A Skyscraper-Sized Solar-Wind Tower Could Become North America's Tallest Structure

Can a 2,250-foot-high wind tunnel generate electricity more cheaply than coal? 

The city council of San Luis, Arizona, a town of 15,000 on the Mexico border, last week approved the construction of the tallest structure in North America, a 2,250-foot-high concrete tower that would generate electricity by spraying water on hot desert air at the tower’s top. As the saturated air sinks, the downdraft creates 50 mile-an-hour winds that are forced into tunnels at the base of the tower to drive electricity-generating turbines.

“Our tower makes roughly about half the power of a traditional nuclear power plant,” Ronald Pickett, the chief executive of Solar Wind Energy Tower (SWET), the company behind the $1.5 billion project, told investors during a March conference call. “Enough to power a city of 700,000 to a million people.”

And the price of that carbon-free power would be cheaper than coal-fired electricity, he claimed.

Déjà vu.

Nearly eight years ago, I traveled to Australia to report on another quixotic scheme to build a giant tower in the middle of nowhere to produce renewable energy. Like Pickett, Roger Davey was a 60-something entrepreneur running a penny stock company. (SWET’s stock was trading at 2 cents a share this morning.) Davey’s EnviroMission had grand plans to build a 1,600-foot tower in the Australian outback that would create an updraft rather than a downdraft to generate electricity.

As I wrote in Business 2.0 magazine:

Rattling down a red dirt road on the edge of the Australian outback, Roger Davey hits the brakes and hops out of a rented Corolla. With a sweep of his arm, he surveys his domain - 24,000 acres of emptiness stretching toward the horizon, the landscape bare but for clumps of scrubby eucalyptus trees and an occasional sheep.

It's a dead-calm antipodean winter's day, the silence of this vast ranch called Tapio Station broken only by the cry of a currawong bird. Davey, chief executive of Melbourne renewable-energy company EnviroMission, aims to break ground here early next year on the world's first commercial "solar tower" power station.

"The tower will be over there," Davey says, pointing to a spot a mile distant where a 1,600-foot structure will rise from the ocher-colored earth. Picture a 260-foot-diameter cylinder taller than the Sears Tower encircled by a two-mile-diameter transparent canopy at ground level.

About 8 feet tall at the perimeter, where Davey has his feet planted, the solar collector will gradually slope up to a height of 50 to 60 feet at the tower's base. If Stanley Kubrick had put a power station in 2001: A Space Odyssey, it would've looked like this. Acting as a giant greenhouse, the solar collector will superheat radiation from the sun. Hot air rises, naturally, and the tower will operate as a giant vacuum. As the air is sucked into the tower, it will produce wind to power an array of turbine generators clustered around the structure.

The project never got off the ground after EnviroMission failed to obtain government funding and Davey set his sites on—you guessed it—Arizona. In 2010, the company secured an agreement with a Southern California utility to sell electricity from a pair of 2,400-foot towers, just 322 feet shy of the world’s tallest building. Although the technology was proved on a small scale in Spain in the 1980s, EnviroMission could not attract financing and lost the utility contract.

SWET faces even more hurdles. The company has lost $8.9 million over the past three years, according to a Securities and Exchange filing. “Our independent auditors have expressed substantial doubt about our ability to continue as a going concern, which may hinder our ability to obtain future financing,” SWET stated in the March report.

The company did not respond to an email request for information about its technology and financing.

SWET’s tower technology apparently has not been proved at any scale, though on the investor call Pickett said, “It’s not a mystery. It’s a known science.”

He dodged a question about how much water a tower will consume but said a supply has been secured for the Arizona project. Building towers in the Middle East and other desert regions will require diverting some electricity production to desalinate seawater, he said.

The company will not actually build the towers, according to Pickett, but will collect fees for licensing the technology to developers as well as royalties based on a project’s electricity production. He said SWET expected to collect an initial $18 million licensing fee as well as $8 million to $12 million in annual royalties for each project. He said developers in Chile, India and the Middle East have expressed interest in the technology.