Sustainable Electrical Energy Harvesting via Electrified Flow

Abstract

Water covers over 70% of the Earth’s surface and serves as a ubiquitous reservoir of mechanical and thermal energy. Despite the immense potential of hydro-energy, existing harvesting technologies—specifically Liquid-Solid Triboelectric Nanogenerators (LS-TENGs) and Hydrovoltaic Electricity Generators (HEGs)—suffer from inherent limitations such as low energy conversion efficiency and low power density. This dissertation proposes novel high-performance energy harvesting devices tailored for two distinct hydrodynamic conditions: internal flows and external flows, by leveraging advanced charge transfer mechanisms and synergistic coupling effects. For internal flow energy harvesting, this study introduces a Two-Phase Flow Energy Device (TPED) that utilizes a direct charge transfer mechanism to overcome the limitations of conventional electrostatic induction. By introducing an air–water two-phase flow and modulating surface potentials using electronegative (FEP/PTFE) and electropositive (PU) materials, the device effectively suppresses Stern layer formation and mobilizes ions. Two configurations were developed: a Tube-type TPED for scalability and a PDMS channel-type TPED for design flexibility. Notably, the PDMS channel-type TPED achieved a superior energy conversion efficiency of 5.93% and a power density of 13.2 mW/m³. The device generates a self-rectified direct current (DC) output, eliminating the need for external bridge rectifiers, and demonstrates practical utility by powering commercial LEDs through a compact stacking design. For external flow energy harvesting, a Galvanic–Hydrovoltaic Coupled Electricity Generator (GHEG) is proposed to address the low power density of conventional HEGs. Unlike traditional devices that rely on a single zeta-potential surface, the GHEG integrates glass fibers modified with opposing zeta potentials (APTES-coated for positive and FAS-17-coated for negative) to maximize ion utilization efficiency. Furthermore, by integrating an aluminum–copper electrode pair, the device synergistically couples the hydrovoltaic effect with the galvanic effect. This novel architecture achieved a high-power density of 4.46 μW/cm² using a 0.1 M KCl solution—surpassing existing hydrovoltaic devices by over twofold. In conclusion, this research establishes a robust framework for harvesting energy from electrified flows. By elucidating the mechanisms of charge separation and transport at liquid–solid interfaces, this work demonstrates scalable, cost-effective, and high-efficiency solutions for sustainable power generation, paving the way for self-powered sensing systems and large-scale blue energy applications.