Design and development of large-scale vanadium redox flow batteries for engineering applications

Vanadium redox flow battery (VRFB) energy storage systems have the advantages of flexible location, ensured safety, long durability, independent power and capacity configuration, etc., which make them the promising contestants for power systems applications. This report focuses on the design and development of large-scale VRFB for engineering-oriented applications. Begin with the analysis of factors affecting the VRFB for engineering-oriented applications, then the design method and process of large-scale VRFB are studied. After that, the optimal portfolio of the key materials and components are selected by orthogonal experiment. On that basis, a 25 kW VRFB stack consists of 60 single cells in series with an active electrode area of 3400 cm2 is developed with an energy efficiency (EE) of over 78 % at rated power and basically 75 % at 1.4 times rated power. The voltage dispersion coefficients of 0.25 and 0.56 at the end of charging and discharging process respectively, indicate that the stack possesses excellent voltage consistency and the electrolyte distribution is relatively uniform in the stack. A steady EE of approximate 77.3 % during 20 cycles and more than 76 % at 40 degrees C reveal that the 25 kW VRFB stack is provided with high-temperature property and cycling stability essential for engineering applications.