The formation and distribution of wind energy resources in my country

Zhu Ruizhao, Chinese Academy of Meteorological Sciences The distribution of wind energy resources in my country has a very close relationship with the weather and climate background. From the distribution map of wind energy resources in my country, it can be clearly seen that areas with rich and relatively abundant wind energy resources in my country Mainly distributed in two large belts. 1. The Three North (Northeast, North, and Northwest) regions are rich in wind energy power density of 200 to 300 W/m2 or more, and some can reach more than 500 W/m2, such as Alashankou, Dabancheng, Huitengxile, and Xilinhot. The number of available hours for Huitengliang and others is more than 5,000 hours, and some can reach more than 7,000 hours. The formation of this wind energy-rich belt is mainly due to the geographical location of the Three North Region in mid-high latitudes. In winter (December-February), the entire Asian continent is completely controlled by the Mongolian high pressure, with its center located in the northwest of the Republic of Mongolia. Small waves of cold air continue to flow southward from the high pressure and enter our country. At the same time, there are also mobile high pressures (anticyclones) moving southward from time to time. This type of high pressure invades my country through roughly four routes. One originates from Novaya Zemlya in Russia and enters my country via Northwestern Asia and the Mongolian People's Republic. It is called the northwest route because it is northwestward; the second originates from the ocean south of Iceland and passes through Russia and Kazakhstan, basically The first one enters my country's Xinjiang from west to east, and is called the Western Route; the third one originates from the Taimyr Peninsula in Russia, and enters my country from north to south via Northwest Siberia and the Mongolian People's Republic, and is called the Northern Route. ; The fourth route originates from the Eastern Siberian region of Lake Baikal in Russia, and enters Northeast my country and North China, which is called the Northeast Route. Except for the northeast route, these four routes generally pass through the Mongolian People's Republic. When passing through, the Mongolian high pressure is supplemented and strengthened by new cold high pressure. This high pressure can often quickly move south and enter our country. Due to the vast area of ??Eurasia and the low temperatures in the northern region, it is the area with the most frequent cold high pressure activity in the northern hemisphere. my country is located on the east coast of Eurasia, which is the only way for cold high pressure to move south. The Sanbei area is the frontier of cold air invading our country. Generally, the front of cold high pressure is called a cold front. When a cold front passes, strong winds often appear 200km behind the cold front, which can cause a level 6~10 (10.8~24.4m/s) Strong wind. For the utilization of wind energy resources, it is a high-quality wind that can be effectively utilized. From the Sanbei region to the south, as the cold air travels a long distance from its source to the middle and lower reaches of the Yellow River and then to the middle and lower reaches of the Yangtze River in my country, the surface temperature increases, causing the original cold and dry airflow properties to gradually change to cooler and moister airflow properties. , (called denaturation), that is, the cold air gradually warms up, and the air pressure difference also becomes smaller at this time, so the wind speed gradually decreases from north to south.

Eastern my country is located on the east and southeast sides of the Mongolian high pressure, so the prevailing wind direction is northerly. The actual northerly angle differs only depending on its position relative to the center of the Mongolian high pressure. The prevailing wind direction is mostly from the northwest in the Three North Areas, and in the vast area south of the lower reaches of the Yellow River in the Qinling Mountains, the prevailing wind direction is between the north and the northeast. Spring (March to May) is the transition season from winter to summer. Due to the rising surface temperature, the intensity of the Mongolian high pressure in mid- and high-latitude areas has significantly weakened since April, and at this time, the Indian low pressure (continental low pressure) ) and its low-pressure trough extending to the northeast have controlled South my country. At the same time, the Pacific subtropical high has gradually invaded the South China coast from the Philippines to the north. The strength, weakness, ebb and flow of these high and low pressure systems have But it plays an important role in my country's wind energy resources. In spring, these types of airflows frequently cross each other in our country. Spring is the season with the most cyclone activity in my country, especially in Northeast my country and Inner Mongolia, causing strong winds and sandstorms in Inner Mongolia and Northeast China. Similarly, there are more cyclone activities in Jiangnan, but they cause spring rain and the rainy season in South China. This is also a major reason why wind resources in the Three North Areas are richer than those in the south. The wind direction across the country is no longer as stable and changeless as the winter monsoon, but the northerly wind is still dominant, but the southerly component of the wind has increased significantly. The surface pressure distribution in East Asia in summer (June to August) is completely opposite to that in winter. At this time, it is no longer clear that the Mongolian high pressure in mid- and high-latitudes is retreating to the north. On the contrary, the Indian low pressure continues to develop and control the Asian continent, which is the most prosperous season of the year. The Atlantic subtropical high pressure also expands northward and westward toward the continent. It can be said that the summer weather and climate changes in the East Asian continent are basically controlled by the strength and interaction of these two circulation systems. As the Pacific subtropical high extends westward and jumps northward, the eastern part of my country can be affected by it. The western part of this high pressure brings abundant precipitation to the southeastern airflow and southwesterly airflow. However, due to the small pressure difference between high and low pressure, the wind speed Not big, summer is the season with the lowest wind speed in the whole country. In summer, there is thermal low pressure on the mainland and high pressure on the sea. The isobars between high and low pressure are almost distributed in a north-south direction in eastern my country, so the southerly wind prevails in the summer monsoon. Autumn (September to November) is the transition season from summer to winter. At this time, the Indian low pressure and the Pacific high pressure begin to decline significantly, while the Mongolian high pressure in mid- and high latitudes begins to become active again. Because the winter monsoon comes quickly and remains stable, it is not like the back-and-forth pattern of the mid-spring summer monsoon that represents the winter monsoon. At this time, my country's southeastern coast has gradually been affected by the edge of the Mongolian high pressure, and the south China coast has changed from the southeasterly wind in summer to the northeasterly wind. The winter monsoon situation has been established in the Sanhoku region in autumn. There are mostly stable northerly winds in various places, and the wind speed begins to increase.

2． Rich areas along the coast and its islands. The annual effective wind energy power density is more than 200 W/m2. If the wind energy power density line is parallel to the coastline, the wind energy power density of coastal islands is more than 500 W/m2, such as Taishan, Pingtan, Dongshan, Nanlu, Dachen, Shengsi, Nan'ao, Matsu, Magong, Dongsha, etc. The number of available hours is about 7000-8000 hours. This area, especially the southeastern coast, is rolling hills from the coast to the inland, so the wind energy-rich areas are only within 50km of the coast. Further inland is not only not the wind energy-rich area, but also It has become the smallest wind energy area in the country. The wind energy power density is only about 50 watts/m2, which is basically an area where wind energy cannot be utilized. The weather and climate background of the coastal wind energy-rich belt is basically the same as that of the Sanbei region. The difference is that the ocean and the continent are composed of two completely different materials. There are obvious differences in the radiation and thermodynamic processes of the two. The energy exchange between the atmosphere and the ocean is very different. The ocean temperature changes slowly and has obvious thermal inertia. The continental temperature changes quickly and has obvious thermal sensitivity. The ocean is warmer than the continent in winter and cooler than the continent in summer. The influence of this sea-land temperature difference affects every time cold air reaches the sea in winter. When the wind speed increases, coupled with the smooth surface of the ocean and low friction, the wind speed is generally 2-4m/s higher than that on the mainland. The southeastern coast is also affected by the Taiwan Strait. Whenever cold air arrives from the south, the wind speed increases due to the narrow tube effect. This is the area with the best wind energy resources in my country. Coastal areas can be affected by tropical cyclones every summer and autumn. When the wind speed of a tropical cyclone reaches level 8 (17.2m/s) or above, it is called a typhoon. A typhoon is a circular cyclone with a diameter of about 1,000km. The central air pressure is extremely low. The typhoon center is within 0-30km of the typhoon eye. The weather in the typhoon eye is good and the wind speed is very low. The weather is the worst on the outer wall of the typhoon eye, and the maximum damaging wind speed occurs within this range. Therefore, generally as long as the typhoon does not land directly in front of the area, the wind speed is generally less than level 10 (26m/s), and its impact is on average 800~1000km. In the direct longitude range, whenever a typhoon makes landfall, a strong wind process can occur along the coast of my country, and the wind speed is basically within the wind speed range cut out by the wind turbine. It’s a good opportunity to fully generate electricity.

There are 11 landfalling typhoons in my country every year, and Guangdong has the most landfalling typhoons every year, 3.5 times, followed by Hainan 2.1 times, Taiwan 1.9 times, Fujian 1.6 times, Guangxi, Zhejiang, Shanghai, Jiangsu, Shandong, The total number of typhoons in Tianjin and Liaoning is only 1.7. It can be seen that the areas affected by typhoons decrease from south to north, and the wind energy resources are also larger in the south and smaller in the north. Due to the rapid increase in central air pressure after the typhoon makes landfall, and the overlapping mountains running from northeast to southwest along the southeastern coast, the strong winds formed are only within a few dozen kilometers from the coast. The power density of wind energy has dropped sharply from 300w/m2 to less than 100w/m2. In summary, cold air in winter and spring and typhoons in summer and autumn can affect the coast and its islands. Compared with the inland, this area forms a rich wind energy zone in my country. Due to the narrow tube effect of the Taiwan Strait, the southeast coast and its islands are the best wind energy rich areas in my country. Our country has more than 18,000 kilometers of coastline and more than 6,000 islands. This is an area with great prospects for the development and utilization of wind energy. 3． In inland wind energy-rich areas, outside the two wind energy-rich zones, the wind energy power density is generally below 100w/m2, and the number of usable hours is below 3,000 hours. However, due to the influence of lakes and special terrain, wind energy is also abundant in some areas. For example, the wind energy near Poyang Lake is greater than that in surrounding areas. The wind energy in Hengshan Mountain in Hunan, Huangshan Mountain in Anhui Province, and Taihua Mountain in Yunnan Province is also greater than in the flat areas. But these are limited to a small area, not as large as the two major belts, especially the Sanbei region, which is larger. The Qinghai-Tibet Plateau is above 4000m above sea level. The wind speed here is relatively high, but the air density is low. For example, the air density at 4000m is roughly 67% of that on the ground. That is to say, with the same wind speed of 8m/s, the wind energy power density on the plain is 313.6 w/m2, but it is only 209.9w/m2 at 4000m, and the annual average wind speed here is 3~5m/s, so wind energy is still in the average area.