reverse thermal chimney tower

A bizarre concept: Copied from Eco Geeks at http://ecogeek.org/component/content/article/3783
Written by Philip Proefrock on 12/06/12
Solar towers are again getting some notice. According to recent news, a company called Clean Wind Energy, Inc. is trying to build a 3,000 foot (914 meters) tall tower to produce electricity. When the tower is operational, the company expects to have, on an hourly basis, "1,100 to 1,500 megawatt hours available for sale to the power grid."

Solar power towers are one of the more unusual concepts we've come across at EcoGeek. More properly, we should be calling them something like 'thermal chimney towers' to differentiate them from the solar towers which are targets for fields of solar reflectors.

To further complicate the matter, there are two types of solar chimney towers: updraft and downdraft. Updraft towers require a large area covered with transparent material to heat the air at the base of the tower in order to make it rise through the chimney. Downdraft towers pump water to the top of the tower where it is sprayed as a fine mist to cool the air and induce it to fall. In both cases, wind turbines at the base of the tower are turned by the moving air to produce electricity.

The tower that Clean Wind Energy is proposing is of the downdraft type, which may be problematic in the American desert southwest, where water is already scarce. Treehugger's article on the project also notes one of the major drawbacks to this kind of power generator: "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."

Several years ago, we first noted that Enviromission, an Australian company with an updraft tower design, was trying to get their first solar power tower built in Arizona. That company found Arizona more conducive to their business model than building a tower in the Australian desert, and their project also seems to be moving slowly forward. Whether either one of these towers (or both) gets built remains to be seen.

via: Treehugger