Flowbatteri

Flowbatteri is a rechargeable electrochemical energy storage device in which energy is stored in liquid electrolytes that flow through external tanks and are pumped through a central electrochemical reactor. The energy capacity is determined by the volume of electrolyte in the tanks, while the power output is determined by the size of the electrochemical cell stack and the rate of electrolyte circulation. In operation, two electrolyte streams flow through a cell stack separated by a membrane or separator. Redox reactions occur at the electrodes, and electrons travel through an external circuit. In redox flow systems, the same element can be used in different oxidation states; the vanadium redox flow battery (VRFB) is the most developed and uses vanadium ions in both electrolytes to minimize cross-contamination.

Types include vanadium redox flow batteries, iron-chromium and all-vanadium systems, zinc-bromine flow batteries, and other chemistries. All share decoupled energy and power, enabling large energy storage by enlarging tanks without changing the power sections. Advantages include scalable energy storage, long cycle life, low risk of thermal runaway, and suitability for large-scale grid storage and renewable integration. Disadvantages include relatively low energy density, higher capital cost for membranes and pumps, electrolyte management challenges, and system complexity.

Applications prioritise grid storage, load leveling, and backup power for renewables. History notes that redox flow concepts emerged in the 1980s, with significant development of VRFBs led by Maria Skyllas-Kazacos at the University of New South Wales. Ongoing research focuses on reducing material costs, improving energy density and efficiency, and expanding chemistries for broader deployment in energy systems.