Close to the wind (CP 2/2009)

The use of wind energy presents a challenge for both technology and materials. With RELIUS high-tech coatings for rotor blades, BASF’s Industrial Coatings unit has made a name for itself in the industry.

The stresses and strains to which the rotor blade of a wind turbine is exposed at 90 meters above the ground are truly immense. Reaching top speeds of up to 300 kph, forces are exerted on the tips of the blades, which bend several meters.

(Picture: BARD Engineering GmbH)

In the world of technology, the 60 meter long blades are regarded as the largest objects to have ever had to withstand such stresses and strains. Even an aircraft that can fly speeds of up to 900 kph does not have to withstand such forces on account of the lower atmospheric density.

What is more, rotors are under constant attack from UV radiation, salt water and air pollution. Consequently, strength and resistance are essential properties for wind turbines. Jörg Hermes, Global Sales Manager for Wind Energy at RELIUS, uses a metaphor to express this: “Imagine a car driving constantly at 200 kph through the rain.

Damage would start to appear after a few months. A rotor blade has to withstand conditions that are even harsher than this for a period of between ten and twenty years – without becoming damaged.”

Solid and light The demands on the design of the rotors and the materials used are correspondingly high. The largest and most modern blades are made from glued glass and carbon fiber mats into which epoxy resin is injected under a vacuum.
	Attractive location: At sea, wind can be twice as powerful as on land. (Picture: fotalia)

The high-tech design ensures the exceptional level of stability and flexibility that is required, while keeping the blades thin and light. The valuable construction is protected by special coatings that are no less sophisticated.

They are also flexible and cannot flake off, for example, when the blades bend. They are erosion and abrasion resistant and withstand UV radiation. And they are matte so as to prevent reflections, which could, for example, pose a hazard to air traffic – a property that is difficult to achieve without solvents.

RELIUS solved this technical challenge at an early stage, enabling the company to enter the rotor blade coatings business in the mid-1990s. “At the time, we were the first company that could produce the special coatings required without solvents,” recalls Hermes.

This was an innovation that flung the doors wide open for the coatings producer within the industry and allowed it to become a close development partner. Hermes: “Working with our customers, we have constantly optimized our systems with regard to costs and performance.”

Not least of all, this includes a device for checking the erosion and rain resistance of coatings. The tailor-made device is rare in the industry and consists of a rotating disk onto which a coated test specimen is fastened and made to turn for hours at 500 kph through a curtain of water drops.

It was not long before RELIUS was supplying virtually all of the major blade manufacturers in Europe and, since 2006, it has also acquired manufacturers of complete wind turbines as partners. “Thanks to the global activities of these partners, our products are used on virtually every continent,” says Hermes.

This in turn has made it easier for RELIUS to gain a foothold in markets outside of Europe such as India, Canada and China. The company is now about to launch its products onto the U.S. market, where so far most components for wind turbines – including the rotor blades – have been imported. Today the U.S. market, which was the fastest growing wind energy market in 2008, is in the process of developing its own production capacities.

GE, the largest American wind turbine manufacturer, is leading the way, and they have already qualified the coating products from Industrial Coatings Solutions RELIUS worldwide for their installations.

The same applies to other leading global wind energy plant manufacturers with whom RELIUS maintains close partnerships, including the German company Enercon, Suzlon from India and China’s second largest manufacturer Dongfang. The RELIUS coating systems, which are suitable for all types of rotor blades available on the market, are used around the world in over 25,000 wind energy plants.

Rough sea

Offshore wind turbines constitute a segment in which RELIUS, thanks to its special coating processes adapted to the rigors of the rough sea, ranks among the most important suppliers of rotor blade coatings.

A promising outlook, since the significance of offshore plants is constantly growing, as suitable land-based sites become increasingly rare in important markets such as Germany.

Furthermore, wind farms at sea are attractive because, depending on the location, the wind there can be twice as powerful as on land and therefore yields more power. Some 300 offshore wind turbines are based in the North Sea alone; the first German offshore wind farm is now planned about 100 km northwest of the island of Borkum.

In an area measuring 60 square kilometers, it will comprise 80 wind energy plants, five megawatt wind turbines in each case, which are currently the most efficient and largest in the world.

This is the first ever, and an endurance test for the industry – the North Sea is up to 40 m deep, the sea and climate are unpredictable, and some 100 km of power cables have to be laid under the sea bed. This mammoth project is being implemented by the Bremen-based plant manufacturer BARD Engineering with RELIUS as the sole supplier of the coating materials for the rotor blades.

Construction started in spring of 2009. By the end of 2010, “BARD Offshore 1” is expected to be supplying electricity for around 400,000 households. A nearshore test plant just off the coast at Hooksiel north of Wilhelmshaven was started up in fall of 2008.

The five megawatt rotor is the same type that will subsequently be used out at sea. For BARD as well as for RELIUS, this is the starting signal for a groundbreaking project.

Big step: The first German offshore wind farm is being implemented in the Nort Sea – supported by RELIUS as exclusive coatings partner. (Pictures: BARD Engineering GmbH)

www.bard-offshore.de
www.relius.de