Wireless transmission of electricity over a distance: prospects, methods and existing devices without wires

When it first appeared, alternating electric current seemed like a fantasy. Its inventor, the brilliant physicist Nikola Tesla, at the turn of the 19th and 20th centuries investigated the problem of wireless transmission of electricity over long distances. So far, this problem has not been fully resolved, but the results are encouraging.

Ultrasound for energy transmission

Any wave carries energy, including high frequency sound waves. There are three approaches to wireless electricity transmission:

• transferring electrical energy through conversion to another form of energy at the source and reverse conversion to electricity at the receiving device;
• creation and use of alternative conductors of electricity (plasma channels, columns of ionized air, etc.) );
• use of the conductive properties of the Earth's lithosphere.

The ultrasound method belongs to the first approach. In a special type of ultrasound source, when power is applied, a directed beam of high-frequency sound waves is generated. When they hit the receiver, the energy of the sound waves is converted into an electric current.

The maximum distance for power transmission without wires is 10 meters. The result was obtained in 2011 by representatives of the University of Pennsylvania during a presentation at the exhibition "The All Things Digital". This method is not considered promising due to several of its shortcomings: low efficiency, low voltage obtained and limitation on the strength of ultrasound radiation by sanitary standards.

Application of electromagnetic induction

Although most people are not even aware of this, this method has been used for a very long time, almost from the very beginning of the use of alternating current. The most common AC transformer is the simplest wireless power transmission device, only the transmission distance is very short.

The primary and secondary windings of the transformer are not connected in one circuit, and when alternating current flows in the primary winding, an electric current arises in the secondary. In this case, the transfer of energy occurs through an electromagnetic field. Therefore, this method of wireless power transmission uses the conversion of energy from one type to another.

A number of devices have already been developed and are successfully used in everyday life, the operation of which is based on this method. These are wireless chargers for mobile phones and other gadgets, and household electrical appliances with low consumption. electricity during operation (compact CCTV cameras, all kinds of sensors and even TVs with LCD screens).

Many experts argue that electric vehicles of the future will use wireless technologies to charge batteries or generate electricity for driving. Induction coils (analogs of the primary winding of a transformer) will be installed in the roads. They will create an alternating electromagnetic field, which, when a vehicle passes over it, will cause an electric current to flow in the built-in receiving coil. The first experiments have already been carried out, and the results obtained give rise to restrained optimism.

Of the advantages of this method, it can be noted:

• high efficiency for short distances (of the order of several meters);
• simplicity of design and mastered application technology;
• relative safety for human health.

The disadvantage of this method - the small distance at which the transmission of energy is effective - significantly reduces the field of application of wireless electricity based on electromagnetic induction.

Using different microwaves

This method is also based on the conversion of different types of energy. Ultra-high frequency electromagnetic waves serve as a carrier of energy. For the first time this method was described and practically implemented in his installation by the Japanese physicist and radio technician Hidetsugu Yagi in the twenties of the last century. The frequency of radio waves for transmitting electricity wirelessly ranges from 2.4 GHz to 5.8 GHz. An experimental setup has already been tested and received positive feedback, which simultaneously distributes Wi-Fi and powers low-power household electrical appliances.

The laser beam is also electromagnetic radiation, but with a special property - coherence. It reduces energy losses during transmission and thus increases efficiency. Of the advantages, the following can be noted:

• the possibility of transmission over long distances (tens of kilometers in the Earth's atmosphere);
• convenience and ease of installation for low-power devices;
• the presence of visual control of the transmission process - the laser beam is visible to the naked eye.

The laser method also has disadvantages, namely: a relatively low efficiency (45-50%), energy losses due to atmospheric phenomena (rain, fog, dust clouds) and the need to locate the transmitter and receiver in the field visibility.

Solar energy prospects

The intensity of sunlight outside the earth's atmosphere is several tens of times higher than on the earth's surface. Therefore, in the future, according to futurologists, solar power plants will be located in near-earth orbit. And the transfer of accumulated electricity, in their opinion, will be carried out without live wires. A transmission method that copies lightning discharges will be developed and applied; it is planned to ionize the air in one way or another. And the first experiments in this direction have already been carried out. This method is based on the creation of alternative wireless electric current conductors.

Received in this way from near-earth orbit, wireless electricity is impulsive in nature. Therefore, for its practical application, powerful and inexpensive capacitors are needed, and it will also be necessary to develop a method for their gradual discharge.

Most effective method

Planet Earth is a huge condenser. The lithosphere mainly conducts electricity, except for small portions of it. There is a theory that wireless transmission of energy can occur through the earth's crust. The bottom line is this: the current source reliably contacts the earth's surface, alternating current of a certain frequency flows from the source to the crust and spreads in all directions, at certain intervals in the ground are placed receivers of electric current, from which it is transmitted consumers.

The essence of the theory is to accept and use the current of only one given frequency. As in a radio receiver, the frequency of receiving radio waves is adjusted, so in such electrical receivers the frequency of the received current will be adjusted. Theoretically, by this method it will be possible to transmit electricity over very long distances if the frequency of the alternating current is low, on the order of a few Hz.

Prospects for wireless electricity transmission

In the near future, the mass introduction of the PoWiFi system, consisting of routers with a transmission function, is expected electricity for several tens of meters, and household appliances, which are powered by receiving electricity from radio waves. Such a system is currently being actively tested and is being prepared for widespread use. Details were not disclosed, but according to available information, the "highlight" is that it uses the synchronization of the electromagnetic fields of the source and receiver of wireless electricity.

In the very distant future, the option of abandoning the use of traditional power plants on a global scale is being considered - solar stations in low-earth orbit will be usedconverting the energy of sunlight into electrical energy. Electricity will presumably be transmitted to the planet's surface through ionized air or plasma channels. And on the earth's surface, conventional power lines will disappear, and more compact and efficient systems for the transmission of electricity through the lithosphere will take their place.