Google's energy unit has entered into a deal to buy wind power from NextEra Energy for the next 20 years to power data centres.

The deal comes less than three months after the giant Silicon Valley Internet search company invested US$38.8 million in two wind farms in North Dakota, developed by NextEra Energy Resources, that generate enough energy to power more than 55,000 homes.

Google Energy will begin buying wind power from July 30 from NextEra's facility in Iowa at a predetermined rate, Urs Hoelzle, Google's senior vice president of operations, said in a blog on Google's website.

"Incorporating such a large amount of wind power into our portfolio is tricky, but this power is enough to supply several data centres," Hoelzle added.

Google has pushed ahead in addressing climate change issues as a philanthropic effort through its Google.org arm.

The often-quirky company said in late 2007 that it would invest in companies and do research of its own to produce affordable renewable energy -- at a price less than burning coal -- within a few years.

The company's Google Energy unit, formed in December, allows the company to buy large volumes of renewable energy from the wholesale power market.