How to determine the wind speed and direction of a wind turbine?
The power generation efficiency and operational stability of wind turbines are highly dependent on accurate measurements of wind speed and direction. The wind speed determines the energy input scale, and the wind direction affects the angle of the blades to the wind, both of which together determine the output power and load distribution of the unit. This article will briefly introduce the core measurement methods for wind speed and direction, covering mechanical, ultrasonic, and high-precision sensor technologies, providing technical references for wind farm design and operation.
1、 Wind speed measurement method
1. Mechanical anemometer
Principle: By utilizing the linear relationship between the rotational speed of the wind cup or blade and the wind speed, mechanical motion is converted into electrical signals through a speed sensor.
Three cup anemometer: Three wind cups are installed at equal angles on a vertical axis, driven by wind to rotate, and the speed is proportional to the wind speed. Its starting wind speed is low (0.5-1m/s), suitable for harsh environments such as dust, rain, and snow, but there is a lag, making it more suitable for measuring average wind speed. For example, a 100m high wind tower usually installs three cup anemometers at heights of 30m, 50m, 70m, etc., to synchronously record multi-layer wind speed data.
Propeller anemometer: Multiple blades rotate around a horizontal axis, and the speed is proportional to the wind speed. It is usually linked with a wind vane to ensure that the blades are always aligned with the wind direction. Its structure is compact, but the propeller blades are susceptible to wind and sand wear and require regular maintenance.
2. Ultrasonic anemometer
Principle: Based on the ultrasonic propagation time difference method, the wind speed is calculated by measuring the difference in the propagation speed of ultrasonic waves in the forward/reverse wind direction.
Four probe ultrasonic anemometer: Four probes are paired to form two sets of wind measurement units. Each set of probes calculates the relative wind speed by measuring the time difference of ultrasonic propagation in the air; By combining two sets of data, a three-dimensional wind speed vector can be obtained. It has no mechanical wear and has a fast response time (<1 second), but the cost is high, and rainy or snowy weather may affect measurement accuracy. For example, large wind turbines provide real-time high-precision wind speed data through ultrasonic anemometers, supporting pitch control and power optimization.
3. High precision anemometer
Principle: Using ultrasound without alignment technology, real-time measurement of wind speed and direction data is achieved, eliminating the directional dependence of traditional mechanical sensors.
Ultrasonic fusion sensor: integrates multiple sets of ultrasonic probes, eliminates environmental interference (such as temperature and humidity) through algorithms, and outputs wind speed data with an accuracy of ± 0.1m/s. It is easy to install and does not require regular calibration, but the cost is 30% -50% higher than traditional sensors. For example, a certain wind farm analyzed the distribution of wind resources through high-precision anemometers and optimized the layout of units, resulting in an 8% increase in annual power generation.
2、 Wind direction determination method
1. Mechanical wind vane
Principle: Using the asymmetrical structure of the wind vane at the beginning and end, it rotates around the vertical axis under the action of wind force, pointing towards the direction of the wind.
Single wing wind vane: composed of a tail wing, a pointing rod, a balance weight, and a rotating main shaft, with the center of gravity located at the axis of the support shaft, and can freely swing. Its installation needs to be at a 90 ° angle to the prevailing wind direction and corrected for direction according to the local magnetic declination. The wind direction is represented using the 16 azimuth method (such as NNE, ENE) or the angle method (rotating clockwise with due north as the reference). For example, a wind farm in a mountainous area installed a streamlined wind vane on the top floor of the wind measurement tower, combined with a three cup anemometer, to complete wind resource data collection.
2. Ultrasonic anemometer
Principle: Calculate the wind direction angle through the propagation time difference data of multiple sets of ultrasonic probes.
Three arm ultrasonic anemometer: Three sensor arms are installed vertically and horizontally, and the wind direction vector is calculated by measuring the propagation time difference of sound waves between the arm ends. It has no mechanical wear, fast response speed, but high cost, suitable for scenarios with strict precision requirements.
3、 Basis for selecting measurement methods
Environmental adaptability: Ultrasonic or high-precision sensors are preferred in areas with dust, rain, and snow to avoid wear and icing issues with mechanical sensors.
Cost constraint: Mechanical sensors are optional for small and medium-sized wind farms, while ultrasonic or high-precision sensors are recommended for large or offshore wind farms to improve data reliability.
Accuracy requirement: High precision sensors (error<± 0.2m/s) are required for wind resource assessment, while medium precision sensors (error<± 0.5m/s) can be used for unit control.
4、 Conclusion
Accurate measurement of wind speed and direction is the foundation for efficient operation of wind turbines. Mechanical sensors have low cost but frequent maintenance, ultrasonic sensors have strong adaptability but high price, and high-precision sensors balance accuracy and convenience. In practical applications, it is necessary to comprehensively select based on environmental conditions, cost budget, and accuracy requirements to achieve the optimization of wind farm power generation efficiency and equipment life.
