Developers of zinc bromine and vanadium “flow” battery technologies – who for years have toiled tirelessly in the shadows of the juggernaut that is the lithium-ion battery industry with little reward for their troubles – are having a brief moment in the sun.

Whether that turns into a more durable moment depends on how things develop at the cutting edge of the energy transition – more specifically at the “medium-duration” storage niche of four hours to 12 hours.