What is the power generation efficiency of wind turbines in areas with low or unstable wind speeds?
This is a very good question and one of the core challenges faced by the wind power industry in expanding its market. Simply put, in areas with low or unstable wind speeds, the power generation efficiency of traditional wind turbines does indeed significantly decrease, but through a series of targeted technological innovations and overall solutions, economically feasible development can already be achieved.
Below are several detailed explanations:
1、 Challenge: Why does efficiency decrease?
The cubic relationship between wind speed and power: The output power of a wind turbine is directly proportional to the cube of wind speed. This means that if the wind speed is reduced by half, theoretically the power generation will be reduced to 1/8 of the original. Therefore, low wind speeds are destructive to power generation.
Cut in wind speed limit: Traditional wind turbines have a "cut in wind speed" (usually 3-4 meters/second), below which the turbine cannot start generating electricity.
Unstable wind speed: Frequent fluctuations in wind speed can lead to frequent start stop, yaw, and pitch changes of the wind turbine, which not only increases mechanical losses but also cannot operate stably on the optimal power curve, resulting in low overall capacity utilization.
High turbulence intensity: Unstable winds often accompany high turbulence, increasing the load on the fan. To ensure safety, sometimes it is necessary to reduce power operation or shut down.
2、 Solution: How to improve power generation efficiency in low wind speed/unstable areas?
In response to these challenges, modern wind power technology, especially low-speed wind turbines, has developed mature solutions:
1. Increase the sweeping area:
Extending the blades: This is the most direct and effective method. Longer blades can capture more wind energy and generate enough torque to drive the generator even at low wind speeds. The impeller diameter of modern low-speed fans is getting larger and larger.
Optimize aerodynamic design: adopt more advanced airfoil and blade shapes to enhance wind energy capture efficiency.
2. Reduce the cut in wind speed and rated wind speed:
By improving the control strategy and generator design, the cut in wind speed can be reduced to 2-2.5 meters per second or even lower.
Reduce the 'rated wind speed' (the wind speed that reaches full power) to enable the wind turbine to reach rated power at lower wind speeds.
3. Raise the height of the tower:
The wind speed increases with height (wind shear effect). By using a higher tower, the hub can be placed at a higher and more stable height with higher wind speeds, significantly increasing power generation.
4. Advanced intelligent control technology:
Intelligent pitch and torque control: Accurately adjust blade angle and generator torque based on instantaneous wind speed, maximize energy capture, and reduce the load caused by unstable wind.
Predictive control: combining with LiDAR to measure the wind speed prospectively, adjust the fan status in advance, smooth the power output and reduce mechanical shock.
Collaborative control of wind farms: Optimize the operation strategy of wind turbines throughout the entire wind farm, reduce the impact of wake, and increase the total power generation of the entire site.
5. Model design suitable for specific wind conditions:
Design enhanced wind turbines for wind fields with high turbulence and complex terrain (such as mountainous areas) that can withstand more complex loads and maintain efficient operation.
3、 Comprehensive effect and measurement indicators
After the above optimization, the annual equivalent full operating hours of modern low-speed wind turbines can reach over 2000 hours in areas with lower wind speeds (such as an average annual wind speed of 5.5-6.5 meters/second), which has economic development value. In traditional high wind speed areas (with an average annual wind speed of over 8 meters per second), this number may be between 3000-4000 hours.
Key measurement indicator - Levelized Cost of Electricity (LCOE):
The ultimate evaluation criterion is not simply 'efficiency', but the cost of power generation. Through the above technology, although the cost of a single unit (especially the blades and tower) may increase, it significantly increases the power generation in low wind speed areas, thereby reducing the levelized electricity cost per kilowatt hour, making the overall project have a return on investment.
4、 Future Trends
Bigger and customized: Wind turbines continue to develop towards larger blade diameters and higher tower structures, and provide highly customized solutions for different wind resource areas.
Combined with energy storage: For areas with unstable wind speeds, "wind power+energy storage" (such as battery energy storage) will become a standard configuration to smooth output, participate in grid frequency regulation, improve power quality, and achieve more friendly grid connection.
Distributed and community wind power: In areas with low wind speeds but close to electricity loads (such as the central and southeastern regions of China), installing a single or several low wind speed wind turbines can directly supply power to the park or community, reducing transmission losses, and its economic benefits are becoming apparent.
summary
In areas with low or unstable wind speeds, the power generation efficiency of traditional standard wind turbines is indeed not ideal. However, specially designed modern low wind speed wind turbines have been able to efficiently capture wind energy through a series of technologies such as aerodynamic optimization, intelligent control, and increasing size and height, transforming wind resources that were previously not valuable for development into economically feasible electricity. Therefore, the "power generation efficiency" in these regions has shifted from a technical challenge to an optimization issue through comprehensive technical solutions, and has become an important growth market for global wind power development.
