According to Bob Bellemare, president of UtiliPoint, an international consulting company, carbon fiber is an impending trend for wind turbines. Smaller size (such as 22m long) is generally used for large and inexpensive E-glass fiber reinforced plastics. The resin matrix is ​​mainly unsaturated polyester, and vinyl ester or epoxy resin can also be used. Larger blades (such as Above 42m) CFRP or hybrid composites of CF and GF are generally used, and the resin matrix is ​​mainly epoxy. Ramesh Gopalakrishnan, global manager of wind energy blade engineering at GE, said that designers have chosen carbon fiber for blade design in the search for lightweight, high-strength materials. Therefore, glass fiber and carbon fiber are the two most important materials in current blade manufacturing.
The blade is the most basic and critical component in the wind turbine. Its good design, reliable quality and superior performance are the decisive factors for the normal stable operation of the unit. The harsh environment and continuous operation for a long time, the requirements of the blades are: light weight and the best fatigue strength and mechanical properties, can withstand extreme conditions such as storms and the test of random load; the elasticity of the blade, inertia when rotating The vibration frequency characteristic curve is normal, and the load transmitted to the entire power generation system has good stability; corrosion resistance, ultraviolet radiation, and lightning strike performance are good; the cost of power generation is low, and the maintenance cost is the lowest.
To meet the above requirements and improve the economy of the unit, the increase in the size of the blades can improve the economics of wind power generation and reduce costs. The blade length has grown from 4.5m in 1980 to 61.5m today, and the capacity has grown from the original 55kW to today's 5MW. In 1970, the wind turbine blades were mainly made of steel, aluminum, or wood. Today, most of the materials selected are E-glass fiber reinforced plastics (GFRP). Carbon fiber composite materials (CFRP) have been used at present, and the development of blade materials conforms. The development of large-scale and light-weight blades.
Wooden leaves and cloths
Modern micro- and small-scale wind turbines also use wooden blades, but wooden blades are not easily distorted. Large and medium-sized wind turbines seldom use wooden blades. Wooden blades also use strong wooden beams as the longitudinal beams to bear the forces and bending moments that the blades must bear during operation.
Steel beam fiberglass skin blades
In modern times, steel vanes or D-shaped steel beams are used as the longitudinal beams, steel plates are used as rib beams, and the inner structure of foamed plastic covered with fiberglass skin is generally used in large-scale wind turbines. The section of the steel pipe of the longitudinal beam and the D-shaped steel from the root to the tip of the blade should be gradually reduced to meet the requirements of the twisted blade and reduce the weight of the blade, that is, to make the beam of equal strength.
Chord-length extruded blades such as aluminum alloy
The chord-length blades extruded from aluminum alloy are easy to manufacture, can be continuously produced, and can be distorted according to the design requirements. The shafts and flanges connecting the blade root and the hub can be realized by welding or bolting. Aluminum alloy blades are lightweight and easy to process, but they cannot be made from blade roots to blade tips that are tapered, because the extrusion process is not yet resolved in countries around the world.
Fiberglass blade
The so-called glass fiber reinforced plastic (GFRP) is a reinforced plastic made of a glass fiber or a carbon fiber in which a plastic such as an epoxy resin or an unsaturated resin penetrates into different lengths. The reinforced plastic has high strength, light weight, and aging resistance. The surface can be re-wrapped with glass fiber and coated with epoxy resin, and other parts filled with foam plastic. The quality of glass fibers can also be improved by surface modification, sizing and coating. LM Glass Fiber Company is currently working on the development of full-fibre glass blades up to 54m in cost per unit kWh.
Fiberglass composite blades
At the end of the last century, the blades of large and medium-sized wind turbine generators in industrialized countries of the world basically used composite steel longitudinal beams, laminated glass steel rib beams, and composite materials of metal structures with blade roots and hubs. Wind turbine rotor blades use different composite materials depending on the length of the blade. The most commonly used materials are glass fiber reinforced polyester resin, glass fiber reinforced epoxy resin, and carbon fiber reinforced epoxy resin. Studies in the United States have shown that the use of radio frequency plasma deposition to coat E-glass fiber can reach the level of carbon fiber resistance to tensile fatigue, and this treatment can reduce inter-fiber fretting wear that can actually cause damage. . LM Glass Fiber Co., Ltd. further developed glass fiber reinforced plastics with 61m large-scale blades of carbon fiber selected only at the ends of the crossbeams and blades to develop 5MW wind turbines.
Carbon fiber composite blades
With the increase in the power of single-unit power generation, the length of blades is required to increase, and its application in wind power generation will also continue to expand. For the blade, stiffness is also a very important indicator. Studies have shown that carbon fiber (CF) composite material blade stiffness is two to three times that of FRP composite blades. Although the performance of the carbon fiber composite material is much better than that of the glass fiber composite material, the price is expensive, which affects its large-scale application in wind power generation. Therefore, the world's major composite materials companies are conducting in-depth research on raw materials, process technology, and quality control in order to reduce costs.
Yesterday, we used wood or metal materials; today we use fiberglass; tomorrow, we use carbon fiber; then tomorrow tomorrow, we will use nanomaterials?
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