Raindrop-Driven Energy Harvesting Inspired by Leaf Fluttering

To address the climate crisis, the demand for renewable energy sources as alternatives to fossil fuels is steadily increasing. One of the less explored methods is utilizing raindrop energy. When raindrops impact soft surfaces like leaves at high speeds, they generate torque that causes the leaves to bend. Inspired by this phenomenon, we propose an energy harvesting device using a piezoelectric cantilever beam to generate electricity from the impact of raindrops. To optimize the conversion of kinetic energy into electrical energy, we evaluated the influence of beam length scales on energy conversion efficiency. We investigated the vibration and voltage response of a piezoelectric beam to a single water droplet, and further conducted experiments with a series of droplets to simulate more realistic rain conditions. Experimental results demonstrate that the aspect ratio of the beam significantly affects energy conversion. We then measured the power generated by the device under actual rainy conditions to assess its practical applicability. The field test results reveal a power relationship between rainfall intensity and power output. This study highlights the potential of harnessing rainfall for electricity generation, which can be used alongside other renewable energy sources.