Novel solutions for closed-loop reverse electrodialysis: Thermodynamic characterisation and perspective analysis

Abstract

Closed-loop Reverse Electrodialysis is a novel technology to directly convert low-grade heat into electricity. It consists of a reverse electrodialysis (RED) unit where electricity is produced exploiting the salinity gradient between two saltwater solutions, coupled with a regeneration unit where waste-heat is used to treat the solutions exiting from the RED unit and restore their initial composition. One of the most important advantages of closed-loop systems compared to the open systems is the possibility to select ad-hoc salt solutions to achieve high efficiencies. Therefore, the properties of the salt solutions are essential to assess the performance of the energy generation and solution regeneration processes. The aim of this study is to analyse the influence of thermodynamic properties of non-conventional salt solutions (i.e. other than NaCl-aqueous solutions) and their influence on the operation of the closed-loop RED. New data for caesium and potassium acetate salts, i.e. osmotic and activity coefficients in aqueous solutions, at temperature between 20 and 90°C are reported as a function of molality. The data are correlated using Pitzer's model, which is then used to assess the theoretical performance of the whole closed-loop RED system considering both single and multi-stage regeneration units. Results indicate that KAc, CsAc and LiCl are the most promising salts among those screened.

Design and experimental study of a small scale adsorption desalinator

“…Shahzad et al presented an increased overall efficiency of the hybrid process [15], while Thu et al reported that hybridisation increases the distillate output of an existing MED plant [16]. Another promising application for adsorption desalination as well as other thermal desalination methods is the combination with Reverse Electrodialysis [17] to generate electricity from low-grade heat in a closed-loop system [18,19]. Membrane distillation [20,21], MED [22], and adsorption desalination [23] have been proposed for the application in closed-loop systems.…”

Thermolytic reverse electrodialysis heat engine: model development, integration and performance analysis

“…Carati et al [14] presented a theoretical analysis on SGP HE, focusing on the effect of different saltwater solutions, namely NaCl, ZnCl2 and sodium hydroxide (NaOH) water solutions, on the performance of a unit constituted of a distiller and an ideal SGP unit. Similarly, Giacalone et al [15] performed a theoretical analysis concerning the influence of different salt-water solutions, namely NaCl, LiCl, potassium chloride (KCl), potassium acetate (KCH3CO2), caesium acetate (CsCH3CO2) and sodium acetate (NaCH3CO2) water solutions, on the performance of SGP HEs consisting of single and multi-stage regeneration units. Micari et al [16] experimentally investigated the performance of a RED unit fed by aqueous solutions of binary salt mixtures.…”

Thermally Regenerable Redox Flow Battery

“…Heat-to-electricity efficiency vs power density of state-of-the-art technologies to harvest low-temperature heat reported in literature. Red points: thermal regenerative electrochemical cycle systems (TREC); [12,14,48] Black points: thermal electrochemical cell devices (TEC); [20,49,50] Blue points: thermo-osmotic energy conversion technologies (TOEC); [51,52] Orange points: pressure-retarded osmosis systems (PRO); [2,23,53] Purple points: reverse electrodialysis devices (RED), [27,40,54,55] Brown points: TRCBs; [36,56] Green stars: TRBs. [41]…”