Long blades, sharp turns (from cranestoday)

As wind turbines get bigger, so do their rotor blades. That makes wind energy more economic, but it is a major headache for trailer manufacturers and transport firms. Will North reports

When Siemens began building wind turbines thirty years ago, its biggest generated 30kW, and used 5m rotor blades. This June, the company produced the first of its new B75 Quantum range of 75m long blades, designed for 5MW turbines.

The new B75 Quantum blades are designed for offshore use. But, even on land, wind turbine blade sizes are growing every year. Collett and Sons is a UK-based special transport and consulting firm. Managing director David Collett says, "Turbines are getting bigger, and the rotor size larger: three years ago, a large blade was 40m long; two years ago it was 45m long; now, we're seeing the first 51m blades. There are already 60m blades on the market.

"The first 51m blades have already been installed in the UK, on a single turbine, by RePower. On the consulting side of our business, we've seen a lot more planning applications for wind farms using bigger blades. There's a marked difference in transport between a 45m and a 51m blade, and more of an impact on moving them. It creates other problems as it seems to be the point at which you need to consider a lot more street furniture being removed, and have to do a lot more work on the planning side."

Samsung Heavy Industries and Green Breeze have been testing new, bigger wind turbines at the Zephyr Windfarm Project in Watford, Ontario, in Canada. The firms erected four turbines this February. World Logistics Consulting were hired to transport the turbine components. The nacelles, tower sections, and hubs were shipped from South Korea to Windsor Port, Ontario, 100mi from the job site.

The four accompanying sets of blades were transported from Little Rock, Arkansas, 1,000m away in the USA. Each set had three blades destined for one rotor, with each blade measuring 43.8m long and weighing 25t.

This, World Logistics Consulting reports, was one of the biggest scheduling headaches. Working over weekends, the company was able to deliver each set of blades in less than a week, leaving enough time to bring in the remaining components from Windsor Port.

As well as the scheduling issues involved in three 2,000mi round trips, World Logistics Consulting faced technical challenges. Spring came early in Canada this year, meaning the 95t nacelles threatened to sink into the muddy road at the job site. The company needed to lay gravel, and then stone slabs, to make sure the transporters remained upright and stable when the nacelles arrived. The wind was another challenge. As the transport firm delivered the blades, there was again a risk they could tip the trailer over.

This June, Austrian special transport firm Prangl was hired to carry three Enercon blades in convoy from Magdeburg in Germany to Mönchhof in Austria. The three blades each measured almost 50m; the three axle tractors and three- and four-axle trailers used to carry them reached a total length of 55m. At the widest point, the trailers and load measured 4m across.

Prangl reported that its drivers needed to exercise extreme caution when joining and exiting the motorway to avoid obstacles like road signs. But, with steerable trailers, the journey went without incident.

Collett says problems with obstacles are frequent when moving long turbine blades: "Once you're off motorways in the UK, you see that we have an ancient road network. There are more humps and bumps, more problems with horizontal and vertical alignment.

"If it's moving one or two turbines, then temporary works are the solution. For bigger farms, [developers and local councils] tend to do the work on a permanent basis. It's not just about the initial delivery, but 20 years of service. So, if we have to contraflow a roundabout, it is usually designed and left so that we can navigate it in the future."

Careful project planning is a vital part of Collett's job. But, even the best logistician can't move a 60m blade on a trailer designed for one half the size. That takes planning on the part of firms and manufacturers. Collett says, "We've tried to plan ahead with trailer replacement. We consider that we have equipment suitable to 60m blades. The trailer manufacturers have been very diligent in designing new trailers. And the turbine manufacturers have seen they have a problem and are talking to them. We work sometimes hand-in-hand with the trailer manufacturers, and sometimes through the wind turbine manufacturers."

A secret world
Faymonville sales manager Arnold Luxen says it can be hard work knowing what will come next from the wind turbine manufacturers: "A closer cooperation between trailer manufacturer and turbine manufacturers would be beneficial. The turbine or wind tower manufacturer keeps the design and development a secret.

"Sharing information about new developments would enable us to advise them about technical solutions and to develop adapted transport solutions in advance. One of our strengths is that we can adapt very quickly, and can design, develop and build something new in very short length of time."

It's not just the size of the blade that matters, but its shape. Joachim Kolb, market research and development manager at TII Sales, the sales organization of Scheuerle, Nicolas and Kamag trailers, says, "The form of the blades, with a twist, is becoming more difficult to transport. That means the blade takes up more space on the road. That affects all dimensions.

"We recently handled a blade of 78m, and showed it at the EWEA wind show in Copenhagen this year. That blade was designed for offshore, but often the first test machines are placed on land. We're now used to blades with lengths up to 58m, but can go up to lengths of 78m: real monsters.

"It's essential that trailers have hydraulic axle suspension, with big 60° steering angles. With these long blades, it is very hard to handle roundabouts. You very often have to go the wrong way round, to avoid tight turns. Even on motorways, users may need to exit using the opposite exit, to avoid corners."

Luxen says customers should be clear about the sort of job they aim to tackle: "For blades with lengths over 60m, we advise customers to choose pendulum axles. As well as triple-extendible trailers, we offer the possibility to move axles to the front or rear, extending the front or rear overhang. In some cases, customers need to have more overhang. In others, they need to lift the blade, to move over the ground. So we can mount the blade on a sledge, which fits on rails on the platform, to increase or reduce the rear overhang.

"This allows the customer to change the trailer configuration while travelling: not on the road, while driving, but they can stop and adjust the axle-spacing or move the blade forwards or backwards.

"Sometimes, there is just rough track up mountains or from roads to the final erection site: a few hundred metres or a few kilometres of just packed earth. The problem is not just on mountains, but also on national roads. In France, a country with the most roundabouts, it is difficult going even on main roads. In this case, by using pendulum axle with more steering angles, and moving blades forwards or backwards, you have more turning options to overcome these problems."

Faymonville and Scheuerle aren't the only trailer manufacturers tackling this market. Goldhofer launched its own triple-extendible trailer, the SPZ-P 3 AAA in 2010. The company said at the time, "For the first time we've developed a transport vehicle with a maximum length of more than 62m, thanks to triple telescoping. Extremely long rotor blades can be delivered directly to the construction site. The pendular axles with a steering angle of 60° provide the vehicle with optimum manoeuvrability and enable the balancing of unevenness, both in height as well as in lateral direction. In combination with optional sliding sleds , the vehicle can be shortened while loaded to deal with narrow passages and obstacles. The heavy loading capacity of the extension spines makes this possible."

Nooteboom's product for this market is the Teletrailer range: again, the trailers can be triple extended, for trailer load floor lengths of 'well over' 48m. The company says its unique pre-cambered beams mean that the load floor can be retracted or extended while loaded, and kept perfectly flat. The triple-extendible trailer for wind turbine blades is branded as Telestep. The trailer has been designed so that loads up to the maximum coupling weight can be positioned right behind the gooseneck.

The most visually striking, if highly specialised, turbine blade product of recent years though is Scheurle's blade adapter, which tilts blades in the air to allow them to be carried around obstacles. Kolb says, "We got an enquiry from Swiss special transport company Voser. They had to climb the Nufenen pass, transporting a 38m load through eight hairpin bends with radiuses of around 15m. We connect the blade to the tilting platform on the trailer as you would to the hub. We did a lot of studies, which we've included in a matrix in the operations manual, showing what angle you could lift the blade to at different wind speeds, with different trailer inclinations lengthways and sideways.

"On one successful transport in Germany, the blade adaptor worked with the trailer inclined at 15° lengthways, and 8° transversally. The axle suspension stroke wasn't high enough to stop one tyre leaving the ground, but it was not a problem. For safe transport, users should always travel with the blade down: lifting the blade raises the centre of gravity up. When they arrive at a narrow area, say a 90° turn, they can just press two buttons to bring the blade up to the position they need, make the turn, and then lower it.

"The blade adaptor can be used on fifth wheel towed trailers and self-propelled. On its first job, in Switzerland, it was towed by a truck for 15km. On the second job, in Germany, it travelled on a six-axle self propelled unit. The blade attachment can be transferred between any TII Group trailers."

Kolb believes demand for solutions like these will continue:

"Clients are going more and more inside forests to build windfarms. They need a solution for very tight curves, without cutting down trees."

Collett agrees: "As soon as a bigger machine is available, developers want it."