Aug
22
An evening walk with my wife revealed to me something about wind turbines. We were walking in a garden that happens to be set in a valley right below two large industrial turbines. I bet these have cut-in speeds of 20 mph (granted- I’m familiar with home, rather than wind turbines, but I’m sure they require a lot of wind). In addition, the two turbines are two different sizes. By swept area, I’d think that one is at least 1/3 bigger. This area also does not ever appear to be windy. I had often commented to my wife how odd I found it that such large turbines could function right there- it feels like the doldrums of a desert landscape
Last night we were out at the gardens, and for the first time I saw these wind turbines totally still. The small one was moving in furtive spurts, but nothing solid. Granted, it was the kind of hot desert day where the only air movement is the visible wave of heat rising. It was a clear demonstration of a particular phenomenon to me, though- cut-in speed. This is the basic speed that wind has to blow to make the turbines on a wind tower move. There wasn’t enough wind to move the big turbine.
Then night started falling, the Earth cooled down, and canyon breezes began anew. Pretty soon, both turbines were turning. I noticed a particularly interesting phenomenon at this point. Just before dusk, the smaller turbine was turning faster than the large one. Then as wind picked up more and more, the larger turbine was actually making more revolutions than the smaller one.
This whole situation was a clear demonstration of something of which we all need to be aware. When choosing a wind power system, sizing, testing, and careful selection are all of utmost importance. If you live where I do, it’s probably best to either have a small turbine or a huge tower. It also showed me another principle, however. If you live in some of the places where I used to live (shores of Lake Michigan for example), you’d be well advised to buy a larger turbine. I noticed on this walk that when the wind picked up, the larger turbine picked up more wind and moved faster. Not only can it turn faster, it is probably turning a larger magnet. The net benefit is greater- but only if you have the kind of wind necessary to make it turn. Bare this in mind whenever you think about building your own home green power systems.
And as always- good luck building!
Damon Westchester is the editor of build-green-power.com.
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