Charge–Discharge Performance of a Novel Undivided Redox Flow Battery for Renewable Energy Storage

The redox flow battery is ideal for utility-scale renewable energy storage applications. In this work, a novel undivided battery employing porous flow through electrodes is investigated. Because of low charge–discharge efficiencies reported in previous work employing high superficial electrolyte velocities and current densities, three electrolyte systems are investigated here at two concentrations (0.02 and 0.1 M) employing low-current densities and superficial velocities: [Ru(acac)3] in acetonitrile, [Fe(bpy)3(ClO4)2] in acetonitrile, and VOSO4 in aqueous sulphuric acid (all-vanadium system). The highest energy efficiencies are obtained with the all-vanadium system: 13.4% for 0.02 M electrolyte and 12.0% for 0.1 M electrolyte.