Array configurations for higher power generation in piezoelectric energy harvesting

Electric power generation efficiencies using a vibration of a piezoelectric element with array configurations were discussed. We have been investigating the piezoelectric energy harvesting using a polyurea thin film, which can be fabricated on the micro array structure. In our previous work, it was predicted that the higher power generation efficiency could be obtained with the shorter cantilever configuration. To realize the piezoelectric energy harvesting device with the larger volume energy density, the energy conversion efficiencies of the different array configurations were investigated. The energy conversion efficiencies and the volume energy densities of the energy harvesting element with several array configurations were calculated through the finite element analysis (FEA). Two energy harvesting devices with the different array configurations were designed. In the same volume of 22 × 19 × 1 mm³, the large array configuration has two long cantilevers (18 × 9.5 × 1 mm³) and the small one has eight short cantilevers (9 × 4.25 × 1 mm³). The 1-mm-thick piezoelectric zirconate titanate (PZT) elements were attached on the surface of each aluminum cantilever. The harmonic vibration in the vertical direction at the fundamental resonance frequencies of the cantilevers was applied by using a vibration generator, and the electric power generation was measured by connecting the load resistance. The larger volume energy density as an electric power generator could be obtained with the shorter array configuration. The larger output power was generated with the larger applying vibration. The relationship between the load resistance and the output power was investigated. The maximum output power of 2.8 mW and the conversion efficiency of 8.07% were achieved with the vibration velocity of 0.7 mm/s and the load resistance of 51 k¿.