Body heat thermoelectric energy harvesting for self-powered wearable electronics

Over the past several years there has been significant development in low power wearable wireless electronics which can be powered from energy harvesting systems rather than from batteries. In this paper we present a thermoelectric energy harvesting system using human body heat to power wearable electronics. The main focus of this paper is to present a power management system suitable for this application. The voltage produced from the human body is small in quantity (∼100mV). Ultra- low voltage boost converters and output voltage regulators have been designed for low power wearable electronics. This work considers the human arm/wrist as a source of heat, placing a thermoelectric generator (TEG) with a heat sink on a wrist using a watch like prototype. The TEG was tested with a body to room temperature difference ΔT=5°C producing 1.54 mW. The harvested and regulated power is 0.278 mW sufficient for a wearable wireless sensor (WSN) node [1].The proposed power management and dc-dc converter circuit operates with an input voltage as low as 30mV. 24% efficiency is achieved from the boost converter stage whilst the dc-dc converter stage gives approximately 75% efficiency. The average end-to-end efficiency is 18%.