# Wind Turbine Technology Trends
## 3 Discussion
### Onshore Wind Turbine Development
#### 3.1.1 Wind Turbine Blades
Leading wind turbine manufacturers are optimizing features such as twist angle, chord length and blade geometry. Worldwide, the horizontal design of wind turbines with three blades predominates. The blade rotation system is used because of its efficiency, allowable noise level, and durability. Many alternatives to this design have been explored but discarded due to higher cost and lower efficiency. Research [14] shows that greater cost efficiency is achieved by building turbines with a larger rotor diameter. However, this may soon change as the increasing dimensions increase the problem of transportation and assembly, which will impose limits. Systematic minor improvements in the design of rotor blades and other wind turbine assemblies will then become a higher priority. A wind turbine rotor blade goes through more material fatigue cycles in one year than an airplane wing does in its entire lifetime, so this is the biggest concern of wind turbine manufacturers and operators. Metal is not satisfactory in this regard, so wind turbine blades are made of polyester, epoxy resin reinforced with glass fibers, or fiberglass. Carbon fiber or Kevlar are also used as reinforcing materials to protect against breakage or cracking. The company Enel Green Power is developing an innovative blade made of a special technical fabric [15]. This fabric makes it possible to generate more energy, reduce manufacturing costs and facilitate recycling at the end of the blade's life. Due to the orthotropic mechanical properties of the composite, the structural properties of the sheet are determined by the orientation of the fibers. In their paper, [PERSON] et al. [16] present the advantages of optimizing the angle of each layer of the composite. They report that the inclined structure increases the critical wind speed for the defined control system and the electrical system by 10%, which contributes to a higher efficiency of the wind turbine. Composites with glass and carbon fibers are used for the production of wind turbine blades to achieve higher strength, lower weight, and better corrosion resistance. The main problems related to these materials are their availability, biodegradability, risk to human health and the high cost of their production. For this reason, research is being conducted on the possibility of replacing these materials with natural fibers [17; 18]. The development of fabrics based on natural fibers for the production of composites is a new technology that can solve the challenge of balanced mechanical properties of composites. In the work of [PERSON] et al. [19], alfa and wool fibers were used as reinforcement for the development of four fabrics and low viscosity unsaturated epoxy resin as matrix. The fabrics were fabricated applying the taffeta weaving technique. The vacuum forming process was chosen to obtain the hybrid composite because it offers superior advantages. The results of static tests of this reinforced composite indicated an enhancement in tensile and flexural strength. [PERSON] et al. [20] investigated the suitability of a new composite of bamboo fibers and recycled plastic for the manufacture of wind turbine blades. The percentage of fibers in ten samples ranged from 2.5% to 25%. The results showed that as the percentage of bamboo fibers in the sample increased, the tensile strength and impact fracture also increased. The authors conclude that the composite with 25% bamboo fibers is suitable for wind turbine rotor blades. Segmentation of rotor blades could speed up the process of manufacturing rotor blade parts, machining and coating to protect the surface. However, segmentation brings challenges in terms of minimizing the common mass, load transfer between segments, and logistics [21; 22]. Also worth mentioning is the ability to apply 3D printing technology and simulate wind turbine operation for additional verification and improvement of wind turbine operation [23]. QBlade is an open-source program for wind turbine calculations.