Japan's largest city gas provider Tokyo Gas (9531.T), opens new tab said on Tuesday it will buy a 21.2% stake in the WindFloat Atlantic operational floating offshore wind power project in Portugal to gain experience in operation and maintenance.

Floating offshore wind is at an early stage in Japan but the country considers it as essential to its goal to become a major offshore wind power producer as part of decarbonisation efforts.

The government has a goal of 10 gigawatts (GW) of offshore wind projects, including bottom-fixed and floating, by 2030 and up to 45 GW by 2040.

Tuesday's deal marks Tokyo Gas's first direct investment in an overseas floating offshore farm.

WindFloat Atlantic operates small, 25-megawatt (MW) floating wind farms off the Atlantic coast, and is majority-owned by Ocean Winds, a joint venture between Portugal's main utility EDP (EDP.LS), opens new tab and French company Engie (ENGIE.PA), opens new tab.

The project is the world's first semi-submersible floating offshore wind farm and has been operational since 2020.

It uses a floating foundation system developed by Principle Power, a U.S. technology startup in which Tokyo Gas bought a stake in 2020.

Tokyo Gas said the system is exceptionally stable and has proven ability to operate under severe weather conditions.

"We aim to leverage the knowledge gained from the collaboration to work towards the commercialisation of floating offshore wind farms in Japan," Michiko Hirose, senior general manager at Tokyo Gas, told reporters.

Under the deal, Tokyo Gas will buy the WindFloat Atlantic stake from Ocean Winds and Principle Power. The transaction is expected to close by year-end, but terms were not disclosed.