Physics / mechanism
Long-duration energy storage (LDES) covers discharge durations of 8–100+ hours, targeting the gap lithium-ion cannot economically fill. Three dominant form factors: (1) Flow batteries (vanadium, iron-air) — energy and power decoupled, capacity scales with electrolyte volume, round-trip efficiency 65–80%, vanadium systems at ~$200–300/kWh installed but commodity-price-sensitive; (2) Thermal storage (Antora Energy) — renewable electricity converts to heat stored in solid carbon blocks at 1,500–2,000°C, discharged via thermophotovoltaic (TPV) cells, round-trip efficiency ~50–60% but capital cost potentially <$10/kWh at scale; (3) Iron-air batteries (Form Energy) — oxidation/reduction of iron pellets, ~$20/kWh target, low self-discharge, 100-hour discharge demonstrated at pilot scale. Key parameters across all: levelised cost of storage (LCOS), cycle life, self-discharge rate, and materials availability.
Competitive landscape
Competing approaches include pumped hydro (dominant installed base, geography-constrained), compressed air (CAES, limited sites), and hydrogen storage (round-trip efficiency ~30–40%, cost still high). Within electrochemical, zinc-bromine and organic flow chemistries compete on cost. Antora’s TPV discharge competes with Stirling-cycle and ORC thermal-to-electric conversion.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.