Optimization criteria of flow-electrode and feed water flow rate to achieve positive net power of flow-electrode capacitive mixing

Flow-electrode capacitive mixing (F-CapMix) produces continuous electricity due to infinite ion storage capacity of the flow-electrode. Researchers have predicted that achieving positive net power from F-CapMix is difficult due to the high pumping energy consumption of flow-electrodes. In this work, the power densities and net power densities of F-CapMix were evaluated under different flow rate condition of feed water (FW) and flow-electrode (FE) using low-and high-viscosity FEs. The power densities increased with a FE flow rate increment and a flow rate reduction of the FW. The power density difference under low and high flow-rate ratios between the FE and FW was small. As the power densities tended to become saturated with the flow rate ratio increase, indicating that a fast flow of the FE in F-CapMix is not necessary. Positive net power densities were achieved at low flow rates. The difference in the net power densities between high-and low-viscosity FEs was smaller than the power density difference between the two FEs, due to the high pumping energy consumption of highly viscous FE. Based on these results, the criteria for flow-rate optimization for the F-CapMix positive net power were suggested.