Green energy start-up Makani Power has come a long way from its origin as a gleam in a some kite-surfers' eyes. Friends Corwin Hardham, Don Montague and Saul Griffith founded the company in 2006. Its goal: to generate energy from thin air. Makani's tethered carbon fiber wings fly between 800 and 1,950 feet above the ground while their mounted rotors generate electricity, serving as a wind turbine in mid-air. The benefits of height are the powerful and more consistent winds found at high altitude.

Here, Makani's airborne wind turbine sits on the runway prior to a test flight in Alameda, California.