Your Energy Skyscraper Questions, Answered
David Ferris Former Contributor
I write at the intersection of energy, climate and business.
Solar Wind Energy's depiction of its energy tower.
A post I did earlier today about a giant energy tower proposed on the U.S.-Mexico border generated a large number of questions and comments. A reason for the confusion is that the project creator, Solar Wind Energy Inc., did not initially respond to my requests for information. But after the story climbed north of 25,000 views, I got a phone call from Ron W. Pickett, the company's president and CEO.
Here I have paraphrased some of his answers to your questions.
How much would it cost to build a downdraft tower? $1 billion, plus $100 million to pipe the water in from the Sea of Cortez in Mexico. Additional money would be needed to build a desalination plant, but the company has not yet arrived at a number. Costs for the water would be shared between the two plants the company wants to build in Arizona and another two planned for in Mexico itself, in Sonora state.
Where would the money come from? Pickett said the company wouldn't need to generate much of its own capital because it would license the technology to a project developer. The company is in talks with "a very credible, notable development company noted for its energy accomplishments," Pickett said.
Has a scale model been built? I was astonished to hear that the biggest physical scale model the company (or anyone else) has built is "about four feet tall," Pickett said with a chuckle. "There's nothing unknown, and no unknown algorithms, in this system," he added. The company is confident in its computer-aided design models, and plans to move directly from four feet tall to 2,250 feet tall -- the tallest structure ever built in North America.
How can humid air create a downdraft? (Note: the structure, called a downdraft tower, is essentially a colossally large cylinder with an open top, and the tower creates its own internal wind by spraying water droplets into the tower mouth. The moist air drops and accelerates to up to 50 miles per hour.)
The tower works on the same principle as the downdrafts that can be the bane of aviators. In a downdraft, a column of moist, high air can rush violently toward dry, lower, and lower-pressure air, especially if the temperature at the base is significantly lower than at the top. Pickett expects a 40° F difference between the temperature at the mouth and the base of the tower, with the denser air at the bottom achieving its coolness through evaporation. A large part of the company's proprietary technology is using historical and real-time temperature and humidity data in order to fine-tune its sprayers. "We make those pressures by having regular, predictable dry air and adding a certain amount of water to it," Pickett said.
Will the tower really need 1,000 permanent employees? In fact, Pickett said, the number has been downgraded to 750 employees per tower. These would mainly be responsible for maintenance of the 25 generating plants that surround the base of the plant (scaled down from the 52 I reported in the original story).
How much water would it use? Pickett wouldn't say -- or didn't yet know -- how much water the tower would need, but he did claim that the tower would be able to recapture and reuse about 75 to 80 percent of the water it uses.
What would it look like? The tower would be about 1,200 feet wide at the top and 1,500 feet wide at the base, and would be made of concrete. At first the company had hoped to build it out of steel, but then costs ran too high. The tower, Pickett said, "from a distance will look like a big cooling tower, only bigger."
David Ferris
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