By Gemma Simpson, 8 June 2007 13:31
NEWS
US researchers have produced a system which delivers power to devices without the need for wires.
A team from the Massachusetts Institute of Technology (MIT) lit a 60 watt light bulb from a power source two metres away and with no physical connections between the source and the appliance.
The "WiTricity" device - the term coined by the MIT team to describe the wireless power phenomenon - uses magnetic fields to deliver power to the gadgets remotely.
The charger sends power to the gadget using magnetic induction, which is the ability to change a magnetic field to produce an electrical current.
Wireless from A to Z
Click on the links below to find out moreĀ
A is for Antivirus
B is for Bluetooth
C is for The Cloud
D is for dotMobi
E is for Email
F is for FMC
G is for GPS
H is for HSDPA
I is for i-mode
J is for Japan Air
K is for Korea
L is for LBS
M is for M2M
N is for NFC
O is for Operating systems
P is for Pubs
Q is for QoS
R is for Roaming
S is for Satellite
T is for TV
U is for UMTS
V is for Virgin
W is for WiMax
X is for XDA
Y is for Yucca
Z is for Zigbee
Various methods of transmitting power wirelessly have been known for some time - such as radio waves or wi-fi.
But while such examples are excellent for the wireless transmission of information, it is not feasible for substantial power transmissions because radio waves and wi-fi radiation spread in all directions and vast amounts of power end up being wasted into free space.
In contrast, WiTricity synchronises the charger and gadget to exchange energy efficiently without leaking much power to other objects.
WiTricity does this by getting the charger and power-hungry device to connect using magnetic fields at 'coupled resonant frequencies'.
Imagine a room with 100 identical wine glasses, each filled with wine up to a different level. If an opera singer sings a sufficiently loud single note inside the room, a glass of a corresponding frequency to the singer's warbles might accumulate sufficient energy to explode, while not influencing the other glasses.
The singer and the exploding glass are 'coupled resonators' - and the WiTricity charger is synonymous to the singer, the gadget to the exploding glass.
While the singer uses sound waves to transmit energy to the glass, WiTricity chargers use coupled magnetic fields to charge gadgets remotely.
The MIT team's design consists of two copper coils - one attached to the power source and the other to the gadget - which respectively produce and pick up the magnetic fields.
Speaking in November 2006, Marin Soljacic, assistant professor of physics at MIT, told silicon.com the device has a three to five metre range.
Soljacic added any power-hungry device would need to be fitted with a card, similar to a wi-fi card in a laptop, to receive the signal and start charging.
The coils currently have a radius of around 10 inches. Soljacic said simpler and smaller designs will be created in the future.
The MIT physicists devised the WiTricity system last year and this is the first time a working example has been unveiled.
Comments
There are 14 comments. Join the discussion
1. John Wilson
It certainly sounds interesting, but I reckon there's bound to be a lot of cynicism (myself included) about the practically of flooding areas with high strength magnetic fields.
For example, surely one issue is not how to get the target device resonating with the transmitter, but being sure that other devices don't.
What happens about 'critical risk' situations such as people fitted with pacemakers, etc?
I think we will need a bit more detail on how these real world situations would be affected before we can be sure that this is a practical future technology and not just a bunch of nerds showing off! :)
2. Benjibober
So it's basicaly a tuned and split-transfomer. The idea's been there for ages, nice that they've pulled it off. The question is what frequency does it operate on - isn't there speculation about the damage that stray electromagnetic fields can do to people and animals - sub-stations, overhead pylons, etc etc..........
3. anonymous
Wireless electricity is definitely something worth keeping an eye on.
I wonder what the implications might be for alternative mobile handset power solutions like Mobile Fuel cells.
Ideally with 'Witricity' one would be able to charge his phone while indoors even while using it, keeping in mind the current limited range that it operates within.
This means we may soon live in a charger free world with unlimited access to power for our devices!
Aditya Kaul
Pioneer Consulting
(a.kaul@pioneerconsulting.com)
4. anonymous
It was interesting that they say this is totally safe. Everybody knows what these waves can do to the human body. Do you sit in a seperate room while everything charges?
5. Paul Evans
What is its electrical efficiency?
6. Karen Challinor
"Imagine a room with 100 identical wine glasses, each filled with wine up to a different level. If an opera singer sings a sufficiently loud single note inside the room, a glass of a corresponding frequency to the singer's warbles might accumulate sufficient energy to explode, while not influencing the other glasses"
yes but the singer is still belting a lot of energy into the room and only a small fraction is being absorbed by the resonant glass, the rest is lost
so this generated field, which has to change with time or you can't really extract energy from it with a static coil, does it pump a lot of energy into a given volume of space of which only a fraction of it gets picked up by the resonant receiver coil ?
because basically it's sounding like a transformer system using free space to couple the coils, which isn't a very efficient way of transferring power
so what are the energy loss figures on this system ? as compared to say a copper cable ?
having a contactless way of transferring power does mean the connections will never wear out but they can be replaced, so is this a cost effective to wear and tear on the connections ?
7. anonymous
Just what we need - more electromagnetics filling up the ether.
Add this to the radiation from mobile phone masts, WiFi, WiMax, ATC Radar, and other microwave and high power transmissions and we will all need to be wearing leadlined skull-caps to stop our sensitive brain synapses getting fried!
8. Graham Kerwood
The BBC carried the same story and said the efficiency was 40%. Copper wire, 99.9% What price global warming!
9. D
Interesting ancient technology.
Do a little research on a man named Tesla.
10. Karen Challinor
40%!!!!!
ok they are low wattage devices but 40% is crap, especially when there is existing technology that is not only simpler and cheaper but more efficient
right now it's not a problem as there are only a few out there
when there's a couple of million out there that'll be megawatts of power being thrown away
here's a big bag full of fivers and a match use the match to set light to the money when you are cold, it's very pretty and it keeps you warm for a bit but it's very wasteful
I'm sure there are better analogies but you get the idea
sheesh 40%!
11. anonymous
My electric toothbrush does this already...
... both the battery-filled handset and the charger are completely sealed in plastic, yet it charges without a (physical) electrical connection.
It simply seperates the primary & secondary coils of a transformer by some palstic and air.
Nothing new under the sun...
12. George Dundon
Interesting, has anbody ever looked at a transformer.
If people are scared of electromagnetic radition at milliwatts of power in wifi, just why do we think they will accept power of hundred of watts around their living room. Not to mention the problem if a piece of your favorite jewellery resonates
still it makes good a good news story
13. MusicFan
Guys,
Go on youtube and search for :
"nikola tesla".
He demonstrated the ability for this and more ages ago. Im sure he also found a problem with this.....the human brain operates at the same resonance that is needed to create the field....
Dont think the americans would ever try and utilise this for mind control would they... After all there not interested in a police state are they...
14. Trevor Andrews
Range and/or efficiency will be so low I can't see it being in the mass market .
Solar panels are the answer, the prime energy is already availabe in abundance.