Fluid flow energy harvester using soft generators

Abstract

This paper reports the design, fabrication, and testing of a soft dielectric elastomer power generator for harvesting energy from fluid flow. A single generator can harvest a wide range of amplitudes and frequencies, and is compliant, compact and lightweight. A DEG energy harvesting cycle combining two harvesting modes, constant charge and constant voltage, was modelled and experimentally validated. A mathematical model was presented which optimises energy production while ensuring it operates within failure limits. This model will help with the design of a suitable control circuit for a given DEG specification. Two different generator prototypes for harvesting energy from fluid flow were built and characterized. Each prototype uses a different energy harvesting mechanism. The first design resembles an ‘eel’ and was designed to extract energy from induced Kármán vortex streets. The DEG energy harvesters were placed across joints. The device was built and tested in flowing water. Based on strain measurements, the DEG energy harvesting model was used to simulate the potential energy gain. For a flow rate of 1.1m/s, it was simulated to generate 522μW. The second design was based on harvesting energy from rotary motion, and intended for coupling to water or air turbines. Multiple DEGs were attached such that they undergo stretching and relaxation when a crank is rotated. A DC motor was used to mimic the output from a turbine and the performance of the DEG was evaluated. Based on measurements, the device was simulated to generate 46.7mW from an input power of 0.3W.