Which energy storage technology is described as long duration and scalable?

• A. Lithium-ion
• B. Flow
• C. Nickel Cadmium
• D. Nickel Metal Hydride

Answer: (B)

Flow batteries deliver energy in a way that naturally supports long duration and scalable storage. In a flow system, the energy is stored in liquid electrolytes held in external tanks, while the power comes from a separate electrochemical stack. Because the energy reservoir can be enlarged by increasing tank size, you can raise the total stored energy without changing the power hardware, and you can also increase power by adding more stacks. This decoupling of energy and power makes flow batteries well suited for multi-hour to day‑scale energy storage.

Other chemistries store energy in solid electrodes, so increasing stored energy typically means bigger or more modules, which isn’t as straightforward or cost-effective for very long-duration storage. Nickel cadmium and nickel metal hydride have longer histories and good cycle life, but their fixed energy density and other drawbacks make them less ideal for scalable, long-duration applications compared to flow chemistry.