Slashdot Mirror
Physicists Promise Wireless Power
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.'"
Umm..
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..
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.
34486853790
Connection too slow for X forwarding? Try "ssh -CX user@host"
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.....
As vaguely mentioned in the article ("A UK company called Splashpower has also designed wire-less recharging pads"), IPT or Inductive Power Transfer http://www.ferret.com.au/articles/f9/0c01c3f9.asp 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.
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.
Wow, I should not post when knackered.
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.
.
I guess truth CAN be stranger than fiction.
.
___ I don't respond to Anonymous Cowards, and I Never Mod them UP.
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.
Oh You POS
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.
There is no mod option "-1: Disagree" for a reason. "Overrated" is not an acceptable substitute. Post something instead.
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%).
Deleted
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.
Nostalgia's not what it used to be.
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?
"Hey, the third matrix movie would have been good except for the plot,story, and acting." --AC
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.
Ummm... he actually made one... and caused an earthquake...
http://www.intuitor.com/resonance/tesla.html
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.
A computer once beat me at chess, but it was no match for me at kick boxing. Emo Philips
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.
Service guarantees Citizenship! Questions Guarantee GITMO.... Amerika Uber Alles!
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).
Full-Featured GPL Web Hosting Control Panel
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?
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?
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way