Wireless Power


By Tom R. Halfhill

Thanks to technologies like Wi-Fi, Bluetooth, and cellular telephony, more networks and consumer electronics are going wireless. It’s great to be liberated from cumbersome wires and cables, enjoying the freedom to communicate from almost anywhere. Wouldn’t it be even better if our wireless gizmos could be powered wirelessly?

Think of it: no more power cords, wall warts, batteries, or chargers. It’s an age-old dream. Electronics pioneer Nikola Tesla experimented with wireless power transmission in the 1800s. Today, RFID chips power themselves using energy beamed from their wireless readers. I have a science-fiction novel from the 1930s that envisions airliners in 1980 powered by “wireless ray.”

Unfortunately, 1980 has come and gone without wireless electric airplanes. The problem with wireless power transmission is that beaming that much energy through the air would cook anything in its path. So researchers are working on another approach that also intrigued Tesla: ambient power generation. The idea is to generate power where it’s needed by exploiting environmental energy sources.

Solar cells are the best-known example of this technology. The most interesting research, however, taps other ambient energy sources, such as background vibrations, temperature changes, and human motion. The blanket term for this technology is “energy harvesting” or “parasitic power.”

For instance, a company called EnOcean makes self-powered wireless network nodes for industrial applications. One clever device is a wireless light switch. Flipping the switch uses your finger’s kinetic energy to generate a tiny surge of electricity—just enough to power a tiny radio that transmits an on-or-off signal to the light bulb. The bulb still needs line power, but the switches are wireless and can be located anywhere and moved anytime.

Other power harvesters generate electricity by absorbing vibrations from factory equipment, vehicles, or ships, or by leveraging temperature changes in the air or water. The University of Pennsylvania invented a backpack that generates a surprising amount of power from the wearer’s normal gait. Others are working on power-generating shoes and solar-cell clothing.

Power harvesting won’t keep your hungry notebook computer running without batteries any time soon. But smaller devices like MP3 players, wireless headsets, remote sensors, and even cellphones could be powered this way—and it’s not science fiction any more.

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