Battery storage with salt water

28.11.2024

A Dutch start-up has launched a pilot plant for the long-term storage of energy using salt water. Two energy companies are supporting the project.

Water plus sodium chloride - the Dutch company Aquabattery uses these basic materials to store energy. For ten years, the start-up has been researching how to imitate a process that takes place in body cells in batteries. A pilot plant has now gone into operation, which should be able to store energy for up to ten hours. The developers want to use the findings from this project to bring the saltwater battery to market maturity by 2026.

The project is being supported by energy giants Verbund and Statkraft, among others. The pilot plant is located in Delft, on the campus of the Deltares research facility. It has an output of 5 kW and a capacity of 50 kWh.

Over the next twelve months, its scalability and commercial realization will be investigated, as the Austrian energy supplier Verbund describes the goal. "Innovations for the energy transition must now be implemented more quickly and scaled up on the market," says Verbund division manager Franz Zöchbauer about the cooperation. He believes that long-term storage systems based on salt water could soon play an important role.

Electricity from acid plus base

The Dutch company's battery technology imitates the natural salt transfer at cell membranes in the body. Biological cells regulate the ratio between fluid and salt via the membranes, for example after physical exertion. In the battery, salt water flows through a stack of membranes to which an electric field is applied. The membranes act as ion exchangers. The water dissociates into hydrochloric acid (HCl) and caustic soda (NaOH). Acid and base are stored in separate containers.

To discharge the battery, acid and base are pumped back through the membrane stack, they mix and electricity is generated. The power output depends on the surface area of the electrodes. The storage time depends on the electrolyte volume. Such flow batteries should therefore be easily adaptable for different applications.

The disadvantage compared to lithium-ion batteries is the lower energy density. To achieve the same performance, saltwater batteries must therefore be larger and heavier.

Author: Manfred Fischer, E&M powernews