Monday, January 25, 2010

More information on Wind Turbines

Some people have questions about the size and looks of a turbine.

Here is a picture of a pair of turbines in the water. These are in Europe.

The base is about 20 feet in diameter at the waterline. The hub height would be about 300 feet high. This type of construction is called monopile. Basically a huge pile driver drives in the base, then the tower and turbine are mounted on top. I have been told it takes less than a week to install one.

Here is a diagram of foundations:

Note the monopile is used up to 30 meters (100 feet) depth. Driving in the pile is the cheapest way of installing a turbine. I suspect our bottom is too hard, so this may not be practical. In that case we would use a gravity style base. A gravity base is the most common foundation for in-water turbines.

The "tripod" style base is for deeper water, and would probably not be an option for us.

Two issues that will certainly come up, so they must be discussed: noise and flicker.

Aren't turbines noisy?

Honestly, I do not know yet. Most public specifications about turbines show that the noise generated is less or about the same as ambient. In other words, when the wind is blowing 20 knots, there is a lot of other wind noise from trees. Certainly around the islands the surf is very noisy on windy days. Fishing boats are much louder.

On the other hand, there are a lot of people on the Internet complaining about turbine noise. Certainly a few of the folks on Vinalhaven are upset about the noise. When I visited Vinalhaven the noise was minimal, but it was not windy when I was there.

There are ways to mitigate noise by detuning it for certain wind velocities and directions.

We, everybody in the community, have to learn about the noise issues firsthand and decide if these are insurmountable issues.

Isn't flicker a big problem?

Unlike noise, flicker is not a serious problem. Flicker is the shadow caused by the spinning turbine blades. Flicker can only happen on sunny days near sunrise and sunset. In the middle of the day the sun is high so the shadow is very short and close to the base of the turbine. Flicker can never happen to the south of the turbines (in the northern hemisphere). Flicker does not happen for a long time since the shadows move with the sun. If a house was in the shadow of our turbines (rather unlikely since the turbine will be in the water), the exact time can be calculated, so on sunny days (there is no flicker or shadows on foggy days) a turbine could be stopped for a few minutes on a few specific days until the house is out of the shadow.

Flicker gets a lot of play on the Internet because it is very easy to make a dramatic YouTube video. I do not think we will have any issues with flicker.

No comments:

Post a Comment