Auto Generative Capacitive Mixing for Power Conversion of Sea and River Water by the Use of Membranes

The chemical potential (free energy) of mixing two aqueous solutions can be extracted via an auto generative capacitive mixing (AGCM) cell using anionic and cationic exchange membranes together with porous carbon electrodes. Alternately, feeding sea and river water through the unit allows for the system to spontaneously deliver charge and discharge the capacitive electrodes so that dc electric work is supplied. Having a stack of eight cells coupled in parallel demonstrated the viability of this technology. An average power density of 0.055 W m−2 was obtained during the peak of the different cycles, though reasonable optimization suggests an expectation of 0.26 W m−2 at 6.2 A m−2. It was found that 83 ± 8% of the theoretical driving potential was obtained during the operating process. By studying the polarization curves during charging and discharging cycles, it was found that optimizing the feed fluid flow is currently among the most beneficial paths to make AGCM a viable salinity difference power source. Another parallel route for increasing the efficiency is lowering the internal ohmic resistances of the cell by design modifications.