This paper compares the system-level parameters and output power of soft-material and hard-material piezoelectric energy harvesters taking into account the material softening nonlinear behavior. We validate the approach by verifying the compatibility with conclusions available in the literature at material level. Among the results, our system-level characterization confirms that soft-type materials behave intrinsically more nonlinearly and that neglecting their nonlinear behavior can lead to wrong conclusions about the system-level coupling coefficient. Then, we compare the generators in terms of power delivered to a load when actuated by a shaker. The power delivered by the hard-type transducer increases faster than the power delivered by the soft-type transducer when the acceleration amplitude increases which is also consistent with our characterization results and validates the system-level approach.
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