Thermoelectric energy harvesters for powering wearable sensors

The study of thermoelectric energy harvesting on people presented in this paper shows that although power production is affected by many factors such as ambient temperature, wind speed, clothing thermal insulation and person´s activity, it does not directly depend on metabolic rate as shown in the experiment. The relevant thermal properties of humans measured at different ambient conditions are reported. Several thermopiles have been either attached with a strap or integrated into garments in different locations on human body, and power generation was extensively studied at different ambient conditions. Textile covering thermopiles is found not to essentially decrease power generation. Therefore, a hidden energy harvester producing within the 5 to 0.5 mW range at ambient temperatures of 15°C to 27°C, respectively, has been integrated into a shirt and tested on people in real life. The thermoelectric shirt with such energy harvester produces more energy during nine months of use (if worn 10 hours per day) than the energy stored in alkaline batteries of the same thickness and weight.