A Study On Thermoelectric Energy Harvesting System For Human Body Applications

With the rapid development of the sensor technology,embedded computer technology and the wireless communication technology,the wireless sensor network(WSN)has been widely used.Traditional power supply can hardly meet the power requirements of wireless sensor network applications.Therefore to harvest the environmental energy and convert it into electricity as an alternative of traditional power supply for powering wireless sensor networks has drawn more and more attentions.Using thermoelectric elements to harvest energy from heat has been of great interest during the last decade.A thermoelectric element converts thermal energy in the form of temperature differences into electrical energy and vice-versa.The fundamental physical process involved in thermoelectrics is the Seebeck effect.The Seebeck effect is the generation of an electromotive force within two dissimilar metals when their junctions are maintained at different temperatures.Thermoelectric elements have three main advantages:No human intervention is required;they are highly reliable and quiet,since there are no moving mechanical parts;and the materials are environmentally friendly.With respect to portable electronics,the heat generated by humans can be a potential source of energy which can be harvested to power body-worn devices.Previous studies have shown that harvesting thermal energy from our body through thermoelectric means can supply 100’s of μW of available power.A thermoelectric energy harvesting system designed to harvest energy from our body though thermoelectric generators is presented in this paper.The proposed system is based-on a two-stage boost scheme with self-startup ability.A maximum power point tracking technique based on the open-circuit voltage is adopted in the boost converter for high efficiency.Experimental results indicate that the proposed system can harvest thermoelectric energy from the human body and run a microcontroller unit and a wireless sensor node when the ambient temperature is lower than 26℃ and the wind speed is more than 1.2m/s.The harvest system and wireless sensor node can be self-powered with minimum thermoelectric open-circuit voltage as 75 mV and input power of 88.9uW.With a self-startup scheme,the proposed system can self-start with a 20 mV input voltage.Low power designs are applied in the system to reduce the quiescent dissipation power.It results in better performance considering the conversion efficiency and self-startup ability compared to commercial boost systems used for thermal energy harvesting.