Wireless Power Transmission: Tesla Revisited

In the late 19th century, Nikola Tesla, among other inventions, dreamed up wireless electric distribution. He drew up plans for a tower, about 57 meters tall, that he claimed would transmit power to kilometers away. However, he run out of funding before he could finish towers.

Then, a few years ago, Marin Soljačić, an assistant professor of physics at MIT started searching for ways to transmit power wirelessly. Instead of pursuing a long-distance scheme like Tesla's, he decided to look for midrange power transmission methods that could charge--or even power--portabl­e devices such as cell phones, PDAs, and laptops.

So far, the most effective setup consists of 60-centimeter copper coils and a 10-megahertz magnetic field; this transfers power over a distance of two meters with about 50 percent efficiency. The team is looking at silver and other materials to decrease coil size and boost efficiency. "While ideally it would be nice to have efficiencies at 100 percent, realistically, 70 to 80 percent could be possible for a typical application," says Soljačić.

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