Technology  »   Wireless data connections are common—now scientists are working on wireless power

Wish you didn’t have to plug in your laptop and cellphone? A team of researchers from MIT may have just the thing for you. Yesterday, at the American Institute of Physics’ Industrial Physics Forum in San Francisco, Marin Soljacic, Aristeidis Karalis, and J.D. Joannopoulos described a scheme that would let devices get their power the same way they get their data: through the air.

Of course, transferring energy wirelessly is nothing new in itself. Electricity is routinely transferred in this way in transformers using induction; radio frequency identification chips are energized by radio waves emitted from RFID readers; and for years, researchers have worked on transferring energy over long distances using microwaves. But there are obvious limits. Although a lot of power can be passed through a transformer, the energy typically can be transmitted only a few millimeters inside the transformer. RFID readers do have a longer range, but little power can be transmitted to the chips. Microwave systems can transmit fair amounts of power over long distances, but they are bulky and have to use a tightly focused beam that must be precisely pointed at the receiver to keep the energy from being hopelessly dissipated.

Although it’s only a theoretical analysis, what’s important about the MIT team’s work is that it could open the door to transmitting enough energy to power electronic devices efficiently over a middle range—several meters—without having to worry about exactly where the receiver is in relation to the transmitter.

To understand how the MIT idea works, we first have to look at how a regular omnidirectional radio transmitter works. Electrical energy is pumped into such a transmitter, and the energy is then carried away by radio waves that radiate in every direction. So the amount of energy that can be picked up by a receiver located at any given point away from the transmitter’s antenna is only a fraction of the total amount of energy being put into the transmitter.

Complete Article:

http://spectrum.ieee.org/nov06/4735