Turbines Ready for Takeoff
Like the wing of a propeller plane without a cockpit, a Makani Airborne Wind Turbine stirs the air in a California field where it is being tested to capture high-altitude wind power.
Anyone
who has climbed a mountain, a tower, or even a tall tree knows that
winds get stronger at greater heights. There's less drag resistance from
objects on the ground. That's why wind energy prospectors typically
weld their expensive turbines to high towers, because the most important
factor in power production is how fast the wind blows past the blades.
But what if turbines could reel in the power whirling above the reach of those tall towers?
Airborne
wind energy pioneers, from North America to Italy and Australia, aim to
find out. The technology is still in its infancy, although Makani's
system—pictured above—has received notable backing from Google's
philanthropic arm and the U.S. government. The concept also gained
support in a new study published September 9 in the journal Nature Climate Change,
which focused on the steady, fast high-altitude currents, and concluded
that there's enough power in Earth's winds to be a primary source of
near-zero-emission electric power as the global economy continues to
grow through the 21st century.
Resembling a drone aircraft on a string, the Makani Airborne Wind
Turbine takes flight at its test site, the decommissioned U.S. Navy air
station at Alameda on San Francisco Bay.
By eliminating 90
percent of the material associated with a conventional wind
turbine-largely by getting rid of the tower—the designers say they hope
to reduce cost while accessing stronger winds.
The winged device
is tethered to the ground and flies in large vertical circles at
altitudes between 800 and 1,950 feet (250 and 600 meters). Its four wind
turbines rotate as the craft moves. According to Makani Power, the
speed of the craft increases along with wind speed.
Makani
Power's website says the company is developing a 600-kilowatt (kW)
prototype. That's considered the size of a medium commercial wind
turbine; for comparison, a 600 kW land-based turbine installed in 2009
at University of Maine at Presque Isle generated
680,000 kilowatt-hours of electricity in its first year, enough to
power about 60 average U.S. homes. But an airborne wind turbine might
deliver more or less power, depending on the boost of stronger, more
consistent winds or the cost of trickier operation.
Makani was
founded in 2006 and received $10 million in initial start-up capital
from Google's foundation, plus support from the U.S. Department of
Energy.
One of Makani's three co-founders, Corwin Hardham, has told reporters he was inspired by his hobby of kite-surfing.
It's not a coincidence that Alameda has a beach that is popular with
Bay Area kite-surfers. It also isn't far from Google headquarters; the
company's founders, Sergey Brin and Larry Page, are known to be avid kite-surfers.
Courtesy: NGC
