How much wind is enough wind?
I live in the kind of area that looks on a wind map like it could never possibly support a wind turbine. One of my favorite places to go walking with my wife is under two giant (I’d guess 100 meter) wind turbines. One is larger than the other. I had commented to her how amazing it as that these things moved at all. Granted- their location is carefully thought out and they are placed incredibly high. But still- it had long surprised me that they moved at all.
When I was out there last night, I noticed for the first time that the larger turbine wasn’t moving at all and the smaller one was barely moving. “Sort of figures, I thought.” It was a clear demonstration of a particular phenomenon to me- cut-in speed. This is the speed necessary to move a wind turbine. Clearly, the light breeze wasn’t doing it. It simply didn’t move fast enough to move the big turbine or to move the small one in any significant way.
But then something interesting happened. The Earth cooled, night fell, and the turbines started spinning. More interestingly, the larger turbine seemed to start moving slower than the small one, but as night progressed, began moving faster and faster till it seemed to be moving even faster than the small turbine. Despite their weight, the larger blades simply caught more air, making them move faster than the smaller blades.
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.
