[kirksmith]

Hey, thank you!

The liquids are reusable, and are charged and discharged repeatedly without needing to replace the fluids. In other words the system is closed with respect to mass, only electrical energy (and minor amounts of thermal) are transferred in and out, reversibly. Flow batteries are similar to so-called reversible or regenerative fuel cells for this reason.

The answer to how long it lasts depends on many factors, and we hope to provide a clearer picture of that in our work.

In a well-designed system, they can last extremely long in comparison to, say, lithium-ion batteries. This is because flow batteries have different degradation pathways that are less severe and, if present, can usually be overcome through other solutions (e.g. electrolyte rebalancing, see ESS's "proton pump").