Wireless power transfer is an idea that’s more than 100 years old. In the 1890s, physicist and electrical engineer Nikola Tesla proposed beaming electricity through the air. However, soon thereafter, power cables became the commonly accepted means of transporting electricity across distances. But with the widespread adoption of small, portable devices with batteries in need of constant recharging, people’s attention is again turning to wireless power. In fact, the startup Powercast, based in Ligonier, PA, has, using a different approach from that of the MIT team, developed a wireless power system that can transmit low wattages across a distance of about a meter. To start, the company is targeting devices with low power consumption, such as sensors, but it’s hoping to ramp up to more power-hungry gadgets in the future.
One concern that people might have, says Sir John Pendry, professor of physics at Imperial College in London, is health effects. “There will be safety issues, real or imagined,” he says. “After all, the power has to pass through space in some form or other, and pass through any bodies lying in its path. The [MIT] team has minimized this problem by making sure that the power is mainly in the form of a magnetic field, a form of energy to which the body is almost entirely insensitive.”
Based on calculations, Soljačić believes that the scheme is safe, even for people with implanted medical devices, such as pacemakers. Although the researchers have not made a detailed study to test how the system interferes with pacemakers, Soljačić says that they don’t expect it to interact strongly with objects that don’t resonate at the same frequencies used to transfer power.
At this point, the team has applied for a number of patents and is planning to commercialize the technology, although the researchers expect that it could take a few years before devices with such wireless power systems will make it to consumers. In the meantime, the team is exploring different materials and alternate coil geometries to try to extend the range and ramp up the power.
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