SIEMENS

Back in the 1990s, engineers came up with the daring concept of building a rotor blade that would react elastically in order to shed some of the unwanted loads resulting from atmospheric turbulence or the extreme wind conditions associated with storms. The resulting stress reduction would extend the blades’ service life, make larger rotor diameters possible — and thus boost energy production.

For some time, however, specialists weren’t able to create accurate models of the intricate interactions between aerodynamics and structural deformations. But then three years ago, a 30-member team at the Siemens R&D Center in Boulder, Colorado, took on the challenge of developing such a rotor blade. Support for their endeavor came in the form of innovative simulation software and the combined expertise of the specialists at the research center, which was established in 2008. “This type of innovative rotor technology and design was completely new to Siemens,” says Andy Paliszewski, director of the Siemens R&D center in Boulder. “It promised to reduce the cost of energy produced by wind.” The goal of the experts was clear: to exploit innovations that will make wind power cheaper than electricity produced with fossil fuels.

The team in Boulder therefore went right to work in what was a huge creative effort. Thanks to the commitment of all the members of the team and collaboration with colleagues in Denmark, it proved possible to complete the design of a 53-meter-long rotor blade — the Aerolastic Tailored Blade (ATB) — in just a few months. The blade, which is curved like an Arabian scimitar, twists as it deforms under the force of the wind. It thus reduces stress loads on the rotor, the nacelle, the tower, and the foundation. Furthermore, the ATB design makes it possible to build longer rotor blades and thus increase energy output.
In the past, it was possible to fit wind energy facilities in the 2.3-megawatt (MW) output range with blades up to 49 meters in length. But with the introduction of the ATB design, these facilities can now be equipped with new blades that are four meters longer. And that means roughly eight percent more energy. The first prototypes began operating this year under diverse weather conditions at wind farms in the American Midwest. It’s therefore no surprise that U.S. energy companies are very interested in the new technology.

Siemens Wind Power is a very international organization today. But it wasn’t always that way. Just a few years ago it was very much a Danish operation. Many research and development employees still work in the Danish cities of Brande and Aalborg, but a lot has changed over the last couple of years. The Wind Power division’s headquarters has been moved to Hamburg, Germany, for example, and new technology core expertise centers have opened around the world. Whereas Boulder focuses mainly on rotor technology, the division’s facility in Keele in the UK specializes in power generation, while the center in Aachen, Germany, focuses on electrical technology, electronics, and gearboxes.
For a long time now, Aalborg has not been the only production location for new rotor blades. In order to be able to serve the world’s two biggest wind power markets onsite, Siemens now manufactures rotor blades in Fort Madison, Iowa, and Shanghai, China. The decision to open an R&D Center in Boulder in 2008 was not based solely on the desire to establish a broader presence on the U.S. market. “There were many reasons for choosing Boulder,” says the Wind Power division’s Chief Technology Officer, Henrik Stiesdal, who works out of Brande. “The U.S. is home to a large number of engineers and scientists with outstanding qualifications in technical fields. Although some of them are themselves from different countries around the world, it’s difficult to convince them to come to Europe — not to mention Brande, which has only a few thousand residents. Boulder, however, is an attractive location for such young talents.”

The city of Boulder also happens to be a center for wind power technology. In fact, it’s home to institutes like the National Renewable Energy Laboratory (NREL) and the National Center for Atmospheric Research (NCAR), both of which work closely with Siemens. Last but not least, the U.S. government offers subsidies for research into renewable energy sources. All told, the Boulder team’s mission was clear from the beginning: to optimize the rotors. Development of ATB technology was one of its first major projects, and although it was coordinated with staff in Denmark, the Boulder team mainly ran the show.
“When operating research centers in different time zones — the difference between Boulder and Brande is eight hours — you have to figure out a way to overcome this disadvantage,” says Stiesdal. “One of the key solutions is to have the development team, in this case the people in Boulder, have ownership of specific technologies. This approach has also worked very well at our other international centers of expertise.”

Cooperation across Time Zones. The team led by Kevin Standish, a rotor technology engineering manager from the Siemens R&D office in Boulder, has impressively demonstrated that the trust placed in them was well deserved. The largest challenge has been communication with headquarters in Denmark. Many of the experts from Denmark traveled to Boulder for longer stays. What’s more, the engineers in Boulder frequently came in to work earlier and their colleagues in Denmark stayed later in the office. In this way, at least two hours a day were available for phone calls or videoconferencing to discuss pressing issues.

Other challenges the team faced included the creation of new design tools and finding new ways to integrate areas as varied as aerodynamics, software, and materials science. Last but not least, the new ATB technology had to develop from the concept stage to a prototype blade in Aalborg within a few months without compromising quality. But the Siemens-experts succeeded — not least thanks to close collaboration across department borders and a combination of existing technologies, such as proprietary Integral Blade single-shot infusion technology. To achieve their goal they also incorporated a number of new materials and manufacturing techniques. “The team has only just begun to explore ATB technology,” says Standish. “Its full potential will play a significant role in helping to further reduce the cost of energy produced by wind.”

The height of wind turbines continues to increase — giant white towers with rotor diameters well over 100 meters are no longer a rarity. Moreover, the first Siemens blade design to incorporate some elements of ATB technology resulted in the “B75” — the world’s longest — for its flagship 6 MW direct-drive wind turbine. “Without the early advances in design tools and processes resulting from ATB technology exploration, the design of the B75 would never have been possible,” Standish reports.
The first B75 blades were mounted on a turbine off the coast of Denmark in August 2012 — but this achievement by no means marks the end of the development process. “Sometime in the future we will probably see a 10 MW turbine with 100-meter rotor blades,” says Stiesdal. “Without a doubt, ATB technology from Boulder has played a key role in getting us to this point.”