Efficient conversion of “mixing energy” to electricity through capacitive mixing (CapMix) has been limited by low energy recoveries, low power densities, and noncontinuous energy production resulting from intermittent charging and discharging cycles. We show here that a CapMix system based on a four-reactor process with flow electrodes can generate constant and continuous energy, providing a more flexible platform for harvesting mixing energy. The power densities were dependent on the flow-electrode carbon loading, with 5.8 ± 0.2 mW m–2 continuously produced in the charging reactor and 3.3 ± 0.4 mW m–2 produced in the discharging reactor (9.2 ± 0.6 mW m–2 for the whole system) when the flow-electrode carbon loading was 15%. Additionally, when the flow-electrode electrolyte ion concentration increased from 10 to 20 g L–1, the total power density of the whole system (charging and discharging) increased to 50.9 ± 2.5 mW m–2.
Hatzell MC, Hatzell KB, Logan BE (2014) Using Flow Electrodes in Multiple Reactors in Series for Continuous Energy Generation from Capacitive Mixing. Environ Sci Technol Lett 1: 474–478. Available: http://dx.doi.org/10.1021/ez5003314.
Funding for this work was provided by a National Science Foundation Graduate Research Fellowship to M.C.H. (Grant DGE1255832) and K.B.H. (Grant DGE1002809) and a grant from the King Abdullah University of Science and Technology (KAUST) (Award KUS-I1-003-13).