Everyone is always talking about those popular kinds of alternative energy, solar and wind. But take note trend watchers: Google is investing big time in geothermal energy.

Really, Google is investing big time in clean technology. They already put $20 million into two solar companies: eSolar Inc. and BrightSource Energy Inc. Their wind company investments are at $10 million, in the form of Makani Power Inc. in Hawaii. This latest investment is divided between two companies and a university program.

$6.25 million goes to Sausalito, California company AltaRock Energy Inc. that "develops and commercializes geothermal technology to produce clean, renewable power."

Another California company, Potter Drilling Inc. of Redwood City received $4 million. The company does hard rock drilling technology, including Engineered Geothermal Systems (EGS), which involves creating reservoirs to enhance geothermal locations that would otherwise not be viable or economically feasible.

To round out the ten million, Google presented a $489,521 grant to Southern Methodist University's Geothermal Lab. This will go toward updating North American geothermal mapping.

Alternative energy: good for the environment, good investments!