Figure 2. The long, slender wing of Steve Fossett’s Global Flyer was designed to maximize lift and minimize drag. Similar aerodynamic principles apply to the structure of a wind turbine blade and can be used to guide design decisions.
If you look at a traditional aircraft wing, and then imagine the design thought that stretches it into the very long, slender wing of the Global Flyer, you can see that it’s all about lift and low drag at slow speed. And it’s not a big structural step from that wing to a wind turbine blade. Now think about the ever-increasing scale of wind turbines dictated by market pressures for greater economic efficiencies. Add materials advances in composites and hybrid laminates, and you can see how expertise in new-generation aircraft wing design and advanced analyses translates logically into wind blade engineering.

However, in the booming wind energy market, the “bigger is better” mantra is already coming up against reliability issues. Even today’s current standard (33-40 meter, 1.5 MW) wind blades see an average failure rate of 20 percent, according to Sandia National Laboratories’ estimates. Sandia conducts ongoing applied research in conjunction with academia and industry to increase the viability of wind technology by improving turbine performance, and has hosted annual wind blade workshops since 2004.

Design and Performance

Fortunately, for the engineering community, design solutions to performance issues involving wind turbine blades parallel techniques already in use for aircraft wings: the way blades behave, and structurally fail, make them suitable for analytical methods that have matured over decades in aerospace. For example, while smaller wind blades used to power homes rotate faster than the standard blades used by utilities, as blades get bigger, rotation speed decreases and the primary required design load changes from centripetal force to flap-wise lift that can be analyzed like an aircraft wing. Furthermore, the aeroelastic effects of larger wind blade-tip deflection, and resulting load-change issues, can be compensated for with stiffer, stronger materials in much the same way as aircraft wing-tip deflection is controlled. Although these materials need to be as lightweight as possible, stiffness and buckling stability become even higher priorities as blade (or wing) length increases. And fatigue life remains an issue for any component operating in harsh environments over long periods of time.

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