Investigation of Reverse ElectroDialysis Units by Multi-Physical Modelling

Reverse electrodialysis (RED) is an electrochemical membrane process that converts the salinity gradient energy between two solutions into electric current, by using ion exchange membranes. A novel multi-physical approach for RED modelling is proposed. 2-D simulations of one cell pair with tertiary current distribution (Nernst–Plank equation and local electroneutrality) were performed. Moreover, the Donnan exclusion theory was implemented for simulating double layer phenomena. Transport phenomena and electrochemical behavior were well described. The influence of membrane/channel configuration, dilute concentration and feeds velocity on the process performance was assessed. For a dilute concentration ≤ 0.01M, stacks with profiled membranes reached lower resistances and higher net powers (up to 4.4 W/m2) with respect to stacks with empty channels, thus suggesting that only in some cases the profiles lead to a performance enhancement.