Maximum Charge Generation in a Piezoelectric Generator

The piezoelectric generator of this investigation provides a method to convert mechanical energy into electrical energy. A pulse conditioning stage is also included in the generator. Although the energy density of the generator is not extremely high in comparison to batteries, its durability, compactness, and long shelf-life are advantageous in certain applications. The piezoelectric generator consists of commercially available piezoelectric elements arranged in a stack and electrically connected in parallel. A steel mass is dropped on the piezoelectric stack and serves as a source of mechanical energy. The piezoelectric generator is, at most, 50% efficient due to its internal capacitance. In this investigation, the piezoelectric generator has a 0.15 muF internal capacitance. The piezoelectric generator is connected to an external 0.1 muF capacitor through a rectifier diode. The external capacitor is used as an intermediate energy storage, or pulse- conditioning stage. Results show the piezoelectric generator produces 0.3 J of energy which is higher than generators of previous studies. The maximum energy storage time was not measured in this investigation but is limited by the dissipation of the external capacitor. Peak mechanical forces of approximately 18 kN were measured along with maximum generator voltages of 1.4 kV.