A Maryland company, Solar Wind Energy Inc., proposes to build a giant tower near San Luis, Arizona, located on the U.S. – Mexican border south of Yuma.
I reported on this story in March, 2013 in my Wryheat blog (see original story), when it was first announced. Inside Tucson Business (ITB) reports some updates in an August 8, 2014 story.
The proposed tower, essentially a hollow cylinder, is planned to be 2,250 feet tall, 1,200 feet wide at the top, and 1,500 feet wide at the bottom. It would be the second tallest structure on the planet. This project is described by David Ferris in a March, 2013, Forbes article here with an update here. In the ITB article, “Ronald W. Pickett, president and chief executive officer of Solar Wind Energy Tower Inc., said he expects the plant, when completed, to generate 425 megawatts of electricity each year.” The project will cost $1.5 billion, apparently from private investors.
The technology is based on work done in Israel in the mid-1970s (see Wikipedia article here). The tower is supposed to work as follows: Water is sprayed into the air at the top of the tower. This makes the ambient air heavier and cooler, causing it to drop down the tower at up to 50 mph. It exits the tower by passing through turbines which produce electricity. You can see a more detailed explanation and a short video at the website of Solar Wind Energy here. As far as I can find out, the technology has been tested only with a 4-foot model. The Arizona project will be the first practical test.
About 100 megawatts would power the plant itself, according to the Forbes story. After all, it will be necessary to pump water from the source to the plant, then 2,250 feet up to the top of the tower. That leaves a net production of 325 megawatts. According to the ITB story, the average home uses “12 megawatt hours of electricity annually.” If those numbers are correct, then this billion dollar project will power 27 homes (325/12 = 27), or is there some confusion between megawatts and megawatt hours?
This project will use 8,000 acre-feet (2.6 billion gallons) of water per year, the equivalent use of about 1,500 residences. In my original story, the company had proposed to build a pipeline from the Sea of Cortez and a desalinization plant. Apparently, though, these plans fell through. Now, according to ITB, the San Luis city council will supply untreated city water to the project, in other words, the project will pump groundwater. Mr Pickett claims,”We will be taking water out of the ground and putting it back through evaporation, so we will not be a net user of water.” I think that statement is highly misleading at best. “Putting it back through evaporation,” will be a neat trick. The air exiting the bottom of the tower will be very humid. But getting the water contained in the humid air to produce local rain to replenish the underground aquifer seems problematic to me. I think also that the residents of San Luis are not going to like humid air coupled with their natural high temperatures. According to the Israeli research, a plant of the proposed size will humidify the air enough to make “a community even 100 kilometers away… unpleasantly affected.”
Another red flag, which nobody has mentioned, is that the tower will be built in an area that is highly prone to earthquakes. What effect will a magnitude 5 earthquake have on a 2,250 hollow cylinder? The ITB story says the cylinder will be made of concrete which does not react well to shear stress unless it is heavily reinforced.
Using the Arizona Geological Survey’s hazard viewer, I produced the inserted map which shows the incidence of earthquakes of magnitude 5 and greater. San Luis and the proposed tower lie in the southwest corner of Arizona within the cluster of past earthquakes.
While the reported scheme is a “down-draft” tower, there are also schemes with “updraft” towers.
Remember these?
Solar Updraft Towers, an alternate, alternative energy source