Using atmospheric temperature variations for thermal energy harvesting for wireless sensors

Using more and more sensors, an increase in complexity and quantity of wiring is the consequence. This can be solved by using wireless sensors which are powered by energy harvesting. For this purpose, thermal energy harvesting by using atmospheric temperature variations is investigated by using a test setup in a climate cabin with a 65 minutes temperature cycle with minimum temperature of -40°C for 6 minutes. The results shown a maximum reached temperature difference is 37.5 K which results in 6 mW electrical power the chosen thermos-electric generator (TEG) produces. Utilizing an energy-harvesting power management unit to the setup results in a maximum electrical energy conversion efficiency of 92% and a maximum electrical storage power in a supercapacitor of 5.5 mW. The overall electrical energy the TEG generates is 8.85 J. The total energy that is stored in the supercapacitor is 7.85 J, which is an overall energy conversion efficiency of 89%. The results of using two identical TEGs parallel in the same thermic setup shows the limitation of this.