Scientists light bulb with “wireless electricity”

June 8 (Xinhuanet) — Scientists may have signaled an end to electric cords and batteries when they lit a 60-watt light bulb from a power source seven feet away without using a physical connection. The researchers have named their concept “WiTricity” as in “wireless electricity.”    MIT physicist Marin Soljacic started thinking years ago about how to transmit power wirelessly so his cell phone could recharge without ever being plugged in.

    The problem with wireless power transmission is that broadcasting energy in all directions can be very wasteful because a vast majority of power ends up being squandered into free space.

    Soljacic and his colleagues devised WiTricity based on resonance. Two objects resonating at the same frequency tend to exchange energy efficiently, while interacting weakly with objects not resonating at the same frequency.

    Instead of sound, the MIT physicists focused on magnetic fields. Most common materials interact only very weakly with magnetic fields, so little power would get wasted on unintended targets.

    “The fact that magnetic fields interact so weakly with biological organisms is also important for safety considerations,” said Soljacic’s colleague, MIT physicist Andre Kurs.

    The scientists designed two copper coils roughly 20 inches in diameter that were specially designed to resonate together. One was attached to the power source, the other to a light bulb. The practical demonstration of their earlier theoretical work managed to power the light bulb even when obstacles blocked direct line of sight between the source and device, findings detailed online June 7 in the journal Science.

    The researchers demonstrated roughly 40 percent efficiency in power transfer. Kurs told LiveScience they are currently working on improving the efficiency of the power transfer as well as the maximum distance allowed.

    “For the moment, we are focusing on power transfers on the order of 100 watts although, in principle, more power could be transferred,” he added.

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