Wind Measurement

Wind Measurement

Wind measurements are taken as a part of evaluation of possibilities for building of wind power plant on a given location, in order to decrease risks. It is of great importance: An effective selection of micro location for measurement (reference point) Installation of the measuring station with the appropriate measuring equipment Maintenance of measuring stations The analysis of data

Wind measurements are taken as a part of evaluation of possibilities for building of wind power plant on a given location, in order to decrease risks.

It is of great importance:

  • An effective selection of micro location for measurement (reference point)
  • Installation of the measuring station with the appropriate measuring equipment
  • Maintenance of measuring stations
  • The analysis of data on the wind characteristics.

In the micro location selection it is necessary to choose a location without obstacles (houses, trees, rocks) that could create leeward and slow down or obstruct the movement of wind. Accessibility, location near power grid and out of protected natural areas are preferred. High altitude locations, because of low air temperatures, can also cause problems during the wind measuring process.

A typical measuring system consists of:

  • Anemometers
  • Wind vanes
  • Steel cabinet
  • Data logger
  • GSM/GPRS communication system
  • Barometric pressure sensor
  • Humidity-temperature sensor
  • Solar panel, fig. 2.

Figure 2. Components of a measuring system

Measuring equipment is located on the measuring tower, which can be classified according to height and design. According to the design, there are lattice steel poles and pipe poles, fig. 3. According to the height, there are:

  • up to 40 [m]
  • 50-60 [m], which is commonly applied
  • 70-100 [m].

 

Figure 3. Pipe pole and lattice steel pole

Anemometers measure the horizontal wind speed (velocity), a crucial parameter for any wind site assessment, fig. 4a. Each anemometer should be individually calibrated and given a certified calibration report, according to international standards. The number of anemometers applied at one mast can vary from a minimum of 2 sensors up to 6 sensors.

Wind vanes determine wind direction, fig. 4b. A detailed understanding of the wind direction on a site enables the best possible positioning of wind turbines. To avoid obstruction, wind vanes should be located at the top of the tower and at least 1,5 [m] below the top anemometer.

 

Figure 4. (a) Anemometer, (b) Wind vane,
(c) Humidity-temperature sensor, (d) Barometric pressure sensor

The cabinet will protect your data logger against weather and condensation damage, theft and vandalism. Optional components, such as a GSM/GPRS communication module, barometric pressure sensor, battery and surge protection, can also be accommodated within the cabinet. Cabinets are typically mounted at a height of approximately 6 m and padlocked for protection from vandalism and theft.

Figure 5. (a) Data logger, (b) GSM/GPRS
communication system

Data loggers offer a wide range of possibilities and are the core of every wind measuring station, fig. 5a. They are robust, reliable, low in energy consumption, and have a nonvolatile memory of 4 MB with a capacity for 2,000,000 recorded values, that enables automated data acquisition and storage during several months or even years. Data are stored in standard text files which substantially facilitates the analysis using standardized programming tools. The self-contained measuring system runs even in extreme weather conditions and in remote areas, being reliably supplied with power by a 10, 20 or 50 W solar panel.

Communication with data logger can be made from a remote location with PC/Laptop in three ways:

  • GSM/GPRS System (email or text messages)
  • Satellite, if no GSM network is available
  • Direct interface at measuring station.
  • Measuring data can be accessed at any time, e.g. daily, several times a week, or monthly.

Thermal sensors measure the air temperature, while humidity sensors measure the air humidity; they are often applied in combination to reduce costs, fig. 4c. The calculation of air humidity does not directly influence a wind site assessment, but knowing this parameter helps assessing the potential for ice build-up at the measuring location. The temperature sensor should always be mounted at a height of at least 10m to ensure sufficient distance from heat radiating from the earth.

Barometric pressure sensors (barometers) measure the air pressure, fig. 4d. Air pressure and air temperature should be evaluated for an accurate wind site assessment, however, because this data could be obtained from nearby heather stations, air pressure sensors are not considered an essential part of a measuring system.

Author: Mirnesa Čajić / Energis

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