Effect of spacer geometry on reverse electrodialysis stack performance

Abstract

Reverse electrodialysis (RED) is a promising technology capable of directly converting salinity gradient energy into electrical energy. Spacers are key components of RED stacks that significantly influence their performance. This study proposes a three-dimensional multiphysics model for the RED process, grounded in the Nernst-Planck equation framework. Using this model, the effects of woven spacers on RED performance were investigated in terms of concentration polarization, pumping power consumption, and shadow effect. The results indicate that spacers with reduced thickness (h_ch) and increased filament pitch (l) demonstrate superior overall stack performance. Under optimal solution velocity conditions, when h_ch is 50 μm, the maximum net power density is 177 % higher compared to the scenario where h_ch is 200 μm (with l/h_ch = 3). Additionally, when l/h_ch = 5, the maximum net power density is 17 % higher than that observed when l/h_ch = 2 (with h_ch = 100 μm). Furthermore, the shadow effect of the spacer is primarily determined by its geometric structure and is less influenced by operating conditions.