Looking back at the height of the hub of the domestic fan, the highest level is about 120m, the difference is 30m, and the height is close to 10 floors.
Is the height of the tower the higher the better? Why are foreign wind power manufacturers desperately trying to increase the height of the hub, and the domestic power in this area is not that big?
Economics is the key
Determining whether to adopt a higher tower height depends mainly on economic benefits. Increasing the height of the tower will inevitably lead to an increase in the cost of the tower and the foundation. Therefore, the improvement of the power generation caused by the tower tube needs to be more effective. The final economic benefits of the unit will be improved.
Generally speaking, when the wind shear is greater than 0.15, the economic efficiency of using the higher tower height will be improved; and when the wind shear is less than 0.05~0.08, the economic efficiency of using the lower tower height will be more obviously improved; When the wind shear is between 0.08 and 0.15, the effect of changing the height of the tower on the economic benefits is not obvious, so it is generally preferred to use a lower tower height.
Influencing factors of wind shear
Wind shear is the tendency of the wind speed at different heights to decrease with height due to the friction of the surface. The degree of wind shear is usually measured by the wind shear index.
The main influencing factors are: microscopic topography, surface roughness, and atmospheric stability.
1. Microscopic topography. For complex terrain wind fields, wind shear is greatly affected by microscopic topography. At the top of the ridge, the wind shear is usually small, and even negative shear occurs. For a simple terrain wind field, wind shear is usually slightly larger.
2. Surface roughness. The surface roughness is mainly affected by the topography and vegetation of the earth's surface. In areas with severe desertification, the wind shear is usually small. In areas with high greening and large forest coverage, the wind shear will be too large.
3. Atmospheric stability. When the temperature near the surface is low, the atmosphere tends to be stable; on the contrary, when the temperature near the surface is high, it tends to be unstable; and when the temperature is moderate, the atmospheric stability is neutral.
When the atmosphere is in an unstable state, the momentum exchange between the wind speeds at different altitudes is very high, and the wind shear index is small. On the contrary, when the atmosphere is in a stable state, the momentum exchange between the wind speeds at different altitudes is weak, and the wind cuts. The index is large (the wind shear at this time is mainly affected by topographic factors).
Why is Europe raising the height of the tower?
First of all, the terrain is simpler. Although the European wind field has gradually evolved from a simple terrain to a medium-complex terrain in recent years, overall, the complexity of the domestic wind field is incomparable, so there is no significant reduction in wind shear in microscopic terrain. effect.
Second, the vegetation is relatively dense. On the one hand, dense vegetation can improve the surface roughness and increase the initial wind shear; on the other hand, the transpiration of vegetation can take away a lot of surface heat, making the atmosphere tend to be stable, while keeping the wind shear not weakened. .
Second, Europe has a higher latitude. The latitude of most parts of Europe is higher than that of Beijing. The surface temperature will not be too high for most of the year, and there will be extreme and extreme nights in the Nordic region, which will also make the surface temperature tend to be lower and the atmosphere stable. Degree tends to be stable, further maintaining wind shear.
Whether the high tower is suitable for domestic wind farms
For this problem, we use the exclusion method, the areas with complex micro-topography and the areas with severe desertification are not in conformity, thus basically eliminating the complex terrain areas of the northwest region and (represented by Guizhou Guizhou). The possibility of applying high towers in other areas exists, but specific analysis of the surrounding environment of the wind field is also required, and the wind measurement data is used for judgment.
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