Can Body Heat Harvesting Power Wearables?

Researchers at North Carolina State University (NCSU) have developed a new design for harvesting body heat and converting it into electricity for use in wearable electronics.

The experimental prototypes are lightweight, conform to the shape of the body, and can generate more electricity than previous lightweight heat harvesting technologies, according to researchers.

As part of the study, researchers also identified the optimal site on the body for heat harvesting.

“Wearable thermoelectric generators (TEGs) generate electricity by making use of the temperature differential between your body and the ambient air,” said Daryoosh Vashaee, an associate professor of electrical and computer engineering at NC State and corresponding author of a paper on the work. “Previous approaches either made use of heat sinks – which are heavy, stiff and bulky – or were able to generate only one microwatt or less of power per centimeter squared (mW/C2). Our technology generates up to 20 mW/C2 and doesn’t use a heat sink, making it lighter and much more comfortable.”

The new design begins with a layer of thermally conductive material that rests on the skin and spreads out the heat. The conductive material is topped with a polymer layer that prevents the heat from dissipating through to the outside air. This forces the body heat to pass through a centrally-located TEG. Heat that is not converted into electricity passes through the TEG into an outer layer of thermally conductive material, which rapidly dissipates the heat.

“In this prototype, the TEG is only one centimeter squared, but we can easily make it larger, depending on a device’s power needs,” said Vashaee, who worked on the project as part of the National Science Foundation’s Nanosystems Engineering Research Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) at NC State.

“The goal of ASSIST is to make wearable technologies that can be used for long-term health monitoring, such as devices that track heart health or monitor physical and environmental variables to predict and prevent asthma attacks,” he said.

The research also found that the upper arm could be an optimal location for heat harvesting as well.

The final document on the research is titled, “Wearable thermoelectric generators for human body heat harvesting” and authored by Melissa Hyland, Haywood Hunter, Jie Liu, Elena Veety and Daryoosh Vashaee, NCSU.