Components of today’s turbines can be categorized into tower, blades, and nacelle (including turbine transmission), each with specific and diverse material requirements.
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The ongoing transition to a decarbonized energy sector has positioned wind power as one of the fastest growing energy sources today, with hundreds of thousands of wind turbines providing over 740 GW of capacity in the world. To achieve the climate goals of the Paris Agreement, this capacity must increase almost tenfold by 2050 according to the International Renewable Energy Agency (IRENA) (Future of wind, 2019).
This places the utmost importance on continuing to optimize the efficiency, durability, recyclability and cost-effectiveness of wind turbines through intelligent engineering design and material selection.
Historical materials and designs
The first wind turbine producing electricity was created by James Blyth in 1887 and powered the Scottish inventor’s holiday home. The turbine was 10 m tall with a wooden tripod tower, semi-cylindrical canvas sails and a vertical main rotor shaft.
The following decades saw the development of this design and selection of materials with varying degrees of success. For example, in 1945, the largest turbine in the world at the time suffered a catastrophic failure of one of its two steel blades after only a few years of intermittent use, while a little later a design with three blades of composite construction was operational for 11 hours without maintenance. years before it was dismantled and installed in the Danish Energy Museum (Mishnaevsky et al., 2017).
It was not until the 1970s, amid soaring fuel prices, that rapid development was achieved and turbine designs and materials began to converge towards those commonly seen today. today. This includes tubular steel towers, three composite blades and a horizontal main rotor shaft.
To take advantage of higher wind speeds and reduced turbulence at higher altitudes, turbine towers can reach heights of nearly 180 m. This results in enormous static, dynamic and cyclic loading due to factors such as turbine self-weight, wind shear and blade rotation.
To resist buckling from such loads, towers are usually made of tubular steel fabricated in sections and tapered upwards. Although standard structural steel (S235 and S355) is normally used, various sub-grades are common for offshore applications where high levels of corrosion and wave loading must also be considered (Igwemezie et al., 2018).
To combat transportation restrictions and the costs of increasingly large steel lower sections of taller towers, hybrid concrete-steel construction is proving increasingly popular. This uses concrete for the lower portion of the tower while maintaining the smaller diameter tubular steel sections higher up, which can result in total turbine cost savings of over 12% and better structural rigidity (Huang et al. al., 2022; Chen et al., 2020).
Turbine blades can reach speeds of up to 180 mph at their tips and are subjected to immense aerodynamic, inertial and gyroscopic loads. They must therefore be made of rigid and light materials resistant to hypercyclic fatigue.
By exhibiting such properties, glass fiber reinforced polymer (GFRP) has become the most common material for blade construction. Depending on the location in the blade, it is either used monolithically or in combination with a base material such as balsa wood in a sandwich construction.
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GFRP boards typically use a thermoset as the polymer matrix and contain approximately 75% by weight fiberglass for longitudinal reinforcement. Alternatives to replacing or supplementing glass fibers include carbon, aramid and basalt, which result in stiffer, lighter but more expensive composites.
The search for larger capacity turbines continued to lengthen the blades (now reaching up to 118 m) and stimulate the development of these composites. A possible future development lies in the inclusion of nano-reinforcements, such as carbon nanotubes or graphene, within the composite matrix. This should significantly increase blade life and facilitate longer blades through improved strength, toughness and fatigue resistance (Zhou et al., 2016; Ma and Zhang, 2014).
Nacelle and Generator
The nacelle refers to the protective cover at the top of the tower that houses the turbine driveline (including the generator, gearbox, and low and high speed shafts). Although under considerably less severe loading than turbine blades, the nacelle also commonly uses GFRP in sandwich construction. The core material is usually a polymer foam, which also forms the stiffeners often found throughout the nacelle to support workers and maintenance equipment.
Much of the turbine driveline is produced from various alloy steels and cast irons, the generator, however, may contain a more diverse range of materials depending on type. The most common is the double-fed induction generator (DFIG), containing mainly magnetic steel and copper.
However, the most popular type of generator with new turbines and especially offshore ones is the permanent magnet generator (PMG). PMGs are smaller, lighter, more efficient, and more reliable than equivalent DFIGs, but have a higher capital cost. Part of this cost is due to the presence of rare earth elements alongside magnetic steel and copper, including neodymium (Nd), praseodymium (Pr), dysprosium (Dy) and terbium (Tb ) (Lacal-Arantegui, 2015).
Generators of even smaller dimensions, lighter weight and more efficient operation than PMGs seem close to commercialization. These generators use superconducting rotor windings, at high (-180°C) or low (-260°C) temperatures, to give a much stronger magnetic field and potentially meet the demand for larger capacity turbines.
Last year, a turbine with a high temperature superconducting generator (HTS) was successfully tested for 6 months in Denmark. Despite having a higher capital cost than PMGs due to superconducting wire (containing gadolinium and barium) and cryogenics (liquid helium), HTS generators have shown tremendous promise as a cost-effective and high-performance solution, in particular for large turbines with a capacity greater than 10 MW. (SKF, 2021).
References and further reading
Irena.org. 2019. The future of wind. [online] Available on :
Mishnaevsky, L., Branner, K., Petersen, H., Beauson, J., McGugan, M. and Sørensen, B., 2017. Wind Turbine Blade Materials: An Overview. Materials, 10(11). https://www.mdpi.com/1996-1944/10/11/1285
Igwemezie, V., Mehmanparast, A. and Kolios, A., 2018. Material Selection for XL Wind Turbine Support Structures: A Corrosion Fatigue Perspective. Marine works, 61, pp.381-397. https://www.sciencedirect.com/science/article/pii/S0951833917304859
Huang, X., Li, B., Zhou, X., Wang, Y. and Zhu, R., 2022. Geometric optimization analysis of hybrid steel-concrete wind turbine towers. Works, 35, pp.1125-1137. https://www.sciencedirect.com/science/article/pii/S2352012421007487
Chen, J., Li, J. and He, X., 2020. Design Optimization of Hybrid Steel-Concrete Wind Turbine Tower Based on Improved Genetic Algorithm. The structural design of high-rise and special buildings, 29(10). https://www.researchgate.net/publication/340255062_Design_optimization_of_steel-concrete_hybrid_wind_turbine_tower_based_on_improved_genetic_algorithm
Zhou, H., Mishnaevsky, L., Yi, H., Liu, Y., Hu, X., Warrier, A. and Dai, G., 2016. Hierarchical Carbon Fiber/Carbon Nanotube Reinforced Composites: Effect of the distribution of CNTs on the shear strength. Composites Part B: Engineering, 88, pp.201-211. https://www.sciencedirect.com/science/article/pii/S1359836815006654
Ma, P. and Zhang, Y., 2014. Prospects of carbon nanotubes/polymer nanocomposites for wind blade materials. Renewable and Sustainable Energy Reviews, 30, pp.651-660. https://www.sciencedirect.com/science/article/pii/S1364032113007570
Lacal-Arántegui, R., 2015. Use of materials in wind turbine electricity generators – state of the art and future specifications. Cleaner Production Journal, 87, pp.275-283. https://www.sciencedirect.com/science/article/pii/S0959652614009779
SKF, 2021. Out of reach. Low weight. The superconducting future of wind power. [online] Blog on the management of wind farms. Available on :