WiTricity - Power Without Wires
Even in the 1800s, electricity-obsessed physicist Nikolai Tesla proposed that electricity could be transmitted distances through the air. A fictional account of which is depicted in the 2006 film The Prestige, in which Tesla is played by David Bowie.
And, of course, Tesla was right as far as it goes. Electromagnetic fields contain power which can be used to induce electrical power inside electronic devices - a process known as induction.
In fact, many generators function through induction - by rotating large magnets inside solenoids (cylinders of densely wound conducting wires), thus generating electrical currents. Transformers use close-range induction to transfer power within them, as well.
I was once shown a flashlight that contained a movable magnet inside of a solenoid. I think they're fairly common now, but I don't have one yet. Shaking the flashlight causes the magnet to move, which induces an electrical current in the flashlight. Presumably some sort of capacitor system allows the flashlight to retain the current, slowly releasing it as you use the flashlight. When the light begins to dim, you just shake the flashlight again to charge it back up.
Of course, there are several problems with using this sort of induction for regular power distribution, such as in your home. Aside from logistical problems of magnetic power or solenoid wire density, the power is radiated outward in all directions, causing the loss of much of the energy. Also, this could be potentially harmful to humans (imagine the scares about living near power lines or cell phones giving brain cancer significantly increased), but it could definitely wreak havoc with nearby electrical systems. A field powerful enough to run your computer could cause your telephone to short out, to choose a random (and non-scientifically/mathematically confirmed) example, if not your pacemaker!
The question of how to have induction-like effects without actually irradiating an area with a powerful EM field had never really been considered until MIT physicist Marin Soljacic (apologies for missing out on some accents due to formatting issues) set to work on it. In a November 2006 paper in Annals of Physics, "Efficient wireless non-radiative mid-range energy transfer (which is explained for laymen in this press release), he set out the theoretical framework, supported by computer models, for a system in which a "non-radiative" magnetic field would be created that would only be "picked up" by electronic devices specially designed to "resonate" with that field.
In the theoretical paper, they predict a possible range of a couple of meters. And, in fact, that is just what they did - about a month ago, they were able to power a 60 Watt light bulb from a power source 7 feet (just over 2 meters) away! The efficiency of the energy transfer was approximately 40%, fitting the theoretical model predictions to within 5% (generally a 10% agreement on such things is still considered successful).
Related Articles:
- Science Journal - abstract of "Wireless Power Transfer via Strongly Coupled Magnetic Resonances" (subscription or Science Pay per Article required for the full paper)
- MIT News Office (press release) - Goodbye wires...
- Marin Soljacic, Ph.D., MIT project lead: Wireless Power Transfer - WiTricity
- National Academy of Engineering of the National Academies, WTOP Radio report (brief, but link to audio) - Wireless Power
- PC World - MIT Researchers Complete Wireless Electricity Test
- ABC Radio, Australia interview - American bright sparks invent wireless power
Comments
This is a very poorly written article. The writers choice of words is almost an obvious deception for people to be led to believe he is “edumacated” (in his terms as engineers would view his article) on the following matter… reads like a children’s book to actual real engineers. Quite pathetic.
Nick, thank you for your comments. If there is a factual error in the article, I urge you to either let me know here or by e-mail at physics.guide@about.com. I do apologize for the lack of technical precision in the article. I am not an engineer, and my “edumacation” is in physics, not engineering. Though I studied electromagnetic theory in college, I do confess that I haven’t had an actual electronics class since high school, so I may have gotten some technical aspect of the article incorrect … it’s certainly possible, and I welcome any such corrections that are sent my way.
As for reading as a “children’s book,” I consider that somewhat of a compliment, though it clearly wasn’t intended that way. About.com has to service a wide readership range, and the Physics site is in the Education section, which means that much of our traffic may well be students who are not necessarily familiar with scientific terminology such as induction and solenoid, and that is why terms like that must be explained. It is a tough balancing act, since I know we also get people who are far more familiar with a given topic than I may be … but those people clearly don’t need me to explain it in the same fashion that those unfamiliar with it might.
Again, if there is a factual problem in this or future articles, I would encourage you to clearly point them out so that I can fix them as soon as possible.
Thanks,
Andrew
You told him! I actually found it very interesting, being a fairy “edumacated” person myself. I hope to see this technology in use soon!
Well put Andrew, Personally as a student of physics I found that article to be quite interesting.
All i have to say is this really, for people trying to get into physics and for young children searching the web for relevant topics in physics. It would be rather crule and unusual to use heavy terminalogies to over complicate matters.
As for pathetic, I’d say that pointing something out in that fasion Isn’t exactly wise is it? Nor cleaver or big.
As for the implications for this technology, this could mean alot of changes within the civil engineering sector, which I personally look forwar to.
Roo
This article is of really poor quality, with factual errors and disjointed ideas.
I think the level of science at ‘about.com’ is fab. I’m a science teacher and have had some novel ideas about lessons using your website – many of my colleagues use them. As a source of information you are brilliant and as a source of images for lessons stupendous – I particulary like your “overloaded vehicles” gallery – always good to start a lesson on forces with!