Scientists produce wireless electricity

Plugs and cables could become obsolete after scientists devised a way of recharging electrical devices ranging from laptop computers to lights from a distance.

A team from the Massacussetts Institute of Technology made a 60-watt lightbulb glow using electricity sent wirelessly between copper coils set seven feet apart.

Scientists have known for years that electricity can be transferred without wires, but had struggled to find a practical and efficient way of making it work.

Professor Marin Soljacic used the concept of resonance. Energy can be efficiently transferred between objects that resonate at the same frequency, so he used two copper coils, one transmitting and the other receiving power.

The breakthrough, which has been dubbed WiTricity, was announced by the researchers in the online version of the journal Science. They believe they are between three and five years away from developing a system which could recharge laptops, mobile phones and other devices wirelessly. It could also mean some gadgets would no longer need batteries, eliminating the potential for pollution caused by discarded cells.

Professor Soljacic said: "We have promising ideas as to how to achieve this, so now is a good time to start seriously thinking about commercialisation."

However, up to 45 per cent of the transmitted power was lost before it reached the lightbulb, and Professor Soljacic said the system needed to be twice as efficient before it would be as effective as chemical batteries. Also the copper transmitting coils were two feet high, although there was potential for miniaturising them.

He said the project was inspired by his annoyance at being woken up by his mobile phone beeping when he had forgotten to recharge it.