Stealth startup Makani Power, an Alameda, Calif.-based wind energy company, has secured million in second round funding from returning investor Google.org. The 24-member firm, which is playing its plans very close to the vest, has only revealed that it is building huge wing-shaped kites to harness the energy from high-altitude wind.

By some estimates, all the energy contained in wind could satisfy our needs 100-fold, with most coming from high-altitude wind. Tapping into just 1 percent of this energy could meet most of our current needs. In a recent demonstration, scientists from the Netherlands’ Delft University were able to produce 10 kilowatts of electricity by flying a 10-square meter kite attached to a generator.

A kite farm, consisting of multiple kites flying at altitudes of around 800 meters, could generate up to 100 megawatts — enough to power 100,000 homes — they say. Wubbo Ockels, the project’s leader, believes the technology could be commercially viable in as little as 5 years if the funding is there.

Makani also aims to capture that small slice of global high-altitude wind, which it says would be sufficient to supply the world’s current energy needs. Kite Gen, a Milan, Italy-based startup, has developed a theoretical design for a system that would fly 12 sets of lines with four 500-square meter kites on each. It says the system could produce up to 1 gigawatt of power — roughly equivalent to the amount generated by a coal-fired plant.

Makani previously raised million from Google.org in late 2006 and expects its current round to raise upwards of million.