"Power Felt" Charges Your Cellphone Using Your Body Heat

By Lori Zimmer, 02/24/12 - No need to stay tethered to an electrical outlet or worry about your cellphone running out of juice; charging your smart device could soon require no more than a quick jog on the spot, according to Wake Forest University scientists, who have developed a thermoelectric device that converts body heat into an electrical current. Dubbed “Power Felt,” the technology uses temperature differences—that of the room versus your body, say—to create a charge. The best part? A cellphone cover could cost as little as a buck.

Power Felt works its magic by harnessing what’s known as the “Seebeck effect,” the conversion of temperature fluctuations into electricity and vice versa. Composed of tiny carbon nanotubes encased in flexible plastic fibers, the material is designed to look and feel like fabric. Potential innovations, researchers note, include automobile seats that boost battery power, pipe and roof insulation for lowering gas or electric bills, high-tech clothing or sports gear to monitor athletic performance, and “smart” bandages that track patients’ medical needs.

Power Felt works its magic by harnessing what’s known as the “Seebeck effect,” the conversion of temperature fluctuations into electricity.

“Imagine it in an emergency kit, wrapped around a flashlight, powering a weather radio, charging a prepaid cellphone,” says David Carroll, director at the school’s Center for Nanotechnology and Molecular Materials. “Power Felt could provide relief during power outages or accidents.”

Current thermoelectric devices, found in mobile refrigerators and CPU coolers, use a more efficient compound known as bismuth telluride, but researchers say it can cost up to $1,000 per kilogram. Power Felt promises to be more affordable, particularly if demand drums up sufficient volume.

“We waste a lot of energy in the form of heat,” says researcher and Wake Forest graduate student Corey Hewitt. “Generally thermoelectrics are an underdeveloped technology for harvesting energy, yet there is so much opportunity.” Hewitt envisions a jacket that mines body heat through its lining while the exterior remains cold from outside temperatures. “If the Power Felt is efficient enough, you could potentially power an iPod, which would be great for distance runners,” he adds. “It’s definitely within reach.”

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