2014-05-15

Co.Exist

This Giant Tower In The Desert Could Generate As Much Power As The Hoover Dam

The Solar Wind Downdraft Tower will generate huge amounts of power—if it's ever built.

If the Solar Wind Downdraft Tower is ever built in the Arizona desert, it truly will be a wonder of the modern world. At 2,250 feet, it would be taller than the new Freedom Tower in New York (1,776 feet), and 1,000 feet higher than the Empire State Building. It would have 120 huge turbines at its base, and enough pumping capacity to keep more than 2.5 billion gallons of water circulating. And it would have colossal power output: the equivalent of wind turbines spread over 100,000 acres, or as big as the Hoover Dam.

That's the plan, anyway.

The idea goes like this: Water is sprayed at the top, causing hot air to become heavy and fall through the tower. By the time it reaches the bottom, it's reaching speeds of up to 50 miles per hour, which is ideal for running the turbines. The advantage over standard solar and wind energy is the plant runs continuously, day and night. There are no intermittency issues from the sun failing to shine, and you don't need to dust off any solar panels to keep things going. As long as the air is warm enough (which is likely in Arizona), the tower will keep creating draft effects.

The plant itself runs under its own generated energy: about 11% of output goes to pumping the water to the top again, and about three-quarters of the water is collected at the bottom, according to Ron Pickett, CEO of Solar Wind Energy Tower, the Maryland company behind the design.

"This is totally clean energy that actually makes money," he says in an interview. "It makes energy at a cost comparable to if you were using natural gas to power a plant."

See a company video here:

In a sense, the technology is the least complicated thing. People have been working on variants of solar wind towers for more than a century. In the 1980s, engineers in Spain built a 640-foot test tower that pushed air upwards through turbines (by warming the air). It generated power for seven years until it fell over in a storm.

The tougher issue is the enormous expense. To start generating meaningful amounts of power, you need something very large, and very large things tend to be costly. The Arizona project is likely to cost as much as $1.5 billion, according to Pickett.

Solar Wind Energy recently jumped two hurdles to getting the tower realized. First, it won a development rights agreement from San Luis, a city on the Mexico border, that ensures that "nothing else is necessary from the locale to build the tower," Pickett says. That includes a deal with the local utility to purchase power, and the rights to the necessary water, all 2.5 billion gallons of it.

It also agreed preliminary funding with National Standard Finance, an infrastructure fund. That will begin to pay for generating equipment and related costs. Solar Wind Energy will lease back the station over 20 years, and earn a license fee for its design, which it also hopes to see enacted in Chile, India, and the Middle East.

Add New Comment

12 Comments

  • Using billions of gallons of water in the desert seems like a loosing proposition from the start. The links to the other examples are all updraft, as opposed to this downdraft concept. Updraft, requiring no water, seems far more practical and suitable to the desert. It would be interesting to know why they made this choice.

  • Interesting the this design is downdraft, while all the others (linked in article) are updraft. Updraft seems far more feasible in the desert—no water needed.

  • Rich Persoff

    Interesting concept!

    1. Saturating air with water cools it, but also makes it less dense.
    2. Uses for cooled air exiting the turbines?
    3. Effects of regional or diurnal air stagnation - no breeze?
    4. Power to pump water to tops of towers, vaporize it?
    5. Collection & disposal of residual salts from evaporated cooling water?
  • Although a nice concept, this brings yet another problem. If the structure is erected on land, its going to deplete the ground water table rapidly. However, the concept might suit the offshore environment, where water is abundant

  • Can anyone point to the details on how long this has to run (and not be blown over in the wind) before the energy it creates is finally "totally clean energy"?

    In other words, when is the speculated break-even point when it has generated the equivalent amount of energy that it took to create the tower, infrastucture, and other overhead?

    Another way of looking at it is: How much energy is required to spend $1.5 billion dollars?

  • Dustan DuPhily

    I love this new concept but the desert does get cold at night, is the air still warm enough for this tower to work? Any breakthroughs on solar panels that use infrared light at night to generate power?

  • David Richardson

    What about capturing that air and channeling it into a solar furnace that heats it back up and uses the rising air to turn another set of turbines?

  • Michael Zwirn

    Back in 1997, I wrote on this exact same technology from an Israeli proposal then being circulated by an engineer named Dan Zaslavsky, called Arubot Sharav, or "desert wind towers" in Hebrew. (Interestingly wikipedia cites me: http://en.wikipedia.org/wiki/Energy_towers)

    The technology is identical to this proposal for Arizona, and the principle is pretty widely agreed upon, but the scale is so massive that it's hard to develop any functional models unless you build over a kilometer in height. One interesting concept, which your article omits, is the idea that you could spray seawater, or brackish water, at the top of the tower, and then use the energy of the turbines themselves to power reverse-osmosis desalination, which would be particularly attractive in Israel, a water-scarce country next to two oceans.