Wireless transmission of electricity. Wireless electricity

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.

This is how magnetism appears

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 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

Inductive coupling principle

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:

Complete absence of wires;
No power supplies needed;
The need for a battery is eliminated;
Energy is transferred more efficiently;
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.

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 is known to be 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 stopped financing the project. Be that as it may, they started talking seriously about wireless power transmission only 90 years later, in 2007. And while it's still a long way off before power lines completely disappear from the cityscape, nice little things like wireless charging for your mobile device are 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 for basic principles and general schemes ). Today, wireless charging is no longer something super-original or conceptual. Such devices are being sold with all their might (for example, LG demonstrated its chargers at MWC 2013), are being tested for electric vehicles (Qualcomm is doing this) and are 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 goal of creating a universal charger for devices from various manufacturers and brands. In its work, the standard uses the principle of magnetic induction, when the base station consists of an induction coil that creates an electromagnetic field when alternating current is supplied 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 at the forefront in the world of information technology (especially the Starbucks coffee chain, which is in an alliance because it plans to introduce this technology everywhere in its establishments) - they specialize specifically in energy issues. This alliance was formed not so long ago, in March 2012, 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 appearance of an electromotive force in the second conductor and (if the second conductor is closed) an induction 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 , including 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 of devices is, 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 electrical generation 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, resonant 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.

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 accessible 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 use small coils of thick wire as an energy “antenna”; 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; such devices 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 begins to generate using 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 LAN and Bluetooth, wireless power is becoming a popular 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 using a non-contact method - simply by moving them to the desired surface.

Ecology of consumption. Technologies: Scientists at the American Disney Research Laboratory have developed a wireless charging method that makes wires and chargers unnecessary.

Today's smartphones, tablets, laptops and other portable devices have enormous power and performance. But, in addition to all the advantages of mobile electronics, it also has a downside - the constant need to recharge via wires. Despite all the new battery technology, this necessity reduces the convenience of devices and limits their movement.

Scientists at the American Disney Research Laboratory have found a solution to this problem. They developed a wireless charging method that made wires and chargers unnecessary. Moreover, their method allows you to simultaneously charge not only gadgets, but also, for example, household appliances and lighting.

“Our innovative method makes electric current as ubiquitous as Wi-Fi,” says Alanson Sample, co-director and senior scientist at the lab. “It opens the way for further developments in robotics, previously limited by battery capacity. So far we have demonstrated the operation of the installation in a small room, but there are no obstacles to increasing its capacity to the size of a warehouse.”

A system for wireless transmission of electricity was developed back in the 1890s by the famous scientist Nikola Tesla, but the invention did not receive mass distribution. Today's wireless power transmission systems operate mainly in extremely confined spaces.

The method, called quasistatic cavity resonance (QSCR), involves applying current to the walls, floor and ceiling of a room. They, in turn, generate magnetic fields that act on a receiver containing a coil connected to the device being charged. The electricity generated in this way is transferred to the battery, having previously passed through capacitors that exclude the influence of other fields.

Tests have shown that in this way up to 1.9 kilowatts of power can be transmitted through a regular electrical network. This energy is enough to simultaneously charge up to 320 smartphones. Moreover, according to scientists, such technology is not expensive and its commercial production can be easily established.

The tests took place in a room specially created from aluminum structures measuring 5 by 5 meters. Sample emphasized that metal walls may not be necessary in the future. It will be possible to use conductive panels or special paint.

The developers claim that their method of transmitting energy through the air does not pose any threat to human health or any other living beings. Their safety is ensured by discrete capacitors that act as an insulator against potentially dangerous electric fields. published