Dynamics for droplet-based electricity generators

Wang, Xiang; Fang, Sunmiao; Tan, Jianguo; Hu, Tao; Chu, Weicun; Yin, Jun; Zhou, Jianxin; Guo, Wei

doi:10.1016/j.nanoen.2020.105558

Cited by 84 publications

(68 citation statements)

References 29 publications

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“…In an effort to circumvent the inherent bottleneck imposed by the interfacial effect, a novel droplet‐based electricity generator, 24‐26 featuring with a transistor‐inspired architecture, is developed. In such a design, gated by the impinging droplet, electrodes, and dielectric material are connected to form a closed‐loop for charge transfer from the dielectric material with pre‐stored high density charges rather than from the contact electrification of an impinging droplet.…”

Section: Introductionmentioning

confidence: 99%

Harvesting energy from high‐frequency impinging water droplets by a droplet‐based electricity generator

Wang

Song

et al. 2021

EcoMat

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Harvesting energy from water, in the form of raindrops, river, and ocean waves, is of considerable importance and has potential applications in self‐powered electronic devices and large‐scale energy needs. Recently, the droplet‐based electricity generator has shown an increase by several orders of magnitude in electrical output, overcoming the drawback of traditional droplet‐based device limited by interfacial effects. Despite this exciting result, the output performance of this novel droplet‐based electricity generator is limited by relatively low frequency of impinging droplets owing to the formation of a continuous liquid film at high impact frequency, which might hinder its practical applications. To overcome this challenge, here, we report the design of a superhydrophobic surface based droplet electricity generator, referred to as SHS‐DEG, which can timely shed water droplets from the surface without the formation of liquid film at high impact frequency, and thereby generating enhanced average electrical output. Moreover, our SHS‐DEG exhibits many distinctive advantages over conventional design including robustness, long‐term durability, and power generation stability even in harsh environments. We envision that the ability to harvest electrical energy from water droplets at high impact frequency has promising applications in various energy‐harvesting systems.

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Section: Introductionmentioning

confidence: 99%

Harvesting energy from high‐frequency impinging water droplets by a droplet‐based electricity generator

Wang

Song

et al. 2021

EcoMat

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“…1). According to the present understanding, [2,11], this sandwiched structure then behaves as a biased capacitor. Upon contact with water, the capacitor is discharged through the load, which releases the electro-FIG.…”

Section: Introductionmentioning

confidence: 79%

“…The splashing (solid line) and film-rupturing (dashed line) limits are given by Eqs. (10) and (11) surface roughness and liquids suggest that the liquid film will rupture if the droplet impacts a solid wall above some critical Reynolds number Re c 5000:…”

Section: Maximum Impact Velocitymentioning

confidence: 99%

Hydrodynamic constraints on the energy efficiency of droplet electricity generators

Wang¹,

Zhou²,

Riaud³

et al. 2020

Preprint

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Electric energy generation from falling droplets has seen a hundred-fold rise in efficiency over the past year. However, even these newest devices can only extract a small portion of the droplet energy. In this paper, we theoretically investigate the contributions of hydrodynamic and electric losses in limiting the efficiency of droplet electricity generators (DEG). Noting that the electromechanical energy conversion occurs during the recoil that immediately follows droplet impact, we identify three limits on existing droplet electric generators: (i) the impingement velocity is limited in order to maintain the droplet integrity; (ii) much of droplet mechanical energy is squandered in overcoming viscous shear force with the substrate; (iii) insufficient electrical charge of the substrate.Of all these effects, we found that up to 83% of the total energy available was lost by viscous dissipation during spreading. Minimizing this loss by using cascaded DEG devices to reduce the droplet kinetic energy may increase future devices efficiency beyond 10%.

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“…Recently, Xu et al [19] found that dropping a droplet onto a PTFE film supported by an indium tin oxide and overlaid by a piece of aluminum electrode, can generate an instant voltage of up to 100 V, significantly higher than the values of drawing potential [21]. The origin of the high instant voltages has been analytically related to the evolution of the drop-substrate interfacial area [18,42], but its atomistic mechanism remains to be explored. The proposed model in this work may serve as a step-stone towards understanding the energy harvesting from falling onto a pre-charged surface.…”

Section: Discussionmentioning

confidence: 99%

Mechanistic insight into electricity generation from moving ionic droplets on graphene

Zhang

Guo

2021

Sci. China Mater.

Self Cite

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Recent experiments have demonstrated that moving water droplets on polymer-supported graphene can generate electric voltages in graphene. Here, we perform a multi-scale analysis on the mechanism of the generated voltages on the basis of an interplay among the substrate, graphene and ionic water. We find that the attraction of ions in water by substrate dipoles drives charge redistribution in graphene, forming an electric triple layer (ETL) at the water/ graphene/substrate interface, made of an ion layer fixed on graphene, an image charge layer in graphene and a counterion layer in water. As a droplet moves on graphene, dynamic formation of the ETL at its front end drives a flow of charge in graphene. Using Langmuir adsorption theory combined with ab initio calculations, we determine the ion concentration in the ETL and estimate the amount of charge that each ion can draw in graphene. Then, the electric current in graphene is formulated in terms of ion concentration, droplet velocity, graphene thickness and density of substrate dipoles, which well reproduces experimentally measured currents in graphene. These results underscore the importance of tailoring substrate dipoles in optimizing the performance of devices for water energy harvesting and promoting practical applications.

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Dynamics for droplet-based electricity generators

Cited by 84 publications

References 29 publications

Harvesting energy from high‐frequency impinging water droplets by a droplet‐based electricity generator

Harvesting energy from high‐frequency impinging water droplets by a droplet‐based electricity generator

Hydrodynamic constraints on the energy efficiency of droplet electricity generators

Mechanistic insight into electricity generation from moving ionic droplets on graphene

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