WiTricity and wireless energy trasfer.


by -RA-
Tags: energy, trasfer, wireless, witricity
-RA-
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#1
Nov18-07, 07:34 PM
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WiTricity is the recent name adopted for wireless energy trasfer. I was surprised to see this, as I've been told before this is impossible. As this subject has such strong links to the controversial work of Mr Tesla, i figured it belongs here in the skeptismism part. I dont think it has been verified in any peer reviewed literature, but there certainly does seem to be a lot of people that claim to have done it. Its been reported by a lot of well respected news organizations.


http://news.bbc.co.uk/1/hi/technology/6129460.stm
The tangle of cables and plugs needed to recharge today's electronic gadgets could soon be a thing of the past.

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.

from http://en.wikipedia.org/wiki/WiTricity
Unlike the far field wireless power transfer systems based on traveling EM waves, WiTricity employs near field inductive coupling through magnetic fields, which interact far more weakly with surrounding objects, including biological tissue. It is not known exactly why this technology had not been developed. Researchers attribute it to various reasons ranging from the limitations of well-known physical laws, to simply a lack of need.

http://web.mit.edu/newsoffice/2007/wireless-0607.html
MIT team experimentally demonstrates wireless power transfer, potentially useful for powering laptops, cell phones without cords

Franklin Hadley, Institute for Soldier Nanotechnologies
June 7, 2007

http://www.theaustralian.news.com.au...9-2703,00.html
POWER cables and plugs may soon become obsolete because scientists have developed a way to wirelessly charge electrical devices from a distance.

WiTricity can already power a lightbulb over a distance of 2m, and its inventors believe that within three to five years the system would be able to charge mobile phones, laptops, MP3 players and other electronic devices.



Is this a real effect? Its says that WiTricity is a slightly different mechnism to Tesla's wirless energy transfer. I was told back at uni by my teacher that wirelss energy transfer can never happen as it violates some law of physics (i have forgotten which one, [probably thermodynamics]) and that this effect is another unfounded Tesla conspiracy theory. But it seems that some reputable sources have replicated it. Real?
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waht
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#2
Nov18-07, 08:15 PM
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This technology has always been around. But it's inefficient.

The team at MIT achieved 40% efficiency. They powered a 60 watt light bulb from two meters away. If you calculate the power they put in that equals to 150 watts. Almost to power three 60 watt light bulbs.
-RA-
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Nov18-07, 08:48 PM
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Quote Quote by waht View Post
This technology has always been around. But it's inefficient.
It may be inefficiant compared to other methods, but its strange that it is not in use in any applications in the world if the technology has existed for ages. I would certainly prefer to not have to charge up my phone by plug if there were wireless chargers available. Why is there no scientific literature on it if it has been around for so long?

russ_watters
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Nov18-07, 10:21 PM
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WiTricity and wireless energy trasfer.


"Far field wireless power transfer" is what your radio does. And there are millions of pages of literature about it. Radio has quite a number of important uses, but power transfer itself isn't one of them. The reason is obvious: your local radio station puts out many kilowatts of power and your radio only recieves miliwatts.

"Near field wireless power transfer" is what a transformer does, and there are millions of pages of literature about that too. Since the efficiency isn't very good if you separate the coils, it generally just isn't considered useful to place the coils anywhere but right next to each other.
waht
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#5
Nov18-07, 11:07 PM
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Quote Quote by -RA- View Post
It may be inefficiant compared to other methods, but its strange that it is not in use in any applications in the world if the technology has existed for ages. I would certainly prefer to not have to charge up my phone by plug if there were wireless chargers available. Why is there no scientific literature on it if it has been around for so long?
The only device in wide spread use that uses wireless charging is an electric tooth brush, and sometimes electric shavers. There is no scientific literature because the principles of operation are taught in high school physics classes. The only usefulness is a convenience of placing an object to charge within a couple meters of the wireless base set. Even the team at MIT that achieved an amazing feat of 40% efficiency, still used a narrowed directional field, rather than an omni-directional one which would be even more convenient.
Ivan Seeking
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#6
Nov19-07, 02:11 AM
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One variant of this idea is RFID technology, which has its origins in a famous case of espionage in which the Soviet Union was able to monitor high level discussions at NATO headquarters by means of a gift containing a remotely powered transmitter. This all took place I think in the early sixties, so the technology has been in use for at least that long.
Anticitizen
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#7
Nov24-07, 02:23 AM
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I'd love to be able to place all my gadgets (cell phone, pda, camera, bluetooth headset, whatever) in a bowl or mousepad-sized 'placemat' and have them all charge overnight without having to fumble for proprietary charger cords and finding unused power outlets.
ray b
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#8
Nov25-07, 01:50 PM
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side question
if you live near/under really hi-volt transmission lines
would a backyard coil of wires pick up usefull amounts of power?
what is the legal position of such a rig?
has it been done or tryed?
russ_watters
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#9
Nov25-07, 05:22 PM
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Yes, it could pick up useful amounts of power (so I have heard). It would be illegal. Not sure if it has been tried.
Ivan Seeking
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#10
Nov25-07, 05:40 PM
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It has been tried and done; so I've heard.

IIRC, the power lines are arranged to minimize these losses.


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