Aquion Energy, the US saltwater battery designer, struck a deal on February 27 with one of Japan’s largest electric power companies, Kyushu Electric, to provide storage for solar power in Kagoshima Prefecture, on southern Japan’s Kyushu Island.

The EIWAT Storage I project can store 122kW of energy in the Aspen 48M-25.9 battery. The power is generated by a solar array provided by the French energy management and automation firm Schneider Electric working with the Japanese firms EIWAT Solar Company and Re-Energy, an energy storage provider.

The battery has a 100% depth of discharge, the company says, with a cycle life of 3,000 to 70% retained capacity.

This is the largest project to date in Japan for Aquion, which developed its Aspen battery using a salt water-based electrolyte, which the firm claims makes the technology completely safe as the battery cannot overheat.

The Aspen batteries are made using aqueous hybrid ion chemistry, composed of the saltwater electrolyte, manganese oxide cathode, carbon titanium phosphate composite anode and a synthetic cotton separator, says the firm.

The battery is the first to receive the so-called ‘Cradle to Cradle’ certification, devised in 1992 by the non-profit Cradle to Cradle Products Innovation Institute and licensed as a certification system in 2010, for environmental sustainability.

“This water-based system moderates the maximum temperature that the battery can reach – it is impossible for any internal reactions to drive the battery above 100°C, since at this temperature, all of the water will evaporate leading to an open circuit condition,” said a company official.