Energy harvesting from von karman vortices in airflow for autonomous sensors

In this paper an innovative energy harvesting system based on a piezoelectric converter to extract energy from airflow and use it to power autonomous sensors is presented. The converter is embedded as a part of a flexure beam that is put into vibrations by Von Karman vortices detached from a bluff body placed upstream. The results of experimental characterization show that higher conversion effectiveness is obtained for flow velocities where the frequency of the vortices matches the resonant frequency corresponding to the first flexural mode of the beam. The possibility to power autonomous sensors has been shown by developing an energy management and signal conditioning electronic circuit plus two sensors for the transmission of a RF signal from which temperature and flow velocity can be extracted. A harvested power of about 100 μW with retransmission intervals below 2 min have been obtained.