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1. What is the coherent Doppler wind lidar?

Coherent doppler Lidar adopts doppler system and USES heterodyne detection technology to obtain information of doppler frequency shift. So, radial velocity distribution can be calculated by this process.


Coherent doppler Lidar working in the infrared band which is not visible to the human eye. It realizes the detection which is from ground to the low altitude of 4000 meters of the atmospheric wind field without blind area. It also has a very high temporal resolution (seconds), spatial resolution (30 meters) and accuracy (0.1 m/s) or less. This kind of Lidar can enhance the ability of low altitude detection. What’s more, parameters such as three-dimensional wind field within the boundary layer of the atmosphere can be obtained continuously. It's the only wind measurement that can be done in a few kilometers.  


2. What is the technical difference between Doppler wind Lidar and other wind Lidar?

Continuous-waveCwLidar 

When measuring wind speed, a continuous-wave Lidar focuses a laser beam at a continuous distance, and The pulsed Lidar has a fixed focus, which focuses the laser beam emitted by the device at a specified height. The measuring range of CW(Continuous wave) Lidar depends on the transmitting distance of continuous beam, so the maximum measuring range is 300m, which can only be used as vertical wind tower or nacelle type wind measurement, and cannot be used for 3D-scanning measurement. Continuous wave system can lead to distance miscalculation in a strong context. However, Pulsed Lidar has a continuous measurement range, depending on the duration of the pulse, and can be accurately measured at any distance, even at 5km.


Direct detection Lidar

Direct detection Lidar using the correlation of aerosol concentrations on different rays to measure wind speed across a cross-section.It requires a low-noise detection environment and is more sensitive than coherent Lidar in detecting light. Under a specific atmospheric conditions, the comparison of the two data shows that the detection time of direct detection Lidar is much longer than that of doppler Lidar. So far, its turbulence parameters have not been obtained.

Doppler Rayleigh Lidar

Rayleigh scattering occurs on small particles and molecules. Doppler shifts are measured by complex interferometers that require temperature management systems, photosensitive cameras, and complex image processing systems. It is also highly sensitive to light, the main advantage being that it does not rely on aerosol content to measure wind data at high altitudes.


3. The difference between Doppler Lidar and acoustic radar

Compared with acoustic radar, doppler Lidar is an independent wind measurement method. Acoustic radar is very sensitive to atmospheric conditions and is susceptible to rain, snow, noise, temperature, humidity and pressure conditions. Acoustic radar is also affected by terrain and environmental obstacles. Because the speed of sound is significantly slower than the speed of light, resolution of acoustic radar is low, and a data preprocessing system is needed to reduce the loss caused by a large amount of invalid data in a year. The Lidar provides high data availability and accuracy at high altitudes, as well as high resolution for different seasons.

4. The difference between Doppler Lidar and wind tower

Traditional wind tower can be replaced by Lidar. It has the advantages of small volume, low power, three-dimensional scanning, long detection range, unattended operation, and can be carried by vehicle and ship, reusable at any time, low cost and maintenance costs.

 

Compared with Lidar, the wind tower has poor mobility, high cost and maintenance cost, and there are also some problems such as accuracy of anemometer, wind field calibration, self-interference, complicated terrain engineering implementation and one-time use.

5. Features and advantages of 5-beam Doppler Lidar

The vertical doppler Lidar is used to measure the relevant data of horizontal wind speed, wind direction and vertical airflow velocity at a height of 40m to 240m on the ground. It is used to optimize the accuracy of direct vertical wind velocity measurement methods and tilt angles, and to measure vertical and horizontal turbulence intensity. Unlike other beams, the 5-beam scan is derived from vertical orientation and provides a direct measurement of the wind vector. The vertical doppler Lidar provides accurate measurements of vertical wind speeds at altitudes of 40 to 240m.

The vertical doppler Lidar is very important in detecting yaw, which directly affects the fan selection, layout and productivity. When vertical wind speed and horizontal wind speed are combined, they can be used to determine the atmospheric stability that plays an important role in wind field productivity.

6. Features and advantages of 3D-scanning Doppler Lidar

The three-dimensional scanning doppler Lidar can provide users with the wind speed and direction data starting from 80m in the vertical direction, with a resolution of 30m and a maximum height of 4000m. Script scaning mode can also be used to customize the scanning method, for a variety of test conditions for wind field scan records. The data product is highly readable and can be easily moved to other professional data processing software for in-depth processing.

7. Does the WINDPRINT Doppler Lidar need to be calibrated?

The wind print series doppler Lidar does not require calibration because it uses the continuous laser system to measure wind speed. However, the laser beam output needs to be adjusted by zeroing in the operation window. This setting has been adjusted before delivery, so it does not need to be reset again.

In terms of product quality testing, all ex-factory Lidar products strictly abide by the following quality testing stages:

1. Instrument certification phase, during which environmental tests (vibration, water resistance) and functional tests (quality, performance of all electronic and photoelectric devices and mechanical modules) are carried out on the products leaving the factory.

2. Compare the data after 48 hours and 96 hours in the measurement and inspection phase with the data of reference instruments; At this stage, the measurement performance of the production system is compared with that of the reference radar, whose measurement performance is certified annually by the relevant system.

3. 10 consecutive days of operation certification, 10 days of continuous start-up and operation through the instrument, to find out the early aging of the instrument itself or its parts to improve or replace.


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