In one of the largest investment made by a private equity firm, the Blackstone Group is to invest a combined €2.5 billion ($3.5 billion) into the construction of Germany's biggest ever offshore wind farms, the Financial Times today said.

The paper said that the US-based PE firm, which has secured financing for an 80 turbine wind farm in the North Sea, will announce the deal today.

Blackstone has arranged €900 million loans for the Meerwind project from a consortium of bankers that include Bank of Tokyo-Mitsubishi UFJ, Commerzbank, Dexia, KfW Ipex Bank, Santander and Siemens Bank

The €1.2 billion project, called Meerwind (Seawind) - first announced in 2008, is set to produce enough power to service 40,000 homes.

Construction is expected to start in 2012 and start of full commercial operation is planned by the end of 2013. Meerwind is expected to be one of the first commercial offshore wind farm projects in operation in Germany and Blackstone's largest investment in the renewable energy sector.

The Meerwind project is a joint venture between Blackstone and Windland Energieerzeugungs GmbH, with the PE firm holding 80 per cent and the remaining 20 per cent with the German wind energy company.

Meerwind will be the first German offshore wind park to be built and operated by a private investor.

Meerwind is a 400 MW project located in the German Bight in the North Sea 23km north of the island of Helgoland. The wind farm will consist of 80 wind turbines with a power output of 5 MW each. All turbines will be connected to a farm internal transformer platform to which the grid connection will be installed.

New York-based Blackstone with $35.9 billion under management will also invest around €1.3 billion into 64 wind turbines for which it has already acquired a permit. The construction of this wind park is expected to be completed by 2016.

Blackstone managing director, Sean Klimczak, told the paper that the group was in talks to buy a third German permit as it wanted to create the first ''established offshore wind energy company'' in Europe.