Nowadays electricity is regarded as one of the basic needs of human beings. The traditional power transmission system uses transmission lines to take the power from one place to another, but it is costlier in terms of cable prices and also there exists a certain transmission loss. One maintainable technology leading this charge is a wireless power transmission (WPT) also known as inductive power transfer (IPT).
Wireless power transmission technology is not a new technology. In early 1980, it was explained by Dr. Nikola Telsa. There are three main systems used for wireless electricity transmission: solar cells, microwaves, and resonance. In an electrical device, microwaves are used to transmit electromagnetic radiation from a source to a receiver. The name wireless power transmission states the transfer of electrical power from a source to an electrical device without the help of wires. It involves two coils: a conductor and a receiver coil. The transmitter coil is powered by an AC to produce a magnetic field, which in turn induces a voltage in the receiver coil.
In the whole world electricity transfer from the power station to everywhere is through the wire. Wireless power transfer technology can potentially reduce or eliminate the need for wires and batteries. Wireless transmission is useful to power electrical devices where interconnecting wires are inconvenient, hazardous, or are not possible. Wireless power transfer technology reduces the use of electric wire which is made of copper and aluminum metal. The metal which is used to make electric wire will extinct in the future. If we implement wireless power transfer technology the use of electric wire will reduce. It would be beneficial if in the future, we can implement wireless power transfer technology to transfer power from the power station to everywhere without the need for a wire. In section 2 different categories of wireless power, the technique is discussed, whereas in section 3 represents the various experimental proof of wireless power transfer, section 4 discusses different applications of wireless power transfer and finally, section 5 discusses the potential future application of wireless power transfer technology.
Wireless Power Technique Categories
Non- radiative: In the near field or non-radiative techniques, by magnetic fields using inductive coupling between coils of wire power is transferred over short distances, or by electric fields using capacitive coupling between metal electrodes. In wireless technology, inductive coupling is widely used; phones and electric toothbrushes, RFID tags, and chargers for implantable medical devices like artificial cardiac pacemakers, or electric vehicles are included in its application.
Near-field transfer: In near-field transfer coupling of two coils are needed to transfer power. Through magnetic field coupling, a transformer is transferring energy wirelessly, although it was invented more than 100 years ago. The transfer efficiency drops drastically if we remove the iron core and move the two coils apart. That is why the two coils must be put close enough to each other. This kind of method is already launched in the market. For example, most electric toothbrushes are using wireless chargers, which are much safer than cable chargers in the wet environment.
The frequency of the transmitter and receiver coils is determined by the material and shape of the coil, transfer efficiency will decrease much more slowly when they have moved apart. Prof. Marin Soljacic led a group from MIT, has succeeded in transferring electric energy (60 Watt) between two coils more than two meters apart through a nonradiative electromagnetic field, as shown there is almost no interference with TV, radio or Wi-Fi signals and it happens in the near field usually working at 50 or 60Hz. The major problems are the possibility of an influence on human health. But one thing is that almost all materials that form the human body are non-magnetic, so they cannot interact with the magnetic field, even to several Tesla-like that in a modern MRI machine. Such kind of magnetic-field-is there that is quite safe to people within the transfer range.
Radiative: In far-field or radiative techniques, power is transferred by beams, like microwaves or laser beams also called power beaming. Power beaming techniques can transport energy longer distances. Solar power satellites and wireless powered drone aircraft are proposed applications. :
Far-field transfer: To transfer energy wirelessly over long ranges, the far-field transfer is used.
• Microwaves: In far-field radiative electromagnetic waves are used. A different method uses electromagnetic waves within different wavebands. In the early times, there were many experiments with radio and microwaves. To achieve sufficient directionality, the wavelength of the antennas must be longer. An antenna with a dimension of several meters to several kilometers which requires the speed of light in the air is about 3 x 108 m/s and the wavelength of radio and microwaves is about 1 meter. To transfer energy to smaller objects shorter wavelength is used. The electromagnetic wave used the waveband of radio, TV, cell phone and Wi-Fi, with a signal intensity several orders of magnitude larger.
• Lasers: In the case of the electromagnetic field, also power can be transmitted by converting electricity into a laser beam. That is then pointed at a photovoltaic cell. In the case, the power is beamed at a receiver that can convert it to electrical energy, so this mechanism is generally known as ‘power beaming’ technology. Special photovoltaic laser power converters are optimized for monochromatic light conversion that is applied at the receiver. This technology used in military weapons and aerospace applications.
Various Experimental Proof of Wireless Power Transfer
• Resounding inductive coupling, also known as “electro-dynamic induction” used by Nikola Tesla in 1894 to wirelessly light up phosphorescent and incandescent lamps. That was situated at the 35 South Fifth Avenue laboratory, and later at the 46 E. Houston Street laboratory in New York City. A device called the high-voltage was patented by Nikola Tesla in 1897.
• In 1910 an agreement was held using incandescent light-powered wirelessly by electromagnetic induction. The bottom of a large cylinder was made by using an electromagnet, a coil of wire with the alternating current through it. It creates a magnetic field. Above the magnet’s pole, the lamp is attached to another coil of wire. The magnetic field generates electricity that lights the lamp. The lamp then looks like an original Edison lamp with a carbon filament.
• Rectenna was invented by Brown in 1964 which could efficiently convert microwaves to DC power, and the first wireless-powered aircraft demonstrated in 1964, a model helicopter powered by microwaves beamed from the ground.
• In California 1975 Wireless high-power transmission using microwave experiments in the tens of kilowatts have been performed at Goldstone.
• The first MPT experiment in space was carried out by Hiroshi Matsumoto’s team in 1983. The experiment was called MINIX (Microwave Ionosphere Nonlinear Interaction Experiment).
• In 1987 fuel-free airplane flight experiment was succeeded by the Canadian group with MPT which was called SHARP (Stationary High-Altitude Relay Platform) with 2.45 GHz.
• Several field MPT experiments have been conducted over the years In Japan. A fuel-free flight experiment was conducted successfully by a joint collaborative group using phased-array technology, which was referred to as the Microwave Lifted Airplane Experiment (MILAX) in 1992.
• From the University of Auckland in New Zealand, Professor John Boys and Professor Grant Covic developed systems to transfer large amounts of energy across small air gaps in 1993. In Japan, this system was practically used as the moving crane and the AVG non-contact power supply.
• In 1994-95 power companies and universities made Ground-to- Ground MPT experiments.
• In 1997 at Grand Bassin on Reunion Island, the Microwave Power Transmission experiment was conducted.
• A lightweight unmanned model plane powered by a laser beam was demonstrated NASA’s Dryden Flight Research Center in 2003. Photocells from a beam of infrared light from a ground-based laser-generated the small model plane’s motor were powered by electricity, while a control system kept the laser pointer at the plane.
• Marin Soljačić along with other researchers at the Massachusetts Institute of Technology applied in electromagnetic theory, the wireless power transmission concept based on strongly coupled resonators in November 2006.
• A long-range Microwave Power Transmission demonstration was realized on one of the islands of Hawaii on May 2008. Managed Energy Technologies of the U.S organized the demonstration and involved the wireless transmission of energy.
• Researchers at the University of Korea Advanced Institute of Science and Technology (KAIST) have developed an electric transport system that is called Online Electric Vehicle, OLEV. The vehicles get power wirelessly from cables via non-contact magnetic charging that is kept under the surface of the road. To manage traffic congestion and to improve efficiency by reducing energy consumption, this technique is established. In July 2009 the researchers at the University of Korea Advanced Institute of Science and Technology successfully experimented with a bus by suppling 60% power over a gap of 12 centimeters.
• Kyoto University’s group experiment from an airship to ground with two phased-controlled magnetrons in 2009.
• Hatem Zeine an American physicist, inventor demonstrated how wireless power transmission using phased array antennas can deliver electrical power up to 30 feet in 2013. It uses the same radio frequencies as Wi-Fi.
• Researchers at the University of Washington experiment power over Wi-Fi, at ranges of up to 20 feet in 2015. They also experiment using Wi-Fi that can be used to wirelessly trickle-charge nickel-metal hydride and lithium-ion coin-cell batteries at distances of up to 28 feet.
• Federal Communication Commission (FCC) certified the first mid-field radio frequency (RF) transmitter of wireless power in 2017.
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