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Solar Updraft for Energy Production September 13, 2008

Posted by OldGuy in solar, Wind Power.
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There’s an interesting but still untried approach that combines solar power and wind power.

The principle of Solar Updraft is that a solar collector is laid down across an open field, such as a desert wasteland.  In the center is a tall hollow tower.  The result is an updraft inside the tower.  If one or more wind turbines is placed inside the tower, the constant wind can generate a steady stream of electrical energy, with virtually no carbon footprint once the tower is finished construction.  (Carbon payback on construction is generally 2-3 years.)

Some have suggested the collector field can be fitted with solar storage mechanisms, such as tubes of liquid, which heat during the day and generate a secondary heat source after the sun has gone down.

Unfortunately, most of the concepts involve very tall towers.  A prototype plant with a 200 meter-tall  tower built in Manzanares, Spain in the early eighties, and was operated successfully for several years.  However, a production plant was never constructed, in part because the finished tower will be almost a mile high (1.5km) and 280 meters wide.  And it will take a large amount of land, as currently designed.  The prototype plant included a 44,000-m² collector; the production unit uses a 37 square km collector field.

Of course, you don’t need to leave the collector field empty.  The solar tower proposed for Nambia includes a design to use that collector field as a greenhouse.

It’s an interesting concept.  I’m a little concerned about how they would construct a tower that is nearly 5 times taller than the Eiffel Tower (325 m).  It would be twice as tall as the world’s tallest building, the Burj Dubai in downtown Dubai (still under construction), which will be 688m (160 floors) when finished.

The expected power output – 400MW of energy – is impressive, but I wonder whether it might be better to stick with more, smaller towers, even if they generate less  energy each.

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sources:

http://www.inhabitat.com/2008/09/10/solar-updraft-towers-in-namibia/

http://www.sbp.de/en/html/solar/aufwindkraftwerk.html

http://en.wikipedia.org/wiki/Solar_updraft_tower

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