Renewable Power Generation by Reverse Electrodialysis Using an Ion Exchange Membrane
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 rene...
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| Autores principales: | , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/7ec07d13bf7844f285e942292954b444 |
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| Sumario: | 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 (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>q</mi><mi>f</mi></msub></semantics></math></inline-formula>) and salt-concentration difference (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>Δ</mo><mi>c</mi></mrow></semantics></math></inline-formula>). The current-voltage (<i>I</i>-<i>V</i>) 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>I</i>-<i>V</i> 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 (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mrow><mi>c</mi><mo>,</mo><mi>m</mi></mrow></msub></semantics></math></inline-formula>) and open-circuit voltage (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ϕ</mi><mn>0</mn></msub></semantics></math></inline-formula>) increase with increasing <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>Δ</mo><mi>c</mi></mrow></semantics></math></inline-formula>. On the one hand, the RED cell’s internal resistance (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>R</mi><mi>c</mi></msub></semantics></math></inline-formula>) empirically reveals a power-law dependence of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>R</mi><mi>c</mi></msub><mo>∝</mo><mo>Δ</mo><msup><mi>c</mi><mrow><mo>−</mo><mi>α</mi></mrow></msup></mrow></semantics></math></inline-formula>. On the other hand, the open-circuit voltage shows a logarithmic relationship of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>ϕ</mi><mn>0</mn></msub><mo>=</mo><mi>B</mi><mo form="prefix">ln</mo><mo>Δ</mo><mi>c</mi><mo>+</mo><mi>β</mi></mrow></semantics></math></inline-formula>. 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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