today's WSJ: Scientists Demonstrate "Wireless" Electricity
By WILLIAM M. BULKELEY CAMBRIDGE, Mass. -- A 60-watt light bulb that glows even though it's not wired to any power source could pave the way for wireless recharging of cellphone batteries and operation of mobile robots, scientists reported. A team of Massachusetts Institute of Technology researchers reported in Science Express, the online publication of the journal Science, that they had demonstrated wireless transmission of electric power by magnetically coupled resonators. They dubbed their technology "WiTricity" for wireless electricity. Marin Soljacic, the physics professor who led the team, said that the technology is sufficiently proved that "now is a good time to start thinking about commercializing it." He said that while further development is needed to improve efficiency, he thinks commercial products could be on a sale in "a few years, if you started working very seriously." He said MIT would handle licensing of the technology. While wireless transmission of electricity over radio waves is well known, it is very inefficient because most of the power is dissipated in directions other than the device that needs the power. Mr. Soljacic's team theorized that two copper coils tuned to resonate in identical magnetic fields would assure that the power was used only where it was needed. Physicists know that resonant objects interact only with objects on the same resonance. For example, when an opera singer holds a note in a room filled with wine glasses filled to different levels, only one glass, which resonates with that note, is likely to shatter. The researcher's technology uses a copper coil, attached to a power outlet to transmit electro-magnetic waves at set frequencies. A receiving coil attached to the base of the light bulb, can receive the power for a distance up to seven feet, making it appropriate for rooms. Mr. Soljacic, a 33-year-old who came to MIT after graduating from high school in his native Croatia, said he thinks manufacturers could include such coils in battery-powered devices such as laptop computers to make automated, wireless recharging possible. He said he started considering the problem several years ago because he kept being awakened in the night by the sound of his cellphone beeping because its battery was getting low and he had forgotten to put it on its charger. The technology doesn't work over long distances, but it functions well within average sized rooms in homes, he said. That might make it possible to build wireless devices that don't require batteries. He noted that many devices such as robot vacuum cleaners and laptop computers run on less energy than the light bulb his team lit up.
