Evaluation of RED power generation performance of PF membrane stacks with different convex structures

Reverse electrodialysis (RED) is a promising technology for harvesting salinity gradient energy from the mixing of seawater and river water. In RED systems, the internal resistance within the flow channels significantly reduces the power density. PF membranes provide an effective approach to reduce the electrical resistance in the flow channels without the use of conventional spacers. In this study, a dashed-line PF membrane was proposed to stabilize the PF structure of ORIGAMI PF proposed in recent years, and the structural and power generation performance were compared among stacks fabricated with flat membranes, dashed-line PF membranes, and solid-line PF membranes. As a result, the dashed-line PF membrane maintained its profile structure for more than two years and exhibited excellent long-term mechanical stability. Although these PF membranes showed a voltage decrease due to concentration polarization, the internal resistance of the stacks was significantly reduced by eliminating the spacer mesh. Consequently, the dashed-line PF membrane exhibited a gross power density of 1.40 W/m², which is approximately twice that of flat membranes and 20% higher than that of the solid-line PF membranes.