An electric vessel has exported electricity back to China's grid, acting like a giant mobile power bank. 

The all-electric tugboat Yungang Electric Tug No. 9 discharged electricity from its battery at a rate of 80 kilowatts, delivering a total of 560 kilowatt-hours (kWh)​ of electricity back to the grid during a seven-hour experiment on Thursday at the Port of Lianyungang. It marked China's first vessel-to-grid (V2G) bidirectional energy flow.

The trial shows that what works for EVs can now be applied to electric ships. It represents a breakthrough in China's development of bidirectional vessel-grid technologies that allow harbor vessels to charge during off-peak hours and discharge power to the land-based grid during periods of peak demand.

The project overcame technical hurdles related to stable high-power charging and discharging control in high-humidity and high-salinity marine environments.

It also offers a new model for the maritime industry's green transformation and expands the ways in which modern power networks can integrate storage, supply and demand.