Wind Parameters To Evaluate For The Erection Of A Wind Park

By Author: Rayford Marks
Total Articles: 186
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Evaluation of wind potential of a location for a future investment in wind energy is comprised by several parameters, all of which have to be taken into account before constructing a wind farm. Terrain topography, proximity to electrical transmission lines, existing roads near the site, available land area and land use, environmental impact, cost of land and political boundaries have to be examined in a preliminary stage. As long as all of these parameters encourage the implementation of a wind park, all of the basic measurement factors should be evaluated.
The results of the measurements of the following parameters are crucial in order to take a final decision to implement a wind farm:
Wind speed: It is the most important factor for evaluating a site’s wind energy potential. The common practice is to afford multiple measurements at several turbine hub heights, in order to determine the wind shear characteristics. Wind speed variation depends of the height of the measurement, so that many types of wind masts are used in order to achieve a real simulation of the output of a potential wind park. Actual hub heights ...
... are usually in the range of 50 to 80 m. Additional alternative heights are simulated in wind simulation programs to make clear the wind speed variation above the terrain.

Cup or propeller anemometers are used in order to measure the wind speed in several wind heights. At least one cup always faces the oncoming wind. The cups convert the wind force to rotational torque, while a transducer converts the rotational movement into an electrical signal. The signal is then sent to a data logger through appropriate cabling. Common data loggers use slope and offset parameters in order to finally calculate the wind speed.
In every wind site evaluation, it is recommended to use redundant anemometers at given height in order to minimize the risk of data loss deriving from a fail in the primary wind sensor. Redundant sensors should be situated so as not interfering with the wind measured by the primary sensor. The measurements from the redundant sensor should be compared with the ones of the primary to determine the accuracy of the primary sensor and possible failures of equipment.
Wind direction: Wind direction frequency is vital for identifying preferred terrain shapes and orientations and for optimizing the layout of wind turbines within a wind park.

Wind vanes are the core element to define the prevailing wind direction. The common types use a potentiometer type transducer that produces an electrical signal in relation to the position of the vane. The electrical signal is transmitted to the data logger via appropriate cabling and relates the vane’s position to a known reference point. It is obvious that the determination of a reference point position –true north, in the most cases- is crucial for the alignment of the wind vane to a specified reference value.

Air Temperature: It is an important factor in determining wind parks environmental conditions and is measured either near ground level or near hub height. It is also used to examine air density, which estimates the wind power density and a turbine’s power output. The air temperature is measured via ambient air temperature sensors.
Solar radiation: Solar radiation, measured in relation to the wind speed could be a significant indicator of the atmospheric stability and could be used in many wind flow simulation analysis and modeling.
Solar radiation is measured via pyranometers. Pyranometers measure direct and diffuse sky radiation, combining both parameters in order to measure the global radiation of a specific wind park area. They should be placed in way that no obstacle will affect their operation by adding shading factors.

Vertical wind speed: It provides details about the turbulence of a site and can predict potential wind turbine loads. The measurement of the vertical wind speed is conducted via a anemometer, located near the upper primary wind speed anemometer.

Barometric pressure: A barometer is used to determine barometric pressure. Barometers use a piezoelectric transducer to provide a signal to the data logger.
All of the above parameters will define a site’s capability of installing a wind park and implementing a worthwhile wind energy investment. A variety of different software tools is used to simulate all of these measurements and conduct a documented feasibility study of the wind project.

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