Flow and mass transfer enhancement in reverse electrodialysis stacks using profiled ion exchange membranes

Power generation by reverse electrodialysis (RED) is a promising technology based on sustainable salinity gradient energy. This study performed numerical simulations using a three-dimensional multi-physical model of a RED cell pair with emphasis on chevron-profiled membranes. The simulations revealed the hydrodynamics and electrochemical behaviors during the RED process and the effects of chevron-profiled membranes on stack performance. The results indicated that the chevron corrugations of chevron-profiled membranes induce periodically upward and downward fluid motion similar to the role of spacers, leading to improved fluid mixing and reduced concentration polarization. Furthermore, these microstructures increased the membrane surface area available for mass transfer and shortened the transport path of ions crossing flow channels, resulting in enhanced ion transport and decreased electrical resistance. Comparisons among RED stacks with different configurations revealed that the RED stack with chevron-profiled membranes exhibits considerably higher net power density than stacks with wave-profiled membranes or woven spacers.