Developing Transistor-Like Water Energy Generator with High Peak Power Density and High Durability

Description

Water energy is one of the most abundant, sustainable and affordable energy sources in the world. Despite extensive efforts, harvesting water energy in the format of raindrop, river/ocean wave, tide and others is a formidable task. Over the past decade, the development of various strategies such as triboelectricity, piezoelectricity, thermoelectricity that convert ambient energy of droplet/wave to electricity has gained increasing attention. In the case of triboelectric nanogenerator (TENG), the peak power density is usually less than 1 W/m2, due to the interfacial nature of power generation. The problem is further complicated when TENG is exposed to extreme environments such as in high relative humidity, in which the surface of TENG is covered by the pinnied liquid and the output performances are compromised. Thus, the rational design of novel devices that sustain large energy conversion efficiency and high durability remains a challenge.In this project, we propose to develop a new water energy harvesting device that can fundamentally resolve the limitations encountered in conventional designs. The device is constructed by the deposition of supersmooth polytetrafluoroethylene (PTFE) electret film on transparent ITO/glass substrate and patterned with another Al electrode. In the case of water droplet-based energy harvesting, we envison that continuous droplet impinging on the supersmooth PTFE film imparts sufficient surface charge storage and stability. Moreover, the spreading of the soft droplet is able to bridge the originally disconnected components in the device into a closed-looped, electrical system, transforming the conventional interfacial effect into a desirable bulk effect. Thus, in analogy to field effect transisitor that consists of source, drain, and gate, the PTFE/ITO, Al electrode and water droplet serves as source, drain and gate, respectively. As a result, such a unique design allows for efficient transfer of charges between source and drain, resulting in dramatic boost in peak power density. On the other hand, the utility of supersmooth PTFE film also naturally avoids the wetting collapse problem encountered on conventional design, allowing for rapid liquid shedding and sustained energy harvesting even in harsh environments. We will also investigate output performances of asproposed devices under different salt concentrations, droplet sizes as well as relative humidities, and probe the fundamental mechanisms responsible for the performance enhancement from the perspective of circult analysis and molecular dynamics simulation. As an extention to the fundamental study, we will also explore the its applications such as in flexible electronics as well as harvesting wave energy.