​The way to heaven leads through the eye of a needle: Before the components of a wind turbine system – tower segments, the nacelle, and the rotor blades – can be installed on-site under maximum technical demands and rise up to a height of 140 meters (460 feet) they have to arrive first. And that entails a logistical effort of mammoth proportions due to their size and their weight.

We’ve all seen the long-load trailers carrying the rotor blades in parking facilities along the freeway – up to 60 meters (200 feet) long, they’re parked there until traffic subsides around 10 p.m. and they can continue their journey. By that time, they’ve already overcome a number of obstacles. Traveling on highways or freeways is no special feat – at least that’s what one might think. However, the comparatively small radii of freeway entrance ramps now and then make it necessary to lift the load across the guardrails. Plus, the special heavy-duty trucks have to leave the freeway at some point in time to reach their destinations on backroads. Unsurprisingly, wind turbine manufacturers make maximum use of trains and riverboats to transport the huge components across long distances, but even so, the moment of truth when the heavy cargo has to hit the road will inevitably arrive. And that has been the case increasingly often since wind power has begun to burgeon.

A job with no routines

“We know when a transfer starts,” explains Florian Dufresne, “but we can never be sure when it will arrive.” As amazing as that may sound: these jobs are never routine business. Every route, every transport is unique. Even though the title of his job with wind turbine manufacturer Senvion is that of a “local transport manager” Dufresne no doubt ranks among Europe’s most experienced logisticians for special transports of wind power systems. He handles a thousand of them per year.

A job that keeps him on the road? No, says Dufresne, who manages almost every part of it from his desk at the office. Asked if in the digital age he had access to a database with cornering radii, overhead clearances, the widths of underpasses, and the load ratings of bridges, he matter-of-factly comments that there’s no such thing. Reconnoitering the respective route is the responsibility of the freight hauler. “We can safely transport our wind power systems to the intended sites only by working as a team with their drivers and route planners. And they do exactly what should actually be a contradiction in terms – hauling heavy cargo and improvising. In fact, unforeseeable challenges that have to be spontaneously resolved on the ground keep cropping up,” Dufresne says with obvious respect for the work of the haulers.

Blade lifter raises rotor

Like during a rotor transport to Lussac-les-Églises on the High Plateau in Central France. Initially, no-one saw any possibility to maneuver the more than 60 meter (200 foot) long special trucks through the narrow streets of the centuries-old country town. But, thanks to technology, it proved to be possible after all. “We simply raised the rotor blades on one side using the blade lifter and edged them through the streets that way.”

Solving the problem by means of the special lifting vehicles subsequently led to totally different challenges. Because they have to provide a stable counterweight to the huge rotor blades, they’re extremely heavy – a blade lifter including the rotor blade tips the scales at 120 metric tons (132 short tons). Consequently, old bridges in particular pose a problem as their load carrying capacity is insufficient. In this case, the team will lay a heavy-duty auxiliary bridge above the actual bridge.

60 meters, 120 metric tons, 10 centimeters

Centimeters or inches may pose even greater problems than the 60 meters (200 feet) or 120 metric tons (132 short tons). As wind turbine towers keep getting taller, the towers, which have to be transported to the site in several segments, grow in terms of diameters as well. What doesn’t grow, though, are the overhead clearances of road or railroad underpasses. So far, Dufresne emphasizes, solutions have always been found. In the case of the tower segments, the technology of the trucks helps – the special low-bed trailers are able to hydraulically lower their cargo beds down to 10 centimeters (4 inches) of ground clearance and will then edge their way forward underneath the bridge. However, the trailers must not bottom out on any bumps in the road surface under any circumstances, plus the overhead clearance is only about the breadth of a hand, too.

Logistics with diplomacy

The haulers’ route scouts are resourceful no matter what and discuss the routes they’ve reconnoitered with transport manager Dufresne. “There’s not a lot I need to tell my hauling colleagues – they’re absolute pros: I can rely on their planning 100 percent.” Instead the part of the Senvion logistician is to discuss the project with all the other stakeholders, approving authorities, private highway operators and, above all, the people on the ground. At that time, he’s a diplomat first and foremost, having to alleviate the concerns of mayors and county officials that the special transports won’t cause any damage. Plus, he has to explain why the journey of the giants has to be routed through their region in particular even though the wind farm will be established at a remote location. “We can never take the shortest possible route. To cover a distance of one kilometer, the convoys often travel ten, 15 or more kilometers on the road. A bridge with a sufficient load rating may be located five kilometers farther to the east, but then an underpass that’s too low may have to be given a wide berth. So one kilometer is added to another and approvals must be obtained again and again,” explains Dufresne.

In spite of extensive preparations and ample experience, there’s always a chance of unforeseen things to happen. Once, Dufresne relates, there was an unannounced construction site – the trucks concerned were stuck for three weeks. Even driving forward is extremely challenging, but backing up is practically impossible with a 60-meter (200 foot) trailer.

Systems are becoming larger and larger

The further the development of ever more powerful wind turbines progresses the more difficult the transports become – because higher rated capacity also means taller towers, heavier nacelles, and longer rotor blades. Rather than calling them more difficult, Dufresne would call them more demanding – or more challenging. Explaining the implications, he says: “As a result of the fast dimensional growth in technology, our experiences with specific routes soon lose their value.” Things that are still possible with 120 tons may fail with 140. “We now even have to see familiar routes we’ve used many times before in a new light.”

Local challenges

In view of the many challenges that ground transportation entails one would expect the hauling of components for offshore wind farms to their sites at sea to be child’s play. Yet even maritime transport encounters bottlenecks. Here’s an example to illustrate the point: The components for wind farms produced at the Labrador harbor in Bremerhaven have by now become so large that they can no longer be shipped through the narrow lock at the fishing harbor to the seaside loading quay. Instead of using the simple route across the water the components now traverse the town – as a heavy transport – before being loaded onto a special vessel and heading for the open sea. There – far away from the shore – the ship lifts itself out of the water on huge steel struts and mutates into a mounting platform for the towers, nacelles, and rotors. Now only the wind as an adversary can delay their installation – the wind, though, is the reason why the components are here.

1.148 Million people

are employed in the wind energy sector worldwide, compared to 500,000 in 2009. In total, the sector generates annual sales of 94 billion euros. However, due to falling prices and growing competitive pressures, especially from Asia, many manufacturers are fighting for survival. With sales of ten billion euros (2018), Vestas Wind Systems A/S from Denmark is the world market leader, followed in second place by Siemens Gamesa and the Chinese manufacturer Goldwind in third.

Sources: IRENA, REN21, GWEC

Schaeffler enhances wind efficiency

© Schaeffler

Transmission, rotor shaft, generator, yaw control, blade adjustment – Schaeffler has been producing bearing solutions, analysis and monitoring tools for wind turbines for more than 30 years. Predictive monitoring is a recent addition to the portfolio. Together with Bonfiglioli, the market leader in transmissions for yaw control and blade adjustment, Schaeffler has developed a compact Industry 4.0 package. It combines the measuring systems SmartCheck (on the housing) and TorqueSense (on the shaft) into a new condition and torque monitoring system. It not only detects and limits peak loads and their frequency but also recognizes impending failures at an early stage due to the SmartCheck vibration diagnostics. The resulting major advantage: repairs can be planned and performed on days with little or no wind.