Energy from Salinity Gradients

Monday, 2 October 2017: 09:20
National Harbor 10 (Gaylord National Resort and Convention Center)
S. Chittur Krishnaswamy (School of Advanced Sciences VIT University India)
Osmotic power or salinity gradient power (SGP) is the energy available from the difference in the salt concentration between seawater and river water. Two practical methods for this are reverse electrodialysis (RED) and pressure retarded osmosis (PRO). SGP can be generated from reversible mixing of two kinds of water with different salt contents. A process for generating potential from salinity concentration gradient produced in single cell (25 cm2) and multi-cell assembly is presented. The salinity gradient is created using a fuel cell type cell with a micro-porous ion exchange membrane, both anionic (AEM) and cationic (CEM). The study was performed for various gradients.  Salt : Fresh, from 100 : 0 to 16000 : 0 was established using NaCl solution, in the electrode chambers. A potential of 25 mV/cm was realized at ambient temperatures and pressures for a bipolar AEM/CEM cell. The achievable potential is still below theoretical value.  The performance was optimized for various static and dynamic flow rates of the saline and fresh water. For this purpose the cell flow field was simulated using ANSYS and the flow field design was optimized for maximum coverage of the cell area. The cell performance can further be optimized for various Membrane Electrode System (MES) structure. Cyclic Voltammetry (CV) studies were made to understand the redox process.  The electrochemical and electrical efficiency was discussed for various gradients and flow rates. The higher the salinity gradient the larger is the potential generated. This is limited by the membrane characteristics. The membrane characteristics have been studied for optimal ion crossover for various gradients and flow.