Blackstone said Friday that it had finalised 1.2 billion euros ($1.7 billion) in financing to build what it says will be the the biggest German offshore facility to date.
The fund added that it has also obtained permission for its WindMW unit to develop a second site, putting its cost at 1.3 billion euros.
The first farm, to comprise 80 turbines built by the German group Siemens, is to become operational in 2013 with a generating capacity of 288 megawatts.
Requiring around 100,000 tonnes of steel in its construction phase, the park should provide electricity for 400,000 homes and reduce carbon dioxide emissions by one million tonnes, a Siemens statement said.
The turbines will be huge, with rotors that measure 120 metres (390 feet) in diameter, and are to stand in water more than 20 metres (66 feet) deep.
Siemens presents itself as the world's leading manufacturer of offshore wind turbines.
Financing for the second project, designed for 63 turbines, should be finalised in 2013 and it is to be completed by 2016.
Blackstone senior managing director David Foley welcomed "the progress and positive impact on the economy that can be achieved when private capital works in partnership with government, entrepreneurs and industry."
Blackstone executive director Sean Klimczak added during a press conference that "this project would not exist without the KfW programme," in reference to an alternative energy financing plan backed by the German state-owned bank.
Klimczak also said he hoped the arrival of Blackstone to the market for alternative energy "will make investors think about these opportunities."
He estimated that offshore energy sites would provide "fair returns" on investment for those willing to take a chance on it.
But there were also greater risks compared with investing in onshore wind energy plants, Klimczak acknowledged.
A key issue in either case is wind supply, which is not completely certain despite thousands of computer simulations, plus the fact that the turbines are to be located around 50 kilometres (30 miles) from the German coast.
"This is not about planting a pole in a farm somewhere," Klimczak noted.
Peter Giller, who runs Blackstone's wind projects in Germany, said offshore construction was less of a challenge than connecting the offshore grid to a land-based network.
Development of wind farms off the north coast of Germany will force the country to quickly build a high-capacity network to get the power to poles of economic activity in the south.
Germany, the first industrialised nation to announce it will abandon nuclear power, "has demonstrated tremendous leadership in supporting private offshore wind development," Giller said.
The country foresees total generating capacity of 20,00-25,000 megawatts by 2030 in the North and Baltic seas.
Energy producers expect European wind power generation to triple by 2020, with tens of thousands of new wind turbines, an industry body said last week.
The European Wind Energy Association (EWEA) released its figures in a new report aiming to influence EU energy policy after 2020.
By the end of last year, the 'Pure Power' report said, wind power produced about 5.3 percent of demand across the EU's 27 states, some 182 Terawatt hours (TWh). Its share is tipped to reach 15.7 percent by 2020, or 581 TWh.
Investment is expected to rise from 12.7 billion euros of annual investment in 2010 to 26.6 billion euros in 2020, with 40 percent of that investment going into offshore wind farms.