Thermoelectric Power of Ion Exchange Membrane Cells Relevant to Reverse Electrodialysis Plants

Abstract

A thermoelectric cell is designed and experiments are carried out in order to measure Seebeck coefficients of ion exchange membranes at different constant concentrations of NaCl in water. The purpose of the investigation is to explore how a temperature gradient may be applied to increase the efficiency of saline power plants, in particular, of the process of reverse electrodialysis (RED). To evaluate measurements and RED applications, we derive an expression for the thermoelectric potential for a cell with a single membrane and for a RED unit cell. The Seebeck coefficient is interpreted in terms of the Peltier heat of the cell, and further expressed in terms of transported entropies. We find the Seebeck coefficient of the cell, after correcting for temperature polarization, by gradually increasing the membrane thickness. The contribution to the Seebeck coefficient from the membrane varied between 1.41 and 0.98 mV/K in FUMASEP FKS-PET-75 cation exchange membranes, and between 0.56 and 0.48 mV/K in FUMASEP FAD-PET-75 anion exchange membranes. The precision in the results is 1%, for NaCl concentrations between 0.03 and 0.60 mol/kg. Measurements on the RED unit cell with water samples taken from realistic fresh-and saltwater sources confirmed that a temperature difference has a significant effect, increasing the emf by 1.3% per kelvin of temperature difference.

Perspectives on Thermoelectric Energy Conversion in Ion-Exchange Membranes

“…The temperature profile of such a cell cannot be accurately modeled without knowledge of the (large) Peltier effects [ 14 ]. It was probed that thermoelectric contributions to the cell potential can improve the cell performance in the otherwise isothermal reverse electrodialysis cell [ 20 , 63 ].…”

“…The aim of this work is to review state-of-the-art knowledge on thermoelectric energy conversion in cells with ion-exchange membranes. The hope is to provide a basis for further explorations of their use, i.e., in reverse electrodialysis (RED) [ 18 , 20 ]. In a RED concentration cell, isothermal alternating compartments of sea water and brackish water separated by ion-selective membranes permit the production of electric power [ 21 ].…”

“…In a RED concentration cell, isothermal alternating compartments of sea water and brackish water separated by ion-selective membranes permit the production of electric power [ 21 ]. Recent work demonstrates that a thermoelectric potential can be added to the RED concentration cell to increase the electromotive force by 10% per 20 K difference for given electrolyte conditions [ 20 ]. The class of ion exchange materials may provide cheaper cell components than presently used and help make renewable technologies more competitive.…”

Short-Circuit Current in Polymeric Membrane-Based Thermocells: An Experimental Study

“…The interest in membrane-based systems to convert low grade heat into electricity is increasing [ 9 , 12 , 13 , 14 ]. Jokinen et al [ 15 ] carried out the first experimental studies into thermoelectric power generation using ion-exchange membranes, using a cell with Ag|AgCl electrodes at the same temperature.…”

Giant Thermoelectric Response of Nanofluidic Systems Driven by Water Excess Enthalpy

“…liquid-solid slip [1,[21][22][23]. However, the possibility to use nanofluidic systems as thermoelectric converters has only been discussed very recently [24][25][26][27][28][29]. Traditional thermoelectric semiconductors offer high thermoelectric performance at room temperature, but their use is limited owing to their toxicity and rarity [26].…”