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MIT demos wireless power

Boffins at Massachusetts Institute of Technology (MIT) this week demonstrated wireless electricity, or “a vision of the future” as they call it.

A team made up of MIT’s Department of Physics, Department of Electrical Engineering and Computer Science, and the Institute for Soldier Nanotechnologies (ISN) was able to light a 60W light bulb from a power source seven feet away. There was no physical connection between the source and the appliance.

The MIT team refers to the technology as “WiTricity” and envisions it as a future wireless power platform for cell phones, household robots, mp3 players, laptop computers and other portable electronics capable of charging themselves without ever being plugged in.

After discounting electromagnetic radiation, such as radio waves, which spread in all directions and waste energy, as well as lasers, which are impractical and require an uninterrupted line of sight, the team settled on magnetically coupled resonance.

The concept WiTricity is based on finds that two resonant objects of the same resonant frequency tend to exchange energy efficiently, while interacting weakly with extraneous off-resonant objects. For example, a child on a swing must pump her legs at the natural frequency of the swing in order to impart substantial energy.

Electromagnetic resonators couple mostly through their magnetic fields and are able to identify the strongly coupled regime in this system, even when the distance between them is larger than the size of the resonant objects. This way, efficient power transfer is enabled.

The MIT team said that magnetic coupling is 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 demonstration design consists of two copper coils, one attached to the power source, which filled the space around it with a non-radiative magnetic field oscillating at MHz frequencies. The non-radiative field mediates the power exchange with the coil on the receiving unit, specially designed to resonate with the field.

Power levels more than sufficient to run a laptop could be transferred over room-sized distances nearly omni-directionally and efficiently, without line of sight. Eventually, this could eliminate the need for batteries altogether.

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