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Over the last 30 years, blades have grown 15 times in size – able to harvest more energy than ever. The first commercial wind turbines had a capacity of 30 kW with 5 m rotor blades. By comparison, today’s Siemens 8 MW wind turbines feature a 75 m blade, a number that corresponds to the wingspan of an A380 airplane. This results in a rotor diameter of 154 m – the world’s largest rotor in operation today. As the blades increase in size, so too does the importance of finding ways to lower the weight and increase stability – for lower costs, easier transport, and increased safety.
To date, three major innovations in blade technology have been introduced: the IntegralBlade®, the Quantum Blade, and its successor – the next-generation Aeroelastically Tailored Blade.
In 2000, the first major blade-technology advancement was the development of IntegralBlade® technology. This is a process that casts a blade in one piece to eliminate weaker areas at glue joints and delivers blades of optimum quality, strength, and reliability. Siemens remains the only wind turbine manufacturer to use blades cast in one piece in a closed process.
In 2011, the Quantum Blade technology was introduced. Quantum Blades are lighter than previous models, but retain their superior strength. Since 2011, all new rotor blades have been designed as Quantum Blades. Like their predecessors, they are produced using the IntegralBlade® process. Siemens redesigned the blade tip, so that it minimizes loads and reduces noise levels.
The first commercial version of the Quantum Blade was the B55. The latest, the B75 Quantum Blade, is a full 20 meters longer. It combines enormous strength, low weight, and superior performance. The root section uses “flatback” profiles to minimize root leakage and increase lift. If the B75 blade had been conventionally produced, it would have weighed 10 to 20 percent more – heavier blades lead to higher loads and require stronger supporting structures in the nacelle, tower, and foundation. The unique combination of smart blade profile and low weight helps to reduce the cost of energy.
The second-generation Quantum Blade incorporates Aeroelastically Tailored Blade (ATB) technology. The coupling of blade bending and twisting represents a major advantage over classic rigid blades. Thanks to their innovative aeroelastic properties, rotors with ATB technology can be larger in diameter, while still staying within the turbine load envelope for the nacelle, tower, and foundation. As a result, customers can profit from an increasing annual energy output. Blades of up to 75 meters in length are available; all made from fiberglass-reinforced epoxy utilizing the state-of-the-art IntegralBlade® manufacturing process, eliminating weaker areas at glued points.
The latest addition to Siemens expanding line of blade innovations is the hybrid carbon blade. This design uses hybrid carbon technology together with aeroelastic capabilities for peak performance. The hybrid carbon blade is designed in collaboration with LM Wind Power and offers maximum yield in its class. This technology benefits from being less sensitive to manufacturing defects compared to full carbon blades, and from the proven Hybrid Lightning Protection System. The blade’s lightweight design is ideal for the larger rotor used on onshore low wind sites, and has the ability to harvest maximum energy while staying within the design load envelope.
The hybrid carbon blade is additionally equipped with DinoTail® Next Generation and Vortex Generators for improved performance and reduced noise levels. All of Siemens’ blades are tested at the R&D facilities in Aalborg, Denmark. We continue to set new industry benchmarks for component testing by running every component, including blades, through a highly accelerated lifetime testing simulation (HALT), with some components tested for up to 25 years.
To further boost the efficiency of blades, the Power Curve Upgrade package, which is designed to provide increased energy production, comes into play. Included in the package are the aerodynamic accessories DinoTail, DinoShell, and Vortex Generator. These add-ons can also reduce noise emissions.
DinoTails are serrated flaps that, true to their name, resemble the tail fin of a stegosaurus dinosaur. They are mounted at the airflow breakaway edge close to the blade tip, which accounts for most of the noise – and energy – produced by the blade. By decreasing turbulence on the trailing edge, DinoTails can enhance lifting performance while still keeping local acoustic emissions to a minimum.
DinoShells, as applied on Siemens turbines, are fixed control surfaces attached from the blade shoulder toward the root. They effectively increase lift, especially on the root section of the blade closest to the hub.
Vortex Generators are designed to improve the airflow over wind turbine blades and thus enhance aerodynamic performance. They do this in the so-called boundary layer – the region of flow very close to the blade’s surface. The power-curve upgrade was first installed in 2010. The result? A potential increase of up to 5% in annual energy output.
The blade is the highest point of the wind turbine and its most exposed component. For optimal blade protection, the Siemens lightning protection system helps prevent failures caused by lightning strikes.
It is incorporated into the IntegralBlade® design, with receptors strategically placed on the blade surface. All the main components of a turbine, including the nacelle, blades, controller, and tower, have extensive lightning protection integrated into their design. When a wind turbine suffers a lightning strike, whether onshore or offshore, the system provides the lightning with a safe path through the turbine and down into the electrical grounding. This safe path reduces the likelihood of damage to the main components.