ENERGY CONVERSION FROM SALINITY GRADIENT USING MICROCHIP WITH NAFION MEMBRANE

When a concentrated salt solution and a diluted salt solution are separated by an ion-selective membrane, cations and anions would diffuse at different rates depending on the ion selectivity of the membrane. The difference of positive and negative charges at both ends of the membrane would produce a potential, called the diffusion potential. Thus, electrical energy can be converted from the diffusion potential through reverse electrodialysis. This study demonstrated the fabrication of an energy conversion microchip using the standard micro-electromechanical technique, and utilizing Nafion junction as connecting membrane, which was fabricated by a surface patterned process. Through different salinity gradient of potassium chloride solutions, we experimentally investigated the diffusion potential and power generation from the microchip, and the highest value measured was 135 mV and 339 pW, respectively. Furthermore, when the electrolyte was in pH value of 3.8, 5.6, 10.3, the system exhibited best performance at pH value of 10.3; whereas, pH value of 3.8 yielded the worst.

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Space Charge Enhanced Ion Transport in Heterogeneous Polyelectrolyte/Alumina Nanochannel Membranes for High-Performance Osmotic Energy Conversion

Journal of Materials Chemistry A ◽

10.1039/d1ta08560c ◽

2021 ◽

Author(s):

Chen-Wei Chang ◽

Chien-Wei Chu ◽

Yen-Shao Su ◽

Li-Hsien Yeh

Keyword(s):

Ion Transport ◽

Space Charge ◽

Energy Conversion ◽

High Performance ◽

Salinity Gradient ◽

Clean Energy ◽

Energy Resources ◽

Global Energy ◽

Energy Demands ◽

Selective Membrane

Capturing osmotic energy from a salinity gradient through an ion-selective membrane is regarded as one of the renewable clean energy resources to solve the increasing global energy demands. However, suffering...

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Energy Harvesting from Brines by Reverse Electrodialysis Using Nafion Membranes

Membranes ◽

10.3390/membranes10080168 ◽

2020 ◽

Vol 10 (8) ◽

pp. 168 ◽

Cited By ~ 1

Author(s):

Ahmet H. Avci ◽

Diego A. Messana ◽

Sergio Santoro ◽

Ramato Ashu Tufa ◽

Efrem Curcio ◽

...

Keyword(s):

Energy Conversion ◽

Electrochemical Properties ◽

Cation Exchange ◽

Power Density ◽

Electrochemical Impedance ◽

Salinity Gradient ◽

Superior Performance ◽

Reverse Electrodialysis ◽

Nafion Membranes ◽

The Impact

Ion exchange membranes (IEMs) have consolidated applications in energy conversion and storage systems, like fuel cells and battery separators. Moreover, in the perspective to address the global need for non-carbon-based and renewable energies, salinity-gradient power (SGP) harvesting by reverse electrodialysis (RED) is attracting significant interest in recent years. In particular, brine solutions produced in desalination plants can be used as concentrated streams in a SGP-RED stack, providing a smart solution to the problem of brine disposal. Although Nafion is probably the most prominent commercial cation exchange membrane for electrochemical applications, no study has investigated yet its potential in RED. In this work, Nafion 117 and Nafion 115 membranes were tested for NaCl and NaCl + MgCl2 solutions, in order to measure the gross power density extracted under high salinity gradient and to evaluate the effect of Mg2+ (the most abundant divalent cation in natural feeds) on the efficiency in energy conversion. Moreover, performance of commercial CMX (Neosepta) and Fuji-CEM 80050 (Fujifilm) cation exchange membranes, already widely applied for RED applications, were used as a benchmark for Nafion membranes. In addition, complementary characterization (i.e., electrochemical impedance and membrane potential test) was carried out on the membranes with the aim to evaluate the predominance of electrochemical properties in different aqueous solutions. In all tests, Nafion 117 exhibited superior performance when 0.5/4.0 M NaCl fed through 500 µm-thick compartments at a linear velocity 1.5 cm·s−1. However, the gross power density of 1.38 W·m−2 detected in the case of pure NaCl solutions decreased to 1.08 W·m−2 in the presence of magnesium chloride. In particular, the presence of magnesium resulted in a drastic effect on the electrochemical properties of Fuji-CEM-80050, while the impact on other membranes investigated was less severe.

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Harvesting Natural Salinity Gradient Energy for Hydrogen Production Through Reverse Electrodialysis Power Generation

Journal of Electrochemical Energy Conversion and Storage ◽

10.1115/1.4035835 ◽

2017 ◽

Vol 14 (2) ◽

Cited By ~ 6

Author(s):

Mohammadreza Nazemi ◽

Jiankai Zhang ◽

Marta C. Hatzell

Keyword(s):

Energy Efficiency ◽

Power Density ◽

External Load ◽

Salinity Gradient ◽

Electrical Power ◽

Ionic Current ◽

Electrical Energy ◽

Hydrogen Energy ◽

Mixing Processes ◽

Reverse Electrodialysis

There is an enormous potential for energy generation from the mixing of sea and river water at global estuaries. Here, we model a novel approach to convert this source of energy directly into hydrogen and electricity using reverse electrodialysis (RED). RED relies on converting ionic current to electric current using multiple membranes and redox-based electrodes. A thermodynamic model for RED is created to evaluate the electricity and hydrogen which can be extracted from natural mixing processes. With equal volume of high and low concentration solutions (1 L), the maximum energy extracted per volume of solution mixed occurred when the number of membranes is reduced, with the lowest number tested here being five membrane pairs. At this operating point, 0.32 kWh/m3 is extracted as electrical energy and 0.95 kWh/m3 as hydrogen energy. This corresponded to an electrical energy conversion efficiency of 15%, a hydrogen energy efficiency of 35%, and therefore, a total mixing energy efficiency of nearly 50%. As the number of membrane pairs increases from 5 to 20, the hydrogen power density decreases from 13.6 W/m2 to 2.4 W/m2 at optimum external load. In contrast, the electrical power density increases from 0.84 W/m2 to 2.2 W/m2. Optimum operation of RED depends significantly on the external load (external device). A small load will increase hydrogen energy while decreasing electrical energy. This trade-off is critical in order to optimally operate an RED cell for both hydrogen and electricity generation.

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A biomimetic nanofluidic diode based on surface-modified polymeric carbon nitride nanotubes

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.10.130 ◽

2019 ◽

Vol 10 ◽

pp. 1316-1323 ◽

Cited By ~ 7

Author(s):

Kai Xiao ◽

Baris Kumru ◽

Lu Chen ◽

Lei Jiang ◽

Bernhard V K J Schmidt ◽

...

Keyword(s):

Energy Conversion ◽

Carbon Nitride ◽

Salinity Gradient ◽

Low Cost ◽

Ion Selectivity ◽

Porous Membranes ◽

Potential Applications ◽

Gradient Energy ◽

Surface Modified ◽

Polymeric Carbon

A controllable ion transport including ion selectivity and ion rectification across nanochannels or porous membranes is of great importance because of potential applications ranging from biosensing to energy conversion. Here, a nanofluidic ion diode was realized by modifying carbon nitride nanotubes with different molecules yielding an asymmetric surface charge that allows for ion rectification. With the advantages of low-cost, thermal and mechanical robustness, and simple fabrication process, carbon nitride nanotubes with ion rectification have the potential to be used in salinity-gradient energy conversion and ion sensor systems.

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Power Generation From Concentration Gradient by Reverse Electrodialysis in Ion Selective Nanochannel

ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels ◽

10.1115/icnmm2009-82208 ◽

2009 ◽

Author(s):

Dong-Kwon Kim ◽

Chuanhua Duan ◽

Yu-Feng Chen ◽

Arun Majumdar

Keyword(s):

Power Generation ◽

Concentration Gradient ◽

Ion Selectivity ◽

Electrical Energy ◽

Anodic Bonding ◽

Channel Height ◽

Cmos Process ◽

Surface Charges ◽

Reverse Electrodialysis ◽

Counter Ions

In this article, ion selective nanochannels are studied to generate electric power from concentration gradient by reverse electrodialysis. When nanochannels bring into contact with aqueous solution, the surface of nanochannels acquires charges from ionization, ion adsorption, and ion dissolution. These surface charges draw counter-ions toward the surface and repel co-ions away. Therefore, when an electrolyte concentration gradient is applied to nanochannels, counter-ions are transported through nanochannels much more easily than co-ions, which results in a net charge migration of ions. Gibbs free energy of mixing, which forces ion diffusion, thus can be converted into electrical energy by using ion-selective nanochannels. Silica nanochannels with heights of 26 nm and 80 nm fabricated by glass-silicon anodic bonding were used in this study. We experimentally investigated the power generation from these nanochannels placed between two potassium chloride solutions with various combinations of concentrations. The power generation per unit channel volume increases when the concentration gradient increases, while it decreases as channel height decreases. The highest power density measured is 26 kW/m3. Our data also indicates that the efficiency of energy conversion and the ion selectivity increase with a decrease of concentrations and channel height. The best efficiency obtained is 24%. Compared with ion-selective membranes, nanochannels promise more reliable operation since they are readily compatible with standard CMOS process and do not shrink and swell in response to their environment. Power generation from concentration gradient in ion selective nanochannels could be used in a variety of applications, including micro batteries and micro power generators.

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Finite elements-based 2D theoretical analysis of the effect of IEX membrane thickness and salt solution residence time on the ion transport within a salinity gradient power reverse electrodialysis half cell pair

Desalination and Water Treatment ◽

10.1080/19443994.2013.807905 ◽

2013 ◽

Vol 51 (34-36) ◽

pp. 6429-6443 ◽

Cited By ~ 7

Author(s):

Etienne Brauns

Keyword(s):

Finite Elements ◽

Theoretical Analysis ◽

Ion Transport ◽

Residence Time ◽

Salt Solution ◽

Salinity Gradient ◽

Membrane Thickness ◽

Half Cell ◽

Cell Pair ◽

Reverse Electrodialysis

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Harvesting Natural Salinity Gradient Energy for Hydrogen Production Through Reverse Electrodialysis (RED) Power Generation

ASME 2016 Power Conference ◽

10.1115/power2016-59565 ◽

2016 ◽

Author(s):

Mohammadreza Nazemi ◽

Jiankai Zhang ◽

Marta Hatzell

Keyword(s):

Power Density ◽

Current Density ◽

Salinity Gradient ◽

Electrical Energy ◽

Hydrogen Energy ◽

External Resistance ◽

Membrane Area ◽

Reverse Electrodialysis ◽

Gradient Energy

There is an enormous potential for energy generation from the mixing of sea and river water at global estuaries. If technologies are developed which are capable of converting this energy into a usable form (electricity or fuels), salinity gradient energy may be able to dramatically increase the worlds supply of renewable energy. Here we present a novel approach to convert this source of energy directly into hydrogen and electricity using Reverse Electrodialysis (RED). RED relies on converting ionic current to electric current using multiple membranes and redox based electrodes. A thermodynamic model for RED is created to evaluate the electricity and hydrogen which can be extracted from natural mixing processes. With equal volumes of HC and LC solutions (0.001m3), the maximum energy extracted is found to occur with 5 number of membrane pairs. At this operating point, 0.4 kWh/m3 can be extracted as electrical energy and 0.95 kWh/m3 of energy is extracted as hydrogen energy. The electrical energy conversion efficiency approaches 15%, whereas the hydrogen energy efficiency is 35%. Overall, the maximum system conversion of Gibbs free energy to electrical and hydrogen energy approaches 50%. The results show that as the number of membrane pairs increases from 5 to 20, the hydrogen power density decreases from 13.2 W/m2 to 3.7 W/m2. Likewise, the power density from electrical energy decreases from 1 W/m2 to 0.3 W/m2. This is because of increase in the total membrane area as increasing the number of membrane pairs. The stack voltage increased from 1.5V to 6V as the number of membrane pairs is increased from 5 to 20. This corresponds to an increase in internal resistance from 600 Ω.cm2 to 2400 Ω.cm2. Long term trade-off between improving the system voltage, while decreasing the system resistance will be crucial for improved long term RED performance. Furthermore, optimum operation of RED, depends on proper selection of external resistance. A small external resistance will increase hydrogen energy and decrease electrical energy, particularly using a small number of membrane pairs. With the fixed small external resistance, as increasing the number of membrane pairs, the difference between internal and external resistance increases. Therefore, the load potential and current density do not increase considerably. For the cases analyzed with 8.29 Ω.cm2 external resistance, the maximum current density increases from 11.1 mA/cm2 to 12.4 mA/cm2 as the number of membrane pairs increases from 5 to 20. Likewise, the load potential rises from 92 mV to 102 mV.

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Salinity gradient power: influences of temperature and nanopore size

Nanoscale ◽

10.1039/c5nr07563g ◽

2016 ◽

Vol 8 (4) ◽

pp. 2350-2357 ◽

Cited By ~ 43

Author(s):

Shiojenn Tseng ◽

Yu-Ming Li ◽

Chih-Yuan Lin ◽

Jyh-Ping Hsu

Keyword(s):

Salinity Gradient ◽

Electrical Energy ◽

Reverse Electrodialysis ◽

Salinity Gradient Power

Harvesting electrical energy by nanofluidic reverse electrodialysis.

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Miniaturized Salinity Gradient Energy Harvesting Devices

Molecules ◽

10.3390/molecules26185469 ◽

2021 ◽

Vol 26 (18) ◽

pp. 5469

Author(s):

Wei-Shan Hsu ◽

Anant Preet ◽

Tung-Yi Lin ◽

Tzu-En Lin

Keyword(s):

Energy Harvesting ◽

Energy Conversion ◽

Membrane Fouling ◽

Salinity Gradient ◽

Electrical Energy ◽

Clean Energy ◽

Internal Resistance ◽

Power Extraction ◽

Gradient Energy ◽

Energy Harvesting Devices

Harvesting salinity gradient energy, also known as “osmotic energy” or “blue energy”, generated from the free energy mixing of seawater and fresh river water provides a renewable and sustainable alternative for circumventing the recent upsurge in global energy consumption. The osmotic pressure resulting from mixing water streams with different salinities can be converted into electrical energy driven by a potential difference or ionic gradients. Reversed-electrodialysis (RED) has become more prominent among the conventional membrane-based separation methodologies due to its higher energy efficiency and lesser susceptibility to membrane fouling than pressure-retarded osmosis (PRO). However, the ion-exchange membranes used for RED systems often encounter limitations while adapting to a real-world system due to their limited pore sizes and internal resistance. The worldwide demand for clean energy production has reinvigorated the interest in salinity gradient energy conversion. In addition to the large energy conversion devices, the miniaturized devices used for powering a portable or wearable micro-device have attracted much attention. This review provides insights into developing miniaturized salinity gradient energy harvesting devices and recent advances in the membranes designed for optimized osmotic power extraction. Furthermore, we present various applications utilizing the salinity gradient energy conversion.

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