A comprehensive study on the effects of operation variables on reverse electrodialysis performance

Abstract

Despite the great prospects of reverse electrodialysis (RED), which directly transforms salinity gradient energy into electricity, new efforts focusing on its optimization are still required before large-scale implementation. RED performance is determined by numerous variables including (i) membrane properties, (ii) compartment and spacer design, (iii) stream concentrations defining salinity gradient, (iv) flow velocity and fluidodynamics. Among them, low salinity stream (LC) concentration and feed flow rates are key operation variables with great impact on power output; thus, this work approaches their parametric analysis through modeling tools. Initially, as novel study, LC salinity influence was deeply analyzed by quantifying its relative contribution to the overall internal resistance while determining the rest of all ohmic and non-ohmic components. Seawater was selected as high concentrated solution (HC), 0.55 M NaCl, due to its global availability for RED exploitation. LC and Reynolds number analysis are needed to select suitable water sources and devise new strategies to adapt RED performance. LC salinity of 0.02 M NaCl and ReHC=3.4 and ReLC=7 allowed to reach the highest net power density. A previously developed mathematical model was used, with simulated results validated in a laboratory-scale plant, offering valuable input for future decision-making in RED operation and upscaling.