Water droplet energy harvesting

Abstract

Harnessing abundant kinetic water energy in diverse forms of river flows, ocean waves, tidal currents, raindrops, and others, is highly attractive to ease the energy crisis and satisfy the demands of scattered sensor network nodes in the Internet of things. Among them, raindrops, widely and ubiquitously distributed in nature and ambient living life, have been extensively explored and regarded as significant renewable energy carriers. Extensive efforts have been made to investigate droplet‐based electricity nanogenerators in fundamental mechanism, performance, and applications for achieving sustainable energy demands of the rapidly developing society over the past decade. In this review, we introduce the remarkable progress in this field and discuss the fundamental mechanisms of droplet energy harvesting technology for achieving high‐power generation. More significantly, a systematic review of droplet energy harvesting in different two‐phase interfaces, including liquid–solid, liquid–liquid, and liquid–gas interfaces, is provided. Finally, this survey reveals that droplet‐based electricity generators present vast potential in the power supply. At the same time, several development challenges and prospective solutions are discussed to spur future technological advancements.

How liquids charge the superhydrophobic surfaces

“…Solid-solid CE has experienced extensive research, and three types of charge carriers 2 , including electrons 3 , ions 4 – 6 , and materials 7 , 8 , have been used to account for the charge generation during CE between different types of solid surfaces. In comparison, liquid-solid CE is still not well understood despite its significance in various applications, such as water energy harvesting, microfluidics, interfacial chemistry, surface wet cleaning, etc 9 – 14 . The main bottlenecks hitherto in understanding the mechanism of liquid-solid CE lie in ascertaining charge carriers, which may involve ions, electrons, or both 15 – 24 .…”

Elastic Droplet-Based Magnetoelectric Generator for High-performance Energy Collection

“…Based on the charge transferring at the liquid/solid interface, numerous scalable models have been proposed for harvesting dispersive water energy, including triboelectric nanogenerators (TENGs), − reverse electro-wetting, − and droplet-based generators. − When the droplets impact the solid surface from a height, a small amount of positive/negative charge at the liquid/solid interfaces is transferred to the external circuit, thereby generating an electric current. Recently, Wang’s group developed a prototype of R-TENG array for harvesting raindrop energy and solar energy, which possessed a high average power density up to 40.8 mW/m 2 .…”