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The team consists of (top to bottom, left to right) Andre Kurs, Prof. John Joannopoulos, Aristeidis Karalis, Prof. Marin Soljacic, Prof. Peter Fisher, and Robert Moffatt. (Source: MIT, Aristeidis Karalis)
A 60-watt bulb illuminates for the future of wireless power

"Wireless" isn't exactly a new concept to computing. Network connectivity, USB devices and even displays had their cords cut in recent years.  Researchers from the Massachusetts Institute of Technology took the final steps towards cutting the last tether of the laptop user: the power cord.

Transmitting power wirelessly is traditionally limited to line-of-sight methods such as microwave or laser, which have a "significant negative effect" on anyone or anything unfortunate enough to be caught in the middle.

Playfully dubbed "WiTricity" by the team, the researchers were able to power a sixty-watt lightbulb from seven feet away using the principle of magnetically coupled resonance. The basic concept is similar to existing electromagnetic inductive chargers, but does not suffer the massive drop in efficiency when distance is increased.

The experiment works as follows. Two magnetic coils resonate at the same frequency.  When one of these coils is attached to a power source, the resonant magnetic field produced by the coil increases dramatically.  The second, unpowered coil "couples" with the resonating magnetic field.  The resonance from the second coil is then converted back to electricity for the device.

The MIT researches are quick to tout magnetically coupled resonance over electromagnetic induction.  Aristeidis Karalis, an MIT graduate student that worked on the project, states, "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."

In addition to increased efficiency, the WiTricity project does not transmit biologically harmful electromagnetic radiation during operation.  Additionally, line-of-sight issues present in microwave technology disappear with WiTricity; magnetic fields are more-or-less unaffected by non-metallic materials in most environments. 

The most current WiTricity experiments use coils approximately 20" in diameter and operate at distances of approximately two meters.  The team hopes to eventually power a notebook from a several meters away.

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RE: questions...
By arazok on 6/11/2007 6:01:07 PM , Rating: 2
When converting gas, hydro, nuclear etc to electric current, you are always dealing with low efficiencies. We're dealing with electric current to electric current, so that loss is already accounted for. A further 60% loss just adds to the total. PSU's in computers are over 90% efficient, and this is what you need to compete with to make this a practical application for home use. People complain about needing 600W PSU's to run their computers. Replacing those with 1200W coils is not an option.

RE: questions...
By audiophi1e on 6/11/2007 8:01:24 PM , Rating: 2
I disagree. This thing would probably still be very useful at 40% efficiency. Most things that you would like to be truly wireless don't consume *that* much power: laptop, satelite speakers (rear channel), etc. If a laptop requires let's say 60W, you only need to deliver about 200W~250W to ensure 60W delivery. Rear channels consume maybe 50W each maximum. Same story. You only need to deliver 200W each to power those babies. Some people will be more than happy to pay for that difference for the convenience and aesthetic advantage and having no power cords for certain things.

Now here's the catch: once this thing becomes commercial, and assuming the maximum range becomes fairly good--let's say 100ft--how do you prevent your neighbor from stealing your power?

It's just like your neighbor leeching your unsecured Wifi connection.

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