Boosting efficiency in wind turbine production

Covestro and SAERTEX® develop materials for new process with manufacturing technology from HÜBERS / Successful test with 45 meter-long polyurethane spar cap.
Covestro, SAERTEX® and HÜBERS have developed an innovative technology for the manufacture of rotor blades for wind power plants. They have now achieved another milestone by successfully producing a prototype of a 45 meter-long spar cap. The spar is the core of the structural framework and has to accommodate the full wind load.

Actively contributing to climate protection is a central element of the sustainability concept at Covestro, formerly Bayer MaterialScience, a leading manufacturer of polymer materials. One of the key focal points in this commitment is the generation of power from renewable sources, and first and foremost from wind power. Numerous countries are now pursuing this sustainable form of power generation, although some state subsidies are being cut. As a result, the demand for cost-effective processes for manufacturing even bigger and more efficient wind turbines is greater than ever.

Together with SAERTEX®, a leading manufacturer of woven fiberglass, and HÜBERS as partner for the process technology, Covestro has developed an innovative technology for manufacturing rotor blades in line with precisely these requirements. The new process features a whole new approach to combining polyurethane resin with woven fiberglass. The partners have now successfully produced the prototype for a 45 meter-long spar cap at the Institute of Composite Structures and Adaptive Systems of the German Aerospace Center (DLR) in Stade. A video report is available at The spar is the core of the structural framework and has to accommodate the full wind load.

Advantage for polyurethanes

Kim Klausen, Head of Covestro’s global Center of Excellence for Wind Power in Otterup, Denmark, says, “Stability and durability are the key properties for rotor blades.” He further explains: “Our polyurethane resin offers clear advantages over epoxy resins in this application: We achieve a higher glass transition temperature and low shrinkage. The reaction of the polyurethane resin also generates less heat.”

Marc Schrief, managing director at SAERTEX®, adds: “Our woven fiberglass ensures the stability of the compound. They are thoroughly impregnated with the polyurethane resin and form a high-strength component. What’s more, they help to lower the weight of the rotor blades.” The 45 meter-long rotor blade would weigh eight metric tons overall. The spar cap made from polyurethane and glass fibers accounts for approximately a third of the total weight.

Vacuum infusion – process of choice

The half-shells for the rotor blades are manufactured using a vacuum infusion process. This involves placing core materials and woven fiberglass into a mold and sealing the structure hermetically with a film. After applying a vacuum, the infusion process begins with introducing the liquid polyurethane resin. HÜBERS Verfahrenstechnik Maschinenbau GmbH has developed a manufacturing technology that enables controlled mold filling.

“Our system uses pumps to actively convey the material. The use of sensors to control pump pressure ensures strict adherence to the planned pressure curve and thus to the material kinetics when filling the mold,” says Clemens Dieckmann, project engineer at HÜBERS.

Cost savings thanks to efficient production

Over the last few years, the process sequence for manufacturing the rotor blade has been repeatedly optimized. For example, the infusion process can be completed in a relatively short space of time, thanks to the vacuum that is applied. The curing process starts when the mold is subsequently heated and is much faster than when using epoxy resins. There is no need for post-curing.

“That brings a considerable cost saving for manufacturers,” says Klausen. “Additional improvements in blade design and the intelligent use of composites, coatings and adhesives could help deliver even more weight savings.”

Covestro is exhibiting at the Wind Turbine Blade Manufacture conference from November 30 to December 2 in Düsseldorf, Germany, and is looking forward to talking with visitors.

About Covestro

With 2014 sales of EUR 11.8 billion, Covestro is among the world’s largest polymer companies. Business activities are focused on the manufacture of high-tech polymer materials and the development of innovative solutions for products used in many areas of daily life. The main segments served are the automotive, electrical and electronics, construction and sports and leisure industries. Covestro, formerly Bayer MaterialScience, has 30 production sites worldwide and employs approximately 15,700 people (calculated as full-time equivalents) at the end of September 2015.


With an annual turnover of approx. EUR 270 mio., SAERTEX® family company is the global market leader in the manufacture of multiaxial fabrics and core materials for the fabrication of fiber-reinforced composites. The wind, boat and shipbuilding, transportation, as well as construction, sports and aviation industries, rely on composites with lower weight and enhanced stability thanks to SAERTEX® reinforcing materials made from glass, carbon and aramid fibers. With some 1,200 employees and ten production sites on five continents, as well as an active distribution network in more than 50 countries, the SAERTEX® Group is globally positioned, to satisfy the rising demand for advanced-technology composite solutions.


HÜBERS Verfahrenstechnik Maschinenbau GmbH is specialized on systems for the processing of casting resins and impregnation compounds. Targeted research and development of tailored processes for material preparation, mixing, metering and forming is conducted in close collaboration with users and materials manufacturers at the company’s headquarters in Bocholt, Germany. The systems are employed worldwide in the electrical engineering and electronics, medical technology, automotive and aerospace industries, as well as for specialty applications.

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This release may contain forward-looking statements based on current assumptions and forecasts made by Covestro AG. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. These factors include those discussed in Covestro AG’s public reports, which are available on the Covestro website at Covestro assumes no liability whatsoever to update these forward-looking statements or to conform them to future events or developments.