Optimum thermoelectric energy harvesting for wearable system applications

The limitations in wearable devices are the battery size, weight, and its limited life time. By placing thermoelectric generator (TEG) on human body, wearable devices with micro-power operations can be powered continuously. In this paper, a thermoelectric energy harvesting technique is presented to power a micro-power wearable watch. The output voltage of TEGs is required to be higher than a certain voltage level (e.g. 28.5mV) for efficient operations. The required input and output voltages of the TEG are maintained during different activities, environmental conditions, and load conditions. The experimental result shows an output voltage of 5 V at open circuit, and 4.15V when it produces output power of 86.8μW at optimum load resistance of 200 kω. Experimental results are also extended for hybrid energy harvesting using both TEG and solar which provides fast and efficient energy harvesting both indoor and outdoor.