Hybrid-type (d33 and d31) impact-based piezoelectric hydroelectric energy harvester for watt-level electrical devices

• Our study was designed the 4 W level multiple modules with 240 piezoelectric material.
• Electrical output power of single HI-PEH was 56.11 mW.
• HI-PEH output power was 4.3 W from 20 V output voltage and 215 mA output current.
• A 3.2 W commercial LED (SI-M8R04SAD) was operated using the HI-PEH.

Impact-based piezoelectric energy harvesters (PEHs) are used to generate electricity from pulse kinetic energy. Compared with operation in a single mode, utilizing both the d31 and d33 modes of the piezoelectric structure increases the power density of impact-based PEHs. In this study, a d31 and d33 hybrid-type impact-based PEH was designed and practically demonstrated as a power source for watt-level electrical devices requiring less than 10 W. We presented more detailed FEM analysis of the d31 and d33 effect of secondary impacter. The numerical simulations results show the strains in 33-direction of piezoelectric material in presented system are larger than those from the conventional impact-type PEH. As a result, the presented system is expected to generate more power than the d33 mode only PEH. The experimental results from a hydroelectric application consisting of a water turbine, 240 piezoelectric modules, and a multi-array rectifying circuit show that the peak output power generated from the hybrid-type impact-based PEH is 7.24 times higher than that of the conventional impact-type PEH. The proposed system was experimentally developed and it generates 20 V and 4.3 W of output power at optimum load conditions. Another advantage of the watt-level energy harvester is that no impedance matching circuit (such as buck-boost or flyback converter) is required; because the output matched impedance is very low i.e. 100 Ω. In experimentally demonstrated hydroelectric application conditions, the presented system was used as a direct power source to drive the 3.2 W commercial LED bulb. The system efficiency and performance are evaluated, and overall power conversion efficiency of 4.1% is achieved.