The engineering and construction group Sir Robert McAlpine is selling off its North American windfarms business in a deal estimated to be worth up to $1 billion (£506m).

First-round bids are due in this week for RES Americas, which built the world’s largest windfarm last year in Texas.

Suez, the French utility company, and Hastings, an Australian infrastructure fund, are among those in the running, according to industry sources.

Interest in American wind power has been growing since Iberdrola floated its renewables business last year which included PPM Energy, the US company built up by Scottish Power.

Credit Suisse is handling the auction of RES Americas, which comes amid a flurry of corporate activity involving windfarm operations.

International Power is understood to be running the rule over a possible bid for Babcock & Brown’s European windfarm activities, which are estimated to be worth between €2.5 billion (£1.9 billion) and €3 billion.

The business is one of the largest portfolios of windfarm assets to come up for sale in Europe.

The package includes operating assets spread across Portugal, France, Spain, Greece and Germany, as well as several development projects that are due to come on stream between now and 2010.

Separately, Christofferson, Robb & Co (CRC), an Anglo-US hedge fund, has secured funding to develop a £650m offshore windfarm project in the UK.

The 300MW Thanet windfarm will be built seven miles off the Kent coast.

Investec has put up a £130m mezzanine finance deal to part-finance the package. HSH Nordbank and Bank of Tokyo-Mitsubishi are being lined up to provide senior debt.

“This is one of the first deals we’ve seen where a bank is willing to take on development risk for a windfarm project,” said Will Ainger, co-editor of energy intelligence service SparkSpread.

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