Renewable Power Generation by Reverse Electrodialysis Using an Ion Exchange Membrane.

Sourayon Chanda,Peichun Amy Tsai

doi:10.3390/membranes11110830

Abstract

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 () and salt-concentration difference (). 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 () and open-circuit voltage () increase with increasing . On the one hand, the RED cell’s internal resistance () empirically reveals a power-law dependence of . On the other hand, the open-circuit voltage shows a logarithmic relationship of . 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.

Highlights

Salinity gradient energy (SGE) is a promising and abundant source of renewable energy harnessed by utilizing the chemical potential difference between freshwater and seawater
The general I-V trends in Figure 3a reveal a linear decrease of φc with increasing Ic since φc = φ0 − Ic Rc and both φ0 and Rc remain nearly constant for a particular reverse electrodialysis (RED) setup with specified solution concentrations
A RED power generation unit was designed, consisting of two reservoirs separated by a cation-selective Nafion membrane

Summary

Introduction

Salinity gradient energy (SGE) is a promising and abundant source of renewable energy harnessed by utilizing the chemical potential difference between freshwater and seawater. SGE can be captured using several technologies [1,2], such as reverse electrodialysis (RED) [3], pressure-retarded osmosis [4], and electric double layer capacitor [5]. Among these methods, RED has been an attractive, pollution-free alternative to harness the Gibbs free energy of mixing of electrolyte solutions [6]. 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]

Methods

Results

Conclusion