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

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.

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

2017 ◽  
Vol 14 (2) ◽  
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.

Sustainable hydrogen production from seawater and sewage treated water using reverse electrodialysis technology

2019 ◽  
Vol 14 (3) ◽  
pp. 645-651 ◽  
Author(s):  
Mitsuru Higa ◽  
Takeshi Watanabe ◽  
Masahiro Yasukawa ◽  
Nobutaka Endo ◽  
Yuriko Kakihana ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Production System ◽  
Salinity Gradient ◽  
Water Electrolysis ◽  
Direct Conversion ◽  
Pilot Scale ◽  
Hydrogen Energy ◽  
Treated Water ◽  
Reverse Electrodialysis ◽  
Gradient Energy

Abstract A pilot-scale sustainable hydrogen production system using reverse electrodialysis (RED) technology was launched. The system is based on direct conversion of salinity gradient energy (SGE) between seawater (SW) and sewage treated water (STW) to hydrogen production by water electrolysis. The hydrogen production rate was almost the same as the theoretical value. This indicates that the RED hydrogen production system can convert SGE between SW and STW to hydrogen energy at high current efficiency.

scholarly journals Correlations between Properties of Pore-Filling Ion Exchange Membranes and Performance of a Reverse Electrodialysis Stack for High Power Density

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 609
Author(s):  
Hanki Kim ◽  
Jiyeon Choi ◽  
Namjo Jeong ◽  
Yeon-Gil Jung ◽  
Haeun Kim ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Power Density ◽  
Electrical Resistance ◽  
Salinity Gradient ◽  
Power Production ◽  
Pilot Scale ◽  
Ion Exchange Membranes ◽  
Pore Filling ◽  
Membrane Area ◽  
Reverse Electrodialysis

The reverse electrodialysis (RED) stack-harnessing salinity gradient power mainly consists of ion exchange membranes (IEMs). Among the various types of IEMs used in RED stacks, pore-filling ion exchange membranes (PIEMs) have been considered promising IEMs to improve the power density of RED stacks. The compositions of PIEMs affect the electrical resistance and permselectivity of PIEMs; however, their effect on the performance of large RED stacks have not yet been considered. In this study, PIEMs of various compositions with respect to the RED stack were adopted to evaluate the performance of the RED stack according to stack size (electrode area: 5 × 5 cm2 vs. 15 × 15 cm2). By increasing the stack size, the gross power per membrane area decreased despite the increase in gross power on a single RED stack. The electrical resistance of the PIEMs was the most important factor for enhancing the power production of the RED stack. Moreover, power production was less sensitive to permselectivities over 90%. By increasing the RED stack size, the contributions of non-ohmic resistances were significantly increased. Thus, we determined that reducing the salinity gradients across PIEMs by ion transport increased the non-ohmic resistance of large RED stacks. These results will aid in designing pilot-scale RED stacks.

Reverse electrodialysis in bilayer nanochannels: salinity gradient-driven power generation

2018 ◽  
Vol 20 (10) ◽  
pp. 7295-7302 ◽  
Author(s):  
Rui Long ◽  
Zhengfei Kuang ◽  
Zhichun Liu ◽  
Wei Liu
Keyword(s):  
Power Generation ◽  
Energy Harvesting ◽  
Salinity Gradient ◽  
Reverse Electrodialysis ◽  
Gradient Energy ◽  
Ion Transportation

To evaluate the possibility of nano-fluidic reverse electrodialysis (RED) for salinity gradient energy harvesting, we consider the behavior of ion transportation in a bilayer cylindrical nanochannel with different sized nanopores connecting two reservoirs at different NaCl concentrations.

Exergy Analysis-Potential of Salinity Gradient Energy Source

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Arash Emdadi ◽  
Mansour Zenouzi ◽  
Amir Lak ◽  
Behzad Panahirad ◽  
Yunus Emami ◽  
...  
Keyword(s):  
Sodium Chloride ◽  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Exergy Analysis ◽  
Salinity Gradient ◽  
Electrical Energy ◽  
Dead State ◽  
Gradient Energy ◽  
Reference Environment ◽  
Faster Development

Mixing of fresh (river) water and salty water (seawater or saline brine) in a controlled environment produces an electrical energy known as salinity gradient energy (SGE). Two main conversion technologies of SGE are membrane-based processes: pressure retarded osmosis (PRO) and reverse electrodialysis (RED). Exergy calculations for a representative river-lake system are investigated using available data in the literature between 2000 and 2008 as a case study. An exergy analysis of an SGE system of sea-river is applied to calculate the maximum potential power for electricity generation. Seawater is taken as reference environment (global dead state) for calculating the exergy of fresh water since the sea is the final reservoir. Aqueous sodium chloride solution model is used to calculate the thermodynamic properties of seawater. This model does not consider seawater as an ideal solution and provides accurate thermodynamics properties of sodium chloride solution. The chemical exergy analysis considers sodium chloride (NaCl) as main salt in the water of this highly saline Lake with concentration of more than 200 g/L. The potential power of this system is between 150 and 329 MW depending on discharge of river and salinity gradient between the Lake and the River based on the exergy results. This result indicates a high potential for constructing power plant for SGE conversion. Semipermeable membranes with lifetime greater than 10 years and power density higher than 5 W/m2 would lead to faster development of this conversion technology.

scholarly journals Life cycle assessment of salinity gradient energy recovery by reverse electrodialysis in a seawater reverse osmosis desalination plant

2020 ◽  
Vol 4 (8) ◽  
pp. 4273-4284 ◽  
Author(s):  
Carolina Tristán ◽  
Marta Rumayor ◽  
Antonio Dominguez-Ramos ◽  
Marcos Fallanza ◽  
Raquel Ibáñez ◽  
...  
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Energy Recovery ◽  
Large Scale ◽  
Salinity Gradient ◽  
Reverse Electrodialysis ◽  
Desalination Plant ◽  
Gradient Energy ◽  
Seawater Reverse Osmosis ◽  
Reverse Osmosis Desalination

LCA of lab-scale and large-scale stand-alone RED stacks and an up-scaled RED system co-located with a SWRO desalination plant.

scholarly journals Energy Harvesting from Brines by Reverse Electrodialysis Using Nafion Membranes

Membranes ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 168 ◽  
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.

Reverse Electrodialyis Salinity Gradient Power Experiment

2014 ◽  
Author(s):  
Sean Amaral ◽  
Neil Franklin ◽  
Michael Jurkowski ◽  
Mansour Zenouzi
Keyword(s):  
Alternative Energy ◽  
Salinity Gradient ◽  
Experimental System ◽  
Energy Sources ◽  
Anion Exchange Membranes ◽  
Test Results ◽  
Membrane Area ◽  
Reverse Electrodialysis ◽  
Alternative Energy Sources ◽  
Available Energy

Today’s rate of fossil fuel consumption rapidly depletes fuel reserves and leads to a number of adverse environmental effects. Although the scope of these effects has yet to be fully realized, it is clear that the development of alternative energy sources is very important. A relatively new form of alternative energy known as reverse electrodialysis (RED) appears to be one of the promising energy sources of the future. This technology harvests the energy stored in the salinity gradient between two different liquids, and converts it directly into electric power. This power is generated by pumping water through an array of alternating pairs of cation and anion exchange membranes called cells. Various academic sources calculate the available energy to be 1.5 MJ for every cubic meter of sea and river water mixed, making all river basins a potential location for power production. Small prototype systems using 50 cells with areas of 100 cm2 were assembled by a group in the Netherlands, but larger stacks remain to be tested. An understanding of the feasibility of RED as a possible energy source relies on testing of cells with larger membrane area and different numbers of membrane pairs. An experimental system was designed with cells 61 cm × 16.5 cm, which will increase the output by nearly a factor of 10. Along with having much larger dimensions than previous systems, the design has an adjustable number of cells in the stack, allowing users obtain test results at a variety of settings. Comparing the output of systems with few cells to systems with many cells will help us to optimize the stack size in terms of hydrodynamic losses. Initial testing of the system resulted in a positive result. The tests showed that the system produced power, and the 1.98 volts measured was 83% of the predicted value. Leakage of the electrode rinse solution contaminated the membranes, and prevented more testing. Once the electrode rinse system is redesigned, more testing will be done.

scholarly journals Chemical and Energy Recovery Alternatives in SWRO Desalination through Electro-Membrane Technologies

2021 ◽  
Vol 11 (17) ◽  
pp. 8100
Author(s):  
Marta Herrero-Gonzalez ◽  
Raquel Ibañez
Keyword(s):  
Renewable Energy ◽  
Salinity Gradient ◽  
Raw Material ◽  
Reverse Electrodialysis ◽  
Bipolar Membranes ◽  
Impact Reduction ◽  
Acid And Base ◽  
Readiness Level ◽  
Gradient Energy ◽  
Membrane Technologies

Electro-membrane technologies are versatile processes that could contribute towards more sustainable seawater reverse osmosis (SWRO) desalination in both freshwater production and brine management, facilitating the recovery of materials and energy and driving the introduction of the circular economy paradigm in the desalination industry. Besides the potential possibilities, the implementation of electro-membrane technologies remains a challenge. The aim of this work is to present and evaluate different alternatives for harvesting renewable energy and the recovery of chemicals on an SWRO facility by means of electro-membrane technology. Acid and base self-supply by means of electrodialysis with bipolar membranes is considered, together with salinity gradient energy harvesting by means of reverse electrodialysis and pH gradient energy by means of reverse electrodialysis with bipolar membranes. The potential benefits of the proposed alternatives rely on environmental impact reduction is three-fold: (a) water bodies protection, as direct brine discharge is avoided, (b) improvements in the climate change indicator, as the recovery of renewable energy reduces the indirect emissions related to energy production, and (c) reduction of raw material consumption, as the main chemicals used in the facility are produced in-situ. Moreover, further development towards an increase in their technology readiness level (TRL) and cost reduction are the main challenges to face.

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