Abstract
Salinity gradient (SG) energy is a renewable and clean energy resource that exists worldwide from the change in Gibbs free energy when two solutions with different salinities are mixed. More recently, concentration flow cells (CFCs) have been introduced as a new technology for SG energy recovery with the highest reported power density output to date as a result of the utilization of both the electrode potential and Donnan potential. In this study, multiple CFCs are connected to form a consecutive number of stacks, and systematic analysis is conducted to investigate the influence of both parallel and series electrical wire connections on the overall performance. For both wire connections, an effective increase in the overall power output with an increase in stack size is observed. The power densities normalized to the membrane area are however lower (3.7 W m−2 in series and 5.8 W m−2 in parallel, for 5-stacks) than that of the individual cell unit (8.9 W m−2) because the back of the stack experiences cumulative mixing. Additionally, as a result of an ionic cross-conduction causing a parasitic current in the series cell, the parallel wire configuration is demonstrated to be more successful in the CFC stack than the series.