I. Introduction
Energy harvesters convert ambient energy into electrical energy and are used in a growing number of applications to supply Wireless Sensor Nodes (WSNs) [1]–[3]. Typical fields of application of WSNs in Industry 4.0 are automotive applications, medical implants, embedded sensors in buildings and bridges, industrial applications and so on. This paper is focused on vibration energy harvesters [4]–[7] and in particular on Resonant Electromagnetic Vibration Energy Harvesters (REVEHs) [8]–[12]. In Fig. 1, the REVEH equivalent electric circuit [13–14] is shown.
Resonant Electromagnetic Vibration Energy Harvester equivalent electric circuit.