Power generation performance of a bench-scale reverse electrodialysis stack using wastewater discharged from sewage treatment and seawater reverse osmosis

Abstract In this study, we evaluated steady state power generation performance of a bench-scale RED stack with an effective membrane area of 40 m2 under different flow rate conditions using brine discharged from a seawater desalination plant and water discharged from a sewage treatment plant. Constant current operation was enabled to evaluate the steady state power output of the stack as the salt concentration profile inside the stack approached equilibrium. In addition, external current loading allowed for measurements of respective resistance of the stack, including membrane resistance, solution compartment resistance with spacers, and the resistance of each electrode; these measurements allowed for an estimation of the intrinsic stack performance when the electrode resistance was negligible. The evaluation of energy conversion efficiency revealed that 25–66% of the salinity gradient energy (SGE) was consumed in the stack and converted to electricity with a conversion efficiency of 17–26%. Furthermore, energy conversion analysis while considering the SGE loss due to both salt leakage and electrode reaction showed an energy conversion rate of 50%. Finally, the existence of flexible membrane deformation was proposed under different flow rates to obtain higher net power output. The obtained results are promising for use in full-scale RED implementation.