Google Inc. often strays from its core mission of organizing the world's information online.

But investing in green, or renewable, energy is the company's most prominent real-world endeavor.

In addition to reducing its own 'carbonfootprint' through solar panels atop its Mountain View, Calif., headquarters, and increasing the energyefficiency of its data centers, Google's initiatives include developing technology that could cut the cost of building solar thermal power plants. It just signed a landmark 20-year contract to buy energy from a wind farm in Iowa, where Google has a data center. And the company got attention this fall by announcing a multimillion-dollar investment in a planned offshore wind-energyproject called the Atlantic Wind Connection.

The Wall Street Journal sat down with Bill Weihl, Google's green energy czar, and Rick Needham, green operations business chief, to talk about Google's investments in the wind market and solar technology. Here are edited excerpts of the conversation.

THE WALL STREET JOURNAL:

Why do you make investments in wind projects that won't directly result in cheaper energy prices for Google?

MR. WEIHL: Our goal is to solve long-term problems in the world or set the company up for long-term growth. We took a risk around our data centers to improve energyefficiency, and that panned out really well. We experiment in investments, like with the Atlantic Wind Connection. There's all sorts of reasons why that project might stall at some point. But it could be very catalytic, enabling enormousinnovation. Some projects may fail, but venture capitalists do that all the time.

WSJ: Do you think about your return on investment?

MR. NEEDHAM: Yes. We don't share ROI publicly, but the returns are good enough that we're willing to invest.

WSJ: Why did you sign a power purchase agreement with a wind farm in Iowa?

MR. WEIHL: The wind PPA [power purchase agreement] is not an investment. We made a 20-year commitment to buy [electricity] from that wind farm. That's very different from how people buy energy credits. This is the only way realistically for a developer to have the certainty of a contract with a credit-worthy counterparty. They can get debt financing and free up money for another project.

For us, it's a hedge against rising energy prices over the long term. We're not disclosing details of the contract, but it starts out with a slow escalation [in price]. It's a much slower escalation than we would expect to see in the energy markets in general. For our data centers, we already have power contracts in place. So if we sign that power purchase agreement today, we're buying that power but we can't use it. We can sell the energy on the wholesale market.

WSJ: Tell me about your solar thermal technology project.

MR. WEIHL: We're not yet ready to disclose details. The fundamentals are we're developing solar thermal power generation to concentrate the sun's rays and generate hundreds of megawatts through mirrors called heliostats.

WSJ: Can clean energy technology become a core business?

MR. WEIHL: We're not an energy company and don't have such ambitions, but we want to help drive technology. I think that in a couple of years, we'll have [solar thermal] technology ready to be commercialized. Most likely we'd license it to get it to market.

WSJ: What roadblocks do other companies face in making their facilities energy-efficient?

MR. WEIHL: In many organizations you find that the person who [runs] facilities and has that budget is different from the person who pays operating costs. At Google on the data-center side, [one person] owns facilities and the operational costs to run those facilities. They focus on the total cost of ownership.

WSJ: Which companies do you admire for their 'green' work?

MR. WEIHL: Wal-Mart does a lot with cutting waste in their supply chain and packaging. They had an initiative to get their suppliers to report to the Carbon Disclosure Project, a reporting mechanism to measure their carbonfootprint. They have 100,000 suppliers.

MR. NEEDHAM: Procter & Gamble. They have good goals. Like their development of Tide [laundry detergent] that works with cold water. And they're driving their supply chains to think about carbon and sustainability.