Wireless energy transmission becomes a reality

What chaos is the charger for laptops, mobile phones, PDAs . that may soon disappear - according to a US research team that has just published a new study of energy (electricity ) can convey without using wires by using a special resonant antenna.

The researchers used this system to feed a 60 W light bulb 2 m away from the transmitter and said the system could be scaled down for use in mobile devices (laptops, mobile phones . ) without causing power losses.

The idea of ​​power transmission was launched in early 1900 by Serbian inventor Nikola Tesla before the grid was widely available. Tesla came up with the idea of ​​a world with wireless power using a high-voltage " Tesla coil " system.

Although this idea has not yet been successfully implemented, it may cause dangers by high-voltage electric fields, but recently the idea of ​​wireless power transmission has begun to attract more research. Unfortunately, these systems often use the broadcast type in every way so the transmission efficiency is very poor, and so many people have assumed that creating a unidirectional transmission system is impractical by it. Requires an ideal transmission line between transmitter and receiver.

Figure 1. Experimental photo with 2 resonant antenna coils illuminating an electric bulb.

Last year, physicists at the Massachussetts Institute of Technology (MIT) proposed a way to eliminate these difficulties by using non-radiative " ephemeral " electromagnetic waves. These waves are usually produced along with the waves used in today's wireless communications, but decay very quickly when they emit from the antenna. Marin Soljacic and colleagues say that if the receiver can resonate with the transmitter, the " fleeting field " will induce an electric current. In this way, non-resonant objects that are placed in the field will either disconnect the signal or absorb most of the energy produced by the field.

Recently, Soljacic's group has been testing this idea. Using published theory, they created a pair of copper antennas in the form of rings. One is connected to the power supply system while the other is connected to a 60 W light bulb placed 2 m away. When they give an alternating current, it creates a magnetic field and the resonator links with the second coil, thus inducing a current. MIT's team claims that this current can light bulbs with a transfer efficiency of up to 40%, just as their theory assumes.

Figure 2. Decay of distance-transfer efficiency (Science Express June 7, 2007).

Although the antenna used here is half a meter in diameter, Soljacic and his colleagues say it is possible to create a much smaller system for use with portable mobile devices without causing obstructions on bulky size. This also means that it is possible to allow the design of subcutaneous implantable electronic circuits for medical use without the need to use a complicated electrical wiring. These results have just been published in Science Express on June 7, 2007.

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According to PhysicsWeb.org & Science Express, Vietnam Physics