The 8-to-24-hour bracket is the next storage problem.
Short-duration lithium is solved. Seasonal storage runs through hydrogen. The interesting commercial window sits in between — and almost none of it is lithium.
Utility-scale batteries are deploying at record pace, almost all of them lithium-iron-phosphate with two-to-four hours of duration. This is the right product for the grid service it provides — intra-day arbitrage and frequency regulation — and the technology is now a commodity.
The next problem is different. As wind and solar reach very high penetration in any given market, the question stops being 'how do we move electricity from noon to evening?' and becomes 'how do we move it across a three-day weather system?' That is the 8-to-24-hour bracket.
Why lithium loses here
Lithium's cost curve improves with cycles per day. In the 8-to-24-hour bracket, cycles per day drop toward one. The chemistry is therefore used inefficiently and other chemistries become economically competitive even at lower round-trip efficiencies.
What wins instead
Iron-air (multi-day), aqueous sulphur-based flow, vanadium-redox flow, and novel thermal storage are the four chemistries we track most closely. Each has a different economic window; each has been demonstrated at meaningful scale in at least one industrial project.
We want to see pack-level cycle life at full depth-of-discharge before any serious diligence cycle. Laboratory cycle data is a useful starting point but no longer sufficient evidence for an investment.
§ Notice
This note reflects the firm's working view at the time of publication. It is not investment advice and is not an offer or solicitation. May be cited in full with attribution to Orrery.