Alameda, California, has a long history of welcoming advanced airborne machines: at various times, the city has been home to a Pan Am seaplane hub, a public airport called the San Francisco Bay Airdrome, and a major naval air station. All have since closed, but much of the related infrastructure — cavernous hangars, control towers, vast stretches of runway — remain.
A company called Makani Power decided to take advantage of these aviation leftovers and now occupies a hangar, tower, and fire station on the old naval station grounds. Founded by a trio of kiteboarders in 2006, Makani (Hawaiian for "gentle wind") is perfecting a flying wind turbine that can capture wind at higher altitudes — where it’s more powerful and consistent — and turn it into energy on the ground. The idea: to deliver more energy with more consistency than conventional wind turbines, with lower costs, fewer materials, and a smaller footprint.
The company's latest Airborne Wind Turbine prototype, Wing 7, just completed its first successful test flight last month. Attached by a tether to a base station, it flies in a loop at an elevation of 1300 feet, with flaps (like on an airplane wing) that are controlled by an onboard computer; rotors capture wind as it flows across the wing, converting it to electricity using small generators. Through the tether, electricity runs back to the ground and into the grid. On launch and landing, the wing hovers like a helicopter, and can be reeled back into the base station when conditions are less than optimal.
Because the entire wing operates at the high tip-speed of a conventional wind turbine, it’s more efficient at creating more power. Material costs are low. With its lightweight aluminum, glass, and carbon fiber, the kite-like wing is about 10 percent of a conventional turbine's mass, with no need for a huge concrete tower or the safety radius normally required.
Makani plans to deploy its flying turbines on land, first with a 30-kilowatt turbine, the M30, meant for emergency or off-grid use, that will lay the foundation for a larger, utility-grade 600-kilowatt turbine, the M600. The larger turbine is designed for use in arrays like on conventional wind farms, but with less space and materials needed. With the M600, the company says it can access close to 70 percent of the continental U.S. (by contrast, conventional wind turbines can only be used in 16 percent of the continental U.S.). In flat, windy places like Kansas, where there’s easy access to the energy grid, the cost will be just a little less than conventional wind turbines, but in general, Makani’s airborne turbines are estimated at less than half the cost of conventional wind.
Though it's years away, Makani's ultimate goal is a 5-megawatt system, the M5, for offshore use over deep water, where conventional turbines aren't viable. The company's recent acquisition by Google — which has invested more than a billion dollars in renewable energy technologies, including wind farms, rooftop solar, and solar-thermal as part of its Google X research program — is a sign that flying wind power, as fanciful as it might seem, holds a lot of promise.