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.