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Vertical Axis Wind Turbines

January 1, 2001
Paul Gipe

Ventilators and Squirrels in a Cage



Portions of the following have been adapted from Wind Power for Home, Farm, & Business published by Chelsea Green (spring 2004).


Like ducted turbines, a perennial favorite of hucksters and charlatans is, for lack of a better word, squirrel cage rotors. Many are nothing more than roof-top ventilators repackaged as "wind turbines". As ventilators, they work fine. It's when someone tries to couple them to a generator that they quickly learn why wind turbines use two or three slender, airfoil-shaped blades. Most hucksters, however, never progress that far. They never build actual wind turbines, and perchance that they do, they never measure the "wind turbine's" performance. Of course, they wildly exaggerate the potential of these breathtaking new inventions.

Doug Selsam, himself an inventor, has tried to understand why consumers--and the news media--are so gullible. His explanation: ventilators and squirrel-cage rotors are easy to understand, modern wind turbines much less so. After all, a roof-top ventilator with its entire swept area covered with blades looks like it will capture more wind than a modern wind turbine with only a few blades, some with--unbelievably--only one.

In a 2002 internet scam, a company peddling ventilators as "wind turbines" claimed their product would produce nearly five times more electricity than a conventional wind turbine of the same size. Naturally, for this "superior" performance they would charge 2-3 times more than for a real wind turbine. The company asserted that they were "thinking outside the box," a catchphrase of 1990s management gurus. They certainly were. They were not even close to the box. They were on another planet where the laws of physics don't apply.



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