Wind blades train transport

Wind blades are normally carried by ship and truck.

By the way every now and than I see cases of train transportation: for instance Siemens moved 141 set of wind turbine blades (for the amazing total of 423 blades) to Portland General Electric's Biglow Canyon Wind Farm. Siemens is also transporting towers and nacelles via rail to various project locations throughout the U.S., so it seems that sometimes this is a reasonable option.

Vestas too is experimenting train transport: in the video embedded you can see how blades are transported from the factory in Germany to the wind farm in Denmark.

And the list is not ended: Enercon took a Marco Polo grant to move his blades by train.

Marco Polo is a UE found for modal-shift or traffic avoidance projects and projects providing supporting services which enable freight to switch from road to other modes efficiently and profitably.

The Grant (€1 268 577) for the ENERCON Tri-Modal project involves using rail and ship to move components and parts from Germany to Viana do Castelo in Portugal, as well as to installation sites throughout Europe.
Discover more about Tri Modal here

Maximum wind farm internal road gradient

This is another standard problem I found in the wind farm I’m working with: mountainous areas, with difficult access and very strong inclination.

The standard maximum slope imposed by several manufacturers (for instance Repower and Gamesa) for safe transport on gravel roads is about 6% to 7%. Above 7% other technical solution may be necessary, depending on the trailer used to pull the T1 and the nacelle.

With an average quality track surface a 6x6 tractor unit can pull the nacelle approximately up to a 9%-10% slopes.

Than it is necessary to pull the truck with a bulldozer, using a steel bar or a steel cable (see pictures below). In this case the inclination was around 15%, and we used a D8R Caterpillar and a steel cable), without particular problems.

It must be noticed that in steep sections long horizontal alignment are preferable respect to closed bends.

What we normally do in extreme cases (above 15%) is to build a ramp using concrete slabs or an asphalted road: this solution is not only more expensive, but can also introduce additional problems, such as the need for environmental authorizations or from other authorities.

Here you have a 17% asphalted curve:

Concrete slabs are normally cast on site on a layer of aggregate stone, and they have dowel bars for load transfer and sealed contraction joints. An initial texturing is made with a burlap drag or a broom device, while final texturing is made with a spring steel tine.

You can find more information on the subject in the JPCP Design and Construction Guide

Jointed Plain Concrete Pavements Design Construction Guide

 

Vertical transitions curves in wind farm

The main problem with turbine tower trailers is that they are very low.

For this reason we normally use long transition curves in vertical alignment, with a parameter of the parabola (Kv) of 400 or even more. This is the best approach, as for instance the alternative of a minimum length definition of the transition is not effective (the result will depend on the difference between entry and exit slope).

If shorter, more aggressive changes in vertical alignment are made (mainly at the end of a slope, when the horizontal crane pad is reached) there is the risk of having the trailer stuck as in the pictures below.

The height below the tower is just a few centimeters, so this is one of the critical points to check in a constructive project of a wind farm.

As a bonus I post also one of the incredible manoeuvres I’ve seen in the real word, a truck almost flying in a mountainous wind farm.

 

UPDATE 02/04/2020: 

I have been asked to define more in detail how is defined the Kv parameter mentioned in the post.

I am referring to this formula:

L = Kv x  (i% / 100)

Where:

L = Length of the parabola

i% = absolute value of difference between slopes (for instance, changing from 3% to -2% it would be 5%)

I think that in some road design software (like Civil 3D) you have to use the K value but multiply it by 100.

If you are unsure about the result I would recommend you to do a “full scale” test of the results.

You can do it plotting the resulting alignment at a 1:1 vertical / horizontal scale the alignment and after use an AutoCAD block representing the blade trailer. It will help you to see how many cm you have below the trailer in the lowest part.

This method is not 100% accurate (it does not consider the shock absorbers) but it is better than nothing.

Wind Turbine erection: 2 cranes working together

To lift the biggest component of the WTG, such as the tower segments or the blades, two cranes are used at the same time.

A principal crane, normally a Liebherr 1600 or a Demag CC2800, is helped by a smaller crane, often a rubber-tired rough terrain crane, for instance a Terex RT1120.

Both cranes start lifting the component at the same time - for instance in the attached pictures you can see how they hold a segment of tower.

Then, when it is a few meters above the ground, the secondary crane stop lifting the component while the principal crane continues the lift: doing this manoeuvre, the tower is rotated 90 degrees and can be positioned.

Narrow track cranes

In wind farms construction usually at least 2 cranes are needed: a main crane to lift component such as tower segments, blades and rotor and a smaller crane called "auxiliary" that help the main crane during the lift operations to manipulate the wind turbine component.

The auxiliary crane can also be used to move steel rebars, embedded rings or anchor cages and so on.

If the main crane is on crawlers it can be found in two types - "standard track" and "narrow track" cranes.

Standard track cranes needs around 10 meters of width, depending on the model, to move on access roads. For this reason, due to the increasing number of wind farms in areas with environmental problems or in mountainous regions narrow track cranes are a winning option – they need only 6 meters, and can help save money in civil works and in dismantling, transportation and subsequent re-erection of the crane.

Terex-Demag CC 2800 is one of the available models, while an alternative is the Liebherr LR1600/2. They can move with a mounted boom, on a gradient around 10º.

When they are in an open position on the crane pad, ready for lifting, they can occupy even more space of a normal crane – they need around 14 meters.

Both cranes are designed especially to hoist 75-100 tonne gondolas up to hub heights of between 90 and 130 meters above ground level.

Nacelle Trailer (Low Loader)

Nacelle trailer (also called low loader) is one of the special vehicles currently used to carry WTG components from the factory to the wind farm.

His peculiarity is that it’s very low, only a few centimetres above the road: this is to allow transportation on public road, where bridges with a free height of 5 or less meters are common.

The weight of the nacelle is very near to the maximum that can be transported by road: in some cases, for instance with the Vestas V112, the drive train is carried separately from the rest of the nacelle and than it’s assembled on site.

There are even vehicle developed expressly for a wind turbines manufactures, such as the Nooteboom MEGA wind mill transporter developed for Vestas that allow savings as it is possible to load / unload without the use of a crane.

The average low loader has from 6 to 8 wheels, and the platform can be closed after the unload of the nacelle: fully extended the trailer is almost 30 meters, while closed is about 20 meters.

Carrying blades with a balloon

In very complicated wind farms blades and sometimes other components are carried by helicopters – an expensive solution, to be used only as “last option”.

What I’ve discovered today is that a balloon was used by CL CargoLifter to carry the blades in a small scale test made for Nordex at the former airport of Neuhardenberg using a 9 meters balloon on December 2007.

CL CargoLifter GmbH & Co. KG is company founded by former Cargolifter AG shareholders - Cargolifter AGfiled for bankruptcy in 2002, trying to develop an "Air Crane" to carry bulk load flying.

The balloon was filled with almost 300 cubic meters of hydrogen in nearly 90 minutes, and clinged at a winch. After the test, the balloon was quickly deflated, in only 5 minutes.

According to their study, a 40 meters diameter balloon is needed to lift a mounded rotor with 3 blades.

 

Wind turbines components transport problems

 

Transport related problems occupy a relevant percentage of time in my department.

It’s no big surprise, considering that the models that we are selling (V90, V100 and V112) have blades up to 55 meters.

Usually we have 3 different kinds of problems:

  • Bending radius
  • Vertical transition curves (for instance on top of hills)
  • Weight

Depending on the curve radius and the angle between the back and forward tangents, a widening may be needed. Unfortunately, due to the number of variables it’s really difficult to find a closed formula or to define this extra widening on an easy-to-use table.

For this reason, we use a software developed especially to solve this problems (AutoTURN, developed by Transoft solutions).

It is not the only available software: for instance below you can see one of this simulations, courtesy of Nooteboom and developed with their "in house" software for a 90 degrees V112 bend:

 

For the vertical transition curves the problem is more complicated, as there are even more variables (extension of the shock absorbers, number of wheels, height of the load and so on). For this reason we normally made a 3D model to work with, but this is a really time consuming work.

Below, and example of a problem I had to solve in 2010; it is a new curve that we built on an existing road because the existing curve radius (on the left) was too small. Due to the strong height difference from the beginning and the end of the new bend the trailer was touching below, and I've had to modify it after the construction. I've asked for an as-built of the situation, prepared a 3D model and defined point by point the new geometry.

 

The weight of the loaded truck is the third problem we face. Normally the nacelle is the heavier components, and the biggest problem is on the bridge we have to cross when we have to reach the construction site. If the bridge is relatively new usually it is possible to find the project or to know the load it is supposed to carry – the big problem comes with old bridge (sometimes even in stone) we meet around the world: in this case the only solution is to study it with the help on an external engineering.