Comparison between overall and respective electrical rectifications in array of piezoelectric energy harvesting

The article compares two different electrical rectifications employed by a piezoelectric harvester array. The first type consists of parallel connection of harvesters followed by an AC-DC full-bridge rectifier for overall electrical rectification. The second type allows for respective electrical rectification of each individual harvester, and then connecting them all in parallel. The former exhibits stronger electromechanical coupling effect for enhancing output power. The latter is capable of avoiding charge cancelation for improving bandwidth. The analysis of the electromechanical response of these two types is provided with full derivations for the second case. The predictions of displacement and output power are compared with the experiment and the results show good agreement. Two recommendations are offered from the present studies. First, suppose the power dissipations due to voltage gaps across the rectifiers are insignificant compared with the amount of output power realized by each individual harvester. The piezoelectric harvester array with respective electrical rectification exhibits better performance than that with the overall rectification from the broadband point of view at the cost of reducing peak power. On the contrary, if the amount of power dissipations can not be neglected or the harvester exhibits the strongly coupled electromechanical response, it is recommended to employ the harvester array allowing the mixed parallel/series connections switched by DPDT (Double-Pole Double-Throw). The array of the mixed type with overall electrical rectification exhibits performance significantly outperforming the array with respective electrical rectification from the point of view of broadband and power enhancement.