One of Japan's largest trading groups plans to treble its investment in green energy in the United Kingdom - to more than 600 million pounds in the next few years.

A few days after the group - the Marubeni Corporation - paid 200 million pounds to become a co-owner of a vast wind farm off the coast of southern England, it announced it planned two further investments of the same size in the UK.

Energy experts said that it was the first time that a Far-East business group had committed to such a huge investment, and that it reflects the world's interest in the UK's increasing drive for renewable energy.

The deal saw Marubeni conclude agreement with Danish company Dong Energy to buy a 49.9 per cent stake in the 172-megawatt Gunfleet Sands wind farm near the Essex coast.

The site, located in the Thames Estuary, south-east England, produces green power equivalent to the annual electrical consumption of about 125,000 UK households. The first energy from Gunfleet Sands was produced in August 2009 and the whole wind farm went into production in the spring of 2010.

Dong Energy is one of the largest wind farm operators in the United Kingdom and it has a 50 per cent share in the London Array that will be the biggest UK wind farm - a projected 1,000MW of energy - under construction offshore in the outer Thames Estuary.

The London Array site will cover 230 square kilometres (90 sq miles) between Margate in Kent and Clacton in Essex. The first foundation was installed in March 2011 and phase one is expected to be completed at end-2012 at a cost of 2.2 billion euros.

Marubeni's executive officer Masumi Kakinoki said: "We are delighted to have reached an agreement with Dong Energy for this important partnership; it is especially significant as it is the first investment by a Japanese company into an offshore wind power project.

"We are paying close attention to the offshore wind power sector and Dong Energy, the world-leading company in this sector. We believe the sector represents a tremendous growth opportunity not only in Europe but in Japan and the Americas as well," he added.

After the Gunfleet Sands acquisition, Marubeni's total global power-generating capacity increased to just under 8,800 MW, including 450MW of renewable energy assets.

Dong Energy's chief executive officer, Anders Eldrup, said: "We see this partnership with a well-established and prominent Japanese company as a vote of confidence to renewable energy in general and Dong Energy in particular. We believe the further development of the offshore wind industry will be based on bringing together different kinds of investors with an interest in this field. We are proud of being recognised internationally as an attractive partner and a market leader within offshore wind."

The Danish company is one of the leading energy groups in northern Europe and is headquartered in Denmark. It says its business is based on procuring, producing, distributing and trading in energy and related products.

Dong is strongly involved in the production and expansion of renewable energy in the UK with the company operating the offshore wind farms of Burbo Bank (90MW), Barrow (90MW), Walney 1 (184MW) and Gunfleet Sands (172MW).

The Gunfleet site is located about seven kilometres south-east of Clacton-on-Sea, Essex. The project consists of two parts, Gunfleet Sands 1 with 30 turbines, and Gunfleet Sands 2 with 18 turbines. The capacity of each turbine is 3.6MW, giving the whole Gunfleet project a total capacity of 172MW. The rotor diameter of the turbines is 107 metres (m), with a maximum height of 129m from blade tip to sea level.

Other UK green power investors include the ScottishPower company that has 21 wind farms in the UK comprising more than 500 wind turbines. ScottishPower also has a share of a 103-turbine wind farm in Wales together with Eurus Energy UK, a subsidiary of Tokyo-based Eurus Energy Holdings Corporation.

The Swedish energy company Vattenfall owns three wind farms, and Fred Olsen, the Norwegian company that also runs several cruise liners, owns four wind farms in the UK, comprising a total of 130 turbines.