A battery built for the hours after sunset

CMBlu's water-based storage offers a different route from lithium-ion. Understanding it means separating chemistry, hours of delivery and evidence from deployment.

Select an underlined term for a short explanation.

When solar production falls in the evening, a storage operator needs to know more than how powerful a battery is. How long can it keep delivering? German manufacturer CMBlu is pursuing that question with SolidFlow, a system that combines solid storage materials with a water-based flow architecture. Its product description says the design avoids lithium and cobalt and is intended for extended discharge.

In an electrochemical battery, charging stores energy in chemical form; discharge makes that energy available to an electrical circuit. The electrolyte allows ions to move inside the system while electrons travel through the outside circuit. This familiar principle does not prescribe one particular material. The chemistry and physical arrangement can change, which is why a stationary battery need not be a larger version of a phone battery.

CMBlu lists a unit with 10 kilowatts of power and 100 kilowatt-hours of energy capacity. Dividing those ratings gives ten hours: a useful first illustration of why the two quantities belong together. It is not a guarantee of ten hours under every operating condition. A project specification must also explain usable capacity, losses and the conditions under which the ratings apply.

Commercial interest is developing alongside the technology. In February 2026, CMBlu reported a conditional framework agreement signed with Uniper on 20 January, with possible battery deliveries beginning in 2027. The release describes a 5-gigawatt-hour pathway and a completed site acceptance test. It also records Uniper's view that large-scale performance and economics still need demonstration. A supply framework is consequently different from a completed storage fleet.

For a solar operator, the next useful comparison is practical: how much electricity returns, at which hours, after what costs and servicing? Avoiding selected minerals answers a supply-chain question, but cannot answer all of those operating questions. Long-duration storage becomes valuable when its measured delivery matches the job. The promise here is another technical option for that job, with scale-up evidence still part of the story.