Anemometer Heights and Configuration

The heights and configuration of anemometers – can have a significant impact on the quality of a wind resource measurement campaign. With an insufficient number or poor choice of heights, you might not get an accurate measurement of the wind shear and hub- height wind speed. With improper configuration and orientation of the mounting boom (a horizontal support which positions the anemometers away from the tower structure), tower influences might affect the accuracy of your wind measurements. This section provides guidance on wind industry best practice for determining sensor heights and configurations.

Anemometer and Vane Heights

The following guidelines govern the selection of anemometer and vane heights for most island sites:

  • Every tower should have at least two levels of anemometers, and preferably three.
  • One of the heights should be as close as possible to the expected turbine hub height.
  • The highest anemometers, if mounted on horizontal booms, should be at least the same vertical distance below the top of the tower as the horizontal booms are mounted off the side. This is intended to minimise effects of flow over the top (known as 3D flow effects).
  • The lowest anemometers should be mounted above trees, buildings, and other obstacles.
  • Within the above limitations, the heights should be spread as widely apart as possible to minimise the uncertainty in wind shear.
  • Anemometers should not be placed near obstructions (such as communications antennas), or just below guy wire rings.
  • Every tower should have at least two levels of wind vanes, and the vanes should be installed on booms that are 1-2 m below the nearest anemometer booms. If it is not practical to mount a vane on its own boom, then it should be placed on the anemometer boom about halfway between the anemometer and the tower face. This ensures that the vane disturbs the anemometer readings only when the anemometer is already in tower shadow, as discussed below.
Hub HeightTower Height (m)Example Anemometer Heights (m)Example Vane Heights (m)
303015, 2713, 15
373415, 3113, 28
554020, 30, 3728, 35
605025, 35, 4733, 35
806032, 47, 5745, 55

While every situation is different, Table 1 gives some examples of suitable tower and anemometer heights for different turbine hub heights. The selected hub heights for island environments are often lower than those for mainland projects. This is illustrated in the table 1, which provides example monitoring heights for given turbine hub heights. The direction vanes are suggested to be placed 2 m below the anemometers. (It is assumed that surrounding trees and buildings are less than 15 m in height.)

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