Performance comparisons of piezoelectric energy harvesters under different stochastic noises

Harvesting energy utilizing the electromechanical coupling mechanism of piezoelectric materials in a noise environment has become important for developing applicable micropower generators. Although a variety of configurations have been proposed to harvest ambient vibration energy driven by deterministic excitations and the energy conversion efficiency of classical one degree of freedom piezoelectric energy harvesters with a purely resistive circuit has been analyzed systematically, crucial questions still remain on how to design system parameters to maximize the performance under different ambient noises. Here, combining the moment method of random processes theory and the energy balance equation, we explore the performance of piezoelectric energy harvesters with and without an inductor excited by Gaussian white noise, exponential correlation noise, and bounded noise, respectively. The exact closed-form expressions of the mean square voltage, averaged output power, and efficiency are presented, and the effects of dimensionless system parameters and noise parameters on the performance metrics are illustrated in detail. Monte Carlo simulations are performed to validate the analytical predictions. The expressions given in this paper are useful in comparing the two types of piezoelectric energy harvesters under different ambient excitations and provide a key to design optimized harvesters operating in a more suitable environment.