Intel's Wireless Power Play

A research project cuts the electric cord, wirelessly charging an electronic device.

Last Thursday, Intel researchers demonstrated 45 research projects, ranging from ray-tracing algorithms for better animation to organic photovoltaics for flexible solar cells, at the Computer History Museum, in Mountain View, CA. But the project that received the most attention by far was the demo of a wirelessly charged iPod speaker. The speaker was attached to a copper coil with a 30-centimeter diameter, and it was powered by magnetic fields produced from a second coil, with double the diameter, nearly a meter away.

Resonant rings: The speaker in the center of this coil is wirelessly powered by the magnetic field produced by another, larger coil (not pictured) plugged into a power supply about a meter away. Credit: Kate Greene

Intel's wireless power project, first announced at the company's developer forum last August, bears a strong resemblance to a project announced by researchers at MIT in 2007, which was featured as one of the TR10 top emerging technologies of 2008. Similar to the MIT project led by Marin Soljacic and the prototypes developed by the spinoff startup WiTricity, the Intel project uses magnetic fields to transfer energy; the type of radiation shared between the two coils is nonradiative, which means that it's confined to a short distance of less than two meters.

The idea of wireless power transfer is, of course, not new. Physicist Nikola Tesla proposed it in the late 19th century. However, funding for his projects ran out at about the same time that the modern world decided to take a wired approach. And for more than a century, wires have done the job well enough. But with the advent of portable electronics that seem to need constant charging, wireless electricity is coming back in style, and researchers are exploring ways to make it practical. In addition, plug-in electric vehicles are another motivating factor, as plugging in a car (or forgetting to plug one in) is a burden that consumers may not want to bear.

The modern approach that WiTricity and Intel are taking makes use of the phenomenon called resonant coupling, in which objects can exchange energy with each other only when they are tuned to, or resonate at, the same frequency. Specifically, both groups are using magnetic fields for sharing energy because such fields have little known impact on the environment and on people's health, compared with electrical fields.

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For the Intel project, the large coil was hooked up to electronics that produced a current oscillating at seven megahertz. The receiving coil was tuned to the same frequency, and thus is able to accept an energy transfer with about 80 percent efficiency within a range of about a meter, says Josh Smith, the lead researcher on the project. Smith notes that the project is still in its early stages, but he and his team are interested in how the technology could be incorporated into Intel products, such as laptops or other portable devices. "We're building on [what the MIT researchers] demonstrated in 2007 and extending it in different ways," he says. He adds that this team is working on a paper that will expound on the details later this year, and that Intel doesn't have a timeline for products.