The end of the plug? Scientists invent wireless device that beams electricity through your homeby DAVID DERBYSHIRE
Jun. 09, 2007
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Scientists have sounded the death knell for the plug and power lead.
In a breakthrough that sounds like something out of Star Trek, they have discovered a way of 'beaming' power across a room into a light bulb, mobile phone or laptop computer without wires or cables.
In the first successful trial of its kind, the team was able to illuminate a 60-watt light bulb 7ft away.
The team from Massachusetts Institute of Technology, who call their invention 'WiTricity', believe it could change the way we use electricity and do away with the tangle of cables, plugs and chargers that clutter modern homes.
It could also allow the use of laptops and mobile phones without batteries.
The inspiration came when the lead researcher, Dr Marin Soljacic, was standing in his kitchen at night staring at his mobile phone.
"It was probably the sixth time that month that I was awakened by my cell phone beeping to let me know that I had forgotten to charge it. It occurred to me that it would be so great if the thing took care of its own charging," he said.
To turn this dream into reality, Dr Soljacic needed a way of transmitting power wirelessly.
Scientists have known for nearly two centuries that it is possible to transfer an electrical current from one coil of wire to another without them touching.
The phenomenon, called electromagnetic induction, is used in power transformers and electric motors around the world.
However, the coils in motors and transformers have to be close for power to pass from one to another. Attempting to transfer power over distances is impossible.
The breakthrough came when Dr Soljacic realised there was another way of transferring energy through the air.
Rather than sending power from a transmitter to a receiver as a conventional electromagnetic wave - the same form of radiation as light, radio waves and microwaves - he could use the transmitter to fill a room with a 'non-radiative' electromagnetic field.
Most objects in the room - such as people, desks and carpets - would be unaffected by the electromagnetic field. But any objects designed to resonate with the electromagnetic field would absorb the energy.
It sounds complicated, but the result demonstrated by the American team this month was a dramatic success. Using two coils of copper, the team transmitted power 7ft through the air to a light bulb, which lit up instantly.
The scientists say the technique works only over distances of up to 9ft. However, they believe it could be used to charge up a battery within a few yards of the power source connected to a receiving coil.
Placing one source in each room could provide enough power for an entire house.
The receiver and transmitter would not have to be in view of each other.
Professor Peter Fisher, another of the researchers, said: "As long as the laptop is in a room equipped with a source of wireless power, it would charge automatically without having to be plugged in. In fact, it would not even need a battery to operate inside such a room."
The researchers believe there is little to worry about on safety grounds, saying that magnetic fields interact weakly with living organisms and are unlikely to have any serious side effects.
Dr Soljacic said: "When my son was about three years old, we visited his grandparents' house. They had a 20-year-old phone and my son picked up the handset asking, 'Dad, why is this phone attached with a cord to the wall?' That is the mindset of a child growing up in a wireless world.
"Hopefully we will be getting rid of some more wires and batteries soon."