Closed-cycle droplet-based electricity generator for energy harvesting and signal monitoring

Abstract

Water, an energy carrier that stores enormous amounts of energy, is expected to be one of the candidate energy sources for solving the energy crisis and carbon neutrality challenges. Droplet-based electricity generators have been widely studied due to their high efficiency in converting droplet potential energy into electricity and its simple structure. However, current research on droplet-based electricity generators is limited by high spatial footprint, material durability and low-energy-density, which prevents the realization of efficient cyclic output in integrating with diverse electronic components (e.g., integrated circuits, microsensors, microcontrollers). Achieving low-wear, recyclable, high-energy-density output in a single or integrated droplet-based power generation system remains a formidable challenge. Here we propose a closed-cycle droplet-based electricity generator (CC-DEG) that enables efficient conversion of the cyclic motion of droplets confined to the circular tube into electrical energy by stimulation with external mechanical forces. The CC-DEG demonstrates exceptional performance, with a peak open-circuit voltage of 661 V and a peak power density of 71.226 kW/m³. Parametric studies, including frequency, rotational speed, etc., proved the efficiency and stability of the CC-DEG. Furthermore, the CC-DEG can serve as a speed sensor for detecting real-time speed. This innovative design not only greatly minimizes water waste and space occupation, but also offers low-cost fabrication and ease of manufacturing, which provides an ideal strategy for integrating water-based generators into multifunctional sensors.