Is the search giant on its way to becoming a renewable energy giant?

Last week, Google made what sounded like a big investment in solar when it announced that the company bought a 49-percent stake in an 18.4-megawatt photovoltaic farm in Brandenburg, Germany.

But yesterday (April 11), it announced that it was purchasing a $168 million stake (roughly 10 percent) in Brightsource’s 392-megawatt Ivanpah Solar Electric Generating System. In all, the company has now invested more than $250 million in clean energy.

“We have been active in the renewable energy sector for some time, having invested in several innovative companies through Google.org, and more recently, making corporate investments in clean energy projects, like two North Dakota wind farms, an offshore wind transmission line, and these two solar investments over the last week,” said spokesperson Parag Chokshi.

Chokshi could not discuss what type of return on investment the company expected from the projects.

“We're interested in investments that have attractive returns and spur more deployment and development of compelling renewable energy technologies,” he said. “That includes solar photovoltaics in Germany, and power tower technology at Ivanpah here in the U.S.”

“We need smart capital to transform our energy sector and build a clean energy future. This is our largest investment to date,” wrote Rick Needham, Google’s director of green business operations in Google’s official blog. “We’re excited about Ivanpah because our investment will help deploy a compelling solar energy technology that provides reliable clean energy, with the potential to significantly reduce costs on future projects.”

News of Google’s investment in the Ivanpah plant came on the same day that the DOE announced a $1.6 billion loan guarantee to support development of the Ivanpah project. The project is largely being financed NRG.

“We hope that investing in Ivanpah spurs continued development and deployment of this promising technology while encouraging other companies to make similar investments in renewable energy,” Neeham wrote.

Google has plans for further clean energy investments, according to Chokshi. “We are continuing to look for new ways of advancing clean energy,” he said.

But Google isn’t just buying stakes in clean energy projects, it’s also using it to help power its operations. “We have a 1.6 MW solar installation at our Mountain View headquarters,” Chokshi said. “It was built in 2007, and was, at the time, the largest corporate solar installation in the U.S.”