Today, energy storage systems are generally categorized across just two simple dimensions, as utilities ask themselves: How much power can I have? and how long can I have it for?
Power output is a long-understood and accepted metric within the energy industry, however, the market’s understanding of storage duration is still based on the concept of fixed discharge rates, typically observed in lithium-ion technology. Recently, the US Department of Energy (DOE) Pathways to Commercial Liftoff: Long Duration Energy Storage study defined four separate duration categories: short (0-10 hours), inter-day (10-36 hours), multi-day/week (36-160 hours), and seasonal (160+ hours).
