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: AnÂ effective selection of micro location for measurement (reference point) InstallationÂ of the measuring station with the appropriate measuring equipment MaintenanceÂ of measuring stations TheÂ 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:
- AnÂ effective selection of micro location for measurement (reference point)
- InstallationÂ of the measuring station with the appropriate measuring equipment
- MaintenanceÂ of measuring stations
- TheÂ analysis of data on the wind characteristics.
In the micro location selection it isÂ necessary to choose a location without obstacles (houses, trees, rocks) thatÂ could create leeward and slow down or obstruct the movement of wind. Accessibility,Â location near power grid and out of protected natural areas are preferred. HighÂ altitude locations, because of low air temperatures, can also cause problemsÂ during the wind measuring process.
AÂ typical measuring system consists of:
- WindÂ vanes
- SteelÂ cabinet
- DataÂ logger
- GSM/GPRSÂ communication system
- BarometricÂ pressure sensor
- Humidity-temperatureÂ sensor
- SolarÂ panel, fig. 2.
Figure 2. Components of a measuring system
Measuring equipment is located on the measuringÂ tower, which can be classified according to height and design. According to theÂ design, there are lattice steel poles and pipe poles, fig. 3. According to the height,Â there are:
- upÂ to 40 [m]
- 50-60Â [m], which is commonly applied
- 70-100Â [m].
Figure 3. Pipe pole and lattice steel pole
Anemometers measure the horizontal wind speedÂ (velocity), a crucial parameter for any wind site assessment, fig. 4a. EachÂ anemometer should be individually calibrated and given a certified calibrationÂ report, according to international standards. The number of anemometers appliedÂ at one mast can vary from a minimum of 2 sensors up to 6 sensors.
WindÂ vanes determine windÂ direction, fig. 4b. A detailed understanding of the wind direction on a siteÂ enables the best possible positioning of wind turbines. To avoid obstruction,Â wind vanes should be located at the top of the tower and at least 1,5 [m] belowÂ the top anemometer.
Figure 4. (a) Anemometer, (b) Wind vane,
(c) Humidity-temperature sensor, (d) Barometric pressure sensor
TheÂ cabinet will protectÂ your data logger against weather and condensation damage, theft and vandalism.Â Optional components, such as a GSM/GPRS communication module, barometricÂ pressure sensor, battery and surge protection, can also be accommodated withinÂ the cabinet. Cabinets are typically mounted at a height of approximately 6 mÂ and padlocked for protection from vandalism and theft.
Figure 5. (a) Data logger, (b) GSM/GPRS
DataÂ loggers offer a wideÂ range of possibilities and are the core of every wind measuring station, fig.Â 5a. They are robust, reliable, low in energy consumption, and have aÂ nonvolatile memory of 4 MB with a capacity for 2,000,000 recorded values, that enablesÂ automated data acquisition and storage during several months or even years.Â Data are stored in standard text files which substantially facilitates theÂ analysis using standardized programming tools. The self-contained measuringÂ system runs even in extreme weather conditions and in remote areas, beingÂ reliably supplied with power by a 10, 20 or 50 W solar panel.
CommunicationÂ with data logger can be made from a remote location with PC/Laptop in threeÂ ways:
- GSM/GPRSÂ System (email or text messages)
- Satellite,Â if no GSM network is available
- DirectÂ interface at measuring station.
- Measuring data can be accessed at anyÂ time, e.g. daily, several times a week, or monthly.
ThermalÂ sensors measure the airÂ temperature, while humidity sensors measure the air humidity; they are oftenÂ applied in combination to reduce costs, fig. 4c. The calculation of airÂ humidity does not directly influence a wind site assessment, but knowing thisÂ parameter helps assessing the potential for ice build-up at the measuringÂ location. The temperature sensor should always be mounted at a height of at leastÂ 10m to ensure sufficient distance from heat radiating from the earth.
BarometricÂ pressure sensorsÂ (barometers) measure the air pressure, fig. 4d. Air pressure and airÂ temperature should be evaluated for an accurate wind site assessment, however,Â because this data could be obtained from nearby heather stations, air pressureÂ sensors are not considered an essential part of a measuring system.
Author: Mirnesa ÄŒajiÄ‡ / Energis