**4. Conclusion**

The performance of piezoelectric energy-harvesting devices fabricated from the base FRP beam and PZT-based and BT-based ceramics that captured frequencies of 60 Hz was evaluated. The output voltage from the generator is proportional to the displacement of the piezoelectric ceramics. And the output voltages from the bimorph and unimorph generator varied with the applied frequencies. The output voltage increased with the load resistance, on the other hand, the output power showed the maximum at around the load resistance with the impedance of the piezoelectric generators. And the figures of merit of the materials have been discussed in order to provide the guidelines of the piezoelectric material selections. Piezoelectric voltage coefficient, *g*31, is considered to be good parameter to predict the maximum voltages. On the other hand, *d*31*g*31/tanδ, *k*31<sup>2</sup> *Q*m, and *d*31*g*31 are close to the behavior of the maximum power, these material parameters are suitable to evaluate the EH performance. The performance of the power management circuit was evaluated. The constant voltage output was confirmed during oscillations of the piezoelectric generators, showing the systems used in this study have the capability of the power sources. As a conclusion, the results of this work suggested that the piezoelectric material selection and the circuit design are important problems to implement piezoelectric generator to the various applications.
