20-10-2016, 02:54 PM
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Abstract
Currently, wired electricity powers nearly everything. It travels through wires in the form of Alternating Current, and powers most of our devices in the form of Direct Current. In our present electricity generation system we waste more than half of its resources. Especially the transmission and distribution losses are the main concern of the present power technology.
Description of Wireless Electricity
Witricity is nothing but the short name of Wireless Electricity. The basic concept behind this is Magnetic Resonance. Two resonant objects of the same resonant frequency tend to exchange energy efficiently, while dissipating relatively little energy in extraneous off-resonant objects. In systems of coupled resonances, there is often a general "Strongly Coupled" regime of operation. If one can operate inthat regime in a given system, the energy transfer is expected to be very efficient.
Midrange power transfer implemented in this way can be nearly omni directional and efficient, irrespective of the geometry of the surrounding space, with low interference and losses into environmental objects. The above considerations apply irrespective of the physical nature of the resonances. Magnetic resonances are particularly suitable for everyday applications because most of the common materials do not interact with Magnetic Fields, so interactions with Environmental objects are suppressed even further. We were able to identify the strongly coupled regime in the system of two coupled magnetic resonances by exploring Non-radioactive (near-field) magnetic resonant induction at Megahertz frequencies.
Need of Witricity:
Now a days there is a Rapid development of autonomous electronics like laptops, cell-phones, house-hold robots and all the above devices typically rely on chemical energy storage(Battery) .As they are becoming daily needs to present generation, Wireless energy transfer would be useful for many applications as above and they need midrange energy.
Currently, wired electricity powers nearly everything. It travels through wires in the form of Alternating Current, and powers most of our devices in the form of Direct Current. In our present electricity generation system we waste more than half of its resources. Especially the transmission and distribution losses are the main concern of the present power technology.
The resistance of the wire used in the electrical grid distribution system causes a loss of 26-30% of the energy generated. This loss implies that our present system of electrical distribution is only 70-74% efficient. We have to think of alternate technology to transmit and distribute the electricity. The transmission of power without wires may be one noble alternative for electricity transmission.
Prof. Marin Soljacic from Massachusetts Institute of Technology (MIT), is the one who has proved that magnetic coupled resonance can be utilized in order to transfer energy without wires. What's even more interesting is how he came about this idea. Soljacic, just like any of us was fed up of his 'low battery' beeping cell phone and wondered just like any of us if there was a way to get rid of this 'charging problem'.
Abstract
The technology used for wireless power transmission is known as witricity. Wireless power transmission is not a new idea, Nikola Tesla proposed theories of wireless power transmission in the late 1800s and early 1900s. Tesla's work was impressive, but it did not immediately lead to wide spread practical methods for wireless power transmission. Since then many researchers have developed several techniques for moving electricity over long distances without wires. Some exist only as theories or prototypes, but others are already in use. In 2006 researchers at Massachusetts Institute of Technology led by Marine Soijacic discovered an efficient way to transfer power between coils separated by a few meters. They have dubbed this technology as witricity. Witricity is based upon coupled resonant objects.
Radio And Microwave
If resonance is incorporated or not, induction generally sends wireless power over relatively short distance. For very long distance power transmission radio and microwaves are used. Japanese researcher YAGI developed a directional array antenna known as YAGI antenna for wireless energy transmission. It is widely used for broadcasting and wireless telecommunications industries. While it did not prove to be particularly useful for power transmission. Power transmission via radio waves can be made more directional, allowing longer distance power beaming, with shorter wavelengths of electromagnetic radiation, typically in the microwave range. A rectenna is a rectifying antenna, an antenna used to convert microwaves into DC power. Being that an antenna refers to any type of device that converts electromagnetic waves into electricity or vice versa. A rectenna is simply a microwave antenna.
Micro Wave Power Transmission Has Some Drawbacks
» The solar power stations on the moon would require supervision and maintenance. In other words, the project would require sustainable, manned moon bases.
» Only part of the earth has a direct line of sight to the moon at any given time.
Witricity In History
Wireless power transmission is not a new idea. Nickola Tesla demonstrated transmission of electrical energy without wires in early 19th century. Tesla used electromagnetic induction systems. William C Brown demonstrated a micro wave powered model helicopter in 1964. This receives all the power needed for flight from a micro wave beam. In 1975 Bill Brown transmitted 30kW power over a distance of 1 mile at 84% efficiency without using cables. Researchers developed several technique for moving electricity over long distance without wires.
Witricity At Present
In 2006 MIT researchers discovered a new method to provide electricity to remote objects without wires. Wiricity is based on coupled resonant objects. In 2007 researchers implemented a prototype using self resonant coils. In this first experiment they demonstrated efficient non-radiative power transfer over distance up to eight times the radius of the coils. This experiment was done using two copper coils. Each coil act as self resonant system. One of the coils is attached to the electricity source. Instead of irradiating the environment with electromagnetic waves, it fills the space with a non-radiative magnetic field oscillating at MHz frequencies. The non-radiative field mediates the power exchange with the other coil, which is specially designed to resonate with the field.
Conclusion
Witricity is in development stage, lots of work is to be done to use it for wireless power applications. Currently the project is looking for power transmission in the range of 100w. Before the establishment of this technology the detailed study must be done to check whether it cause any harm on any living beings.