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Power pads, which use magnetic induction, are already on the market, like the Palm Pre's chargin Touchstone, shown here. They only work over short distances, though, and require custom form factors.  (Source:

Witricity uses magnetically couple resonance to transmit power over longer distances, as shown here. The company's CEO predicts the company's technology will be ubiquitous within five years. However, health concerns about the powerful magnet fields it uses remain.  (Source: Business Unusual)
Company believes that computers, phones, and EVs will within 5 years be operating without cords

You can't fault WiTricity for its ambition.  As one of several companies looking to market emerging wireless power transmission technologies, WiTricity is making some of the boldest claims.  Among the claims made by the company -- that within a year wireless power will be taking the mobile electronics industry by storm.

The concept of wireless power transmission is a relatively old one.  In the 1890s, Nikolai Tesla was successful in illuminating incandescent light bulbs with wirelessly transmitted power.  However, for decades this research lay dormant and untouched.

With modern telecommunications and interest in signals at an all time high, interest in the topic again picked up.  The Massachusetts Institute of Technology, in particular, developed some intriguing technology that WiTricity would later be founded upon.

Eric Giler, CEO of WiTricity says that power transmission over several feet is an obtainable feat.  He states, "Five years from now, this will seem completely normal.  The biggest effect of wireless power is attacking that huge energy wasting that goes on where people buy disposable batteries.  [And] Electric cars [are] absolutely gorgeous, but does anyone really want to plug them in?"

WiTricity isn't the only player in this new market, though.  Several key technologies, each championed by different companies, are emerging.

One is radio power.  Though only able to transmit small amounts of power, this approach can work over a long distance.  A Pittsburgh, Pennsylvania, company called Powercast is among the pioneers in this field, using its technology to power temperature sensors in large office buildings and to power wireless Christmas trees (sold for $400 a piece).  The company has lit up an LED with radio signals from 1.5 miles away.

Another approach is power pads.  Advantages include low costs and relatively high efficiencies.  Disadvantages include the extremely short distance and need for custom shapes and sizes of pads.  This technology currently is employed in the Palm Pre's recharging stone and in electric toothbrush recharging stands.

WiTricity's technology works on a third type of transmission -- magnetically coupled resonance.  Similar to sound waves, the transmission creates a magnetic field, that devices can convert locally to electricity.  This technology enjoys a middle ground with a bit worse efficiency, a bit longer distance, and moderate costs.  Intel is also working on a more efficient version of this approach.

Despite WiTricity's optimism about its new approach, challenges remain.  A full deployment is estimated to possibly create a magnetic field as strong as the Earth's own magnetic field.  According to recent research, referenced by Menno Treffers, chairman of the steering group at the Wireless Power Consortium, such a strong magnetic field can cause serious health risks.

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RE: Hollywood shows up in science again
By radializer on 9/3/2009 5:33:22 PM , Rating: 2
In terms of raw field strength, the Earth's magnetic field is relatively weak and has a field strength of only 30 ~ 60uT (microTeslas; where Tesla is the SI unit of magnetic field ).

In comparison, the neodymium magnets in your hard drives have field strengths in the 1 ~ 2T range - so they produce a local field that is ~ 33000 times stronger.

I remember working on measurements with superconducting magnets that could get into the 8 ~ 12T ... as obvious, people with pacemakers were not allowed in the vicinity of the lab. Even with good shielding, you could see the effects on any CRT monitor within 25 feet. The screen content would color shift and rotate!

Back to the topic --> Since most of the local EM radiation measurements at people's homes today are in the nT (or nanoTesla) range - the questions of long term exposure effects of even a 30 ~ 60uT field are still valid ones.

By HollyDOL on 9/4/2009 2:20:58 AM , Rating: 4
I'd try to provide less scientific, but more understandable comparison (hopefully)...

Your favourite receiver is built to run with 230V Voltage. Now, what happens if you start feeding it with 300V? It won't work well, does it?

It's same with us and natural EM field. We are built to run in that... any fluctuation from this is going to hurt.

Or... another one... pressure...
human is fine with 101325Pa atmospheric pressure. Notice even small fluctuations cause some people to have health issues (we are talking about <10kPa differences).

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