Influence of the topology for a networked SSHI piezoelectric harvesting configuration

This paper focuses on the influence of the topology of a network of piezoelectric harvesters using the SSHI ( Synchronized Switch Harvesting on Inductor) technology. Generally, an energy harvester is used as a localized and standalone system. In the case of large structure and for large harvested energies, it is usually not easy to increase the size of the piezoelectric patches. In order to harvest energy in the regions of maximum strain of the structure, a networked piezoelectric harvester including many separated piezoelectric patches must be set up with only one output. The main concern is how to connect the piezoelectric elements together and how to implement accurately the SSHI strategy for maximizing the total output power. This paper presents 5 different circuit topologies with or without SSHI enhancement. This work is based upon simulations of a structure with embedded piezoelectric harvesters, made in the Matlab/Simulink environment and using the Simscape library for defining and simulating the electric network. The simulations are done exclusively in pulse mode. For each circuit topology, the total output energy is computed and the optimal harvesting capacitance is defined. The results show the feasibility of grouping various harvesters within a network connected onto a common harvesting capacitance without affecting the extracted energy. The interest of SSHI for networked con figuration is con firmed as well as the need for multiple switching units. The effect of the parasitic capacitances due to the bonding of the piezoelectric patches on a metallic structure is also investigated. This capacitance corresponds to the isolation layer between the structure and the bottom electrode of the piezoelectric patches. Results show that an optimal bonding layer thickness can be found that does not affect significantly the coupling coefficient of the piezoelectric patches and which induces parasitic capacitances that do not affect the network functionality.