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Physicists Promise Wireless Power 411

StrongGlad writes "The tangle of cables and plugs needed to recharge today's electronic gadgets could soon be a thing of the past. Researchers at MIT have outlined a relatively simple system that could deliver power wirelessly to devices such as laptop computers or MP3 players. In a nutshell, their solution entails installing special 'non-radiative' antennae with identical resonant frequencies on both the power transmitter and the receiving device. Any energy not diverted into a gadget or appliance is simply reabsorbed. The system currently under development is designed to operate at distances of 3 to 5 meters, but the researchers claim that it could be adapted to factory-scale applications, or miniaturized for use in the 'microscopic world.'"
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Physicists Promise Wireless Power

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  • Discovered???!??!?? (Score:4, Informative)

    by Anonymous Coward on Wednesday November 15, 2006 @09:36AM (#16850920)

    hello.. Tesla??

    ever hear of that guy??

    yea.. he proposed this well.. 100 years ago..

    incidently.. the security word in the image.. photon.. how appropriate..
  • Re:Loss (Score:5, Informative)

    by jimstapleton ( 999106 ) on Wednesday November 15, 2006 @09:42AM (#16850998) Journal
    Actually, the ironic thing is, if this is using Tesla's principles, it's extremely efficient. Maybe not as much as copper wire, but still rather higher than would be expected.
  • This is using frequency resonation, Tesla's system didn't.

    Think about it this way.

    Lets use sound.. Lets say I make a crystal that vibrates at an exact sound frequency, I can make that frequency sound causing no harm to anyone but that crystal, which will vibrate, and potentially break with intense exposure to the sound. Now of course making a sound intense enough to to shatter the crystal and at the same time cause no harm to ones ears is difficult but its possible.

    Now do this with electromagnetic waves. The real trick is figuring out how not to waste energy pumping it out in all directions. But its about as dangerous as me sitting here 1000 feet from a major radio broadcast station.....
  • by Ummite ( 195748 ) on Wednesday November 15, 2006 @09:54AM (#16851132) Homepage
    Exactly, Tesla did it 100 years ago, and over more than a km distance! But people don't know that guy. Tesla coil, radio transmission, AC electricity etc. The only thing new is the usage, little scale.
  • IPT (Score:1, Informative)

    by Anonymous Coward on Wednesday November 15, 2006 @09:55AM (#16851142)
    As vaguely mentioned in the article ("A UK company called Splashpower has also designed wire-less recharging pads"), IPT or Inductive Power Transfer [] is already a lot more mature and far more on the way to reaching consumers than this technology which has yet to reach prototype stage so I fail to see the significance.
  • Re:Problems (Score:2, Informative)

    by mlk ( 18543 ) <michael.lloyd.le ...> on Wednesday November 15, 2006 @09:56AM (#16851158) Homepage Journal
    It has a range of 5 metres. It is something you would install in your home, not deliver power to a house.

    So someone could sit outside your house, and nick your bb connection and not worry about battery life.
  • 6.4Mhz - Oh Dear. (Score:5, Informative)

    by MrSteveSD ( 801820 ) on Wednesday November 15, 2006 @09:56AM (#16851160)
    This thing is supposed to transmit at 6.4MHz. Searching for 6.4Mhz on Google brings back many many links about devices for which that frequency is important. And we wouldn't just be talking about a little bit of radio interference. This would be high power interference.
  • April Fools! (Score:4, Informative)

    by RobertNotBob ( 597987 ) on Wednesday November 15, 2006 @10:07AM (#16851286)
    This was one of Think Geek's April Folls jokes earlier this year.


    I guess truth CAN be stranger than fiction.


  • by From A Far Away Land ( 930780 ) on Wednesday November 15, 2006 @10:15AM (#16851404) Homepage Journal
    Yesterday the Corus radio network across Canada had a guest on with a study that's presumably scientific but I missed the details, and he found that cell phone radiation poses a 2 to 3 times risk of giving the user tumours. He said the problems with initial studies was the assumption that microwaves at so low an intensity as to not HEAT the subject, could not do damage. But in fact, even low intensity waves cause damage according to his study.
  • by Apocalypse111 ( 597674 ) on Wednesday November 15, 2006 @10:25AM (#16851602) Journal
    Even cell phones are proved to cause cancer...

    No, they're not. Cellular phones don't emit ionizing radiation, all their communications happen in the microwave band. This is not powerful enough to cause cell damage on its own. The thermal effects raise cell temperature a fraction of a degree on the surface of the head (an order of magnitude less than the change experienced by standing in sunlight), and the non-thermal effects show no rigorous evidence of genetic damage. Now, near a base station, the situation is a little different, but don't try to scare John Q. Citizen with unfounded FUD about cellular phones causing cancer.

    More info here [].
  • by q-the-impaler ( 708563 ) on Wednesday November 15, 2006 @10:47AM (#16851912)
    Pardon me... it was "Free Energy"
    link []
  • by Mr Pippin ( 659094 ) on Wednesday November 15, 2006 @10:48AM (#16851932)
    We might ALL know more of Tesla had JP Morgan not stopped his funding. Then again, Tesla had no problem with people getting power for free; which clearly caused issues for Morgan.

    He was also chiefly responsible for the adoption of AC power. Edison was a very strong proponent of DC power distribution, and attacked any advocates of AC power distribution. AC won out for very practical reasons. (power conversion was mostly just a transformer)

    Other than significant infrastructure cost, it's a pity that 3-phase power only enjoys success in commercial settings. It's much easier to make motors and other electricial appliance implementations with 3-phase power.

    Yes, we owe a lot to Mr. Tesla.
  • by delire ( 809063 ) on Wednesday November 15, 2006 @10:50AM (#16851948)
    True. Sadly his plans for wireless-electricity were completely thwarted, interestingly enough, by a refrigeration company that needed low prices for copper in order to enjoy low-cost production for their cooling systems. The reason copper was cheap, of course, was because wired electricity was in demand at the time.

    More on that in here [].

    Next: An engineer working for Ford will be on the cover of Time magazine hailed as a saint for his invention, the Hydroden Engine. No one will find it conspicuous the article is flanked by a full page ad for BP featuring a woman drinking from a pool of crystal clear alpine water.
  • RTFA??!?!? (Score:5, Informative)

    by EComni ( 998601 ) on Wednesday November 15, 2006 @11:12AM (#16852228)
    Maybe the summary got edited to take out the word "discovered", but too many people are chiming in with "Tesla did it!". From the article itself:
    US researchers have outlined a relatively simple system that could deliver power to devices such as laptop computers or MP3 players without wires.
    The concept exploits century-old physics and could work over distances of many metres, the researchers said.
    Old technology
    The team from MIT is not the first group to suggest wire-less energy transfer.
    Nineteenth-century physicist and engineer Nikola Tesla experimented with long-range wire-less energy transfer, but his most ambitious attempt - the 29m high aerial known as Wardenclyffe Tower, in New York - failed when he ran out of money.
    Yes. Tesla did it. We know it. The article knows it and states it plainly. The credit has been given. So can we discuss the actual feasibility for short distances, now?
  • by Colin Smith ( 2679 ) on Wednesday November 15, 2006 @11:32AM (#16852520)
    Batteries still only return a tenth of the energy put into charging them,

    Sorry, this is rubbish. Batteries are generally highly efficient. The efficiency of the system is determined by the charger which can be anything from crap (30%) to excellent (90%).
  • by smellsofbikes ( 890263 ) on Wednesday November 15, 2006 @12:01PM (#16852956) Journal
    Ummm ... I don't know if you're really unaware of physics here, but if you stick a mouse in a microwave and turn the power to 11, the mouse sort of dies.

    The absorption frequencies of DNA might not specifically match cellphone radiative frequencies, but high-power microwave radiation absolutely is dangerous to living tissue. Water absorbs very nicely at most microwave frequencies, and thermally-induced damage to water-containing tissues means the cell has to repair the damage. The thermal damage may be to the DNA, and it may be just to random proteins in the cell, but either way the cell has to start translating/transcribing, and when DNA is unravelled and depaired for transcription, there's a much greater chance of damage to the DNA happening from random processes, free radicals, stuff like that.

    The question is: does sufficient damage happen to living tissue from radiation at the frequency and power density seen in cellphones, and I don't think anyone has positively answered that question yet.
  • by ajs318 ( 655362 ) <sd_resp2@earthsho[ ] ['d.c' in gap]> on Wednesday November 15, 2006 @12:11PM (#16853136)
    It's much easier to make motors and other electricial appliance implementations with 3-phase power.
    The 1950s called, they want their words back. Inverters aren't hard to build. Just turn your AC into DC; then have a three-stage phase-shift oscillator with each output driving a power amplifier. There's your 3-phase AC. You can even change the frequency (which gives you motor speed) and the phase ordering (which gives you direction of rotation) electronically.

    DC brushless motors are everywhere nowadays. In case you've been living under a rock, a DC brushless motor has a permanent magnet for an armature, with alternating south and north poles. Cheap ones have four poles, high-quality ones for true hi-fi record turntables have 16 poles. The stator has coils forming electromagnets with an equal number of poles, and a Hall effect sensor. This senses whether the nearest magnet pole is south or north.

    What will happen when this is powered up is that the magnetic forces will push the armature into a stable position where every north pole on the armature is next to a south pole on the stator, and vice versa. Reversing the current at this point will turn the armature another step. In a "conventional" DC motor, the armature has coils and the stator has permanent magnets; the rotation of the armature is used to reverse the current in the windings by bringing different contacts on the commutator into contact with the brushes. If the stator is not a permanent magnet but an electromagnet, and this is wired in series with the armature coil, then the motor will always spin in the same direction irrespective of which way the current is flowing, since all north poles will become south poles and vice versa, so a series-wound motor will work equally well on DC or AC (though it performs best at low frequencies. Some countries' railways, when first electrified, used series-wound motors; these had to be fed from a special, low-frequency supply of 16.7Hz. rather than the usual 50Hz.). In a brushless motor, each end of the stator coils has two transistors; one which will take it "high" and the other which will take it "low" (and a bit more circuitry to ensure that they never both come on at the same time). So the current can be reversed, or cut off (if both transistors at one or both ends of the coil are off) entirely electronically. The current reversal is controlled by the Hall effect sensor. Speed control is achieved through pulse-width modulation: a control signal of several kHz., with an adjustable duty cycle, is used to turn off all 4 transistors. The longer the transistors are "on", the faster the motor runs. Since the transistors have either next to no voltage across them (when "on") or next to no current through them (when "off"), they dissipate hardly any power.

    As to the stuff about the battle of the currents: I did some research, and it was fascinating comparing it to the present-day battle of the sources. I almost expect Ballmer and co to start killing stray cats and dogs around Redmond with Open Source software just to prove how dangerous it is!
  • Re:Loss (Score:2, Informative)

    by dosquatch ( 924618 ) on Wednesday November 15, 2006 @12:23PM (#16853362) Journal

    you consider transformers to be "inefficient", even though they are the most efficient machines known

    Simple voltage to voltage transformers are incredibly efficient. Power bricks (or "wall warts") are not, because they are not simply transformers. They are also doing half-wave rectification (at minimum 50% power loss), which results in pretty significant thermal losses. Typical DC power bricks are around 30% efficient.

    There are high-efficiency power bricks that do full-wave rectification & can be 95% efficient or better, but what do you think actually comes with your product?

  • by donotdespisethesnake ( 1010769 ) on Wednesday November 15, 2006 @01:00PM (#16854096)
    The plain and simple fact is that DNA does not interact with light at microwave/radiowave frequencies. Therefore DNA can't get damaged by cell phone radiation.

    However, the plain and a simple fact is that DNA gets copied a lot. An awful lot. If any of the many processes involved in copying, or even reading, the DNA were interfered with, then cancer might ensue.

    Despite appearances, many biological processes are poorly understood, particularly the role of electric fields within living organisms. It is quite possible that external electro-magnetic fields have an adverse effect. While there is no obvious evidence of excess cancers caused by RF, the low level effects are pretty much unknown.

  • by Sfing_ter ( 99478 ) on Wednesday November 15, 2006 @01:04PM (#16854204) Homepage Journal
    Ummm... he actually made one... and caused an earthquake... []

    The problem with hiding technology is the telephone/radio/programming issue, where more than one person can come to the same conclusion, albeit via different means/functions/devices.
  • mythbusters (Score:3, Informative)

    by isotope23 ( 210590 ) on Wednesday November 15, 2006 @02:00PM (#16855240) Homepage Journal
    Yes, I saw that episode. I also saw that using a VERY small weight (like 5lbs max) they made the entire steel bridge oscillate. I believe Tesla did not specify how long it would take, only that it would do so. So IMO the theory was sound. If run long enough the oscillations should induce metal fatigue causing the bridge to fail. Too bad they don't have a bridge they could try to destroy, I'd like to see them hook up progressively larger weights to see if they could take it down.
  • by Grishnakh ( 216268 ) on Wednesday November 15, 2006 @02:27PM (#16855714)
    DC brushless motors aren't really DC at all, they're AC. The only reason they're called "DC brushless" is because the motor amplifier is powered with DC, and converts this to waveforms to power the motor. There's two kinds of amplifiers, linear and PWM. Linear amplifiers create true sinusoidal waveforms for driving the motor, while PWM amps, as you might imagine, use PWM in place of sinusoidal waveforms.

    Also, high-quality DC brushless motors/amps use encoders instead of hall-effect sensors because of their greater resolution. HE sensors are usually still used to determine absolute position.

    But back to 3-phase power; yeah, it really doesn't make that much sense for non-industrial applications, because of the extra copper wire you have to run, and the extra complexity. The advent of power electronics has made it unnecessary. Even AC isn't that necessary any more at high power levels: in many places, high-voltage DC (HVDC) transmission lines have been installed instead of AC, because today's sophisticated power electronics are able to convert between AC and HVDC with very high efficiency.
  • by 241comp ( 535228 ) on Wednesday November 15, 2006 @04:21PM (#16858030) Homepage
    No, the laws of thermodynamics say that 100% of the energy will be absorbed... By the receiving device, by the transmitting device or by something else. But 100% of it will be reabsorbed by something, somewhere (well, unless it gets radiated at such a trajectory that it does not encounter any mass capable of absorbing it). The question is, what part of your body resonates at 6.4Mhz (and do you care if it absorbs energy).
  • by QuantumFTL ( 197300 ) on Wednesday November 15, 2006 @06:18PM (#16860256)
    Here's the actual paper [] the article is about.

    Seems to me to be little more than a clever way to couple oscillators using higher order moments (that confine the majority of the energy around the device to be very close as they drop off much faster than inverse squared). The paper contains some interesting preturbation methods for determining how badly other objects in the nearby area would affect such a system, however I haven't had time to go through the math in detail.

    Disclaimer: IANAP (but I do have a degree in physics) - any actual physicists like to comment on the mechanism here?
  • How it works. (Score:4, Informative)

    by Ungrounded Lightning ( 62228 ) on Wednesday November 15, 2006 @09:20PM (#16862848) Journal
    And what makes this not waste energy by pumping it in all directions, or not waste energy when there's nothing around to charge?

    The antenna is composed of more than a dipole - like a quadrupole or more. (Details aren't clear from the article.)

    At large distances the fields cancel out. So energy is not radiated away. At short distances it doesn't cancel out exactly. There another antenna can couple to the transmitting antenna and absorb energy from it.

    It's much like total internal reflection with light trying to make it from inside a high-index-of-refraction material to its lower-index surroundings. If the incident angle is increased beyond the angle where the light would be refracted to be parallel to the boundary surface, there's no direction in which the light wave could add up to non-zero strength. Thus the light can't escape. Since the surface isn't "lossy" and can't absorb the energy, the light is totally reflected. But the fields from the light extend a small distance - like a half-wave or so - from the surface (and cancel out rapidly beyond that). If you bring another piece of high-index material close enough to (or touching) the surface, this field will penetrate it. Now the fields add up in a particular direction and the light can travel beyond the formerly totally-reflecting interface. (That's how you measure the refractive index of opaque things like ketchup, and how some fingerprint readers get a clean image.)

    Most of our insights about light and radio have to do with the "far field" - where the observer is so far from the transmitting antenna that the angle between lines-of-sight to its various parts is negligible. In the direction of antenna nulls there is no field, because the total of the field from all the points on the antenna adds to zero. But get close enough that the angles become significant and the distances - and thus the wave phases - no longer add up the same way. Then you're in the "near field", where the signal doesn't cancel out.

    With this device, as with total internal reflection, you've got an "antenna null" in every direction. There's a significant amount of electric and magnetic field for a quarter-to-half-wavelength from the antenna, but beyond that the field falls off to essentially zero very quickly. Cancelation means the open space acts like a perfect mirror and puts all the energy back into the transmitting antenna before it gets to far-field distances. So there's no load on the transmitter. (The antenna acts like a short or open circuit on the end of the transmission line and bounces all the energy back into the transmitter.)

    But bring a probe close enough to the transmitting antenna that the lines between the probe and the transmitting antenna's parts are no longer near-parallel. Then the differences between the distances to the various transmitting parts deviate from the relationship they had at the large distances. You're "in the near-field" and the signal DOESN'T cancel out. The probe can suck in some of the power, potentially with near-perfect efficiency. The loss of this energy may also disrupt the far-field cancelation a little bit, allowing another part of the energy to leak away. But the leaking energy won't exceed the amount captured, since it consists of the fields that would otherwise have been canceling the energy that was grabbed. And other parts of the receiving antenna - which are at other distances from the transmitting elements so things add up differently - can capture some or all of THAT energy. So the leakage may be very small to non-existent. In that case essentially all the energy lost from the transmitting antenna ends up in the receiving antenna's feedline. The transmitter sees the receiver's load (plus the load of any leakage from imperfect field disruption) and the energy is tranferred with negligible loss.

    Does this make any sense yet?

If I have seen farther than others, it is because I was standing on the shoulders of giants. -- Isaac Newton