January 26, 2023
Journal Article

Defining Long Duration Energy Storage


Accelerating deployment of variable renewable energy is changing the operational characteristics of the electric grid and creating an emerging necessity for storage technologies with extended energy duration capabilities to maintain grid reliability. Extended or “long-duration” energy storage scales for supporting future grids are not yet well-defined today but can be anticipated to grow through estimating gaps in renewable performance of a decarbonized grid. Variable generation resources create a mismatch between when electricity is generated and when it is used; as the amount of variable generation on the grid grows, so too do those mismatches. This paper reviews current uses of energy storage and how those uses are changing in response to emerging grid needs, then assesses how the power generation industry and academia are defining long-duration storage and organizing research efforts to develop commercial technologies. Using an illustrative example of a decarbonized grid, the paper identifies the depth and breadth of future energy mismatches and concludes that two classes of long-duration energy storage will be needed in a decarbonized grid; one class lasting up to 20 hours that can manage daily cycles and one lasting for weeks or months to manage seasonal cycles. This paper elucidates the necessity of long-duration energy storage in a decarbonized grid and may inform long-term planning processes. Grid planners can play an important role in the development of long-duration energy storage technologies through granular identification of long-duration storage needs that creates a market signal for investment in and development of the necessary technologies to provide a reliable and resilient grid of the future.

Published: January 26, 2023


Twitchell J.B., K.R. DeSomber, and D. Bhatnagar. 2023. Defining Long Duration Energy Storage. Journal of Energy Storage 60. PNNL-SA-171006. doi:10.1016/j.est.2022.105787

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