The law of the interaction of electric currents discovered by André Marie Ampere in 1820 laid the foundation for the further development of the science of electricity and magnetism. 11 years later, Michael Faraday experimentally established that a changing magnetic field generated by an electric current can induce an electric current in another conductor. This is how the first electrical transformer was created.
In 1864, James Clerk Maxwell finally systematized Faraday's experimental data, giving them the form of exact mathematical equations, thanks to which the basis of classical electrodynamics was created, because these equations described the relationship of the electromagnetic field with electric currents and charges, and the existence of electromagnetic waves should have been a consequence of this.
In 1888, Heinrich Hertz experimentally confirmed the existence of the electromagnetic waves predicted by Maxwell. His spark transmitter with a Rumkorf coil chopper could produce electromagnetic waves of up to 0.5 gigahertz, which could be received by multiple receivers tuned into resonance with the transmitter.
The receivers could be located at a distance of up to 3 meters, and when a spark occurred in the transmitter, sparks appeared in the receivers. This is how the first experiments were carried out on the wireless transmission of electrical energy using electromagnetic waves.
In 1891, Nikola Tesla, studying alternating currents of high voltage and high frequency, came to the conclusion that it is extremely important for specific purposes to select both the wavelength and the operating voltage of the transmitter, and it is not at all necessary to make the frequency too high.
The scientist notes that the lower limit of frequencies and voltages at which he managed to achieve the best results at that time was from 15,000 to 20,000 oscillations per second at a potential of 20,000 volts. Tesla received a high frequency and high voltage current by applying an oscillatory discharge of a capacitor (see - Tesla's Transformer). He noticed that this kind of electrical transmitter is suitable for both the production of light and the transmission of electricity to produce light.
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In the period from 1891 to 1894, the scientist repeatedly demonstrated wireless transmission, and the glow of vacuum tubes in a high-frequency electrostatic field, while noting that the energy of the electrostatic field is absorbed by the lamp, converting into light, and the energy of the electromagnetic field used for electromagnetic induction in order to obtain a similar the result is mostly reflected, and only a small fraction of it is converted into light.
Even using resonance when transmitted using an electromagnetic wave, a significant amount of electrical energy cannot be transmitted, the scientist argued. His goal during this period of work was to transmit a large amount of electrical energy wirelessly.
Until 1897, in parallel with Tesla's work, studies of electromagnetic waves were conducted by Jagdish Boche in India, Alexander Popov in Russia, and Guglielmo Marconi in Italy.
Following Tesla's public lectures, Jagdish Boche spoke in November 1894 in Calcutta with a demonstration of the wireless transmission of electricity, where he ignited gunpowder, transmitting electrical energy over a distance.
After Boche, namely on April 25, 1895, Alexander Popov, using Morse code, transmitted the first radio message, and this date (May 7, new style) is now celebrated annually in Russia as "Radio Day".
In 1896, when Marconi arrived in Great Britain, he demonstrated his apparatus by transmitting a signal using Morse code over a distance of 1.5 kilometers from the roof of the post office building in London to another building. After that, he improved his invention and was able to transmit a signal along the Salisbury Plain already at a distance of 3 kilometers.
Tesla in 1896 successfully transmits and receives signals at a distance of about 48 kilometers between transmitter and receiver. However, none of the researchers have succeeded in transmitting a significant amount of electrical energy over a long distance.
Experimenting in Colorado Springs, in 1899, Tesla wrote: "The inconsistency of the induction method seems to be enormous compared to the method of exciting the charge of earth and air." This will be the beginning of the scientist's research aimed at transmitting electricity over long distances without using wires. In January 1900, Tesla will make a note in his diary about the successful transfer of energy to a coil “carried out into the field” from which the lamp was powered.
And the most grandiose success of the scientist will be the launch on June 15, 1903, of the Wardencliffe Tower on Long Island, designed to transmit electrical energy over a considerable distance in large quantities without wires. The earthed secondary winding of the resonant transformer, topped with a copper spherical dome, had to excite the earth charge and the conductive layers of air to become an element of the large resonant circuit.
So the scientist managed to power 200 lamps of 50 watts at a distance of about 40 kilometers from the transmitter. However, based on economic feasibility, funding for the project was stopped by Morgan, who from the very beginning invested money in the project in order to get wireless communication, and the transfer of free energy on an industrial scale over a distance, as a businessman, was categorically not satisfied with it. In 1917, the tower, designed for the wireless transmission of electrical energy, was destroyed.
Read more about the experiments of Nikola Tesla here: Resonant method of wireless transmission of electrical energy by Nikola Tesla.
Much later, in the period from 1961 to 1964, an expert in the field of microwave electronics, William Brown, experimented in the USA with paths for the transmission of energy by a microwave beam.
In 1964, he first tested a device (helicopter model) capable of receiving and using the energy of a microwave beam in the form of direct current, thanks to an antenna array consisting of half-wave dipoles, each of which is loaded on highly efficient Schottky diodes. Already by 1976, William Brown had transferred 30 kW of power by a microwave beam over a distance of 1.6 km with an efficiency exceeding 80%.
In 2007, a research group at the Massachusetts Institute of Technology led by Professor Marina Solyachich managed to wirelessly transmit energy over a distance of 2 meters. The transmitted power was sufficient to power a 60 watt light bulb.
Their technology (called WiTricity) is based on the phenomenon of electromagnetic resonance. The transmitter and receiver are two copper coils with a diameter of 60 cm each resonating at the same frequency. The transmitter is connected to an energy source and the receiver is connected to an incandescent lamp. The loops are tuned to 10 MHz. The receiver in this case receives only 40-45% of the transmitted electricity.
Around the same time, Intel demonstrated a similar wireless power transmission technology.
In 2010, the Haier Group, a Chinese home appliance manufacturer, unveiled its unique product at CES 2010, a fully wireless LCD TV based on this technology.
Andrey Povny