Wireless power transmission methods
م.م. محمد حسن علي
قسم هندسة القدرة والمكائن
Open Andre Marie Ampere in 1820 the law of interaction of electric currents, marked the beginning of further development of the science of electricity and magnetism. 11 years later, Michael Faraday experimentally found that the electric current generated by the changing magnetic field can induce an electric current in another conductor. Since the first electric transformer was created.
In 1864, James Clerk Maxwell finally codified experimental data Faraday, giving them a form of precise mathematical equations by which was established the foundation of classical electrodynamics, since these equations describe the relationship of the electromagnetic field with electric currents and charges, and the consequence of this was to be the existence of electromagnetic waves.
In 1888, Heinrich Hertz confirmed experimentally the existence of electromagnetic waves predicted by Maxwell. His spark transmitter with chopper based Ruhmkorff coil could produce electromagnetic waves of a frequency of 0.5 GHz, which can be taken multiple receivers, tuned to resonate with the transmitter.
The receivers can be located up to 3 meters, and in the event of a spark in the transmitter, and there were sparks in the receivers. Since the first experiments in wireless transmission of electrical energy by means of electromagnetic waves have been conducted.
In 1891, Nikola Tesla, being engaged in the study of high-voltage and high-frequency alternating currents, coming to the conclusion that it is imperative for a particular purpose select a wavelength, and the operating voltage of the transmitter, and not necessarily doing too high frequency.
The scientist noted that the lower limit frequency and voltage at which it at the time managed to achieve the best results – from 15,000 to 20,000 oscillations per second at a potential of 20,000 volts. Tesla received the current high frequency and high voltage by applying an oscillating capacitor discharge. He noted that this type of electric transmitter is suitable for the production of light, and for the transmission of electricity to produce light.
In the period from 1891 to 1894 years, scientists have repeatedly demonstrated wireless transmission, and the glow of vacuum tubes in the high electrostatic field, while noting that the energy of the electrostatic field is absorbed by the lamp, transformed into light, and the energy of the electromagnetic field used for electromagnetic induction to produce similar result mainly reflected, and only a small proportion of it is converted into light.
Even applying resonance transmission via electromagnetic waves, a significant amount of electrical energy transfer will not be possible, say scientists. Its purpose in the period of transmission it has a large amount of electrical energy in a wireless manner.
Up to 1897, in parallel with the work of Tesla, the study of electromagnetic waves are: Jagdish Bose in India, Alexander Popov in Russia, and Guglielmo Marconi in Italy.
Following public lectures Tesla, Jagdish Bose stands in November 1894 in Calcutta with a demonstration of wireless power, where it ignites the powder by passing electrical energy at a distance.
After Bose, namely 25 April 1895, Alexander Popov, using Morse code transmitted by the first radio message and this date (May 7, New Style) is now celebrated annually in Russia as "Radio Day".
In 1896 Marconi, having arrived in the UK, has demonstrated his apparatus by passing a Morse code signal over a distance of 1.5 kilometers from the roof of the post office building in London at another building. After that, he perfected his invention and was able to transmit a signal on Salisbury Plain is already at a distance of 3 kilometers.
Tesla were successfuly 1896 transmits and receives signals in the distance between transmitter and receiver is about 48 kilometers. However, a significant amount of electrical energy to pass over a long distance while none of the researchers failed.
Experimenting in Colorado Springs in 1899, Tesla wrote: "The failure of the method of induction seems huge compared to the method of excitation of charge land and air." This will be the beginning of the academic research focused on the transmission of electricity over long distances without the use of wires. In January 1900, Tesla will make in his diary entry about the successful transfer of power to the coil, "staked far field", which was powered by a lamp.
But the most spectacular success of the scientist will launch June 15, 1903 Vordenkliff tower on Long Island for transmitting electrical energy to a considerable distance in large quantities without wires. Grounded secondary coil resonant transformer, topped by a copper spherical dome, was to initiate a land charge and conductive layers of air to be part of a large resonant circuit.
So the scientist was able to power the 200 lamp at 50 watts at a distance of about 40 km from the transmitter. However, based on economic feasibility, project financing was stopped by Morgan, who from the outset invested in the project in order to get a wireless connection and transmission of free energy on a commercial scale at a distance of him as a businessman, categorically did not suit. In 1917, the tower is designed for the wireless transmission of electrical energy, was destroyed.
Read more about the experiments of Nikola Tesla is available here: Resonance method of wireless transmission of electricity Nikola Tesla
Much later, in the period from 1961 to 1964, an expert in the field of microwave electronics William Brown experimented with the transmit beam of microwave energy in the United States.
In 1964, it was first tested device (model helicopter) is able to receive and use the energy of the microwave beam in the form of direct current, through an antenna array consisting of half-wave dipoles, each of which is loaded by a high Schottky diodes. Already by 1976, William Brown carried out the transfer of the microwave beam power of 30 kW at a distance of 1.6 km with an efficiency greater than 80%.
In 2007, a research team at MIT led by Professor Marina Solyachicha able to transfer energy wirelessly over a distance of 2 meters. Transmitted power was enough to power 60 watt bulb.
At the core of their technology (called WiTricity) is the electromagnetic resonance phenomenon. The transmitter and receiver – is resonating at the same frequency two copper coil diameter of 60 cm each. The transmitter is connected to the power source and the receiver – to the incandescent lamp. Paths are set to the frequency of 10 MHz. The receiver in this case receives only 40-45% of the transmitted power.
Around the same time, a similar wireless transmission technologies demonstrated by Intel.
In 2010, Haier Group, a Chinese manufacturer of household appliances, presented on display at CES 2010 a unique product – a completely wireless LCD TV, based on this technology.