Meeting the Growing Need for Long-Duration Energy Storage

The growing deployment of variable renewables has created both need and opportunity for affordable energy storage that cycles over multi-day and longer durations. Low-cost generation combined with storage that adds a per-cycle cost of $0.03/kWh$ or less to the levelized cost of renewable electricity could enable renewable power plants that can compete on cost with fossil fuel generation. Since long-duration storage implies fewer cycles over the system lifetime, the required capital cost is inversely proportional to duration. Storage technologies are needed that have exceptionally low cost of stored energy, while operating at much lower C-rates than typical battery applications. Flow batteries have the flexibility of design to meet these requirements, but only if the underlying chemical cost of storage is low enough. This talk will give examples of use-case and techno-economic analyses that help to define requirements for long-duration storage, and discuss electrochemistries with the potential to meet long-duration requirements. Aqueous sulfur-based flow batteries are one such class, for which recent research progress will be reported.