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in the future. The working principle of the pulsed lidar system is described by Cariou and Boquet (2010). In order to use the standard Windcube for a nacelle-based measurement campaign several adaptations had to be made. The internal deflection mirror with 45 ◦ was removed and the optical axis from the Windcube to the scanner had to be ensured. The software had to be adapted insubstantially: • The Windcube has to be synchronized with the controller unit of the scanner so that the movement of the mirror and the measuring of the laser is synchronized. • The ten arbitrary heights from the ground-based system have been reduced to five arbitrary focus distances in front of the lidar system for the nacelle-based version. With a fixed focus length the scanning figure is described on a cubic surface (Figure 100(left)). It is possible to vary the focus length at each measurement point so that the focus plane is vertical which means a “slicing” of the wind field (Figure 100(right)). • The maximum number of measurement points of a scanning pattern is limited to 49. • The scanning modes are either “Start-Stop” or “Bang-Bang”. At the Start-Stop mode the mirror stops at the measurement point, the measurements involve shooting and averaging the spectra to the line-of-sight wind speed. Afterwards the mirror moves to the next measurement point. The employment of this mode allows to average a higher number of shots which are taken into account to calculate the line-of-sight velocity. The result is a good carrier to noise ratio (CNR) and a higher maximum measurement range. In the ”Bang-Bang”mode the mirror always moves, but decelerates shortly before reaching the measurement point and accelerates after passing the measurement point. In this mode the number of shots to be averaged has to be lowered. This means that the carrier to noise ration (CNR) is worse compared to the “Start-Stop” mode, but the movement is much faster and therefore the temporal resolution is better. Figure 100: Measuring on a cubic shape with a fixed focus length (left) and using variable focus length to “cut” the wind field vertically (right). 8.3.2 Scanner Ascannerdevicewithtwodegreesoffreedomhasbeen developedforthenacellemeasurement campaigns in order to be able to position the laser beam of a standard Windcube lidar system in any direction. The requirements for the development of the scanner system were: • Angle of projection: 53.2 ◦ . In a distance of 1D the measurement area should cover the whole swept rotor disc. 158 DTU Wind Energy-E-Report-0029(EN)
• Flexibletrajectories.Dependingonthedifferentapplications,variousscanpatternsshould be possible. • Highspeedandacceleration.Togetagoodtemporalandspatialresolution,itisnecessary that the measurements are fast and have a high repeatable accuracy. The scanner system developed is based on a single mirror which is moved by a mechanical system with two independent rotation stages (Figure 101(left)). The mirror has a mechanical angle range of ±15 ◦ in the pan and tilt direction (horizontal and vertical). The motors are controlled by an external unit which is synchronized with the Windcube. The two mentioned rotation stages and the supporting structure with the transmission rods form the scanning system which was mounted in a modular way in order to simplify attachment to the standard Windcube ( Figure 101(right)). The scanner was integrated in a second housing so that an adaptation to the original Windcube was easy and water tightness as well as structural stability could be assured. Thus, the orientation of the laser beam and the alignment of the optical axis could be guaranteed. The mirror which deflects the beam in the original Windcube system is removed so that the laser beam goes through both casings and is deviated by the 2-DOF mirror (Figure 102(left)). Figure 101: Scanner assembly (left) and integration to a second housing (right). Figure 102: Way of the laser beam and the optical axis (left) and the assembled system modules (right). 8.4 Scan pattern Measuring the wind field from the nacelle of a turbine makes it possible to gather wind field information (wind speed, wind direction, shear) in a high temporal and spatial resolution. To scan a wind field in any vertical and horizontal direction, the laser beam runs along a predetermined path and executes the measurement at predefined points. For designing a scan pattern the wind turbine simulator WiTLiS was developed (Schlipf et al., 2009). This software supports the development of trajectories considering the motor speed and acceleration. DTU Wind Energy-E-Report-0029(EN) 159
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Remote Sensing for Wind Energy DTU
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Author: Alfredo Peña, Charlotte B.
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4 Introduction to continuous-wave D
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8 Nacelle-based lidar systems 157 8
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12 Complex terrain and lidars 231 1
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1 Remote sensing of wind Torben Mik
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Figure 2: Calibration, laboratory w
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Figure 3: Example of scatter plots
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1.2.3 Summary of sodars Most of tod
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1.3.3 Wind lidars Measuring wind wi
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Figure 6: CW wind lidars (ZephIRs)
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Further developments Furthermore, n
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2 The atmospheric boundary layer S
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Figure 9: Large spatial scale varia
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Du3 Dt Du1 Dt Du2 Dt The three mome
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Figure 13: Consensus relations betw
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ψ z L ∼ − 5 L . For unstable c
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Figure 15: Behavior of the turbulen
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Figure 17: Newly developed models t
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The value of q0 at the surface is d
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the spray is the source of icing on
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u∗2 u∗1 u1(h) = u∗1 k ln h
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Figure 26:Land-seabreeze system,whe
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Figure28:Three dimensionalpicture o
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sufficient information. Finally, we
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Mann, J. (1998) Wind field simulati
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(2010) and comparison under differe
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To get the velocity field from the
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τ(k) [Arbitrary units] 10 3 10 2 1
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(Koopmans, 1974; Bendat and Piersol
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anemometer was installed at each en
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and fSw(f) u 2 ∗ = 1.05n 1+5.3n 5
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and n = 0.468. This spectrum implie
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to be calculated. We do that on a m
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Notation A Charnock constant neutra
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Maxey M. R. (1982) Distortion of tu
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4.2 Basic principles of lidar opera
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4.2.5 Wind profiling in conical sca
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4.3.1 Behaviour of scattering parti
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the beam radius at the output lens.
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from which the value of VLOS is der
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the atmosphere. The SNR 4 for a win
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individual line-of-sight wind speed
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A general approach to mitigating th
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from ±VH sinδ (if the tilt is tow
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as a down draught (of the same abso
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Table 7: Combined results from 28 Z
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in Eastern Jutland between January
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Figure 56: Normalized power curves
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the concept. Developments include i
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References x horizontal position in
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Wagner R., Mikkelsen T., and Courtn
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5.2 End-to-end description of pulse
Page 107 and 108: Scanner Coherent lidar measure the
Page 109 and 110: Figure 62: Radial wind velocity ret
Page 111 and 112: transform in order to use data obta
Page 113 and 114: This wavelength is also the most fa
Page 115 and 116: Eq.(132)isadaptedforcollimatedsyste
Page 117 and 118: 5.3.6 Existing systems and actual p
Page 119 and 120: (Gottshall et al., 2010; Albers et
Page 121 and 122: References Albers A., Janssen A. W.
Page 123 and 124: derived from fluctuations of the wi
Page 125 and 126: Acoustic received echo (ARE) method
Page 127 and 128: Figure 71: Sample time-height cross
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Page 131 and 132: Figure73:Bragg-relatedacoustic(belo
Page 133 and 134: stability (inversion strength) can
Page 135 and 136: Figure 76: Combined soundingwith a
Page 137 and 138: Figure 79: Favorite regions (shaded
Page 139 and 140: Direct detection of MLH from acoust
Page 141 and 142: Engelbart D.A.M.and Bange J. (2002)
Page 143 and 144: 7 What can remote sensing contribut
Page 145 and 146: uyms 9.0 8.5 8.0 7.5 7.0 120 140 16
Page 147 and 148: Bottom of rotor Φ rotation r w u
Page 149 and 150: Height Height Hub 1.6 1.4 1.2 1.0 0
Page 151 and 152: PP rated PP rated 1.0 0.8 0.6 0.4 0
Page 153 and 154: KEprofileKEhub 1.2 1.1 1.0 0.9 0.8
Page 155 and 156: PP rated WS Lidarms 1.0 0.8 0.6 0.4
Page 157: 8 Nacelle-based lidar systems Andre
Page 161 and 162: Figure 104: Sketch of simultaneous
Page 163 and 164: The normal wind direction vector nw
Page 165 and 166: Figure 109: Test site at DTU Wind E
Page 167 and 168: Figure 112: Power curve met mast an
Page 169 and 170: Notation C number of sent photons C
Page 171 and 172: 9 Lidars and wind turbine control -
Page 173 and 174: for three unknowns, it is impossibl
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Page 177 and 178: |GRL| [-] 1 0.8 0.6 0.4 0.2 10 k [r
Page 179 and 180: PSD(Ωg) [(rpm) 2 /Hz] PSD(Ωg) [
Page 181 and 182: 0.04 0.03 ˆk [ rad m ] 0.02 0.63 0
Page 183 and 184: [%] 10 0 −10 −20 −30 MyT Moop
Page 185 and 186: PSD(θ1) [rad 2 /Hz] PSD(Moop1) [Nm
Page 187 and 188: Pel/Pel,max [-] 1 0.98 0.96 0.94 0.
Page 189 and 190: fL weighting function GRL transfer
Page 191 and 192: E. Hau, Windkraftanlagen, 4th ed. S
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Page 195 and 196: vertical (m) 150 100 50 R d 0
Page 197 and 198: With feedback only, on the other ha
Page 199 and 200: Figure 136: Estimated preview requi
Page 201 and 202: Normalized C r = C r P Q 2 W (r) b
Page 203 and 204: Normalized C r = C r P Q 2 W (r) b
Page 205 and 206: Coherence 1 0.8 0.6 0.4 0.2 0 10
Page 207 and 208: Coherence 1 0.8 0.6 0.4 0.2 0 10
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Magnitude Squared 10 8 10 7 10 6 10
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Figure 148: During simulation, FAST
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Figure 149: Collective flap respons
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Magnitude (abs) blade pitch gen spe
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• Measurement coherence, which ca
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Jonkman, B. (2009) TurbSim user’s
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11 Lidars and wind profiles Alfredo
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z [m] 160 100 80 60 40 20 10 15 20
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z [−] zo 1 κ ln 40 38 36 34 32 3
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z [m] z [m] 1000 900 800 700 600 50
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the growth of the length scale, agr
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12 Complex terrain and lidars Ferha
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Figure 158: The ZephIR models which
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Uconst wΑx l h Φ h.tanΦ Figure 1
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Figure 162: Lavrio: The scatter plo
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Figure 163: Panahaiko: The scatter
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References Albers A. and Janssen A.
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Wexler (1968), where the limitation
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13.2.1 Systematic turbulence errors
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where x is the center of the scanni
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The theoretical systematic errors a
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Height (m) 160 140 120 100 80 60 40
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Height (m) Height (m) 160 140 120 1
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RMSPE (%) 70 60 50 40 30 20 10 0 vu
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involves interaction of all compone
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Lindelöw P. (2007) Fibre Based Coh
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plications, including meteorologica
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Figure 173: Rayleigh-Jeans’ appro
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Figure 176: Brightness temperature
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with rain are shown in Fig. 179. A
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This method gives a good accuracy (
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Figure 183: A recent maintenance in
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Figure 185: Temperature profiles in
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References s point in space Sν(s)
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Also the Doppler Centroid anomaly c
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Christiansen et al., 2006). The res
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educe speckle noise, a random noise
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Figure 188: Envisat ASAR wind field
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Figure 190: Envisat ASAR wind field
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Satellites in sun-synchronous polar
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500 overlapping scenes for wind res
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(with the fewest samples). The unce
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Badger M., Hasager C. B., Thompson
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Ren Y. Z., Lehner S., Brusch S., Li
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tracking, climate studies, air-sea
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The modified logarithmic wind profi
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sea ice mask was applied and σ0 me
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QuikSCAT 25 20 15 10 5 Horns Rev Fi
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Figure 203:Example of an ASCAT coas
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References Bourassa M.A., Legler D.
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DTU Wind Energy Technical Universit
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