Melissa Hyland and colleagues at North Carolina State report some neat work with thermoelectric generators (TEG) in clothing. The idea is obvious: use otherwise wasted body heat to generate electricity to power wearable sensors and devices. With new flexible TEG technology, it is now possible to experiment.
The researchers point out that there are number of technical challenges. Generating electricity requires heat differential, as much as you can get. Waste heat off the body isn’t really all that significant, so it needs to be captured and routed to the generator. These collectors and devices have to be small, light, and comfortable to wear, and for practical clothing, they must be rugged (and washable).
Hyland’s group explored placement of their devices on several parts of the body, in a wristband and several locations on a tee shirt. Their results indicate that a patch taped to the upper arm generated the most power compared to the other locations, though, of course, a TEG in the chest of a teeshirt did generate some electric power.
They also found that airflow and the activity of the person affects the power output, generating more heat and heat differential.
The raw amounts of power are rather small, along the lines of 10 microwatts per square centimeter. This is hardly going to recharge you phone or anything like that. But it might power small sensors or other devices, such as medical or environmental monitors.
(I’m pretty sure that this is in the same ballpark as other wearable energy harvesting. But I would need to check carefully to confirm this, so don’t quote me on this point.)
This technology joins other wearable power technologies, photovoltaic and kinetic power generation. These techniques will be important, because we really can’t have our “smart clothing” needing external power or heavy battery packs.
- Melissa Hyland, Haywood Hunter, Jie Liu, Elena Veety, and Daryoosh Vashaee, Wearable thermoelectric generators for human body heat harvesting. Applied Energy, 182:518-524, 11/15/ 2016. http://www.sciencedirect.com/science/article/pii/S0306261916312594