This is an idea that's been around since it was patented by Phillip Carlson in 1975, but it's never been carried out. Now San Luis, Arizona, right on the US-Mexico border, is preparing to bring it to life: a 3,000 foot tall tower built to generate clean electricity from hot dry air and cool water, reported EcoFriend.
The idea behind the downdraft energy tower is actually pretty simple, so long as the hollow structure is tall and in a hot, dry climate. At the top of the tower, air is sprayed with cool water, making it denser and heavier. The air travels downward through the tower, powering wind turbines that generate electricity. This (amusingly old school) video lays it out nicely:
Since Carlon's patent, most of the work on this technology has been done by researchers at the Technion-Israel Institute of Technology, including Dr Ramu Guetta and Prof Dan Zaslavsky, the brains behind the San Luis project.
Of course, there's the problem of dedicating large amounts of water in a desert city to the tower, and the energy required to send it 3,000 feet up. One third of the energy produced by the tower goes to that pumping; it could be worse. Clean Wind Energy, Inc., the company building the tower, estimates that the tower will produce up to 2,500 megawatt hours.
The construction isn't a done deal just yet. The land has been successfully leased and is now in the process of zoning approval. If it all comes together, Arizona, already a growing hub for solar power, could become a real leader in the clean energy game.