(59am) Continuous Power Production from Salinity Gradients Using Concentration Flow Cell Stacks

Salinity Gradient (SG) energy technologies are powered by the Gibbs free energy that is released from the mixing of two solutions with different salinities. This renewable energy source exists worldwide (e.g., in places like river deltas and industrial sites), and investigation of the methods that utilize this energy source have been focused on improving both the economic and electrical efficiency in order to make subsequent commercialization possible. Recently, concentration flow cells (CFC) have been introduced as a new technique with the highest reported power density for SG technologies so far. This improvement is the result of the utilization of both the Donnan potential from Cl- activity across the membrane as well as the electrode potential from Na+ intercalation/deintercalation processes. In this study, multiple CFCs were stacked together with a continuous flow design in order to further increase the power output. Experimental investigation was carried out for a consecutive number of stacks (1-5) using both parallel and series electrical wire connections. The parallel 5-stack exhibited superiority with a 3.1-fold increase in the total power output (8.6 mW) and a 4.6-fold increase in the absolute current (76.1 mA) when compared to the single cell (2.8 mW and 16.6 mA). The series stack exhibited a performance loss which was determined to be the result of an ionic-cross conduction, a phenomenon that has previously been reported in proton exchange membrane fuel cell stacks and microbial fuel cell stacks. Nevertheless, an effective increase in the overall power output with an increase in stack size was observed for both stack configurations. Additionally, the realization of the ionic-cross conduction from the series electrical connection is a key implication for designing a successful CFC stack for commercialization in the future.