Tailoring Membrane Nanostructure and Charge Density for High Electrokinetic Energy Conversion Efficiency

Haldrup, Sofie; Catalano, Jacopo; Hinge, Mogens; Jensen, Grethe Vestergaard; Pedersen, Jan Skov; Bentien, Anders

doi:10.1021/acsnano.5b07229

Cited by 50 publications

(34 citation statements)

References 40 publications

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“…(iv) Conversion Efficiency. e maximum efficiency of energy conversion (η max ) is defined as the ratio of the output power to the input power; however, some researchers [143][144][145] also use an alternate measure for the conversion efficiency using a measure called electrokinetic figure of merit [146], which is based on phenomenological transport equations. e following equation is an alternate form for the maximum efficiency in terms of figure of merit (β):…”

Section: Energy Conversion Through Electrokineticsmentioning

confidence: 99%

Critical Review of Fluid Flow Physics at Micro‐ to Nano‐scale Porous Media Applications in the Energy Sector

Singh

Myong

2018

Advances in Materials Science and Engineering

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While there is a consensus in the literature that embracing nanodevices and nanomaterials helps in improving the efficiency and performance, the reason for the better performance is mostly subscribed to the nanosized material/structure of the system without sufficiently acknowledging the role of fluid flow mechanisms in these systems. This is evident from the literature review of fluid flow modeling in various energy-related applications, which reveals that the fundamental understanding of fluid transport at micro- and nanoscale is not adequately adapted in models. Incomplete or insufficient physics for the fluid flow can lead to untapped potential of these applications that can be used to increase their performance. This paper reviews the current state of research for the physics of gas and liquid flow at micro- and nanoscale and identified critical gaps to improve fluid flow modeling in four different applications related to the energy sector. The review for gas flow focuses on fundamentals of gas flow at rarefied conditions, the velocity slip, and temperature jump conditions. The review for liquid flow provides fundamental flow regimes of liquid flow, and liquid slip models as a function of key modeling parameters. The four porous media applications from energy sector considered in this review are (i) electrokinetic energy conversion devices, (ii) membrane-based water desalination through reverse osmosis, (iii) shale reservoirs, and (iv) hydrogen storage, respectively. Review of fluid flow modeling literature from these applications reveals that further improvements can be made by (i) modeling slip length as a function of key parameters, (ii) coupling the dependency of wettability and slip, (iii) using a reservoir-on-chip approach that can enable capturing the subcontinuum effects contributing to fluid flow in shale reservoirs, and (iv) including Knudsen diffusion and slip in the governing equations of hydrogen gas storage.

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Section: Energy Conversion Through Electrokineticsmentioning

confidence: 99%

Critical Review of Fluid Flow Physics at Micro‐ to Nano‐scale Porous Media Applications in the Energy Sector

Singh

Myong

2018

Advances in Materials Science and Engineering

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“…The first experimental concept of RED was developed by Pattle (in the 1950s), using alternating chambers of fresh and saline water separated by acidic and basic membranes [10]. However, not until recently have there been active theoretical, numerical, and experimental investigations aiming at pilot projects [11,12], efficient membrane materials [13][14][15][16][17][18][19][20][21][22], improved large-scale cell designs [22][23][24][25][26][27][28], and better understanding of the underlying mechanisms at pore-scale charged interfaces [29][30][31] for optimal power outputs [1,17,32,33]. However, it is challenging to carry out rigorous theoretical and numerical analyses to fully compute and accurately predict the electric outputs of a RED system.…”

Section: Introductionmentioning

confidence: 99%

Renewable Power Generation by Reverse Electrodialysis Using an Ion Exchange Membrane

Chanda

Tsai

2021

Membranes

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Reverse electrodialysis (RED) is a promising technology to extract sustainable salinity gradient energy. However, the RED technology has not reached its full potential due to membrane efficiency and fouling and the complex interplay between ionic flows and fluidic configurations. We investigate renewable power generation by harnessing salinity gradient energy during reverse electrodialysis using a lab-scaled fluidic cell, consisting of two reservoirs separated by a nanoporous ion exchange membrane, under various flow rates (qf) and salt-concentration difference (Δc). The current-voltage (I-V) characteristics of the single RED unit reveals a linear dependence, similar to an electrochemical cell. The experimental results show that the change of inflow velocity has an insignificant impact on the I-V data for a wide range of flow rates explored (0.01–1 mL/min), corresponding to a low-Peclet number regime. Both the maximum RED power density (Pc,m) and open-circuit voltage (ϕ0) increase with increasing Δc. On the one hand, the RED cell’s internal resistance (Rc) empirically reveals a power-law dependence of Rc∝Δc−α. On the other hand, the open-circuit voltage shows a logarithmic relationship of ϕ0=BlnΔc+β. These experimental results are consistent with those by a nonlinear numerical simulation considering a single charged nanochannel, suggesting that parallelization of charged nano-capillaries might be a good upscaling model for a nanoporous membrane for RED applications.

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“…In previous studies we have determined ν, σ, and κ H experimentally in ion exchange membranes to evaluate β, hence indirectly η max [16][17][18][19][20]. This was later followed by a direct measurement of η max [21].…”

Section: Introductionmentioning

confidence: 99%

Direct Measurements of Electroviscous Phenomena in Nafion Membranes

2020

Self Cite

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Investigation of electroviscous effects is of interest to technologies that exploit transport of ions through ion exchange membranes, charged capillaries, and porous media. When ions move through such media due to a hydrostatic pressure difference, they interact with the fixed charges, leading to an increased hydraulic resistance. Experimentally this is observed as an apparent increase in the viscosity of the solution. Electroviscous effects are present in all electrochemical membrane-based processes ranging from nanofiltration to fuel-cells and redox flow batteries. Direct measurements of electroviscous effects varying the applied ionic current through Nafion membranes have, to the best of the authors’ knowledge, not yet been reported in literature. In the current study, electroviscous phenomena in different Nafion ion exchange membranes are measured directly with a method where the volume permeation is measured under constant trans-membrane pressure difference while varying the ion current density in the membrane. The direct measurement of the electroviscous effect is compared to the one calculated from the phenomenological transport equations and measured transport coefficients. Within the experimental uncertainty, there is a good agreement between the two values for all membranes tested. We report here an electroviscous effect for all Nafion membranes tested to be κH?κH−1=1.15−0.052+0.035.

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Tailoring Membrane Nanostructure and Charge Density for High Electrokinetic Energy Conversion Efficiency

Cited by 50 publications

References 40 publications

Critical Review of Fluid Flow Physics at Micro‐ to Nano‐scale Porous Media Applications in the Energy Sector

Critical Review of Fluid Flow Physics at Micro‐ to Nano‐scale Porous Media Applications in the Energy Sector

Renewable Power Generation by Reverse Electrodialysis Using an Ion Exchange Membrane

Direct Measurements of Electroviscous Phenomena in Nafion Membranes

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