Physics promises wireless power
By Jonathan Fildes
Science and technology reporter, BBC News


Plugs and wires could soon become a thing of the past
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.

Although the team has not built and tested a system, computer models and mathematics suggest it will work.

"There are so many autonomous devices such as cell phones and laptops that have emerged in the last few years," said Assistant Professor Marin Soljacic from the Massachusetts Institute of Technology and one of the researchers behind the work.

"We started thinking, 'it would be really convenient if you didn't have to recharge these things'.

"And because we're physicists we asked, 'what kind of physical phenomenon can we use to do this wireless energy transfer?'."


How wireless energy could work
The answer the team came up with was "resonance", a phenomenon that causes an object to vibrate when energy of a certain frequency is applied.



This would work in a room let's say but you could adapt it to work in a factory
Marin Soljacic

"When you have two resonant objects of the same frequency they tend to couple very strongly," Professor Soljacic told the BBC News website.

Resonance can be seen in musical instruments for example.

"When you play a tune on one, then another instrument with the same acoustic resonance will pick up that tune, it will visibly vibrate," he said.

Instead of using acoustic vibrations, the team's system exploits the resonance of electromagnetic waves. Electromagnetic radiation includes radio waves, infrared and X-rays.

Typically, systems that use electromagnetic radiation, such as radio antennas, are not suitable for the efficient transfer of energy because they scatter energy in all directions, wasting large amounts of it into free space.

To overcome this problem, the team investigated a special class of "non-radiative" objects with so-called "long-lived resonances".

When energy is applied to these objects it remains bound to them, rather than escaping to space. "Tails" of energy, which can be many metres long, flicker over the surface.

"If you bring another resonant object with the same frequency close enough to these tails then it turns out that the energy can tunnel from one object to another," said Professor Soljacic.


Wireless energy transfer has been thought about for centuries

Hence, a simple copper antenna designed to have long-lived resonance could transfer energy to a laptop with its own antenna resonating at the same frequency. The computer would be truly wireless.

Any energy not diverted into a gadget or appliance is simply reabsorbed.

The systems that the team have described would be able to transfer energy over three to five metres.

"This would work in a room let's say but you could adapt it to work in a factory," he said.

"You could also scale it down to the microscopic or nanoscopic world."

Old technology

The team from MIT is not the first group to suggest wireless energy transfer.

Nineteenth-century physicist and engineer Nikola Tesla experimented with long-range wireless 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.




Wireless power for gadgets

Others have worked on highly directional mechanisms of energy transfer such as lasers.

However, these require an uninterrupted line of sight, and are therefore not good for powering objects around the home.

A UK company called Splashpower has also designed wireless recharging pads onto which gadget lovers can directly place their phones and MP3 players to recharge them.

The pads use electromagnetic induction to charge devices, the same process used to charge electric toothbrushes.

One of the co-founders of Splashpower, James Hay, said the MIT work was "clearly at an early stage" but "interesting for the future".

"Consumers desire a simple universal solution that frees them from the hassles of plug-in chargers and adaptors," he said.

"Wireless power technology has the potential to deliver on all of these needs."

However, Mr Hay said that transferring the power was only part of the solution.

"There are a number of other aspects that need to be addressed to ensure efficient conversion of power to a form useful to input to devices."

Professor Soljacic will present the work at the American Institute of Physics Industrial Physics Forum in San Francisco on 14 November.

The work was done in collaboration with his colleagues Aristeidis Karalis and John Joannopoulos.

I saw that article today in the paper. There is nothing new in it. N. Tesla had the same idea around 100 or so years ago. It has never worked although it can work in a lab type experiment. It has many practical problems and not the least of which is potential health problems associated with electromagnetic radiation. I would not want that flying around my home just to save plugging something in. His statements about tuned resonance are as old as the hills. There are chargers today that you just set the unit in it and it works by induction, another term for what the article talks about. It works best close up and trying to saturate the area of a house let alone the outdoors is just not feasible. I'd be glad to discuss it at greater length if anyone is interested.

It seems feasible to me... Couldn't one look at lightning as a natural example of induction (energy is transfered across great distances from clouds to the earth)? I mean sure this is not the same as resonance, but to dismiss the idea of wireless power altogether is just rediculous. If there is even remote potential it is worth the reasearch. Remember, there was a point in time when people though the earth was flat...

Its definately worth the research, but I feel there are probably problems associated with the frequency laden air within our current lives that are being hidden because of profit margins (radio, TV, mobile phones, microwaves). Adding yet more invisible waves into our lives, especially power, is something I think we could do without.

trojan_libido, I believe you are correct. There is still controversy about the health effects of electromagnetic radiation. There was a scare over that about 15 or 20 years ago that may have been overstated. But, problems have been observed and I do not want this radiation going through my home in high levels. Cops who used hand held radar guns began to notice a high level of cancers compared with cops who used the guns mounted on top of their cars and were not exposed to the radiation. The level or power of the radiation makes a big difference. To power devices takes much more energy than just communicating on a cell phone.



No, lightning is not an example of induction. Lightning is actual electricity that is of such high voltage that it breaks down the resistance of air and travels to earth. Induction involves electric and magnetic fields which are invisible normally, not actual flows of electricity. The flow of electricity through a wire creates these fields around it which is different from the electricity itself. A cell phone gives off a higher frequency of radiation that we can pick up on receivers. A cell phone does not make electricity flow through the air the way lightning does.

Any time you are dealing with electricity, magnetism is involved... Lightning produces extremely powerful magnetic fields, just like running a current through a wire produces a magnetic field in concentric circles. Next time there is a lightning storm go outside with a compas. Lightning is a form of energy transfer. It is not resinant energy transfer persay, but from the definitions of electrostatic induction that I was taught it seems to fit~

Flex, it's certainly true that lightning or any electrical flow produces magnetism. However, lightning is not caused by induction. Examples of induction are in the way a transformer works. Putting any two coils near each other and running an ac current through one of them will cause a current to be produced in the second coil if it's close enough. Lightning is caused by a build up of static charges produced by friction between clouds and air and water molecules. The charge builds up until it gets so high it discharges and goes to another cloud or to earth.



That's true



Resonant circuits are those which are tuned to a certain frequency. Examples of those are found in radios and other communications devices. They work by electromagnetic induction. The antenna picks up the EM radiation such as radio waves and the tuned circuit picks out the channel you want. Lightning is the same as when you shuffle your feet across the carpet and then get a spark and a shock when you touch metal. I hope this helps.

Just a reminder, lightning isnt electricity, its plasma... the so called forth state of matter. Although they may seem similar, there are important diffrences to remember.

What technically is plasma? I know there is plasma welding which is just welding at a rediculous temperature--what classifies the state plasma? Lightning may be plasma, but like you said plasma is a STATE of matter, I don't see what that has to do with electricity except that plasmas react to magnetic fields.

You could say that lightning is plasma but it is also electricity. A simple high voltage arc from a neon sign transformer or other source will be a form of plasma produced by electricity. Plasma is simply a gas that has become ionized. I'm sure there is a more rigorous definition.

What I objected to was statements like this in the article



The writer made it sound like some new discovery had been made and that is not the case or at least no one is talking about it. It sounds like the guy who usually wrote the sports collumn decided to do a science article based on some statement by students at a university.



Ho hum. Let me know when you have something.

Yea when a gas becomes ionized it produces plasma. Plasma conducts electricity and can be influenced by magnetic fields, ionization can occur from heat, dependant on the gas. Atoms and molecules are converted into Ions, which then form plasma.

Whats the relevance to lightning being plasma instead of just electricity? Physics



Its heating up the gas to a high enough temperature to convert the atoms to ions, which produces plasma. I think your talking about quasineutrality, apparently electron densities in lightning can get very high, allowing for strong electrical charges. Lightning is not electricity, it can contain electricity, conduct it and amplify it, but it is not pure electricity.

Plasma has a horde of properties which are too many to list, lightning is more complex than what first appears.

Interesting...So lightning is created by static electricity, but the concentration of electrons is so great that the atoms become ions and thus are no longer electricity, but plasma? And what the hell state of mater is electricity--a solid, or is it not even mater to begin with but just energy? Sorry for all of my stupid questions, it isn't fair to make you all fill in the vast gaps that are left behind from a public school education

No your off base.

Lightning is not created by static electricity, its plasma and created by ionization.

Plasma like many metals can CONDUCT electricity.

Electricity is electrons.

Electrons can be in any state of matter; solid, liquid, gas or plasma.

Electrons become concentrated in plasma AFTER the matter has been converted into plasma, not before. The reason is because plasma is a very good electrical conductor and gases usually arent.

Go read about ionization Flex.

How Lightning Works~

Alrighty I am no longer an idiot (well I guess I am but less so)

but it still seems like the ionization is caused by static? "Static electricity occurs when there are an excess of positive (+) or negative (-) charges on an object's surface. This condition is caused from rubbing certain materials together."

Do you see someone rubbing balloons together in the sky?? Go see if you can make plasma with static electricity. Howver, you CAN create plasma in your microwave (hehehe) using only a single grape, but it may cause some damage to your microwave and lots of pretty colors.

Ionization is mainly caused by heat, also the ionsphere surrounding the earth can be responsible for distribution of excess ions which can allow for them to combine together to form plasma in the air, like during a storm.

You are not stupid, prehaps naive and lacking knowlege in this field yes. Stupidity implies low IQ score and general lack of cognitive health

As far as microwaves are concerned, take a rubber eraser and stick a match in it. Then strike the match and let is burn in the microwave. When you turn that bad boy on you will get a pretty cool show Or just throw a christmas ornament in the microwave that is really entertaining too~

I highly recomend going to the thrift store and getting urself a crappy microwave to do some of these click here

heh, why do I suddenly wonder if BrainMeta is just a bunch of mad scientists and philosophers?

maximus, you make many statements I could agree with but some of your reasoning brings it close to the area of philosophy.



That I certainly would agree with but it is caused by a flow of electricity. You can say lightning is just the plasma because you can see the glowing atoms in the plasma but can't see the electricity itself.



Here I believe you are simply mistaken. Lightning is indeed caused by electricity and that electricity is produced by friction between molecules in the clouds and sky. This is often called static electricity or static charge. Electricity is the movement of electrons. The individual electrons do not move very fast, it's the force that moves fast. It's sort of like a wave moving across a pond. The wave can be powerful and move fast but the water molecules move very little. The charges build up in the clouds until they reach a certain point and have to be released. This causes a plasma arc as you pointed out.

Yeah that is what I was saying, static energy transfer causes the ionization.

You point out one way, but not all ways in which plasma can be created. I have extensivly researched the use of lasers to create plasma by heating the air molecules to approx 2400 degrees which turns from a gas into plasma. Japanese scientists have already successfully created plasma through the use of a high powered laser which heats up molecules in mid air by first refracting the beam and then refocusing the beam at a single point in space, causing the release of ions and the formation of plasma. I am fully aware of electrons role in plasma, however plasma is a state of matter it is not simply electricity as people were first made to believe. It IS matter, which like all forms of matter, it is capable of having electons. In my original post, my intention was to simply point that out.

When I say lightning is more complex than first appears, I am not being philosophical. Lightning causes emmisions on various levels of the electromagnetic spectrum, lightning also causes the release of x-rays and microwaves, as well as light and high sources of heat.

Lightning IS plasma, im not just saying so. Electricity is electrons in motion, Plasma is a more complex form of matter than its three counterparts. All lightning is in the state of matter known as Plasma, its like saying air is a gas, its just a plain and simple fact. I know how static charges work and how they are released, Plasma is a much better conductor of electricity than gas, which is why it is able to produce such high voltages. Plasma is also more readily visible, where as gases are not so readily visible, thus the term "LIGHTning".

When I said lightning is caused by ionization I meant it, your not reading between the lines. Ionization can be caused by static electricity, but without the occurance of ionization, plasma does not form and since all lightning is plasma, no ionization, no lightning. IONIZATION IN LIGHTNING IS CAUSED BY ATMOSPHERIC PRESSURE. So Atmospheric Pressure - Ionization - Lightning. I continously tried to point out Plasma is made by Ionization and that ionization is connected with the ionsphere, which I already stated. If we are talking on a universal scale (I was talking about ionization not lightning), the majority of the plasma which makes up the universe can be traced to sources other than atmospheric discharge or static electricity.

When I responded to Flexs post, I was more or less thinking he was saying static electricity caused lightning or ionization in lightning - where I knew its caused by atmospheric pressure. Now, if we break this down to a Quantum scale, the universe contains massive amounts of plasma, most of which is not by static electricity.

Why do I feel like im constantly having to teach high school science on this forum?

http://amasci.com/miscon/speed.html

Well it looks like I did my fair share of pissing people off in this one. Thanks for the help Maximus~

(one down code buttons )

Meh im not mad at you Flex, you have just got to learn how to understand what is being said. When I say something I usually mean it, if im wrong I usually admit it, especially with the senior members because they will berate you until you do lol. So you should note ive been on brainmeta for a while and when I am right I will damn well fight to prove it.

I kept modifying and remodifying my post, so reread if it looks diffrent to you.

I did make an effort to inform you that static electricity is not the cause of ionization in lightning, you were on the right track with how ionization occurs in the air, but I didnt get a chance to give a thorough explanation on lightning until now.

Sigh* my head hurts, to much talk about lightning, time for some philosophy prehaps (grins).

P.S. Dont take my post personally Xandu, ive had 4 hours of sleep and just worked out at the gym for 3 1/2 hours, im grumpy, hungry, tired and have a headache. So, im not mad, just in a general pissed off mood and it comes through in my posts lol