Using Body Heat to Recharge Cellphone, Laptop

Wake Forest graduate student Corey Hewitt holds a piece of Power Felt developed in the Center for Nanotechnology and Molecular Materials. (Photo: Wake Forest University)

Imagine being able to use your own body heat to recharge your phone or tablet.

Scientists in North Carolina have recently  developed a felt-like fabric that generates power by scavenging for so-called  waste heat, such as body heat.

Right now, many of the electronic devices we use every day, such as cellphones or laptop computers, get their power from batteries.

But, as we  also know, even the best batteries eventually run low on power and need to be recharged.

What the Wake Forest  University scientists have done is develop technology that takes your body heat, along with other waste heat, and convert it to electrical energy.

Ahhhh!!! the battery's dead! (Photo: Ed Yourdon)

Developed at the university’s Center for Nanotechnology and Molecular Materials, the material is made up of carbon nanotubes, tiny tube-shaped materials  made of carbon, which are held in flexible plastic fibers and made to feel like fabric.

The researchers say the thermoelectric technology behind Power Felt uses differences in temperature, such as room temperature versus body temperature, to create an electrical charge.

Professor David Carroll, director of the Center for Nanotechnology and Molecular Materials, says that thermoelectric technology, until now, has been tied to expensive hard ceramic material which is difficult to produce.

While the Power Felt technology might not be as high performing in producing thermoelectric power as its more expensive counterpart, Carroll points out the cost of producing the Power Felt material is much cheaper. Consequently, the total number of dollars per watt of generated power is significantly less in comparison.

Wake Forest physics professor Dr. David Carroll in his nanotechnology lab. (Photo: Wake Forest University)

Carroll says that there are many ways that Power Felt can be used at a consumer level.  Just like with a blanket, you could put the material over a variety of battery-powered devices, or wrap it around things like the handle of a flashlight, to get the extra juice needed to run those devices.

Other practical applications could include lining the seats of an automobile with Power Felt to boost the car’s battery power, insulating pipes or collecting heat from under your roof tiles to generate enough power to lower your gas or electric bills.

“Power Felt is best at supplementing the power that you already have,” says Carroll, adding that the greater the temperature differences, the more power the material generates.

Carroll says that the inspiration for Power Felt came from the concept of organic electronics, which he describes as flexible, printable, throw-away electronic devices.

In developing Power Felt, his team was out to create a textile that could literally be integrated into clothing, and then used to generate enough power, for example, to extend the battery of something critical like a pacemaker.

Thousands of times smaller than the average human hair, carbon nanotubes are extremely long and thin yet strong, making them a key nanotechnology structure. (Photo: NASA)

The whole idea for developing Power Felt technology, says  Carroll, is to try to address the electrical needs of mobile electronics.

“While our team was discussing what could we do to do this, it happened that my wife calls me on my cell phone,” Carroll says, “and if you have one of these smartphones, you could watch the power meter go down. The battery doesn’t last very long. And it became really evident that not just medical devices, but all kinds of devices that we carry with us every day, need supplemental power.”

According to Carroll, one way of providing the extra power needed for these devices is to invent a better, more efficient battery, but the costs of doing that could be very prohibitive.

Another way to do this, he suggests, is to generate power onboard the device by integrating thermoelectrical material, like Power Felt, into the construction of the electronic unit, like the plastic covering on a cellphone.

How much power does this Power Felt technology actually provide?

According to the team, 72 stacked layers in the fabric can yield about 140 nanowatts or 140 billionths of one watt of power. The team is continuing its work on the development of Power Felt and is evaluating several ways to add more nanotube layers and make them even thinner in order to boost output power.

Professor David Carroll joins us this weekend on the radio edition of “Science World.”   Professor Carroll tells us how their invention can easily and inexpensively help give you power to spare.  Tune in (see right column for scheduled times) or check out the interview below.

Other stories we cover on the “Science World” radio program this week include:

• Math may determine best HIV drug combination
• NASA: Moon may still be geologically active
• Study: No evidence “fracking” pollutes groundwater
• Hubble helps astronomers discover alien water world
• Small black hole whips up record-high cosmic winds
• Coconut shells, fruit-pits fuel electricity production