How technical advances are driving flow batteries closer to mass commercialization
cent technical advances are sparking interest in flow batteries by offering the promise of significant cost reductions that could make them better able to compete for market share with solid state storage devices, such as the nearly ubiquitous lithium-ion battery. But full commercialization is still several years off, analysts say.
Worldwide, li-ion batteries represent about 70% of grid-connected battery installations, according to the Department of Energy.
Li-ion’s challenger in the flow battery category is the vanadium-based battery, which accounts for nearly 79% of worldwide flow battery installations.
“Flow batteries have potential and are a good option for some longer duration applications, but they aren’t likely to reach equal market share with solid state batteries for a while,” Colette Lamontagne, a director in the energy practice at Navigant Consulting, says.
Flow batteries generate power by pumping electrolytes from storage tanks to a central stack where the interchange between positive and negative electrolytes creates an electrical charge.
Because the electrolytes can be returned to their respective storage tanks, flow batteries have a more flexible and resilient cycling characteristics than solid state batteries. They can withstand deeper discharge cycles and longer life cycles, making them better suited for long duration applications than most solid state batteries.
Electrolyte storage also allows for great independence of energy and power characteristics. Flow batteries also can be scaled to meet varying requirements more easily than can solid state batteries. The volume of stored electrolytes can be increased or the volume of electrolytes pumped into the stack can be increased. More electrolyte stored in larger tanks translates into the possibility of longer duration applications, a capability that industry analysts expect to drive deployment for storage facilities in years to come.
But flow batteries also have lower efficiencies and larger footprints than solid state batteries. Li-ion batteries have efficiency levels in the high 90% range while the efficiency of flow batteries is in the 75% to 80% range, in part because they incur a parasitic load to run pumps. Flow batteries also have higher operational costs because they involve more moving parts, including membranes that wear out.
Those considerations make is hard to come up with simple cost comparisons. “You need to think of the application when you compare flow and solid state batteries,” Lamontagne says, adding that, because of their footprint, location also matters.