Global warming will weaken the wind in the northern hemisphere？
Researchers at the University of Colorado recently published the latest research results in the journal Nature Earth Science, pointing out that global warming will have a far-reaching impact on the distribution of wind energy resources around the world. By the middle and late part of this century, the available wind energy resources in the northern hemisphere will be greatly reduced, while the wind energy resources in some areas in the southern hemisphere may increase sharply, and the overall wind power development potential will shift to the south.
1. Distribution or transfer of wind energy resources to the southern hemisphere
The polar regions are cold and the equator is warm, and the westerly winds prevail all the year round in the mid-latitudes of the northern and southern hemispheres, which is also called thermal wind. In this wind belt, the average wind speed is greater than other places, and a large number of wind energy resources are gathered, covering many countries in the northern hemisphere, including China. Under the background of climate change, the change of mid-latitude westerly belt will directly affect the utilization potential of wind energy resources.
The latest research results of the University of Colorado in the United States believe that global warming will have a far-reaching impact on the distribution of wind energy resources around the world. By the middle and late part of this century, the available wind energy resources in the northern hemisphere will be greatly reduced, while the wind energy resources in some areas in the southern hemisphere may increase sharply.
Using the simulation results of supercomputer, the researchers discussed the evolution of wind energy resources in two different scenarios of greenhouse gas emission in the future. The first is a medium emission scenario, assuming that carbon emissions reach the highest in the middle of this century and then remain stable; By the end of this century, the concentration of carbon dioxide in the atmosphere is about 1.5 times of the current concentration, and the global average temperature is warming by 1.1 to 2.6 degrees Celsius. The second scenario is a high emission scenario, corresponding to the development mode of slow improvement of energy structure and lack of climate response measures, carbon emissions will continue to increase, the concentration of carbon dioxide in the atmosphere will exceed the current three times by the end of this century, and the global temperature will rise by 2.6 to 4.8 degrees Celsius.
The results show that the wind energy resources in the northern hemisphere will be significantly reduced in both moderate and high emission scenarios, especially in the mid-latitude areas including northwest China, Siberia, Northeast Asia, the United States, Canada, Britain and the Mediterranean coast, that is, along the westerly belt of the northern hemisphere. Under the high emission situation, by the end of this century, the wind energy resources from Inner Mongolia to Northeast China will even be reduced by 10% to 20%.
The wind energy resources in the southern hemisphere will not change much under the medium emission scenario, but will increase greatly under the high emission scenario. Especially in the high emission scenario, by the end of this century, the wind energy resources in eastern Brazil and northeastern Australia will increase rapidly by more than 40%.
2. The reason is that the warming ranges of the North and South poles are different.
This difference may be attributed to the fact that global warming affects the evolution of wind belts in the northern and southern hemispheres in different ways. In the northern hemisphere, arctic warming and sea ice melting are a positive feedback process that promotes each other, so that under the background of global warming, polar warming is more obvious; As a result, the temperature gradient between the equator and the polar regions is weakened, and the wind speed in the mid-latitude westerly belt is reduced as a whole. Some simulation results also point out that due to the significant warming at high latitudes, the cold-warm confrontation between the north and south sides of the mid-latitude region is weakened, and the activity of the storm system is reduced as a whole, which is also a reason for the decrease of wind energy resources.
In the southern hemisphere, especially in high emission scenarios, Antarctic warming is not as obvious as land warming in central South America, southern Africa and Australia. The temperature gradient between this part of the continent and the ocean at the same latitude increases, which becomes the dominant factor in the change of wind belt intensity. Land warming is faster, land thermal depression is enhanced, land-sea pressure gradient is increased, wind speed is increased, and wind energy resources are increased. Except Antarctica, the southern hemisphere continent is mainly distributed in tropical and subtropical regions, so the overall increase of wind energy resources is also most obvious in tropical and subtropical regions. It is worth mentioning that in the middle and high latitudes of South America and Australia, wind energy resources still tend to decrease, similar to the northern hemisphere.
3. The probability of extreme gale in northern Europe has increased.
The confrontation between the cold and warm air masses in the north and south is common in the westerly belt, which is also called the front. If there is a small disturbance in the atmosphere, for example, one side of the air mass moves to the other side actively, and the trajectory of the air mass deflects under the action of geostrophic deviatoric force, it will induce a large-scale atmospheric vortex, which is also called frontal cyclone. From the climate point of view, the area where frontal cyclones frequently occur and pass through is the area "located on the storm track", and the average wind speed is usually larger than other areas.
But if you want to use wind energy, the bigger the wind, the better. Extremely violent gusts will actually cause damage to windmills. The design of windmills is generally based on the criteria such as the maximum wind that can cope with a few years (for example, 50 years), which is directly related to the statistical data of local climate background.
Scientists use supercomputers to simulate northern Europe. The results show that if the global climate warms, the mid-latitude "storm track" will move northward as a whole, and the number of frontal cyclones will decrease, but the intensity of a single storm will increase. As a result, the frequency and intensity of extreme winds in northern Europe will increase. This is not good news for windmills designed according to past climate data standards, and it also means that new wind farms must consider the possibility of withstanding stronger storms in the future.
Corresponding to the extreme wind that may increase, the extreme waves at sea will also increase. The research on the future evolution of wind and waves in the North Atlantic shows that the current "once in 20 years" big waves may appear every 4 to 12 years in 2080; The climate simulation of the North Sea in Europe shows that by the end of the 21st century, the average height of waves will rise by 5% to 8%. Because of the limited land space and greater friction resistance, offshore wind power generation is the hot direction of current development; The double test of wind and waves poses a new challenge to the construction of offshore wind farms in mid-latitude areas. However, in areas with lower latitudes, such as the Mediterranean coast, because the storm track moves northward, the wind and waves in the future climate outlook will be reduced.
4. Warming is a double-edged sword for high latitudes.
In high latitudes or arctic regions, cold weather is one of the reasons that hinder the popularization and application of wind power generation. Windmill blades are exposed to humid air with sub-zero temperature, and once they are frozen, the blades will lose their balance, the resistance will increase, the efficiency of wind power conversion will be reduced, and there are potential safety hazards. According to statistics, in Finland, 9%-45% of windmill stalling events are related to icing. Of course, the problem of icing can be overcome to some extent by designing blades that are not easy to gather ice and snow and using current heating, but it will also make the cost of operation and maintenance higher.
Climate warming may be good news for these areas. Supercomputer simulation results show that at the end of this century, the frost period in high latitudes will be obviously shortened and the frequency of icing will be greatly reduced, regardless of the assumed temperature rise. In some parts of Scandinavia, the icing frequency will even drop by 100%. At the same time, because the storm track moves northward, the high latitude zone will be more frequently affected by the frontal cyclone system, and the potential wind energy resources will become more abundant. As a result, some areas that are not suitable for the layout of wind farms may become new territories for opening up wind energy resources in the future.
Corresponding to the temperature rise, the permafrost zone in high latitudes will be reduced, which will bring both advantages and disadvantages. First, because the scope and depth of frozen soil layer are reduced, it will be more convenient to lay transmission lines and build wind farms. Secondly, if the frozen soil layer continues to melt, how to design the windmill base becomes a problem, because the stress and support relationship between the windmill and the soil will continue to change, and there will be the risk of lodging if it is slightly unbalanced. How to weigh the gains and losses, reduce risks and expand benefits depends on the wisdom of engineers.
Not only for onshore wind farms, but also for offshore wind farms in high latitudes, especially for the region with the fastest growing number of offshore wind farms — — For Europe. The study of future sea ice evolution shows that the number of days covered by sea ice in the North Baltic Sea and the Gulf of Bosnia will be reduced from the current 130-170 days to 0-90 days in the later part of this century, and many areas will not even be frozen all year round. However, the decrease of sea ice will make the foundation stability of offshore windmills worse, and it is more vulnerable to the damage of strong winds and waves. At the same time, rising sea level will also increase the risk that the windmill base will be flooded. However, the melting of glaciers will reduce the salinity of seawater, which will help to slow down the corrosion of seawater to the windmill base and transmission line materials.
Extended reading
The potential of wind farms such as Jiuquan may decline.
At present, the world’s largest wind power base is located in Jiuquan, Gansu, China. By 2012, the installed capacity of wind power has exceeded 6,000 megawatts, which is equivalent to supplying the electricity demand of the whole UK, and this figure is still rising. Gansu is located in the wind energy-rich zone in northwest China-Mongolia, with high wind speed all year round and wind energy density exceeding 150 watts per square meter. It is an ideal place for China to build wind power plants, and it has also played an important role in promoting local employment, taxation and economic development. If the climate warming continues, the potential of wind power in this region is likely to decline, and the potential of existing wind power equipment cannot be fully exerted. Many countries in the mid-latitude zone of the northern hemisphere, including China and the United States, will face the same problems, which will also add more pressure to the realization of human energy conservation and emission reduction goals.
The researchers pointed out that the current assessment and layout of wind power generation capacity are mostly based on past climate data statistics, but rarely consider the impact on the distribution of wind energy resources after the future atmospheric circulation changes due to human activities. The new research provides a new reference for the economy and sustainability of wind power plant layout in the future, and for decision makers to measure and plan alternative energy strategies.