Thermal and efficiency improvements of all vanadium redox flow battery with novel main-side-tank system and slow pump shutdown

摘要

All vanadium redox flow battery is an important energy storage system with the advantages of flexible structure design, large energy storage scale, deep charge and discharge. In the present work, a system model of all vanadium redox flow battery is firstly established including thermal subsystem, electric subsystem and hydraulic subsystem, and the thermal behavior during both charging-discharging and standby phase is investigated. A novel method of main-side-tank system combined with slow pump shutdown is proposed to suppress the undesired temperature rise by reducing the stack state of charge (SOC) at the early standby phase and pre-charge the all vanadium redox flow battery system by cycling electrolyte from the charged stack to the uncharged side-tanks, and then improves the thermal performance and system efficiency. Based on this method, different side- tank volume proportion VP and shutdown time Delta t are considered. Results show that the main-side-tank system with VP = 1 and Delta t = 200 s has the maximum system efficiency improvement of 1.51%, and limits the battery temperature under 27.5 degrees C in a 2-days-cycle. For the specific efficiency improvement and specific temperature drop, the main-side-tank system with VP = 0.2 and shutdown time Delta t = 180 s is the most economical case with the efficiency improvement of 1.20% and battery temperature limitation under 31.1 degrees C.