Nguyen Dinh Ngoc Hai (Clint, Mr), Eng
Electrical Engineer - VATEC
May 31, 2023
In the research and development (R&D) of wind power projects, the wind potential assessment plays a critical role in determining the feasibility of the investment projects by analyzing wind data at the project location.
The wind measurement is required to be implemented prior to the development and approval of the feasibility study report (FSR) for a wind power project, with a minimum measurement period of 12 consecutive months at positions that are representative of the project survey area. The legislation of wind measurement position is specified in Article 5 of Circular No. 02/2019/TT-BCT dated January 15, 2019, by the Ministry of Industry and Trade (MoIT). The selection of wind measurement methods, equipment, and locations must comply with the laws of Vietnam as well as relevant IEC standards.
The most frequently utilized wind data recording technologies worldwide include the method using Met mast, the method using SODAR technology, and method of using LIDAR technology.
I. Method of using Met mast
This is the traditional wind survey method and is widely used due to its high accuracy. Sensors are mounted on the Met mast to collect data such as wind speed, wind direction, temperature, humidity, pressure, solar radiation, etc.
Up to now, the wind survey for wind power plants is based on the Met mast as the standard. The height of the current Met mast is commonly ≥ 100m, which corresponds to the height of the wind turbine intended to be used for the project and must be placed in a position where the airflow through the survey site is not obstructed by obstacles or terrain features that distort airflow. The Met mast is mounted on the ground, all sensors and related equipment are thoroughly tested before installation.
However, to deploy and erect the Met mast, a certain amount of space will be needed to arrange the main foundation and anchor foundation positions, so it will be relatively difficult to carry out wind surveys in rugged mountainous areas or offshore waters,...
II. Method of using SODAR technology
Working principle of SODAR technology:
SODAR (Sound Detection And Ranging) is a meteorological instrument used as a wind - measuring device based on the scattering of sound waves due to atmospheric turbulence. SODAR consists of 03 or more beams at different angles to the vertical allowing a three-dimensional vertical wind cross-section to be obtained. Both the magnitude and Doppler shift of the echo beams can be used to determine wind speed and direction as well as the turbulent structure of the lower atmosphere, up to about 2 km (depending on system output power, audio frequency, atmospheric stability, turbulence, and existing noise environment).
Working principle of SODAR technology
The most typical topology is the “mono-static” SODAR, where the transmitter and receiver are both housed in a relatively compact unit. In addition, most SODAR systems currently on the market are multi-axis Doppler SODAR systems, which means they are capable of detecting signal frequency changes in 03 or more directions and using that data to obtain profiles of wind speed and wind direction. The most basic component of a Doppler SODAR system is the antenna, and this is the part where commercial SODAR systems from different manufacturers vary the most.
Wind measuring device with SODAR technology of AQ System
AQ500 SoDAR used in wind energy development and wind condition monitoring.
Advantage:
- Compact, easy to deploy in any terrain, with high safety, so it will also avoid many problems of legal liability.
- Available in the market.
- High mobility.
- Low installation and operating costs, no regular maintenance required.
- Works even under extreme weather, unaffected by fog.
- Range up to 2km, where a good resolution range is 10-100m.
III. Method of using LiDAR technology
Typical LiDAR station
Working principle of LiDAR technology:
LiDAR (Light Detection and Ranging) is an optical remote sensing technology that does this by emitting laser beams into the air, which collide with particles and aerosols, and then reflect back, by capturing and analyzing reflected beams, the device can calculate the parameters of wind speed and wind direction at different heights. This technology can be deployed on land, at sea and in the air (installed on wind turbines), depending on different applications.
Source: Leosphere
LiDAR can use radiation in the ultraviolet, visible and infrared regions of the electromagnetic spectrum, and each will have different interactions with the atmosphere. Thus, the selection of different scattering processes allows for inferring a wide range of airflow parameters, such as air and wind composition. The small divergence of the laser beam results in a very low beam width, allowing for high resolution even at altitudes of hundreds of meters.
Classification of LiDAR systems:
- Pulsed LiDAR: A laser beam of 1.54 μm wavelength takes measurements of the wind speed in a beamwise direction. To obtain the three-dimensional wind vector, the beam is inclined 30 degrees from the vertical direction and measurements are taken under 04 different azimuth angles.
Source: Leosphere
- Continuous Wave LiDAR (CW): another approach is FMCW LiDAR (or Frequency Modulated Continuous Wave LiDAR), instead of sending pulses over time, FMCW LiDAR sends out a constant stream of laser light (continuous wave) and modifies its frequency at regular intervals (frequency modulated). This technology enables both the determining the location of objects and the precisely measuring their axial relative speed using the Doppler effect.
Working principle of FMCW LiDAR
Advantage:
- Technology has appeared for a long time, reliable data collection.
- Has been widely deployed worldwide.
- Most of the floating manufacturers (Lidar Buoy) in the world use Lidar technology.
- Less space required than traditional Met mast; high mobility.
- Works even under inclement weather.
- Low installation and operating costs, do not require frequent maintenance.
- Can be measured at altitudes up to 300m.
- Compact size, easy to deploy and high security will also avoid many problems of liability.
Conclusion: Renewable energy in general and wind energy in particular are being considered as an inevitable solution and trend of the current energy industry in Vietnam as well as in the world. As fossil fuel sources such as coal and oil become increasingly depleted, causing serious environmental pollution, forcing countries around the world to accelerate the restructuring of the energy industry towards clean and sustainability, opening up great opportunities for the wind power industry to develop. Along with the continuous progress of science and technology, wind measurement technologies are increasingly developed and applied very effectively in the field of survey, monitoring and assessment of wind potential, to serve the development and investment of wind power projects in the future.
VATEC ENERGY ENGINEERING CONSULTING COMPANY is proud to be the leading unit in the field of wind survey in Vietnam, with more than 120 Met masts with height up to 140m and Lidar stations that have been installed for many wind power projects across the country.
References:
[1] Steven Lang, Eamon McKeogh, “LIDAR and SODAR Measurements of Wind Speed and Direction in Upland Terrain for Wind Energy Purposes”, Remote Sensing, 25 August 2011.
[2] Leosphere, “WINDCUBE USER GUIDE”, August 2019.
[3] Outsight, Dec 22, 2022, “How does Lidar work?”. Online available: https://www2.outsight.ai/insights/how-does-lidar-work
[4] https://vatec.vn/
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