San Francisco (CA) - We have cut the phone cord, we have eliminated the need for a cable when connecting notebooks to the Internet and we use wireless headsets. But while audio and data transmissions through the air have become normal in recent years, we still need to carry around cables to recharge our portable devices. New research now indicates that even power may go wireless soon.
Forgetting to recharge that cellphone at night or forgetting the power cable for your notebook or iPod on a business trip are annoyances we have learned to live with. But it appears that researchers from the Department of Physics and Research Laboratory of Electronics at the Massachusetts Institute of Technology (MIT) have found a way to recharge mobile devices wirelessly.
Wireless transfer of energy is nothing new. It has been known in the form of electromagnetic induction, which was discovered by Michael Faraday in 1831. The effect of current in an emitting coil can induce another current in a receiving coil is used today in a wide variety of electric devices, including induction motors. However, electromagnetic radiation is considered to be a very inefficient way to transfer power, as its direction cannot be controlled. Magnetic waves spread in all directions, which means that most of the energy to be lost.
But MIT researcher Marin Soljacic believes that this characteristic of induction, if used right, can transfer energy over longer distances within an electromagnetic field. Instead of covering the environment with electromagnetic waves, "a power transmitter would fill the space around it with a non-radiative electromagnetic field," he said. In fact, he projects that the field can be fine-tuned so only specific devices will pick up the energy. Most energy that is not picked up could be "reabsorbed by the emitter."
"It certainly was not clear or obvious to us in the beginning how well it could actually work, given the constraints of available materials, extraneous environmental objects, and so on. It was even less clear to us which designs would work best," Soljacic said in a prepared statement.
While actual wireless chargers have not been built, Soljacic noted that notebooks one day could recharged within a few meters of the power source. At least theoretically, placing one source in each room, would mean that many wired power sources could become things of the past.