufficient only for the stated purposes. With the help of these technologies it is not yet possible to even illuminate a house, let alone operate large household appliances. Nevertheless, experiments on high-power wireless transmission of electricity are underway and they are based, among other things, on Tesla’s materials. The scientist himself proposed installing around the world (here, most likely, developed countries at that time were meant, of which there were much fewer than now) more than 30 receiving and transmitting stations that would combine energy transmission with radio broadcasting and directional wireless communications, which would allow get rid of numerous high-voltage power lines and facilitated the consolidation of electric generating units on a global scale.

Today there are several methods for solving the problem of wireless energy transfer, however, all of them so far allow achieving results that are insignificant in global terms; We're not even talking about kilometers. Methods such as ultrasonic, laser and electromagnetic transmission have significant limitations (short distances, the need for direct visibility of transmitting devices, 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 involve the use of a magnetic field, or more precisely, a resonant field. magnetic interaction. One of them is WiTricity, developed by the WiTricity corporation, founded by MIT professor Marin Soljacic and a number of his colleagues.

So, in 2007, they managed to transmit a current of 60 W over a distance of 2 m. It was enough to light a light bulb, and the efficiency was 40%. But the undeniable 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 imaging scanner) or with medical equipment ( pacemakers, etc.), nor with other radiation, which means it will not interfere, for example, with the operation of the same Wi-Fi.

What’s most interesting is that the efficiency of the WiTricity system is affected not only by the size, geometry and configuration 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 individually - this solves the problem of connecting many devices to one power source.

For many years, scientists have been struggling with the issue of minimizing electrical costs. Eat different ways and proposals, but still, the most famous theory is the wireless transmission of electricity. We propose to consider how it is carried out, who is its inventor and why it has not yet been implemented.

Theory

Wireless electricity is literally transmission electrical energy without wires. People often compare the wireless transmission of electrical energy with the transmission of information, such as radio, cell phones, or Wi-Fi access to the Internet. The main difference is that radio or microwave transmission is a technology aimed at restoring and transporting information, and not the energy that was originally expended on transmission.

Wireless electricity is a relatively new area of ​​technology, but one that is developing quite dynamically. Methods are now being developed to efficiently and safely transmit energy over a distance without interruption.

How does wireless electricity work?

The main work is based specifically on magnetism and electromagnetism, as is the case with radio broadcasting. Wireless charging, also known as inductive charging, is based on several simple principles work, in particular the technology requires two coils. A transmitter and receiver, which together generate an alternating magnetic field of non-direct current. In turn, this field causes a voltage in the receiver coil; this can be used to power a mobile device or charge a battery.

If you send electric current through a wire, a circular magnetic field is created around the cable. Despite the fact that the magnetic field affects both the loop and the coil, it is most pronounced on the cable. When we take a second coil of wire that is not receiving any electric current passing through it, and a place where we place a coil in the magnetic field of the first coil, the electric current from the first coil will be transmitted through the magnetic field and through the second coil, creating an inductive coupling.

Let's take an electric toothbrush as an example. In it, the charger is connected to an outlet, which sends an electric current to a twisted wire inside the charger, which creates a magnetic field. There is a second coil inside the toothbrush, when current begins to flow and, thanks to the formed MF, the brush begins to charge without being directly connected to a 220 V power supply.

Story

Wireless transmission energy as an alternative to the transmission and distribution of electrical lines was first proposed and demonstrated by Nikola Tesla. In 1899, Tesla presented the wireless transmission of power to a field of fluorescent lamps located twenty-five miles from the power source without the use of wires. But at the time, it was cheaper to wire 25 miles of copper wire rather than build the special power generators that Tesla's expertise required. He was never given a patent, and the invention remained in the recesses of science.

While Tesla was the first person to demonstrate practical possibilities wireless communications back in 1899, today there are very few devices on sale, these are wireless brushes, headphones, phone chargers, etc.

Wireless technology

Wireless energy transfer involves the transfer of electrical energy or power over a distance without wires. Thus, the core technology lies on the concepts of electricity, magnetism and electromagnetism.

Magnetism

It is a fundamental force of nature that causes certain types of material to attract or repel each other. The only permanent magnets are the Earth's poles. The flux current in the loop generates magnetic fields that differ from oscillating magnetic fields in the speed and time required to generate alternating current (AC). The forces that appear in this case are depicted in the diagram below.

Electromagnetism is the interdependence of alternating electric and magnetic fields.

Magnetic induction

If the conductive loop is connected to an AC power source, it will generate an oscillating magnetic field in and around the loop. If the second conductive circuit is close enough, it will capture part of this oscillating magnetic field, which in turn generates or induces an electric current in the second coil.

Video: how wireless transmission of electricity occurs

Thus, there is an electrical transfer of power from one cycle or coil to another, which is known as magnetic induction. Examples of this phenomenon are used in electrical transformers and a generator. This concept is based on Faraday's laws of electromagnetic induction. There, he states that when there is a change in the magnetic flux connecting to a coil, the emf induced in the coil, then the magnitude is equal to the product of the number of turns of the coil and the rate of change of flux.

Power coupling

This part is necessary when one device cannot transmit energy to another device.

Magnetic coupling is generated when an object's magnetic field is capable of inducing an electric current to other devices within its range.

Two devices are said to be mutually inductively coupled or magnetically coupled when they are arranged so that a change in current as one wire induces a voltage at the ends of the other wire by means of electromagnetic induction. This is due to mutual inductance

Technology

Two devices mutually inductively coupled or magnetically coupled are designed so that the change in current when one wire induces a voltage at the ends of the other wire is produced by electromagnetic induction. This is due to mutual inductance.
Inductive coupling is preferred due to its ability to operate wirelessly as well as its resistance to shock.

Resonant inductive coupling is a combination of inductive coupling and resonance. Using the concept of resonance, you can make two objects work depending on each other's signals.

As can be seen from the diagram above, resonance is provided by the inductance of the coil. The capacitor is connected in parallel to the winding. Energy will move back and forth between the magnetic field surrounding the coil and electric field around the capacitor. Here, radiation losses will be minimal.

There is also the concept of wireless ionized communication.

It can also be implemented, but it requires a little more effort. This technique already exists in nature, but it is hardly feasible to implement it, since it requires a high magnetic field, from 2.11 M/m. It was developed by the brilliant scientist Richard Walras, the developer of a vortex generator that sends and transmits heat energy over vast distances, in particular with the help of special collectors. The simplest example of such a connection is lightning.

Pros and cons

Of course, this invention has its advantages and disadvantages over wired methods. We invite you to consider them.

The advantages include:

1. Complete absence of wires;
2. No power supplies needed;
3. The need for a battery is eliminated;
4. Energy is transferred more efficiently;
5. Significantly less maintenance required.

The disadvantages include the following:

• Distance is limited;
• magnetic fields are not so safe for humans;
• wireless transmission of electricity using microwaves or other theories is practically impossible at home and with your own hands;
• high installation cost.

When Apple company introduced its first wireless charger for cell phones and gadgets, many considered it a revolution and a huge leap forward in wireless energy transfer methods.

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

So back in 1893, the famous Nikola Tesla demonstrated the glow of fluorescent lamps to the amazed public. Despite the fact that they were all wireless.

Now this trick can be repeated by any schoolchild 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 managed to light a phosphorus incandescent light 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 transfer of energy.

Most main question and at the same time, the problem with the entire technology of wireless charging and similar methods lies in two points:

• how far can electricity be transmitted this way?

• and what quantity

First, let's figure out what power the devices have and household appliances those around us. For example, a phone, smartwatch or tablet requires a maximum of 10-12W.

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

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

So what methods and methods for transmitting electrical energy without the use of cables or any other conductors has mankind come up with over all these years? And most importantly, why are they still not implemented as actively into our lives as we would like?

Take the same kitchen appliances. Let's take a closer look.

Transferring energy through coils

The most easily implemented method is to use inductors.

The principle here is very simple. Take 2 coils and place them close to each other. One of them is supplied with power. The other plays the role of receiver.

When the current in the power source is adjusted or changed, the magnetic flux in the second coil automatically changes as well. 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 flow.

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

• low power

Using this method, you will not transfer large volumes and will not be able to connect powerful devices. If you try to do this, you will simply melt all the windings.

• short distance

Don't even think about transmitting electricity over 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 apart they need to be before they stop attracting or repelling each other. The efficiency of coils is approximately the same.

You can, of course, get creative and ensure that these two elements are always close to each other. For example, an electric car and a special charging 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 electrical energy 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 solution to the problem in it.

However, no matter how useless all these things may seem, with their help you can still organize beautiful light and music performances.

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

Laser energy transfer

But how can more energy be transmitted over a greater distance? Think about which films we see this kind of technology very often.

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

Of course, with their help you can convey large number electricity over very long distances. But again everything is spoiled by a small problem.

Fortunately for us, but unfortunately for the laser, the Earth has an atmosphere. And it just does a good job of jamming and eating up most of the total energy of laser radiation. Therefore, with this technology we need to go into space.

There have also been attempts and experiments on Earth to test the effectiveness of the method. Nasa even held a competition on laser wireless energy transfer with a prize fund of just under $1 million.

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

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

Let us remember that a simple light bulb has even less useful energy that goes directly into the light. Therefore, it is profitable 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 even 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 transparent to the atmosphere and it does not interfere with their propagation.

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

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

Moreover, this 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.

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

But how to do the reverse transformation? And here two approaches were developed:

• American

• Soviet

In the USA, back in the sixties, scientist W. Brown came up with an antenna that performed the required task. That is, it converted the radiation incident on it back into electric current.

He even gave it his own name - rectenna.

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

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

And here again the shortcomings emerge. Rectennas were assembled using miniature semiconductors. Normal operation for them is the transmission of only a few watts of power.

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

And this is where unsolvable difficulties arise. Firstly, this is re-emission.

Not only will you lose some energy because of it, but you will also not be able to get closer to the panels without losing your health.

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

In the USSR everything was somewhat different. It was not for nothing that our military was confident that even in the event of a nuclear explosion, all foreign equipment would immediately fail, but Soviet equipment 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 decent dimensions, as it is assembled based on lamp technology.

Externally, it 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, a cyclotron energy converter has a number of significant advantages:

• reliability

• high power

• overload resistance

• no re-emission

• low production cost

However, despite all of the above, semiconductor methods of project implementation are considered advanced all over the world. There is also an element of fashion here.

After the first appearance of semiconductors, everyone abruptly began to abandon tube technologies. But practical tests suggest that this is often the wrong approach.

Of course, no one is interested in 20kg tube cell phones or computers that take up entire rooms.

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

As a result, today we have three opportunities to transmit energy wirelessly. The very first one discussed is limited by both distance and power.

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

The first of them started out very encouragingly. In the 2000s, on Reunion Island, a need arose for the constant transmission of 10 kW of power over a distance of 1 km.

The mountainous terrain and local vegetation did not allow laying any air lines power transmission or cable.

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

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

However, at the moment when the practical implementation and construction of energy transmitters and receivers should have begun, 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 back in 1968 by US physicist P. Glaser.

He proposed a not entirely normal idea at that time - to bring to geostationary orbit a huge satellite 36,000 km above the earth. Place solar panels on it 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 the receiver on the ground 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. When reaching the ground there would be only 2GW left. For example, the Krasnoyarsk hydroelectric power station produces 6 GW.

Therefore, his idea was considered, calculated and put aside, since everything initially came down to price. The cost of the space project in those days reached $1 trillion.

But science, fortunately, does not stand still. Technologies are improving and becoming 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 wireless transmission of electricity.

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

Unfortunately, no one will give you a clear answer. Bets are placed 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, a second Nikola Tesla will be born on Earth.

Discovered a law (later named Ampere's law after its discoverer), showing that electric current produces a magnetic field.

• IN 2007 In 2009, a research team led by Professor Marin Soljačić wirelessly transmitted over a distance of 2 m energy sufficient to light a 60-watt light bulb with an efficiency of 40% using two coils with a diameter of 60 cm.
• IN 2008 In 2010, Bombardier proposed a system for wireless power transmission, called "primove" and intended for use in trams and light-duty engines. railway.
• IN 2008 In 2009, Intel employees reproduced the experiments of Nikola Tesla in 1894 and the experiments of John Brown's group in 1988 on wireless energy transfer to light incandescent lamps with an efficiency of 75%.
• IN 2009 In 2009, a consortium of interested companies called the Wireless Power Consortium developed a low-current wireless power standard called "". Qi has begun to be used in portable technology.
• IN 2009 year, the Norwegian company Wireless Power & Communication presented an industrial flashlight it developed that can operate safely and be recharged in a contactless way in an atmosphere saturated with flammable gas.
• IN 2009 In 2018, Haier Group introduced the world's first fully wireless LCD TV, based on Professor Marin Soljačić's research on wireless power transmission and Wireless Home Digital Interface (WHDI).
• IN 2011 This year, the Wireless Power Consortium began expanding the specifications of the Qi standard for medium currents.
• IN 2012 In 2009, the private St. Petersburg museum “Grand Model Russia” began operating, in which miniature car models received wireless power supply through a model of the roadway.
• IN 2015 This year, scientists from the University of Washington discovered that electricity can be transmitted via Wi-Fi technology.

Technologies

Ultrasonic method

An ultrasonic method of energy transfer was invented by students at the University of Pennsylvania and first presented to the general public at the exhibition “The All Things Digital” (D9) in 2011. As with other methods of transmitting something wirelessly, a receiver and a transmitter were used. The transmitter emitted ultrasound; the receiver, in turn, converted what was heard into electricity. At the time of presentation, the transmission distance reached 7-10 meters, and direct visibility of the receiver and transmitter was necessary. The transmitted voltage reached 8 volts; the resulting current is not reported. The ultrasonic frequencies used have no effect on humans. There is also no information about the negative effects of ultrasonic frequencies on animals.

Electromagnetic induction method

Wireless energy transfer by electromagnetic induction uses a near-field electromagnetic field at distances of about one-sixth of a wavelength. Near-field energy itself is not radiative, but some radiative losses do occur. In addition, as a rule, resistive losses also occur. Thanks to electrodynamic induction, an alternating electric current flowing through the primary winding creates an alternating magnetic field, which acts on the secondary winding, inducing an electric current in it. To achieve high efficiency, the interaction must be quite 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 most of the transmitted energy.

An electrical transformer is the simplest device for wireless energy transfer. The primary and secondary windings of the transformer are not directly connected. Energy transfer occurs 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 the use of 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 with it effectively.

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 improved further by changing the control current waveform from sinusoidal to non-sinusoidal transient waveforms. Pulsed energy transfer occurs over several cycles. In this way, significant power can be transferred between two mutually tuned LC circuits with a relatively low coupling coefficient. The transmitting and receiving coils, as a rule, are single-layer solenoids or a flat spiral with a set of capacitors that allow the receiving element to be tuned to the frequency of the transmitter.

A common application of resonant electrodynamic induction is charging batteries portable devices such as laptop computers and cell phones, medical implants and electric vehicles. The localized charging technique uses the selection of an appropriate transfer coil in a multilayer winding array structure. Resonance is used in both the wireless charging panel (transmitting circuit) 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 recharging 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 devices that do not have batteries, such as RFID tags and contactless smart cards, as well as to transfer electrical energy from the primary inductor to the helical resonator of the Tesla transformer, which is also a wireless transmitter of electrical energy.

Electrostatic induction

Laser method

If the wavelength electromagnetic radiation approaches the visible region of the spectrum (from 10 µm to 10 nm), energy can be transferred by converting it into a laser beam, which can then be directed to a photocell of the receiver.

Laser energy transmission has a number of advantages compared to other wireless transmission methods:

• energy transfer over long distances (due to the small divergence angle between narrow beams of a monochromatic light wave);
• ease of use for small products (due to the small size of the solid-state laser - photoelectric semiconductor diode);
• absence of radio frequency interference for existing communications devices, such as Wi-Fi and cell phones (laser does not create such interference);
• possibility of access control (only receivers illuminated by a laser beam can receive electricity).

U this method There are also a number of disadvantages:

• Converting low-frequency electromagnetic radiation into high-frequency radiation, which is light, is ineffective. Converting light back into electricity is also inefficient, since the efficiency of solar cells reaches 40-50%, although the efficiency of converting monochromatic light is much higher than the efficiency of solar panels;
• losses in the atmosphere;
• the need for line of sight between the transmitter and receiver (as with microwave transmission).

Laser power transfer technology has previously been primarily explored in the development of new weapons systems and the aerospace industry, and is currently being developed for commercial and consumer electronics applications in low power applications. Wireless power transmission systems for consumer applications must meet the laser safety requirements of IEC 60825. To better understand laser systems, it should be taken into account that laser beam propagation is much less dependent on diffraction limitations, as spatial and spectral matching of laser characteristics allows increase operating power and distance as wavelength affects focusing.

NASA's Dryden Flight Research Center demonstrated the flight of a light unmanned model aircraft powered by a laser beam. This proved the possibility of periodic recharging through laser system without the need to land the aircraft.

Alternating current can be transmitted through layers of the atmosphere having an atmospheric pressure of less than 135 mmHg. Art. Current flows by electrostatic induction through the lower atmosphere approximately 2-3 miles (3.2-4.8 kilometers) above sea level and by ion flux, that is, electrical conduction, through the ionized region located 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 plasma high-voltage power lines leading directly to the conductive layers of the atmosphere. As a result, a flow of electric current 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 is made possible by a 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 power transmission on a global scale. The installation was not completed due to insufficient funding.

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

Global system transmission of electricity without wires, the so-called “Worldwide 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 been the cause of the Tunguska meteorite that arose as a result of “ short circuit“between the charged atmosphere and the ground.

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 in space.

In 1919, Nikola Tesla wrote: “It is believed that I began work on wireless transmission in 1893, but in fact I had been conducting research and constructing equipment for the previous two years. It was clear to me from the very beginning that success could be achieved through a series of radical decisions. High frequency oscillators and electrical oscillators had to be created first. Their energy had to be converted into efficient transmitters and received at a distance by suitable receivers. Such a system would be effective if it excluded any outside interference and ensured its complete exclusivity. Over time, however, I realized that for efficient work Devices of this kind must be developed 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 Tesla coil's grounded helical resonator and 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. 1119732, January 18, 1902, "Apparatus for Transmitting Electrical Power"). Tesla proposed installing more than thirty transceiver stations around the world. In this system, the take-up coil acts as a step-down transformer with a high current output. 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 radio broadcasting and directional wireless communications, which would eliminate the need for numerous high-voltage power lines and promote unification. electric generators on a global scale.

See also

• WiTricity

Notes

1. "Electricity at the Columbian Exposition", by John Patrick Barrett. 1894, pp. 168-169 (English)
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 (English)
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 (English)
6. Jagadish Chandra Bose (English)
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. Tetelbaum S.I. On wireless transmission of electricity over long distances using radio waves // Electricity. - 1945. - No. 5. - pp. 43-46.
13. Kostenko A. A. Quasi-optics: historical background and modern development trends // Radiophysics and radio astronomy. - 2000. - T. 5, No. 3. - P. 231.
14. A survey of the elements of power Transmission by microwave beam, in 1961 IRE Int.  Conf.  Rec., vol.9, part 3, pp.93-105 (English)
15. IEEE Microwave Theory and Techniques, Bill Brown's Distinguished Career (English)
16. Power from the Sun: Its Future, Science Vol. 162, pp. 957-961 (1968)
17. Solar Power Satellite patent (English)
18. History of RFID
19. Space Solar Energy Initiative
20. Wireless Power Transmission for Solar Power Satellite (SPS) (Second Draft by N. Shinohara), Space Solar Power Workshop, Georgia Institute of Technology
21. 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)
22. Wireless Power Transfer via Strongly Coupled Magnetic Resonances(English) . Science (7 June 2007). Retrieved September 6, 2010. Archived February 29, 2012.,
    A new way of wirelessly transmitting electricity has launched (Russian). MEMBRANA.RU (June 8, 2007). Retrieved September 6, 2010. Archived February 29, 2012.
23. Bombardier PRIMOVE Technology
24. Intel imagines wireless power for your laptop (English)
25. wireless electricity specification nearing completion
26. Global Qi Standard Powers Up Wireless Charging - HONG KONG, Sept.  2 /PRNewswire/
27. TX40 and CX40, Ex approved Torch and Charger
28. Haier's wireless HDTV lacks wires, svelte profile (video) (English) ,
    Wireless electricity amazed its creators (Russian). MEMBRANA.RU (February 16, 2010). Retrieved September 6, 2010.

For many years, scientists have been struggling with the issue of minimizing electrical costs. There are different methods and proposals, but the most famous theory is the wireless transmission of electricity. We propose to consider how it is carried out, who is its inventor and why it has not yet been implemented.

Theory

Wireless electricity is literally the transfer of electrical energy without wires. People often compare the wireless transmission of electrical energy with the transmission of information, such as radios, cell phones, or Wi-Fi Internet access. The main difference is that radio or microwave transmission is a technology aimed at restoring and transporting information, and not the energy that was originally expended on transmission.

Wireless electricity is a relatively new area of ​​technology, but one that is developing quite dynamically. Methods are now being developed to efficiently and safely transmit energy over a distance without interruption.

How does wireless electricity work?

The main work is based specifically on magnetism and electromagnetism, as is the case with radio broadcasting. Wireless charging, also known as inductive charging, is based on a few simple operating principles, in particular the technology requires two coils. A transmitter and receiver, which together generate an alternating magnetic field of non-direct current. In turn, this field causes a voltage in the receiver coil; this can be used to power a mobile device or charge a battery.

If you send electric current through a wire, a circular magnetic field is created around the cable. Despite the fact that the magnetic field affects both the loop and the coil, it is most pronounced on the cable. When we take a second coil of wire that is not receiving any electric current passing through it, and a place where we place a coil in the magnetic field of the first coil, the electric current from the first coil will be transmitted through the magnetic field and through the second coil, creating an inductive coupling.

Let's take an electric toothbrush as an example. In it, the charger is connected to an outlet, which sends an electric current to a twisted wire inside the charger, which creates a magnetic field. There is a second coil inside the toothbrush, when current begins to flow and, thanks to the formed MF, the brush begins to charge without being directly connected to a 220 V power supply.

Story

Wireless power transmission, as an alternative to the transmission and distribution of electrical lines, was first proposed and demonstrated by Nikola Tesla. In 1899, Tesla presented the wireless transmission of power to a field of fluorescent lamps located twenty-five miles from the power source without the use of wires. But at the time, it was cheaper to wire 25 miles of copper wire rather than build the special power generators that Tesla's expertise required. He was never given a patent, and the invention remained in the recesses of science.

While Tesla was the first person to demonstrate the practical capabilities of wireless communication back in 1899, today there are very few devices on sale, such as wireless brushes, headphones, phone chargers and the like.

Wireless technology

Wireless energy transfer involves the transfer of electrical energy or power over a distance without wires. Thus, the core technology lies on the concepts of electricity, magnetism and electromagnetism.

Magnetism

It is a fundamental force of nature that causes certain types of material to attract or repel each other. The only permanent magnets are the Earth's poles. The flux current in the loop generates magnetic fields that differ from oscillating magnetic fields in the speed and time required to generate alternating current (AC). The forces that appear in this case are depicted in the diagram below.

Electromagnetism is the interdependence of alternating electric and magnetic fields.

Magnetic induction

If the conductive loop is connected to an AC power source, it will generate an oscillating magnetic field in and around the loop. If the second conductive circuit is close enough, it will capture part of this oscillating magnetic field, which in turn generates or induces an electric current in the second coil.

Video: how wireless transmission of electricity occurs

Thus, there is an electrical transfer of power from one cycle or coil to another, which is known as magnetic induction. Examples of this phenomenon are used in electrical transformers and generators. This concept is based on Faraday's laws of electromagnetic induction. There, he states that when there is a change in the magnetic flux connecting to a coil, the emf induced in the coil, then the magnitude is equal to the product of the number of turns of the coil and the rate of change of flux.

Power coupling

This part is necessary when one device cannot transmit energy to another device.

Magnetic coupling is generated when an object's magnetic field is capable of inducing an electric current to other devices within its range.

Two devices are said to be mutually inductively coupled or magnetically coupled when they are arranged so that a change in current as one wire induces a voltage at the ends of the other wire by means of electromagnetic induction. This is due to mutual inductance

Technology

Two devices mutually inductively coupled or magnetically coupled are designed so that the change in current when one wire induces a voltage at the ends of the other wire is produced by electromagnetic induction. This is due to mutual inductance.
Inductive coupling is preferred due to its ability to operate wirelessly as well as its resistance to shock.

Resonant inductive coupling is a combination of inductive coupling and resonance. Using the concept of resonance, you can make two objects work depending on each other's signals.

As can be seen from the diagram above, resonance is provided by the inductance of the coil. The capacitor is connected in parallel to the winding. Energy will move back and forth between the magnetic field surrounding the coil and the electric field around the capacitor. Here, radiation losses will be minimal.

There is also the concept of wireless ionized communication.

It can also be implemented, but it requires a little more effort. This technique already exists in nature, but it is hardly feasible to implement it, since it requires a high magnetic field, from 2.11 M/m. It was developed by the brilliant scientist Richard Walras, the developer of a vortex generator that sends and transmits heat energy over vast distances, in particular with the help of special collectors. The simplest example of such a connection is lightning.

Pros and cons

Of course, this invention has its advantages and disadvantages over wired methods. We invite you to consider them.

The advantages include:

1. Complete absence of wires;
2. No power supplies needed;
3. The need for a battery is eliminated;
4. Energy is transferred more efficiently;
5. Significantly less maintenance required.

The disadvantages include the following:

• Distance is limited;
• magnetic fields are not so safe for humans;
• wireless transmission of electricity using microwaves or other theories is practically impossible at home and with your own hands;
• high installation cost.