Saturday, January 14, 2006

Wind Turbine Experiment

When we stay at the cabin and the wind blows at speeds greater than about 40 mph, our wind turbine make a lot of noise. The vendor (Bergey) calls it “fluttering”, but that is a kind word for it. It sounds like a helicopter landing on our roof. This happens because the wind turbine is designed to “furl” at high winds in order to protect itself. When it furls, it actually turns sideways into the wind to get the propellers out of the direct wind and slow them down. At low speeds this is not a problem, you don’t even notice. But, at high speeds it make a tremendous noise.

So, I’ve programmed the wind turbine controller to put it into “slow mode” when the batteries reach 27V. Thus, the wind will never fully charge the batteries (which need to get to 28.8V or so), but will begin to dump any current to a load in the crawlspace—warming it up nicely—when the batteries are above 27V and it is windy. However, above 27V the wind turbine controller will also slow down the rpm of the turbine to about 120 rpm regardless of the wind. Now, if high winds cause a furl, it won’t make noise.

There are several implications of this experiment:

1. The wind turbine will not contribute to battery charging above 27V. I will rely totally on the sun for full charging. So, I may not get a full charge as often, and there is some risk of running the batteries down during a series of cloudy days, even if the wind is blowing. (But, they will still get charged to 27V, which isn’t bad.)
2. It will be much quieter in high winds, as long as the batteries are in pretty good shape. And, when it does get noisy, it won’t last as long because the wind turbine will kick off at 27V.

I’ve run the system like this all day—it is sunny but very windy—and it seems to be working perfectly.

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Posted under: Cabin News • by Rick on 01/14/2006 at 01:28 PM
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