Wind lidar evaluation at the Danish wind test site in Høvsøre

Smith, Dale; Harris, Michael; Coffey, Adrian S.; Mikkelsen, Torben; Jørgensen, Hans Ejsing; Mann, Jakob; Danielian, Régis

doi:10.1002/we.193

Cited by 164 publications

(124 citation statements)

References 2 publications

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“…3 The theoretical spatial and temporal resolution of this system have been thoroughly studied 4,5 and its ability to accurately measure the wind speed has been verified through inter-comparison with data acquired by calibrated cup anemometers. 6 The design of the system offers the possibility of operating in two different modes; a staring mode (laser beam is emitted in a straight line parallel with the orientation of the system) and a conical scanning mode (the laser beam is deflected by a rotating optical wedge prism).…”

Section: Methodsmentioning

confidence: 99%

Direct measurement of the spectral transfer function of a laser based anemometer

Angelou

Mann

Sjöholm

et al. 2012

Review of Scientific Instruments

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The effect of a continuous-wave (cw) laser based anemometer's probe volume on the measurement of wind turbulence is studied in this paper. Wind speed time series acquired by both a remote sensing cw laser anemometer, whose line-of-sight was aligned with the wind direction, and by a reference sensor (sonic anemometer) located in the same direction, were used. The spectral transfer function, which describes the attenuation of the power spectral density of the wind speed turbulence, was calculated and found to be in good agreement with the theoretical exponential function, which is based on the properties of the probe volume of a focused Gaussian laser beam. Parameters such as fluctuations of the wind direction, as well as the overestimation of the laser Doppler spectrum threshold, were found to affect the calculation of the spectral transfer function by introducing high frequency noise.

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Section: Methodsmentioning

confidence: 99%

Direct measurement of the spectral transfer function of a laser based anemometer

Angelou

Mann

Sjöholm

et al. 2012

Review of Scientific Instruments

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“…The lidar is a continuous-wave, coherent Doppler lidar first described in Karlsson et al (2000). Its two main components are a modified directional sensing version of a commercial ZephIR Z150 wind lidar (Kindler et al 2007;Smith et al 2006) and a fast-scanning scanner head (Mikkelsen et al 2011). The scanner head consists of two independently controlled top-mounted rotating prisms, each with a 30 • deflection angle that steers the lidar's line-of-sight within a scanning cone with a full opening angle of 120 • .…”

Section: The Experimentsmentioning

confidence: 99%

Variations of the Wake Height over the Bolund Escarpment Measured by a Scanning Lidar

Lange

Mann

Angelou

et al. 2015

Boundary-Layer Meteorol

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The wake zone behind the escarpment of the Bolund peninsula in the Roskilde Fjord, Denmark, has been investigated with the help of a continuous-wave Doppler lidar. The instrument measures the line-of-sight wind speed 390 times per second in highly resolved 7-m tall profiles by rapidly changing the focus distance and beam direction. The profiles reveal the detailed and rapidly changing structure of the wake induced by the Bolund escarpment. The wake grows with distance from the escarpment, with the wake height depending strongly on the wind direction, such that the minimum height appears when the flow is perpendicular to the escarpment. The wake increases by 10-70 % when the wind direction deviates ±15 • from perpendicular depending on the distance to the edge and to a lesser degree on the method by which the wake height is determined. This finding is supported by a comparison with in situ measurements acquired on the Bolund peninsula.

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“…Smith et al, 2006). In comparison to sonic anemometers, the sampling volume and averaging time of DLs is large (∼ 20 m and 1 s respectively); therefore DLs are unable to resolve smaller scales of turbulence.…”

Section: Introductionmentioning

confidence: 99%

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

et al. 2016

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Abstract. Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w 2 ) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w 2 , reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w 2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w 2 . Through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w 2 . After the autocovariance technique is applied, values of w 2 from the Doppler lidars are generally in close agreement (R 2 ≈ 0.95 − 0.98) with those calculated from sonic anemometer measurements.

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Wind lidar evaluation at the Danish wind test site in Høvsøre

Cited by 164 publications

References 2 publications

Direct measurement of the spectral transfer function of a laser based anemometer

Direct measurement of the spectral transfer function of a laser based anemometer

Variations of the Wake Height over the Bolund Escarpment Measured by a Scanning Lidar

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

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