Comparative study on the performance of a two-cell system of Flow Electrode Capacitive Mixing (F-CapMix) for continuous energy production

In recent years, Capacitive Mixing (CapMix) has garnered growing interest as a novel method for harnessing energy from the salinity gradient between seawater and freshwater. However, the challenge of extracting energy in a continuous way remains to be solved in traditional CapMix system. In this study, we demonstrate the feasibility of achieving continuous energy extraction through the use of a two-cell flow electrode Capacitive Mixing (F-CapMix) system. The performance of the F-CapMix system is evaluated under various experimental conditions including the activated carbon loading, carbon black additives, velocity of the flow electrode and feed water and external resistance in the circuit. The results suggest that the power density of the system can be significantly increased by approximately 800 % or 400 % with an increase in the carbon loading or the addition of carbon black additives, respectively. Meanwhile, reducing the flow rate of the flow electrode and feedwater from 20 mL/s to 5 mL/s was found to improve the system's performance. In addition, it is crucial that the external resistance is matched to the internal resistance of the cell for achieving a maximum power density. These results highlight the potential of F-CapMix and provide guidance for its further optimization. •A two-cell system of flow electrode capacitive mixing (F-CapMix) is developed for the continuous extraction of salinity gradient energy.•Reducing the electronic resistance of the flow electrodes can significantly improve the system's performance.•The performance of the proposed two-cell F-CapMix system can be significantly enhanced by increasing the activated carbon loading of the flow electrode.•By introducing the carbon black to the flow electrode, the power density of the two-cell F-CapMix system was significantly enhanced.