The Shepherds Flat wind farm is expected to be fully operational in 2012 and supply 235,000 average U.S. homes.

Google today said that it will invest about $100 million in the very large Shepherd's Flat wind project in Oregon, its second direct investment in renewable energy in two weeks.

Shepherds Flat is projected to be the largest wind farm in the world, able to generate 845 megawatts and supply enough energy for 235,000 average U.S. homes when it is online next year. GE Energy Financial Services and Caithness Energy are existing owners of the project near Arlington, Ore., which will take up about 30 square miles.

Last week, Google said it invested $186 million in the Ivanpah solar power plant project now under construction, which is its largest stake in a renewable-energy venture. The company is investing in renewable energy, either directly in projects or by betting on green-technology start-ups, to earn a return on its money and help expand renewable energy, said Rick Needham, the director of green business operations at Google.

"We're excited about helping deliver clean energy to the grid and we hope this latest investment encourages other companies to think about ways they can help accelerate the deployment of more renewable energy," he said in a company blog, adding that Google is on the "lookout" for more projects that make business sense.

The Shepherds Flat project is interesting to the technology-oriented people at Google, Needham said, because it will be the first large-scale wind farm that will use direct-drive turbines supplied by GE. Using giant permanent magnets, these turbines can generate electricity without the typical gear box construction, a technology which promises to improve the efficiency and reliability of turbines.

To date, Google has invested $350 million in clean-energy projects. Energy developers Sumitomo and Tyr Energy, a subsidiary of Itochu, are also investing in the Shepherds Flat project along with Google, representing $500 million altogether, according to GE Financial Services.

Under a 20-year power purchase agreement, the wind farm will supply electricity to Southern California Edison. California has a mandate that requires utilities to generate one third of their energy from renewable sources by 2020, which is creating demand for renewable energy.