Design of cantilever harvesters excited by raindrop impacts

Raindrop energy harvesting through piezoelectric devices offers a promising solution to power small sensors, especially in adverse weather conditions when traditional solar panels are less effective. This paper explores the design and development of a piezoelectric cantilever featuring a water-filled tank for harvesting the kinetic energy of raindrops. An analytical formulation of the impact force of the raindrop is proposed. A mathematical model of the dynamics of the harvester excited by the impact of a raindrop is developed and the effects of the design parameters on the generated voltage are deeply analyzed via simulations. Experimental tests are used to validate both the harvester mathematical model and the impact force formulation. Additional experimental tests are performed to simulate real-world conditions through repeated raindrop impacts as well. Subsequently, a simplified mathematical model that takes into account the series of raindrop impacts is developed, making it possible to interpret the effects on the generated voltage.