Power Generation Performance of a Pilot-Scale Reverse Electrodialysis Using Monovalent Selective Ion-Exchange Membranes

Abstract

Reverse electrodialysis (RED) is a promising process for harvesting energy from the salinity gradient between two solutions without environmental impacts. Seawater (SW) and river water (RW) are considered the main RED feed solutions because of their good availability. In Okinawa Island (Japan), SW desalination via the reverse osmosis (RO) can be integrated with the RED process due to the production of a large amount of RO brine (concentrated SW, containing ~1 mol/dm3 of NaCl), which is usually discharged directly into the sea. In this study, a pilot-scale RED stack, with 299 cell pairs and 179.4 m2 of effective membrane area, was installed in the SW desalination plant. For the first time, asymmetric monovalent selective membranes with monovalent selective layer just at the side of the membranes were used as the ion exchange membranes (IEMs) inside the RED stack. Natural and model RO brines, as well as SW, were used as the high-concentrate feed solutions. RW, which was in fact surface water in this study and close to the desalination plant, was utilized as the low-concentrate feed solution. The power generation performance investigated by the current-voltage (I–V) test showed the maximum gross power density of 0.96 and 1.46 W/m2 respectively, when the natural and model RO brine/RW were used. These are a 50–60% improvement of the maximum gross power of 0.62 and 0.97 W/m2 generated from the natural and model SW, respectively. The approximate 50% more power generated from the model feed solutions can be assigned to the suppression of concentration polarization of the RED stack due to the absence of multivalent ions.

Ionic Transport Properties of Cation-Exchange Membranes Prepared from Poly(vinyl alcohol-b-sodium Styrene Sulfonate)

“…In recent years, cation-exchange membranes (CEMs) have received considerable attention from researchers and manufacturers, and have been widely used for various industrial purposes [ 1 ], such as the separation of metal ion pollutants from hard water [ 2 ], chlor-alkali electrolysis [ 3 ], fuel cells [ 4 , 5 , 6 , 7 , 8 , 9 ], electrodialytic concentration or desalination of electrolyte solutions [ 1 , 3 , 10 ], redox flow batteries [ 11 , 12 , 13 ], reverse electrodialysis [ 14 , 15 , 16 ], and hydrogen production [ 17 , 18 , 19 ]. CEMs contain fixed, negatively charged groups that allow cations to pass through the membranes while concurrently rejecting anions.…”

Determination of the applicability of the tungsten-containing material as low-cost electrodes for reverse electrodialysis

“…The problem of electrode materials for reverse electrodialysis is quite acute. Most of the publications generally ignore the issue of electrodes, focusing on ion-exchange membranes [11,17]. The electrode materials described in the literature can be basically divided into two groups.…”

“…The use of combined water treatment and power generation systems is effective [16]. Power generation using solutions of monovalent [17] and polyvalent [18] ions has been studied under laboratory conditions. The works [19,20] show the possibility of scaling the method of power generation by reverse electrodialysis.…”

Comparison of Pressure-Retarded Osmosis Performance between Pilot-Scale Cellulose Triacetate Hollow-Fiber and Polyamide Spiral-Wound Membrane Modules

“…There are two main membranebased technologies that convert SGE into electricity: reverse electrodialysis (RED) [9,11,12] and pressure-retarded osmosis (PRO) [10,13]. RED generates energy by converting counterion permselective transport with ion-exchange membranes to electric current by redox reactions at two electrodes; there have been reports on large-scale RED systems [14][15][16][17]. In contrast, in a PRO system, a semi-permeable membrane (SPM) separates a low-salinity solution, the feed solution (FS), from a pressurized high-salinity solution, called the draw solution (DS).…”