p2pnet - rss feed: Goodbye wires, Hello WiTricity
p2pnet.net news:- Electrical power cables and plugs may soon become things of the past thanks to WiTricity, a technique developed at the Massachusetts Institute of Technology (MIT).
WiTricity, wireless power transfer over two meters (about 6.5 feet), has been achieved from the coil on the left to the coil on the right, where it’s powering a 60W light bulb.
The team which made it happen are: front row, Peter Fisher (left) and Robert Moffatt; second row: Marin Soljacic; third row: Andre Kurs (left), John Joannopoulos and Aristeidis Karalis.
And their experiment opens up a future in which cell phones, household robots, mp3 players, laptop computers and other portable electronic devices could charge themselves without ever being plugged in.
Even better, some of them might not even need batteries at all.
WiTricity is based on using coupled resonant objects, says MIT, going on >>>>>
Two resonant objects of the same resonant frequency tend to exchange energy efficiently, while interacting weakly with extraneous off-resonant objects. A child on a swing is a good example of this. A swing is a type of mechanical resonance, so only when the child pumps her legs at the natural frequency of the swing is she able to impart substantial energy.
Another example involves acoustic resonances: Imagine a room with 100 identical wine glasses, each filled with wine up to a different level, so they all have different resonant frequencies. If an opera singer sings a sufficiently loud single note inside the room, a glass of the corresponding frequency might accumulate sufficient energy to even explode, while not influencing the other glasses. In any system of coupled resonators there often exists a so-called “strongly coupled” regime of operation. If one ensures to operate in that regime in a given system, the energy transfer can be very efficient.
While these considerations are universal, applying to all kinds of resonances (e.g., acoustic, mechanical, electromagnetic, etc.), the MIT team focused on one particular type: magnetically coupled resonators. The team explored a system of two electromagnetic resonators coupled mostly through their magnetic fields; they were able to identify the strongly coupled regime in this system, even when the distance between them was several times larger than the sizes of the resonant objects. This way, efficient power transfer was enabled.
Magnetic coupling is particularly suitable for everyday applications because most common materials interact only very weakly with magnetic fields, so interactions with extraneous environmental objects are suppressed even further. “The fact that magnetic fields interact so weakly with biological organisms is also important for safety considerations,” Kurs, a graduate student in physics, points out.
The investigated design consists of two copper coils, each a self-resonant system. One of the coils, attached to the power source, is the sending unit. Instead of irradiating the environment with electromagnetic waves, it fills the space around it with a non-radiative magnetic field oscillating at MHz frequencies. The non-radiative field mediates the power exchange with the other coil (the receiving unit), which is specially designed to resonate with the field. The resonant nature of the process ensures the strong interaction between the sending unit and the receiving unit, while the interaction with the rest of the environment is weak.
Moffatt, an MIT undergraduate in physics, explains: “The crucial advantage of using the non-radiative field lies in the fact that most of the power not picked up by the receiving coil remains bound to the vicinity of the sending unit, instead of being radiated into the environment and lost.” With such a design, power transfer has a limited range, and the range would be shorter for smaller-size receivers.
Still, for laptop-sized coils, power levels more than sufficient to run a laptop can be transferred over room-sized distances nearly omni-directionally and efficiently, irrespective of the geometry of the surrounding space, even when environmental objects completely obstruct the line-of-sight between the two coils. Fisher points out: “As long as the laptop is in a room equipped with a source of such wireless power, it would charge automatically, without having to be plugged in. In fact, it would not even need a battery to operate inside of such a room.” In the long run, this could reduce our society’s dependence on batteries, which are currently heavy and expensive.
At first glance, such a power transfer is reminiscent of relatively commonplace magnetic induction, such as is used in power transformers, which contain coils that transmit power to each other over very short distances. An electric current running in a sending coil induces another current in a receiving coil. The two coils are very close, but they do not touch. However, this behavior changes dramatically when the distance between the coils is increased. As Karalis, a graduate student in electrical engineering and computer science, points out, “Here is where the magic of the resonant coupling comes about. The usual non-resonant magnetic induction would be almost 1 million times less efficient in this particular system.”
Also See:
MIT - Goodbye wires…, June 7, 2007
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June 8th, 2007 at 6:00 pm
Better not allow BBC anywhere near it!
June 9th, 2007 at 8:58 pm
1. Nikola Tesla was experimenting in exactly this direction about 100 years ago. (Odd how many things he designed that far back that are just now being “invented’ by the cartels.
2. Why this idea that just because ANOTHER mode of power-transmission exists, it must inevitably “replace” existing modes in all instances? Truth be told, the attempt to “replace” everything with a single, standardized approach is, quite simply, evil.
3. No, storage batteries will ALWAYS be a good idea. The wave of the future is multi-power devices (such as the survival radios that you can crank to get emergency power, plug in if available, and use solar.) No reason for this to “replace” anything. Stop thinking in terms of ONE universal approach.