Special Report on Renewable Energy Industry: Development of Wind Power Technology in China

1 Resource distribution and development status

China has a vast territory and abundant wind energy resources. The total amount of wind energy resources that can be developed is 2.86 billion kW. Considering the actual available land area and other factors, the available onshore wind energy reserves are about 80 GW (800 million kW), which can be used offshore. The wind energy reserves are 15 GW, a total of about 95 GW. If the annual on-grid power of onshore wind power is 2,000 hours/year equivalent to full load, it will provide 1.6 trillion kWh of electricity per year. The annual on-grid power of offshore wind power will be 375 billion per year at an equivalent full load of 2,500 hours/year. The power of kWh is about 2 trillion kWh, which is equivalent to the electricity consumption in 2004. However, from the perspective of resource distribution, China's wind energy resources are widely distributed and uneven. The richer areas are mainly concentrated in the following areas (China Meteorological Administration, 2006): 1) The rich belts of the Three North (Northeast, North China, Northwest) regions. The wind power density is above 200-300 watts/m2, and some can reach more than 500 watts/m2. 2) There are abundant belts along the coast and its islands. The effective wind power density is above 200 W/m2, and the wind energy density of coastal islands such as Taishan, Pingtan and Dongshan is above 500 W/m2. 3) Wind power density is generally below 100 watts/m2 in inland wind-enriched areas. However, due to the influence of lakes and special topography, wind energy resources are also abundant in some areas, but they are limited to a small range.

It can be seen that China's wind energy resources are mostly concentrated in areas with sparse population and underdeveloped economic development. The power load in these areas is usually much smaller than that in the southeast coastal areas. Therefore, despite the abundant wind energy resources in China, there is still a great mismatch between its development and utilization, access to the Internet and the matching of power load, which brings obstacles to the large-scale development and utilization of wind energy resources in China.

Since the construction of the first demonstration wind farm in Shandong Rongcheng in 1986, after nearly 25 years of hard work, the installed capacity of wind farms in China has been expanding. Since the promulgation of the Renewable Energy Law in February 2005, wind power has developed rapidly. Especially during the 10th Five-Year Plan and the 11th Five-Year Plan period, China's wind power development has accelerated, and the total installed capacity has increased from 1.26 million kW in 2005 to At the end of 2008, 12.17 million kW, the annual growth rate exceeded 100% China Energy Network, 2009). According to preliminary calculations, China's wind power industry maintained a rapid development in 2009, with new installed capacity exceeding 13 GW during the year and achieving a growth rate of 100% for four consecutive years (Figure 1.3).

2 Technology development

Improving efficiency and reducing costs have always been the direction of the development of wind power technology. At present, the technical means to improve the cost-effectiveness of wind power can be started from the following two aspects: 1 upgrading to large-scale wind turbines; 2 improving design methods to adapt to local wind energy operating environments, such as improving motors, gearboxes, blade design and blade materials, Control the system to promote overall performance and more. The development of wind power technology is mainly reflected in the following aspects:

Fan scale – In the past 20 years, the scale of wind turbines has shown a linear growth trend, which has reached 5-6MW (see Figure 1.4). The rotor diameter of the turbine reaches 126 meters, and wind power technology develops rapidly (IEA, 2008). By improving the blade material (using epoxy-based and fiberglass to reduce the weight of the fan while increasing the load strength), using a low-speed direct generator (the use of direct technology in large-scale wind turbines refers to the application of single-stage in low-speed generators). Drive technology, which reduces the diameter of the generator; in addition, the distributed drive system can also effectively reduce the weight and size), and implement feedback control on the drive and rotor load. In the future, the scale of the fan still has room to rise (R. Thresher, A. Laxson, 2006). However, it is worth noting that the restrictions on the transportation and installation of large-scale wind turbines will become more and more prominent as the size of the wind turbines increases.

Since 1996, the single-unit capacity of new wind turbines in China has been mainly 750-850 kW. Since 2007, the newly-added wind turbines have been converted to megawatts. At present, the capacity of domestic wind turbines has reached 1.5MW, 2MW or even higher (Jiang Liping, 2008). The megawatt direct-drive variable-speed constant-frequency wind turbines and megawatt-class doubly-fed variable-speed constant-frequency wind turbines representing the development direction of the technology have been mass-produced, and the core technologies such as bearings, converters and control systems still rely on foreign manufacturers.

Installation - An increase in the size of the fan will have a major impact on its installation. The increase in rotor diameter and the desire to increase the height of the tower to place the rotor at a higher wind speed will increase the height of the hub. At present, the height of the fan hub has increased from 65 meters to 80 to 100 meters (2.5 to 3.5 MW). With the increase of the hub quality and the height of the tower, the diameter of the tower will inevitably increase, and the thickness of the tower will also be thickened to bear greater deflection and breaking load, which increases the installation cost of the fan. In order to reduce the high cost of using large cranes, a new exploration has been made on the design of the wind turbine tower: on the one hand, the telescopic or self-erecting tower is used, which makes the installation of the engine compartment and the rotor close to the ground, and then uses it. The hydraulics principle raises the nacelle and tower to their operating height. On the other hand, it seeks to transport the nacelle and rotor to the top of the tower using the tower's mounting rails. This method has the added advantage of reducing the nacelle to the ground for full repair, thus reducing the cost of using large cranes. The use of new composite materials and optimized structure of the tower can reduce the weight of the system and reduce production and transportation costs while ensuring stability.

Control System - The control system is the key core component of the wind turbine. In China, there was no cutting-edge technology related to the industry. In the future, the Chinese market will require a MW-class and above variable-speed variable-speed constant-frequency wind turbine control system. In addition, full-state feedback technology with disturbance accommodating control (DAC) and cycle control is also beginning to be applied. The technology uses the control loop to feedback the state of the fan in real time, thereby determining which control to implement and reducing the load on the system.

Offshore wind power technology - Due to the gradual scarcity of terrestrial resources and the proven reserves of offshore wind energy resources, the development of offshore wind power presents a booming scene. Offshore wind turbines are generally larger in size and therefore require higher reliability, while their maintenance and operation are more complex than terrestrial wind power. The mainstream models of domestic manufacturers are doubly-fed; while Goldwind and Xiangdian use direct-drive models. In addition, surveys of wind and wave loads and seabed conditions are also critical to the future development of offshore wind power. The technology that is urgently needed is a floating or fixed platform with low development cost, providing an affordable and reliable platform system for offshore power generation.

In summary, since the beginning of the 21st century, the challenge of wind power technology is mainly to achieve cost-effective wind power generation in areas with low wind speed and high power load, while avoiding obstacles to power transmission. These challenges require wind turbines to increase altitude to increase wind energy acquisition in low wind speed areas; and actively explore offshore wind power technologies in shallow seas and even deep sea areas. The breakthrough point of future technology is: Specially designed permanent magnet generator (the choice of é’•-iron-boron permanent magnet material can make the magnetic flux density of steel close to the magnetic flux density of copper coil, without increasing the quality of equipment, scale And cost), variable-speed power electronic power converters with better performance and greater reliability, smaller and lighter gearboxes, aerodynamic and structural dynamics codes that better predict load changes and adapt to broader climate change Blades made of advanced materials such as epoxy-based materials, control technology that reduces machine compliance but does not increase costs, new towers made from advanced synthetic materials, offshore wind turbines built on floating platforms, improved offshore power collection System (R. Thresher, A. Laxson, 2006).

3 cost analysis

75% of the total cost of wind power is related to the upfront cost, including wind turbines, infrastructure, electronic equipment, and networking. Therefore, unlike fossil energy power generation technology, wind power is a capital-intensive technology. According to the calculation of the European Wind Energy Association, depending on the resource conditions, the investment cost of onshore wind power is 800-1150 Euro/kW, the power generation cost is 4-7 Euro/kWh; the investment cost of offshore wind power is 1250~1800 Euro/kW. The cost of power generation is between 7.1 and 9.6 cents/kWh. The analysis results of the research report published by CIC Securities show that the current construction investment of wind farms is basically 8,000-10,000 yuan per kilowatt, according to 30% of self-owned funds investment, equivalent full-load utilization hours of 1800 hours calculation, calculation 5 The cost of tens of thousands of kilowatts of wind farms is 0.43 to 0.53 yuan / kWh (CIC Securities, 2009).

The Chinese government has set the wind power grid benchmark price to four levels according to the municipal-level administrative boundary: 0.51 yuan/kWh, 0.54 yuan/kWh, 0.58 yuan/kWh, and 0.61 yuan/kWh. Therefore, the current wind power cost in China is lower than the benchmark price of the National Development and Reform Commission. (Notice on improving the on-grid tariff policy for wind power generation, 2009). According to recent research by the World Wind Energy Council on the downward trend of wind power costs, 60% of the decline in wind power costs depends on large-scale development, 40% depends on technological progress, and with the increase in scale, the future wind power costs in China have Further space to fall.

Generally, the basic construction cost of onshore wind turbines accounts for about 10% of the total investment, while the offshore construction cost is up to 40% of the total investment, which results in the offshore wind power investment cost is 50-100% higher than that of similar wind turbines on the land. Even if the sea wind speed conditions are good (generally 20-40% higher than the land), the corresponding power generation cost per kWh will increase by 2 to 4 Euro cents. According to the cost comparison between offshore wind power and onshore wind power calculated by the European Wind Energy Association, the difference between the two can be approximated, that is, the cost of offshore wind power is about 30% higher than that on land. If you consider the cost of submarine cable transmission, the cost of offshore wind power may be about 50% higher than that on land.

4 Development potential

Wind power is the lowest cost renewable energy resource in China except for hydropower. In recent years, the rapid development of wind power has aroused widespread concern of the government, enterprises and society. According to the latest research, China proposed the idea of ​​building a 10 million-kilowatt wind power base and implemented the development policy of “building a large base and integrating into the large power grid”. The specific plans for wind power are as follows: 1) Ten thousand kilowatts of wind power started in Jiuquan, Gansu Province Base planning, setting a target of 11 million kW; 2) Planning and construction of 11 million kW in Hami, Xinjiang; 3) Planning and construction of 57 million kW in Inner Mongolia, including 27 million kW in Mengxi and 30 million kW in Mengdong; 4) Hebei planning in the coastal and northern regions A total of 10 million kW is built in the region; 5) Jilin plans to build 23 million kW in the western region; 6) Jiangsu plans to build 10 million kW offshore wind power base; 7) Shandong also plans to build 10 million kW in coastal areas.

The planned capacity of the seven million kilowatt-class wind power base plus the planned capacity of other provinces will reach 150 million kW by 2020 and reach 320 million kW by 2030.