Japanese startup PowerX is advancing the development of marine battery storage vessels that would be charged at sea from offshore wind farms for transport back to land. The technology can broaden opportunities for siting wind energy systems in deeper waters and obviate the economic and environmental costs incurred by undersea cable construction.

The company is partnering with Japan's largest shipbuilding outfit Imabari to construct the first prototype power transfer vessel, which is slated for completion in 2025. The Power ARK 100 is now under development as a 100 m long trimaran that will be powered by electricity and have a 300 km range. The ship will be equipped with 100 grid-scale batteries offering a capacity of 220 MWh, which PowerX said is enough to power around 200,000 Japanese homes for a day in a single trip. Biodiesel will offer backup and allow for journeys over greater distances, potentially around the globe.

Rendering of the Power ARK power transfer vessel. Source: PowerX

Larger versions will also be produced, including the 150 m long Power ARK 1000 and the 220 m Power ARK 3000, along with an in-house battery manufacturing facility to load these vessels with the cells they need to carry all that energy. In addition, the company intends to build its own automated gigafactory to assemble batteries in Japan from outsourced battery cells. Annual production capacity of 1 GWh is being targeted by 2024 and will ramp up to 5 GWh by 2028. Battery systems produced there will serve the marine, electric vehicle fast-charge and grid-scale storage markets.