"There are a lot of technologies that get to the pilot scale and look promising, but the first few large commercial projects deploying those technologies, financing those can be extremely difficult," Dan Reicher said in an interview at the Clean-tech Investor Summit in Indian Wells, California.

"Often the usual equity and debt players will say come back to us when you've demonstrated this at scale," said Reicher, director of climate and energy initiatives for Google's philanthropic arm, Google.org.

The stage between successfully developing a new technology and amassing scale is often referred in the industry as the "Valley of Death," Reicher said.

Venture capital firms typically pour tens of millions into developing new technologies, Reicher said. But that's not nearly enough to build a utility-scale solar thermal plant, for instance, and that's where Google thinks it can be helpful, he added.

"When you get to building a commercial-scale project in the energy world, you can be looking easily at hundreds of millions or even across the billion dollar threshold," Reicher said. "Over years we'll be looking at hundreds of millions of dollars. So we're very mindful of the Valley of Death."

In addition to considering project finance, Google has already committed US$20 million to funding start-up firms researching solar-thermal and high-altitude wind power.

It is also looking closely at several companies with enhanced geothermal systems, Reicher said. Enhanced geothermal systems, or EGS, create power by pumping water into hot rocks in the ground rather than harvesting hot water already there.

"We arrived at these three technologies because we think they have real promise to move down the cost curve and to be competitive with coal and to get to very large scale," Reicher said.

Google said in November it planned to spend hundreds of millions of dollars to help drive the cost of electricity made from renewable sources below the price of power generated from dirty coal-fired plants.