Gone with the wind: The life and death of a wind turbine rotor blade
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Energy Sector Analysis
The blades, with many composites in their complex structures built from different designs and with varying lengths, are a discontinuous and inhomogeneous source of material, very challenging to recycle.
Gone with the wind: The life and death of a wind turbine rotor blade By Eva Karatairi Feature Editor: Ruben Bischler
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ind turbines, in the form of the tall, slender, two- or threeblade pinwheels, have been capturing the power of wind and producing renewable energy since the 1990s. However, if we do not find end-of-life solutions for the materials of their rotor blades, their profile may not remain as green and sustainable as currently viewed. As the first generation of wind turbines are slowly decommissioned to waste treatment centers and disposal sites, thousands of tons of blades, 15- to 20-m long, are awaiting incineration or perhaps a second chance through reuse or recycle. The next generation of blades, which already needs dismantling, measure up to 60 m in length. For this army of Quixotic giants, no established recycling solution exists. The materials that make up a wind turbine are generally considered as recyclable: valuable rare-earth metals, for example, found in the magnets of some wind turbines generators or metals, such as steel, which make up almost 90% of a wind turbine’s mass and is mainly concentrated in its tower. The blades, however, with many composites in their complex structures built from different designs and with varying lengths, are a discontinuous and inhomogeneous source of material and very challenging to recycle. Of all the components of a wind turbine blade, the most complicated and difficult to manage are the glass and carbon fiberreinforced polymer composites (GFRPs and CFRPs), which, as their names suggest, are glass and carbon fibers surrounded by a polymer matrix, such as an epoxy resin. These hybrid materials, which represent the biggest fraction of a blade’s composition, have been chosen for light and robust blades, which rotate easily, thus harvesting more energy from the wind. GFRPs have a high strength-to-weight ratio that allows the blades to withstand large mechanical loads and to contribute to their overall aerodynamic performance; they are resistant to fatigue and corrosion, characteristics that ensure a long lifetime. They can also be easily affixed with add-on components, such as lightning protectors or leading-edge protectors and heating systems, to improve performance. The requirements for higher power output and the scarcity of sites suitable to host windmills encouraged engineers to design larger rotors with longer blades, in which GFRPs alone could not bear the loads and achieve the stiffness required. CFRP composites, which are much stronger and stiffer per unit of weight than GFRPs, were used more frequently to support the blades at critical spots.
Early enthusiasm for wind turbines pushed the technology beyond full life-cycle analysis, leaving end-of-life considerations for today. “Fiber-reinforced composites are mechanically op
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