Is it pie in the sky or something much more substantial? Some scientists, academics and entrepreneurs are convinced that to meet the world's energy needs and roll back the ravages of global warming, we need only look up.
"A river of energy flows above us," said Cristina Archer, assistant professor of energy, meteorology and environmental science in the Department of Geological and Environmental Sciences at California State University, Chico.
"People talk about oil lakes under the ground, but we have the same [energy resource] in the sky. There's a lot of wind energy up there. It's astonishing. And it's free. It makes sense to tap into that free source."
Archer, also a consulting assistant professor in the department of civil and environmental engineering at Stanford University, is regarded as an authority on high-altitude wind power, or HAWP.
In 2007, working with Ken Caldeira, senior scientist in the department of global ecology at Stanford's Carnegie Institution for Science, she began a six-month research project, crunching through 28 years of global data to determine wind characteristics up to about 7.5 miles.
Her findings, published in the journal Energies earlier this year, revealed immense reserves of sustainable energy at different altitudes and at different times of the year, all around the world.
"The total wind energy in the jet streams is roughly 100 times the global energy demand," Archer wrote. "Because of their abundance, strength and relative persistency, jet stream winds are of particular interest in wind power development."
Archer estimates energy demand at between 2 trillion and 2.5 trillion watts. About 6 miles up, jet stream winds, even though they don't blow hard all the time even at that height, could generate around 200 trillion watts.
Caldeira also focuses on these "large amounts of renewable power available in highly concentrated form," something he describes as a far more abundant energy resource than even the most efficient terrestrial wind or solar sites.
Grabbing the energy
Terrestrial sites can be reached by pickup trucks, and their cables can snake over the ground relatively easily. It's a point Caldeira turns to his advantage: He says power is already transmitted horizontally over hundreds of miles, so, while it might sound like science fiction to some, 6 miles vertically is "relatively nearby."
The challenge then is to suck that energy out of the air and bring it down to earth. Now several entrepreneurs and start-up companies are competing to fill that space ... almost literally.
Magenn Power, originally located in Ottawa before moving to airport facilities at Moffett Field, a former Navy blimp yard in the Bay Area, is staking its claim to airspace at around 1,000 feet.
Magenn has developed the blimp-like Magenn Air Rotor System, a revolving cylinder with three blades spinning in the wind like a paddle steamer wheel turning in water.
On-board generators send electricity down the tether to a transformer and into the grid. Or, says company founder Fred Ferguson, the power could directly supply farms, Third World villages or small island communities — anywhere that is dependent on expensive and polluting diesel generators.
Because devices like the MARS do not fly vertically above their mooring but have a bowed tether like a kite string, at 1,000 feet, this machine would probably need a tether around 2,000 feet long.
"That's not a show stopper," says Ferguson, who points to radar-carrying, helium-filled inflatables used by the military and drug enforcement agencies and tethered up to 15,000 feet using 25,000-foot cables.
Various kite-based businesses are eyeing similar altitudes. Some, flying single kites or connected groups, harness the power generated as they zigzag around the sky; others, like Makani Power, fly a rigid-winged device carrying its own turbines.
Operating in commercial air space is an issue for all HAWP companies but especially Sky WindPower — which plans to tap the wind's potential at up to 27,000 feet, or 5 miles high.
Getting it off the ground
Nettlesome airspace issues aside, the technology to build what are essentially airborne windmills is developing quickly.
Advances in new lightweight, composite materials and high-tech coatings are helping to make HAWP a reality, reducing costs, improving performance and increasing the ability to quickly winch down equipment in the face of storms, lightning or extreme winds.
Ferguson says Magenn is working on a prototype and expects to have a pre-production unit ready by about February. He believes the first commercial MARS unit could be for sale by the end of next year.
Since launching in 2006, Makani has attracted $15 million in research and development funding from Google.org, an encouraging vote of confidence from the investment arm of a company synonymous with innovation.
Makani, based in Alameda, Calif., has run test flights there and in Hawaii using a craft resembling a hang glider wing fitted with turbines; a prototype has already completed a 30-hour, computer-controlled flight.
Corwin Hardham, Makani's co-CEO, says the company hopes to have the kite — which harvests wind power for the grid by sweeping fast, circular patterns — commercially available in three to six years.
While not underestimating the challenges ahead, Hardham is bullish about the fledgling HAWP industry. "People are starting to realize this resource is too large to ignore," he says.
He believes the technology can be scaled up quickly and cost-effectively to obtain "appreciable amounts of energy," and sees a lot of interest, tempered by some skepticism. "The burden is on us to demonstrate we can make it work."
An Italian company, Kite Gen, intends using low-level kites, harnessed to a central hub, to generate power from the motion created by racing across the sky.
Robert Creighton, CEO of WindLift Kite Engine Company in the Wright Brother's old stomping grounds of North Carolina, sees kites as a mobile source of energy for pumping water, charging batteries and other small-scale projects, especially in developing countries.
Len Shepard, however, is taking things to the next level. The CEO of Sky WindPower is initially looking at between 3,000 and 12,000 feet but ultimately hopes to produce electricity at the "utility scale" even higher.
His company, based at Oroville, a Northern California town better known for hydroelectricity, has flown two prototype helicopter-like craft, each with four rotors and onboard generators. Though power is needed to help launch the device, wind then takes over, turning the rotors to maintain altitude and send electricity down the tether.
Shepard says the tether and craft have little environmental impact since they are barely visible and operate in open spaces well away from populated areas. He also believes this technology is much less hazardous for birds and bats than ground-based turbines.
According to the American Wind Energy Association, terrestrial wind power meets only about 1 percent of U.S. electricity demand, so it may not be surprising that HAWP pioneers report some skepticism and resistance.
Doubters and critics single out the danger to aircraft and the potential for lightning strikes as major obstacles in the path of high-altitude wind machines; some also think the weight of many miles of tethers will be too much for the craft to support.
Fair enough, says Shepard, who thinks Sky WindPower should have to prove to doubters that the technology really works. He hopes to be able to do just that by the end of next year.
Archer, the scientist, hesitates to predict when this huge resource will begin to be tapped commercially. "From what I know so far ... it is in the five-to-10-years time frame," she estimated.
The fledgling industry takes a major step along the road to wider acceptance with what is being billed as the world's first high-altitude wind power conference in Chico and Oroville Nov. 5-6.
Archer, who's chairing the event, hopes it may help establish an industry association or council, increasing HAWP's visibility and credibility in the eyes of the public, policymakers, regulators, investors and others.
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