Study on energy loss of 35 kW all vanadium redox flow battery energy storage system under closed-loop flow strategy

Abstract A large all vanadium redox flow battery energy storage system with rated power of 35 kW is built. The flow rate of the system is adjusted by changing the frequency of the AC pump, the energy efficiency, resistance, capacity loss and energy loss of the stack and under each flow rate is analyzed. The energy efficiency of the system is calculated by combining with the pump loss. The results show that with the increase of flow rate, the energy efficiency of the stack is improved and the stack resistance is reduced, but pump loss increases greatly. At 180 mA•cm−2 current density and 110 L/min flow rate, the energy efficiency of the stack reached 77.10% and the system reached 69.49%. In the battery system, the loss of resistance energy accounted for 80.27% of the total energy consumption, and the pipeline and transfer energy loss accounted for 18.73%. Therefore, reducing the energy consumption of the pump and reducing the energy loss of the resistance in the system are very important for improving the energy efficiency of the all vanadium redox flow battery energy storage system.