Rick's Ramblings

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.

Comments:

1. This experiment seems to be working. We had pretty strong winds overnight, but the turbine only fluttered a couple of times, and then only very briefly. The batteries were at 25.2V when we went to bed, and although the heater ran several times overnight, they were still at 25.2V when we woke. This means we got no real charging above that, but that the turbine (which must have been in slow mode most of the night) just kept up with our electricity usage.

   I don’t really understand why it is in slow mode at 25.5V, and would like a litte additional charging. So, I’ve readjusted the target voltage to 28.0V from 27.0V. Now we are getting some additional charging but still no fluttering.

   Posted by Rick  on  01/15/2006  at  08:11 AM

2. I think I can now definitively say that this worked. We are up at the cabin this weekend and we are having relatively high winds (and snow), and the turbine has only furled a couple of times. There is occasional sun, so once the battery voltage gets above about 26V, or so, the turbines starts to slow way down, then the sun kicks in and adds energy to the batteries. They may not be getting a full bulk charge, but they are staying in a range of 24 to 26 Volts, which is fine. And, it is soooo quiet.

   Posted by Rick  on  02/04/2006  at  11:40 AM

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