1 Foreign wind energy development overview According to statistics, the global wind energy resources are at 500000TW*h/year. Considering social, geographical environment and other factors, the actual wind energy resources that can be developed are about 1/10 of the total wind energy resources. Wind power originated in the 1970s. Due to the dual pressures of environment and energy, the US government gave one to develop wind power. The series of preferential policies promoted the development of wind power and made people really understand wind power. Wind power technology is mature in the 1980s. As wind power research institutions and development departments have been established in many countries, the single-machine capacity of wind turbines has doubled, and its availability has increased to over 95%, making wind turbines practical. The grid-connected wind turbines were successfully developed from 20~50kW in the 1980s to 500~800kW in the 1990s. The prototype of 1~2MW wind turbines in the mid-1990s was successfully put into operation. At present, the 3~6MW prototype has also been successfully developed and will be mainly used in offshore wind farms. The main body of investment in wind power has undergone major changes. Countries, regions, power departments, financial institutions, consortia, etc. have raised funds for wind power development and construction. Wind power worldwide is growing at a rate of 30% per year. The cumulative annual installed capacity of the world is shown.
From a global perspective, Germany's wind power generation is at the top of the world, with a cumulative installed capacity of 6,107 MW. The United States' total installed capacity of the world's largest installed capacity of the top four largest manufacturers in 1998 accounted for 70% of the market share. According to the Danish Wind Turbine Manufacturers Association Statistics show that in 1998 Danish manufacturers produced 1210MW wind turbines with a production value of US$1 billion. It is estimated that global wind turbine manufacturers will sell $2 billion. In the 1990s, the wind turbine manufacturing industry grew at an average annual rate of 30%, and will have the same growth rate in the next few years. Wind turbine manufacturing is one of the fastest growing industries in the world.
2 Overview of China's wind energy development China's wind energy resources are extremely rich. The theoretical reserves are 1.6 billion kW, and the total amount of wind energy resources that can be developed and utilized in the country is 253 million kW, which is greater than China's hydropower resources. According to resources, land, transportation, power grid and other conditions, there are about 50 wind farms with recent development conditions, which are distributed in 11 provinces across the country, including Xinjiang Dabancheng, Inner Mongolia Huitengxile, Hebei Zhangbei, Jilin Tongyu, Shanghai Chongming, Guangdong Nan'ao and other places have the conditions of 100MW installed. Since the 1970s, the state has encouraged the development of independent small wind turbines in order to solve the problem of electricity use in western grassland pastoral areas, eastern islands and remote mountainous areas. The domestic wind power research institutions are mainly engaged in the research and development of small wind turbines, and form a considerable scale. At present, there are 180,000 wind turbines in China, which solve the problem of electricity consumption for 600,000 residents in areas that cannot be reached by the power grid. The production capacity, production volume and social quantity of small wind turbines in China are the highest in the world.
In 1993, China clearly proposed to use wind power as an industry. In the year of the year, the state has formulated a plan to ride the wind. This plan aims to establish a joint venture, introduce technology, and absorb and absorb, to achieve independent development, design and manufacture large wind turbines. The family has also developed a “bright project†to develop and utilize renewable energy, including wind energy, to provide electricity for areas far from the grid. Thanks to the government's support, in the mid-to-late 1990s, China's wind energy has achieved rapid development. The number and scale of wind farms have gradually expanded. Many successful experiences have been achieved in construction, operation, management, etc., and preliminary development and construction of wind power has been achieved. Ability and conditions. At present, there are more than a dozen companies in the country engaged in the construction and development of wind farms with a capacity of 2610MW, Denmark with 2,341MW and Spain with 2,836MW. Europe's wind power accounts for 75% of the world. According to the plan, the installed capacity in Europe will reach 40,000MW in 2010, 2020. Years reached 100,000 MW. Denmark plans to use 20% to 50% of the country's electricity consumption, including renewable energy, by 2030. In the past 20 years, the wind turbine industry has developed into a professional high-tech industry. Wind turbine manufacturers are concentrated in a small number of companies, mostly European companies. It is the cumulative output of the world's top 10 wind turbine manufacturers in 2000.
camp. More than 20 wind farms of varying scales have been built, and the installed capacity has exceeded 400 MW. It is the cumulative installed capacity in China.
According to the plan, by 2005, the cumulative installed capacity of the country will reach 1500 MW, and the installed capacity will reach 4,000 MW in 2006-2010. The cumulative installed capacity of the country will reach 7000 MW in 2011~2015. 3 Blade technology progress With the continuous increase of wind turbine capacity, blades The length also increases. The length of the 200 KW wind turbine blade is increased to a length of 21 m of 600 kW. The blade length of 1~2MW wind turbine is 30~40m. The longest blade is about 60m long. Increased blade length greatly increases the difficulty of blade design, materials, and manufacturing. Therefore, the progress of large blade technology is the progress of comprehensive technology of design, materials, technology and equipment.
In addition to the large increase in installed capacity, the development of wind power has a very obvious development in technology. From the power adjustment, there are four main technologies popular in the world: fixed pitch stall control, pitch control, active stall control, and variable speed constant frequency. Most of the current MW-class wind turbines use variable-speed constant-frequency technology. Different adjustment methods of wind turbines have special requirements on the aerodynamic design of the blade and even the blade structure. Blades are one of the key components of wind turbines, involving pneumatics, composite structures, processes, etc., especially the design and manufacture of MW-scale large composite blades is very difficult. Therefore, the price should account for about 18~22% of the unit. The blades in foreign countries are specialized in production, concentrated in the production of several professional companies. The most famous blade company is the LM company in Denmark. By the year 2000, it has produced 60,000 blades. In that year, it produced 7,200 blades, which accounted for 45% of the world market. There are 12 factories in the world with 2,200 employees. A global sales and service network. In this department, there is a department specializing in blade research and development. The main topics are blade structure dynamics, lightning strike, pneumatics, and structural testing. Vesta, one of the world's top ten wind turbine manufacturers, produces blades for itself, and its wind turbines account for 17% of the world market. Germany's NOI mainly produces MW-class wind turbine blades. In recent years, this monopoly by specialized blade producers is being broken. Some well-known wind turbine manufacturers began to produce their own blades, such as Nodex's 1.5MW variable pitch blades, and other large companies such as Bonus, Game8e, and Enercon are also developing MW-class blades.
China has a certain gap with foreign countries in the design and manufacturing technology of FRP blades. Blade technology is the key technology of wind turbines, and large foreign companies are not willing to transfer technology or co-production. In order to make the FRP blades localized, the relevant government departments attach great importance to the research and development of the blades and support the blade project. The research projects include “Seventh Five-Year Plan†and “Small Wind Turbine Foil Blade Series Researchâ€, “Eight Five-Year 200KW Wind Turbine FRP Blade Development Nine Five-Year†*300KW Wind Turbine FRP Blade Development, Research Institute Special Fund *660KW Wind Turbine FRP Blade Industry ". During the "Tenth Five-Year Plan" period, the state listed the MW-class wind turbines as *863* projects, including 1.3MW fixed-pitch stall control wind turbines, 1MW, 1.5MW variable-speed constant-frequency wind turbines. The matching blades are listed as special sub-projects. After years of research, China has developed a series of large-scale wind turbine FRP blades of 200~750KW series, which has formed a batch of children's production and laid the foundation for the localization of wind turbines.
4 Several problems in blade technology The aerodynamic design includes the aerodynamic design of the wind wheel and the calculation of the aerodynamic performance. According to the overall performance requirements of the wind turbine, the diameter of the wind wheel, the number of blades, the rotational speed, the chord length, the leaf thickness and the torsion angle distribution are determined. The aerodynamic shape design uses Wilson's aerodynamic performance to optimize the aerodynamic shape. The theoretical design shape needs to be corrected in consideration of the blade structure and process requirements. When the aerodynamic shape is determined, the aerodynamic performance calculation can be performed. For the fixed-pitch stall control wind turbine, the wind turbine output power, Cp value, thrust and other parameters of different installation angles should be obtained to determine the initial installation angle of the blade and the stall performance of the wind turbine. For the variable-speed variable speed wind wheel, the performance of the wind wheel with different installation angles and different speeds is calculated to determine the adjustment mode of the wind wheel operation. The wind turbine blades are developed from the traditional NACA44 and NACA230 airfoils to wind turbine-specific airfoils, such as NACA63, FX77, NREL-S and so on. These airfoils have a relatively high lift-to-drag ratio, and aerodynamic performance is not sensitive to blade surface contamination. China has not developed its own wind turbine airfoil, which is used abroad. Since the complete aerodynamic performance data on the airfoil is not collected, it has a great influence on the aerodynamic design of the blade.
Commercial large wind turbine blades have a typical structural form. The blade roots are mainly made of glued metal flanges, such as those produced by Vestas; glued metal bolts, such as LM blades; T-bolts, such as those produced by NOI and Aerpac. The root end of the above form has a relatively high bearing capacity, the curve of the root end transition section is soft, and the weight is also light, and the cumbersome appearance of the flange of the flange is changed. The blade profile is basically in the form of a skinned main beam. The main beam can be in the form of an integral box beam, such as a Vestas blade, or in the form of a double channel steel, such as an LM blade, or a ribbed structure. At the fasting front and rear edges of the section, it is determined according to the stability calculation whether or not a sandwich structure is used. The large bending load on the blade is carried by the main beam, and the skin acts as aerodynamic shape and can bear part of the load. This cross-sectional configuration can reduce the weight of the blade, improve the strength and rigidity of the blade, and avoid local instability caused by the bending of the blade. The blade skin is usually reinforced with felt or two-way fabric, and the main beam is reinforced with a relatively unidirectional fabric to increase strength and rigidity. The core material can be PVC foam or Balsa wood. With the increase of length, the weight of FRP blades increases greatly. The blade weight is approximately R29 with the radius of the wind wheel. For example, the blade of a 40m long blade weighs 10T, and the blade of a 50m blade has a weight of 16T. The weight of the blade increases. The fatigue load generated by the blade's own weight also increases the load on other components of the unit. To reduce the weight of the blade, carbon/* fiber hybrids can be used to enhance the blade, such as carbon fiber reinforced main beam, or full carbon fiber reinforced blade. Some foreign experts pointed out that the carbon fiber should be used when the blade is larger than 40m, but LM believes that even larger blades can theoretically use FRP, and the 篼 performance glass fiber/epoxy solution can be used. Even so, the company is conducting research on carbon fiber blades. At present, Nodex has developed a 43.8m carbon/* fiber hybrid blade with a weight of 9.6T. Enercon is being developed for a 112m diameter carbon fiber blade for 4.5MW commercial onshore and offshore wind farms. Enron and N0I Vestas are also developing carbon fiber blades for 3 to 5 MW offshore/onshore commercial applications. According to the analysis of European and American experts, for MW-class large wind turbine blades, carbon/glass fiber hybrid reinforcement can reduce blade weight by 30%, reduce cost by 15%, reduce the national standard of blade tip wind turbine blades and China Classification Society's certification of wind turbines. The specification requires a blade structure test to verify the accuracy of the design and the quality of the manufacturing process. The structural test content is mainly the static strength and stiffness of the blade under the design load, the first-order wave and the vibration frequency of the blade, and the fatigue test. Foreign developed countries of wind turbine manufacturing, such as Denmark, the Netherlands, and the United States, have national-level blade testing centers and are authorized by the government to carry out blade certification. China has not yet established a national wind turbine test center, and the structural test of the blade is carried out at the manufacturer under the guidance of the classification society.
The full-size blade fatigue test is an important test content, and it is verified in the laboratory whether the blade can be used for 20 years. According to the blade fatigue load spectrum, the fatigue load alternation number is 10* times in the 20-year service period. The fatigue loading frequency is generally the first-order frequency of the blade. For large blades at about 1 Hz, the loading speed is 1~2 times/8. To accelerate the fatigue test speed, the load should be increased. The general loading times are 1 to 5 million times. 2~3 months. The test load spectrum shall be determined according to the principle of damage equivalent. We carried out 300kW and 660kW blade fatigue tests in the laboratory, and the tests were carried out 5 million times and passed the certification of the classification society.
Most large wind turbine blades use an open mold process. The pneumatic surface and the working surface half shell are formed on the two female molds respectively. The blade main beam and other FRP components are respectively formed on a special mold and then glued to form an integral blade. The blade forming process has evolved from an early hand lay-up process to a more advanced process. For example, LM uses the VARTM process. The application of this process solves the series of technical problems in forming large FRP components. This process technology increases the fiberglass fiber content and increases the strength. Vestas uses a prepreg process. The German NOI company uses a wet prepreg process. Due to the influence of market, technology and capital, China's FRP blade manufacturers mostly use wet hand lay-up process and cure at room temperature. The process is relatively simple and does not require a warming and pressurizing device. With the development of China's wind power industry, the market needs more quality FRP blades, and adopting advanced molding technology is the only way. At present, domestic manufacturers have begun research work in this area.
Most countries in the world require that the installed wind turbines be certified to ensure their quality. The EU recommends the adoption of IEC standards for uniform certification rules and requirements. The technical standard related to blades in the IEC series of standards is IEC1400-1* Wind Turbine System Safety. This standard specifies blade load conditions, local safety factors, inspection requirements, etc.; IEC1400-23* wind turbine blade measurement technology. It specifies the blade static strong stiffness measurement, frequency measurement and fatigue test method. China Wind Turbine Standards Committee Organization A series of standard specifications have been developed, in which the standard for large wind turbine blades is “Wind Turbine Blades.†This standard basically refers to the IEC standard and Lloyd's standard. The standard selection of materials for composite blades, manufacturing processes, The design of the structure has been stipulated. The China Classification Society has formulated the wind turbine certification specification. The promulgation and implementation of the national standards and certification standards enable domestic manufacturers to design and manufacture the complete machine and components according to the technical requirements equivalent to international standards. Quality control enables products to compete domestically and internationally at a high starting point.
5 The application of important components of the wind turbine on the nacelle cover and the shroud, such as the main shaft, gearbox and motor, are installed in the nacelle cover. Therefore, the nacelle cover mainly protects the equipment from the environment and provides personnel installation and maintenance conditions. The diversion is mainly used to improve the aerodynamic performance of the wind turbine. Although the technical components of these two components are not good in the unit, the wind turbine manufacturers have very strict requirements on their manufacturing, because the appearance quality has an impact on the manufacturer's brand. I worked with Vestas to produce a nacelle cover and shroud for the 660KW unit. Under the guidance of the other experts, the use of the other side of the technology for mold and product manufacturing, has been able to mass production of FRP cabins and shrouds for domestic wind turbine manufacturers.
6 Conclusion Wind energy is one of the few fastest growing industries in the world today. With the increasing emphasis on energy crises and environmental issues, it is expected that wind energy will continue to grow at an idle rate for a long period of time, and it will also become an important application area for FRP composites.
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