Transmission of electricity wirelessly over long distances. Wireless power transmission: history, technology, equipment

Scientists have been studying the issue of transmitting electricity without wires for the third century. IN lately It’s not that the question has not lost its relevance, but rather has taken a step forward, which is only pleasing. We decided to tell readers of the site in detail how wireless transmission of electricity over distances has developed from the beginning to the present day, as well as what technologies are already in practice.

History of development

The transmission of electricity over a distance without wires develops hand in hand with progress in the field of radio transmission, because the principle of operation in these phenomena is in many ways similar, if not the same. Most inventions are based on the method of electromagnetic induction, as well as electrostatic fields.

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

M. Faraday in 1831 established in the process of conducting experiments that an alternating (changing in magnitude and direction over time) magnetic field generated by the flow of electric current induces currents in nearby conductors. Those. Electricity is transmitted wirelessly. We discussed this in detail in the article earlier.

Well, J.C. Maxwell, 33 years later, in 1864, translated Faraday’s experimental data into mathematical form; Maxwell’s equations themselves are fundamental in electrodynamics. They describe how they are connected electric current and electromagnetic field.

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

In-depth research was carried out by the famous scientist Nikola Tesla. He studied alternating current in 1891 high voltage and frequencies. As a result, the following conclusions were drawn:

For each specific purpose, you need to configure the installation to the appropriate frequency and voltage. However, high frequency is not prerequisite. Best results was achieved at a frequency of 15-20 kHz and a transmitter voltage of 20 kV. To get current high frequency and voltage, an oscillatory discharge of a capacitor was used. In this way, it is possible to transmit both electricity and produce light.

At his speeches and lectures, the scientist demonstrated the glow of lamps (vacuum tubes) under the influence of a high-frequency electrostatic field. Actually, Tesla’s main conclusions were that even if resonant systems are used, it will not be possible to transfer a lot of energy using an electromagnetic wave.

In parallel, a number of scientists were engaged in similar research 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. Boche in 1894, ignited gunpowder, transmitting electricity over a distance without wires. He did this at a demonstration in Calcutta.
2. A. Popov transmitted the first message using Morse code on April 25 (May 7), 1895. In Russia, this day, May 7, is still Radio Day.
3. In 1896, G. Marconi in Great Britain 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 work, underestimated in its time and lost for centuries, was superior in parameters and capabilities to the work of his contemporaries. At the same time, namely in 1896, his devices transmitted signals over long distances (48 km), unfortunately this was a small amount of electricity.

And by 1899 Tesla came to the conclusion:

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

These findings would lead to other research; in 1900, he managed to power a lamp from a coil placed in a field, and in 1903, the Wondercliffe Tower on Long Island was launched. It consisted of a transformer with a grounded secondary winding, and on top of it stood a copper spherical dome. With its help, it was possible 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 stopped, and free transmission of electricity without wires was not economically profitable for businessmen. The tower was destroyed in 1917.

These days

Wireless power transmission technologies have made great strides, mainly in the field of data transmission. Thus, radio communications have achieved significant success, wireless technologies such as Bluetooth and Wi-fi. There were no special innovations, mainly the frequencies and signal encryption methods changed, the signal presentation moved from analog to digital form.

If we are talking about transmitting electricity without wires to power electrical equipment, it is worth mentioning that in 2007, researchers from the Massachusetts Institute transmitted energy 2 meters and lit a 60-watt light bulb in this way. This technology is called WiTricity, it is based on electromagnetic resonance of the receiver and transmitter. It is worth noting that the receiver receives about 40-45% of the electricity. A general 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 vehicle. The idea is that a receiver is attached to the bottom of the electric vehicle, and a transmitter is installed on the floor in a garage or other place.

You must position the car so that the receiver is positioned above the transmitter. The device transmits quite a lot of electricity wirelessly - 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 wireless tv, which receives power using similar technology as well as video signals wirelessly. Similar developments are being carried out by other leading companies such as Intel and Sony.

Wireless power transmission technologies are widespread in everyday life, 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 in such kits is usually called the base, 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 couple of meters provided by magnetic induction. In the microwave method, a rectenna (a nonlinear 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 wireless transmission of electricity, there is no need for direct visibility of objects. The downside is that microwave radiation is not safe 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, the advantage is that you do not have to constantly insert and remove the plug from the connector of your smartphone, and therefore the connector will not fail. The downside is the low efficiency; if for a smartphone the energy loss is not significant (several watts), then for wireless charging of an electric car this is quite 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.

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We are presenting a device for transmitting electricity without wires with an efficiency factor of about 100%. In the future, the efficiency value of ≈ 100% will be justified and, of course, we demonstrate this value with our experimental device.

The importance of the problem of wireless transmission of electricity is beyond doubt - overcoming natural barriers (rivers, mountains and valleys); backup power supply, electric transport, solving a number of problems of wireless power supply for household and industrial devices etc. - all these are elements of the named problem.

A little history

The problem of wireless power transmission was first identified at the dawn of the last century by N. Tesla. His demonstration device was based on the method of emitting and receiving electromagnetic waves by an open resonant circuit, which contains an antenna - capacitance and a coil of wire - inductance. The characteristic indicators of Tesla's device are as follows: efficiency = 4%, transmission range - 42 km, maximum dimensions of the antenna tower - 60 m, wavelength - 2000 m. It is significant that in Tesla's device the planet Earth is considered as one of the wires in the transmission of electricity , since the emission and reception of such long waves without grounding is not effective.

After Tesla's experiments, throughout the last twentieth century, all attempts to carry out wireless transmission of electricity with acceptable efficiency were unsuccessful.

In the current decade, work at the Massachusetts Institute of Technology under the direction of M. Soljacic is reported directly or indirectly. Their work is based on the well-known induction, using a magnetic field, method of transmitting electricity, which is implemented by resonant flat inductors. This method ideally provides efficiency = 50%, with a transmission range commensurate with the dimensions of the antenna coils. The characteristic indicators of their demonstration device are as follows: efficiency ≈ 40%, transmission range – 2 m, dimensions of the antenna coils – 0.6 m, wavelength – 30 m.

Energetically closed system

In our device, as in Tesla’s device, the energy carrier is electromagnetic waves, i.e. the well-known Poynting vector operates.

The following has been theoretically substantiated and experimentally confirmed: the transmitting and receiving antennas of the wireless power transmission device form an energetically closed system, partially including the energy of the Earth’s electromagnetic field; through excitation (activation) of the Earth's electromagnetic field in this system, electricity is transferred from the transmitting antenna to the receiving antenna with an efficiency of ≈ 100% (Fig. 1).

Fig. 1

Fig. 2

Using this antenna, it is easy to formulate a problem, the solution of which will ensure the transmission of electricity without wires:

1. The transmitting and receiving antennas must excite (activate) the electromagnetic field of the Earth in a local (limited) region of space;

2. The excited electromagnetic field of the Earth must also be local in space and not consume energy (must be a standing electromagnetic wave between the transmitting and receiving antennas).

The solution to this problem is unrealistic with antennas created on the basis of spatial representations of Euclid's geometry with its famous 5th postulate - the postulate of parallel lines. This postulate in school textbooks reads: Through a point not lying on a given line, only one line parallel to the given one can be drawn.

fig. 3

The celebrity of this postulate lies in the fact that, starting from the 1st Art. BC, for 2000 years the best minds in the world tried unsuccessfully to prove it as a theorem. And so in 1826, the Russian Lobachevsky outlined the foundations of his geometry, in which the 5th postulate of Euclid’s geometry was formulated, in essence, by its negation: Through a point not lying on a given line, it is possible to draw at least two lines parallel to the given one.

fig. 4

And although this postulate is not very consistent with our spatial concepts, Lobachevsky’s geometry is consistent and has been serving physicists well in recent years. For example, Lobachevsky's geometry is involved in the description of a huge range of phenomena from vibrations in mechanical transmission lines to the interaction of elementary particles and processes in the membrane of a living cell.

Pseudo-sphere

True, until 1863, for almost 40 years, Lobachevsky’s geometry was perceived as something unrelated to reality. But, in 1863, the Italian mathematician Beltrami established that all the properties of the Lobachevsky geometry plane are realized on the surface of a pseudosphere - a geometric body whose properties coincide or are opposite to the properties of the sphere. In fig. 5 shows a pseudosphere, and FIG. 6 its generator is a tractrix with asymptote X’X. If the radii of the great circles (parallels) of the pseudosphere and the sphere are equal, one can quantitatively compare their volumes and surface areas.

fig. 5

fig. 6

It is in the form of semi-pseudospherics that the antennas of our device are made; We are demonstrating a device with the following characteristics: efficiency = 100%, transmission range – 1.8 m, maximum size of antenna coils – 0.2 m, wavelength – 500 m, grounding is not necessary.

It should be noted here that the totality of the named characteristics of the demonstration device contradicts the foundations of classical electrodynamics - radio engineering.

What properties of semi-pseudospheric antennas provide such characteristics of our device?

Among more than a dozen extraordinary properties of the pseudosphere, the following deserves attention:

The body of the pseudosphere, infinitely extended in space, has a finite volume and finite surface area.

It is this property of the pseudosphere that makes it possible, with the help of half-pseudosphere antennas, to create a finite, spatially limited, energetically closed system, which is a necessary condition for energy transfer from efficiency = 100%.

The second fundamental problem that is solved in our device concerns the medium filling the mentioned energetically closed system. The point is that only in quantum electrodynamics, the fruit of which are lasers and masers, is the medium considered active. On the contrary, in classical electrodynamics the medium refers to passive objects; it is associated with attenuation, the loss of electromagnetic energy during propagation.

Incredibly, but true, our device activates the Earth’s electric and magnetic fields. These fields are objects of the environment in our device, since they fill the mentioned energetically closed system. The activation of this environment is also a consequence of the properties of the pseudosphere.

The point is that all points on the surface of the pseudosphere are, according to mathematicians, hyperbolic, discontinuous in space. In relation to the semi-pseudospheric antennas of our device, this is equivalent to discontinuities and quantization of the electric and magnetic fields at each point of the wire winding the coils of the semi-pseudospheric antennas. This leads to electromagnetic disturbances - waves, the length of which is commensurate with the diameter of the wire winding the coils of semi-pseudospheric antennas, i.e. In practice, the length of such waves is of the order of 1 mm or less. Such electromagnetic waves, as evidenced by theory and practice, are capable, through the polarization of air molecules or directly, of activating the electromagnetic field of the Earth and thereby compensating for the loss of electromagnetic energy along the path of its transmission in our device. This is also necessary to explain efficiency = 100%.

Not only that, we have announced a generator of excess electromagnetic energy, the energy conversion coefficient (ECE) of which is more than 400%; those. comparable to the KPIs of known heat pumps.

And about the last, third problem that is solved in our device.

It is well known that energy is transferred in space only by a traveling electromagnetic wave, a wave in which the electric and magnetic fields are in phase. This condition cannot be realized at a distance of 1.8 m at a wavelength of 500 m. But it is also well known that the speed of movement of a traveling electromagnetic wave along a straight or curved conductor slows down and decreases in comparison with the speed in free space; The wavelength also decreases. This effect is widely used in electrical and radio engineering in so-called slow-down systems. The reduction in wavelength in these systems ranges from tenths of a unit with straight wires to 30 units with curved (spiral) ones.

It is the effect of slowing down, reducing the wavelength that allows the formation of a traveling wave at short distances in our device.

Indeed, the wavelength of our demo device is reduced to the length mentioned above , which forms a traveling, energy-transferring electromagnetic wave in our device. The wave reduction coefficient in this case is equal to units. This enormous reduction in wavelength also explains the experimental fact that our device operates effectively without grounding the transmitter and receiver of electricity.

Our device uses another amazing property of the pseudosphere:

the volume of the pseudosphere is half the volume of the sphere, while the areas of their surfaces are equal.

From this property it follows that the volume of a sphere, limited by its own surface area, contains two volumes of a pseudosphere, limited by two combined proper surface areas and the third area of ​​the mentioned sphere. This allows us to imagine the volume of a sphere around the Earth, filled with the electric and magnetic fields of the Earth, two volumes of the pseudosphere and, each of which is limited by area and contains half of the electric and magnetic fields of the Earth (Fig. 7). Considering this fact and the fact that our device is inevitably located on only one side of the earth, it is argued that the antennas of our device interact only with half the electric and magnetic fields of the Earth. At the same time, one should not assume that the second halves of these fields are inactive. The following convinces us of this.

fig. 7

Let us remember that most of the laws of physics are formulated for inertial frames of reference, in which time is non-relative (absolute), space is isotropic, the speed of rectilinear motion of electromagnetic waves (light) is absolute, etc. Within the framework of inertial reference systems, it is well known that in free space, when a traveling electromagnetic wave is reflected, a standing wave is formed, in which a separately standing electric wave and a separately standing magnetic wave are distinguished. With a traveling wave length equal to , the lengths of standing electric and magnetic waves are equal to half the traveling wave length, i.e. . It is also important that the period of these standing waves is equal to the period of the traveling wave, i.e. , since the period of a standing wave consists of the sum of two half-periods of the direct and reflected half-waves.

The fact of calculation, and not experimental determination, of a value with an accuracy depending on the accuracy of determining the length of a day on Earth allows us to take a completely new look at a number of problems in physics.

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 relatively new area technology, but quite dynamically developing. 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. The transmitter and receiver, which together generate an alternating magnetic field, do not DC. In turn, this field causes a voltage in the receiver coil; it can be used for nutrition mobile device or charging the 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 electric current to the twisted wire inside charger, creating 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 communication back in 1899, today there are very few devices on sale, these are wireless brushes, headphones, phone chargers, and so on.

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 flow current in the circuit generates magnetic fields that differ from oscillating magnetic fields in the speed and time required to generate AC(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 it happens electric transmission 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 electrical current with 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 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 required;
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.

Regularly looking through foreign achievements in the field of radio engineering, I came across a good device for wireless power transmission, made not on some scarce microcircuits, but quite affordable for self-assembly. Full documentation in English can be downloaded from the link, and here I will give a brief summary in Russian, including some circuit solutions.

Current transceiver coils

Signal oscillogram

The work presents several similar circuit diagrams, differing only in voltage and power. They serve as an energy “antenna” small reels made of thick wire, the transistors are ordinary powerful field-effect ones, so you can assemble all this yourself.

Let us warn you right away - here we are not talking about transmitting energy over many meters, similar devices They are more suitable for other similar devices, where the distance is several centimeters. But the power that “flies” through the air reaches up to 100 watts!

Operating principle

A resonant converter usually operates at a constant operating frequency, which is determined by the resonant frequency of the LC circuit. Once DC voltage is applied to the circuit, it starts generating with the help of transistors. A kind of multivibrator, with a phase shift of 180°. Transistors alternately connect the ends of a parallel resonant circuit to the mass, which allows this circuit to periodically recharge with energy and then radiate it into space.

Practical schemes

Basic scheme

Photo of the finished energy transmitter-receiver

To summarize, we note that wireless power transmission is increasingly being implemented in the field of consumer electronics, industrial, military and medical equipment. Like wireless local network and Bluetooth, both wireless power becomes a relevant option. This allows you to get rid of unreliable buttons, cables, and power connectors. Another area of ​​application relates to transformers, which must meet special requirements such as reinforced or double insulation. And most importantly: electrical safety! Many low-power network household appliances can be powered not through 220 V cords, plugs and sockets, but contactless method- simply moving them to the desired surface.