Wind towers - Just an enjoyable read.

[RustyLugNut]

While you drink your morning coffee you can take in some informative and pleasurable advertising.

The tallest wind power tower in the US, assembled in one hypnotizing video - Vox

[darcane]

Thanks for the link!

The company I work for designs suspended access platforms. The platform they use inside the tower in this video is one of ours. Very cool seeing it in action... I sent it to the rest of my engineering department to check out.

[redpoint5]

Neat stuff. I was surprised to see the tower in the first video taper in stages rather than a continuous taper as seen in the second video.

I always thought the tower anchors had to be very deep to resist the enormous wind loading; I didn't realize they could simply make a wide base and pile dirt on top.

I wonder how feasible it is to use higher strength materials such as carbon fiber to reduce the tower diameter so it will fit under bridges? Perhaps it doesn't have the same crush resistance that concrete does, and I'm sure the cost would be enormous.

Why was steel used in the first place? Seems concrete would be cheaper.

[darcane]

I believe a lot of the reason for how towers are traditionally constructed revolve around the fact that wind farms tend to be in remote places. If you develop parts that can be transported to the site easily and quickly assembled it is cheaper and easier to build. You have a factory churning out parts and on-site is simply assembly.

Cranes are very expensive to have on site. Building all those forms on site and using the crane to lift them in place is probably very expensive comparatively. Because of the remote location, trucking in all that concrete can get very expensive even if the concrete itself is cheap. So, steel ends up being cheaper than concrete.

Concrete production generates a lot of CO2. For an industry that is very concerned about the image of being green, this is a bad thing. Personally, I don't see CO2 as a pollutant, so I think it is much ado about nothing, but it is generally a concern in the industry.

Some manufacturers are starting to build the bottom section out of concrete (~100ft) and the top sections out of steel to get the best of both worlds.

[redpoint5]

For locations where aesthetics is not a concern, why not build the tower using 4 poles, or use guy wires? It would meet the requirement of fitting under bridges, and should use less overall material and cost less.

Building bigger shouldn't have to mean setting up fabrication on site.

[darcane]

Lattice towers were used on small turbines, but tended to have problems with the vibration from the turbine causing high maintenance costs. Intermittent wind speeds cause a cyclical loading, ice buildup on the blade will cause vibration, and even the tower itself blocking the wind in one part of the blade's rotation causes vibration. Concrete or steel tubular towers are generally rigid enough, but the lattice towers typically get bolts that come loose over time. Plus it encouraged birds to nest in the tower (bird kills are frowned upon) and doesn't provide a place for the electronics in modern wind turbines.

There is a new tower from GE that is supposed to resolve these issues. It's a lattice tower, but covered in a polymer fabric to protect from the elements and keep birds out. They have a special bolt that is supposed to better resist loosening from vibration. I haven't heard much about it for a while, so I don't know if it successfully resolved the issues.

[freebeard]

The Plan View Guy Radius is wrong. It takes six cables, not three, to prevent torquing around the vertical axis.

The tower has to be that massive to accommodate the radius of the blade's swing. A vertical axis windmill would require a shorter tower. Replace the tower with a huuuge hemisphere and not only does it absorb ground level turbulence but also increase wind speed normal to its direction, e.g., at the very top. Plus which, the vibrations tangent to the hemisphere are resisted instead of absorbed by it's shape.

Actually, if you put the turbine in the toroidal airflow inside the hemisphere, suddenly all your maintenance is indoors and there is no insult to our avian friends .