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Physicists Promise Wireless Power
Posted by
CmdrTaco
on Wed Nov 15, 2006 08:33 AM
from the having-a-hard-time-buying-it dept.
from the having-a-hard-time-buying-it dept.
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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That would be really cool to see... (Score:4, Insightful)
Re: (Score:3, Interesting)
You don't think there are any safety issues inherent here? I for one was surprised to see no discussion of it at all in the BBC article.
It well could be safe (or at least as safe as any other tech currently in use) but, man, I'd be looking at it very closely myself if I were responsible for bringing it to market.
You have a point. (Score:5, Insightful)
Parent
Re:That would be really cool to see... (Score:5, Insightful)
5) Energy not transferred to laptop re-absorbed by source antenna. People/other objects not affected as not resonating at 6.4Mhz
That was at the bottom of the graphic. So it should be safe (however, seeing as the technology only exists as a computer model and not as reality, I would bet that if there are any safety issues they will only come to light after such a device is actually built)
Parent
Can't be 100% reabsorbed (Score:3, Insightful)
Re:That would be really cool to see... (Score:5, Funny)
Parent
Re: (Score:3, Informative)
Re:That would be really cool to see... (Score:5, Interesting)
Parent
Re:That would be really cool to see... (Score:5, Informative)
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.
Parent
Re:That would be really cool to see... (Score:5, Interesting)
Parent
Re:Maybe it's the heating (Score:5, Funny)
Any one of those could heat up my cells a little bit and give me cancer!
Parent
Discovered???!??!?? (Score:4, Informative)
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..
alexchiu (Score:3, Insightful)
Re:Discovered???!??!?? (Score:5, Informative)
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.
Parent
Re:Discovered???!??!?? (Score:4, Informative)
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.
Parent
RTFA??!?!? (Score:5, Informative)
Parent
Re:Discovered???!??!?? (Score:5, Insightful)
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Re: (Score:3, Informative)
link [arizonaenergy.org]
Re: (Score:3, Interesting)
link [nuenergy.org]
Re: Tesla (Score:4, Funny)
Parent
Re: (Score:3, Informative)
More on that in here [209.85.129.104].
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 a
Re:Discovered???!??!?? (Score:4, Interesting)
Tesla's method of wireless power falls into the latter. Even if there was a copper conspiracy, it would be a good thing, because it stopped money from being poured into an unworkable design. It was based on countless false claims and pseudoscience (random example: The atmosphere above 5km is so thin that it ceases to be an insulator and instead conducts electricity with almost no losses over long distances) -- most of them simply assumptions, without a hint of scientific backing, let alone a calculation on something so critical as efficiency.
Why Tesla is treated in a cultlike fashion ("He said it -- it must be true!") by many people around here is beyond me. He invented some great stuff. He also proposed a good bit of pseudoscience. The two are not mutually exclusive, people. In his later years, he was nearly broke, and was desperate for new contracts. He became OCD. He claimed to have completed a unified field theory, yet no notes on it were ever found. He claimed that spacetime wasn't curved, and thought that Einstein was just bedazzling people and keeping them from the truth. He made astounding claims about what his "death ray" could do, without ever doing the math (obviously -- it was basically an ion drive). He started talking about creating a "wall of light" by using a certain pattern to manipulate electromagnetic waves which would allow spacetime and matter to be tweaked at will. He even proposed a device to take pictures of peoples thoughts, which he thought appeared in the retina. He proposed an earthquake machine, and said he could shatter the world if he built a big enough resonator.
The list goes on.
Parent
Now who's stupid (Score:5, Funny)
Re:Now who's stupid (Score:5, Funny)
Parent
100 years later... (Score:4, Insightful)
Problems (Score:5, Insightful)
laptops and MP3 players? (Score:3, Interesting)
Re: (Score:3, Funny)
Rats are awsome critters, very friendly and social. I finally got them to stop gnawing on my feet. I even still have three toes left!
Great (Score:5, Funny)
wouldn't this (Score:4, Interesting)
6.4Mhz - Oh Dear. (Score:5, Informative)
Re: (Score:3, Insightful)
while you guys are at it... (Score:5, Funny)
thanks!
signed,
technology historians for the realization of past promises
ps: don't think we've forgotten about those rocket cars mr. popular science!
Theoretically speaking (Score:5, Interesting)
Batteries are highly efficient (Score:3, Informative)
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%).
Yey.. tesla did this, many many years ago (Score:3, Interesting)
The only wireless energy source transmission I've seen so far is with RFID tags. have you ever taken one apart? Chek out the
antennea.. much like the tesla antennea.
April Fools! (Score:4, Informative)
.
I guess truth CAN be stranger than fiction.
.
I, For One... (Score:4, Funny)
Microscopic gods.... (Score:5, Interesting)
Hmmm (Score:3, Funny)
Re:Loss (Score:5, Funny)
that's why you're not a genius.
Parent
Re:Loss (Score:5, Informative)
Parent
Aircraft / Faraday Cage (Score:3, Insightful)
The major savings in transmitted power in an aerospace environment would be in weight of wiring. If your transmitter / receiver assembly and waveguid
Re:Tesla ALREADY did it 100 years ago ? so ? (Score:5, Informative)
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.....
Parent
How it works. (Score:4, Informative)
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?
Parent
Tesla and radios. . . (Score:5, Interesting)
You're not alone. It's amazing how the man who is largely responsible for the use of AC power in our society, (Edison tried to champion DC because AC with all it's complex maths was too difficult to understand!), and the radio, (Marconi basically just used Tesla's insights to deliver a viable product for the war effort in WWI), goes unheralded.
There's a reason for this. Tesla worked in such a way which would have exposed the world to ways of thinking about reality which lead to freedom. --Despite his push for exactly the kind of power distribution system described in this article, such thinking would have eventually led to an understanding that all matter, (including elements of the human nervous system), resonates at specific frequencies. This would have led people to question things like cell phones a little more carefully before accepting them.
I've looked and looked, but I cannot find the reference I originally read many years ago now. . . His discovery of the radio was sparked by an incident where he was instantly aware that his mother who was in another country at the time, had just experienced a severe trauma. This experience is what caused him to think along the lines of sympathetic resonance. The science book people of today don't like guys who talk about such things. Again, it's about withholding freeing knowledge from the populace so that they are more easily controlled.
-FL
Parent
Re: (Score:3, Insightful)
Re:Am I missing the point here... (Score:5, Informative)
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 [wikipedia.org].
Parent
Re: (Score:3, Interesting)
A great deal of Tesla's achievements are apocryphal. There is no real proof about claims of wireless power to motors miles away and other things people attribute to him. In reality he was a clever guy but not this victim of forward thinking/backwards government as his myth protrays him as.
Re: (Score:3, Interesting)
Unlike what Tesla thought about the aether, we now know what RF energy is, how it propagates, and how it stores energy. We have a decent command over a large portion of the spectrum under visible light (400 nm and lower), and we understand that the frequency is linked to the relative energy of the RF.
I once created a 20.5 MHz version of this using a car battery, but since there's soo much energy, filtering is almost pointless. I ended up wipin