This document describes a project to extract electrical energy from brine treatment using reverse electrodialysis (RED). The project aims to utilize the concentration gradient between high and low salinity solutions to generate electricity via diffusion through ion exchange membranes. Key points discussed include: - The scientific principles of RED based on Fick's laws of diffusion and Nernst equation. - The proposed system setup using platinum/iridium electrodes and a hexacyanoferrate redox electrolyte between cation and anion exchange membranes. - Results showing the experimental voltage matches theoretical values and optimization of current flow. - Applications including desalination energy reduction and portable emergency power, with limitations around membrane costs and need for further

1. Electrical Energy Extraction of Brine Treatment
Using Reverse Electrodialysis (RED)
Group Members:
Endy Nugroho Dwiputra
Martin Mardjuki
Victor Julistiono Barlian
Project Supervisor: Dr. Narasimalu Srikanth

2. Introduction
Projected Brine Resource 27.3 Kton
Power Conversion 1 W/m2
Potential Power Output 0.03 GWh
Potential Energy Output 0.11 TW
Daily Energy Demand 0.90%

3. Pressure Retarded Osmosis (PRO)

4. Pressure Retarded Osmosis (PRO) cont’d
• Pressure generated by the forward osmosis from low concentration
(LC) to high concentration (HC)
• Pressure is used to turn the mechanical turbine which is required to
produce electricity
• Large space is needed for the turbine, and output is further reduced
due to energy conversion loss
• With more steps in energy conversion towards the net form, there is
higher loss of energy based on thermodynamics, such as waste heat.

5. Reverse Electrodialysis (RED)

6. Reverse Electrodialysis (RED) cont’d
• Using Ionic Exchange Membrane (IEM), which consists of Anionic
(AEM) and Cationic (CEM)
• Membrane selectively passes through the ions of salt concentration

7. Working Principle

8. Working Principle cont’d
• Ion separation rises potential differences
• Potential differences attracts electron
• Electrons generated from redox couple of electrolyte
• Once the circuit is closed, current is generated

9. Scientific Principle
• This project utilize Fick’s second law of diffusion1, as concentration
gradient (chemical potential) decreases with time between HC and LC
as illustrated in figure next slide.
• Diffusion flux continues until equilibrium is achieved. With Fick’s Law,
the waste heat from desalination process is used to heat the solution
to 55-600 C to further enhance the diffusion and kinetics of the ions.
• Furthermore, the alternating stacking of IEM to generate potential
using Nernst equation of electrochemical principle2, which measures
the overall potential from the Gibbs free energy/potential difference
and concentration difference, which RED utilizes mainly.

10. Second Fick’s Law of Diffusion
The concentration gradient difference comparison
between cross and linear flow

11. Setup - Cell

12. Setup - Complete

13. Materials
Electrode:
• Platinum (Pt) is highly inert metal which has standard reduction
potential of +1.2 V3, just behind Gold.
• Coating of Iridium (Ir), which is the most corrosion resistant metal and
has very high melting point further improves lifetime for several
years.
• Recirculating electrode rinse with opposite electrode reactions is
used, so there is low over-potentials, no gas evolution and no net
chemical reaction (as shown in figure below) that lead to low loss of
this RED system3.
• Pt/Ir also has higher mechanical stability for longer operation times
and more proper current collecting system.

14. Materials cont’d
Electrolyte:
• This system is chosen since we employ salts with very distinct
concentrations.
• Hexacyanoferrate system is comparatively quite stable as cyanide ions
bond very well to the ferrous ions, forming complex ions that are
readily dissolvable, resulting in higher pH threshold3.
• Acid such as HCl does not need to be added to acidify the system,
while preventing the formation of highly poisonous HCN gas.

15. Materials cont’d
Electrolyte
• 2 CEMs are used as outer membranes to prevent loss of iron used as
redox couple3.
• Low overpotentials, no gas evolution and no net chemical reactions
that lead to low voltage loss for this system3.

16. Formula
• Power output of RED system

17. Results
• Experimental voltage is similar to theoretical voltage
• Optimisation of experimental current flow
• RED system has limited efficiency using ED cell
THEORETICAL EXPERIMENTAL
Voltage 3.6 V 3.5 – 3.8 V

18. Applications
• Coupling RED with Desalination Process
• Reduce energy footprint (consumption) of Desalination Process
• Meeting points of seawater and river water
• More sites to generate electricity, such as at Marina Barrage
• Brine treatment alternative solution
• Replace energy-consuming diffuser to energy-producing RED

19. Applications cont’d
• Portable emergency water (ED) or electricity (RED)
supply kit
• Survival kit for lost fishermen or travelers; or soldiers war
• Potential future renewable energy system
• Complement solar, hydro, wind, biomass, and geothermal power
upon mature technology development

20. Limitations
• Current Ion Exchange Membrane (IEM) price & cost of scaling up
• Need further research to improve IEM & RED performance, especially
when scaled up
• Availability of cost effective materials, equipment and technology to
get the most optimized performance
• High internal resistance of RED system as it is still less developed
technology and reversal of highly researched and commercialized ED

21. • Reduce resistance from various factors
• Increase concentration difference ratio between HC & LC
• Increase permselectivity of the membranes
• Increase temperature of solutions by utilizing waste heat from
desalination process to improve diffusion kinetics of the ions
• Improve RED cell design (larger cell area, increasing cell dimension,
more number of cells, and narrower intermembrane distance)
• Scale up system to be integrated with complementary technologies
such as RO in desalination plants for better energy efficiency
Future Development

22. Further Works
• More vigorous with major advancement in R&D and evaluation of
performance for improved RED system
• Collaboration with academia, research and industry in this field to
commercialize this technology based on technical performance &
economic considerations
• Funding from Venture Capitalist and Joint Venture with Angel Investor

23. Technical Specs of IEM
Parameters Membrane
PC SA (AEM) PC SK (CEM)
General use standard desalination standard desalination
Membrane type
strongly alkaline,
ammonium
strongly acidic, sulfonic
acid
Transferance number > 0.95 > 0.95
Resistance / W cm2 ~ 1.8 ~ 2.5
Water Content (wt%) ~ 14 ~ 9
Ion exchange capacity n/a n/a
Temperature stability (max / oC) 60 50
Chemical stability (pH range) 0-9 0-9
Burst strength / kg.cm-2 4 to 5 4 to 5
Thickness / mm 180-220 160-200
Reinforcement Polyester Polyester
Permselectivity (0.1 M / 0.5 M
KCl) > 0.93 > 0.95
Ionic form as shipped Cl- Na+

24. References
• 1. M. Leif, The Complete Solution of Fick’s Second Law of Diffusion
with Time-
dependent Diffusion Coefficient and Surface Concentration, Durability
of Concrete in Saline Environement, 1993, pg 127.
• 2. P. O. Ryan, Full Cell Fundamentals, chapter 2.4.3: Reversible Voltage
Variation with Concentration: Nernst Equation, Wiley.
• 3. Veerman, J., et al.. (2010). Reverse electrodialysis: evaluation of
suitable electrode systems. Journal of Applied Electrochemistry, 40(8),
1461-1474. doi: 10.1007/s10800-010-0124-8