Body Heat Powers Devices

Wednesday, February 22, 2012 @ 02:02 PM gHale

A new technology called Power Felt is a thermoelectric device that converts body heat into an electrical current which soon could create enough energy to make a call just by touching it.

Power Felt consists of tiny carbon nanotubes locked up in flexible plastic fibers and made to feel like fabric. The technology, developed at the Center for Nanotechnology and Molecular Materials at Wake Forest University, uses temperature differences – room temperature versus body temperature – to create a charge.

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“We waste a lot of energy in the form of heat,” said Corey Hewitt, a researcher and Wake Forest graduate student. “For example, recapturing a car’s energy waste could help improve fuel mileage and power the radio, air conditioning or navigation system. Generally, thermoelectrics are an underdeveloped technology for harvesting energy, yet there is so much opportunity.”

Potential uses for Power Felt include lining automobile seats to boost battery power and service electrical needs, insulating pipes or collecting heat under roof tiles to lower gas or electric bills, lining clothing or sports equipment to monitor performance, or wrapping IV or wound sites to better track patients’ medical needs.

“Imagine it in an emergency kit, wrapped around a flashlight, powering a weather radio, charging a prepaid cell phone,” said David Carroll, director of the Center for Nanotechnology and Molecular Materials. “Power Felt could provide relief during power outages or accidents.”

Cost has prevented thermoelectrics from wider usage in consumer products. Standard thermoelectric devices use a much more efficient compound called bismuth telluride to turn heat into power in products including mobile refrigerators and CPU coolers, but researchers said it can cost $1,000 per kilogram. Like silicon, they liken Power Felt’s affordability to demand in volume and think someday it could cost only $1 to add to a cell phone cover.

Currently, 72 stacked layers in the fabric yield about 140 nanowatts of power. The team is evaluating several ways to add more nanotube layers and make them even thinner to boost the power output.

There is more work to do before Power Felt is ready for market. “I imagine being able to make a jacket with a completely thermoelectric inside liner that gathers warmth from body heat, while the exterior remains cold from the outside temperature,” Hewitt said. “If the Power Felt is efficient enough, you could potentially power an iPod, which would be great for distance runners. It’s definitely within reach.”

Wake Forest is in talks with investors to produce Power Felt commercially.