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5.3.6 Existing systems and actual performances
In 2013, only a few pulsed lidars are available. Table 13 summarizes the characteristics of
commercial ones, which can be used in the wind industry, meteorology or airport safety. All
are based on coherent detection. In 2011, Pentalum introduced a new pulsed lidar, based
on backscatter correlation on two adjacent beams and direct detection. This technique is
currently under evaluation.
Table 13: Comparison of commercially available pulsed lidars
System Wave Range/ Data Sample pulse PRF Beam
length accuracy update volume duration/ [kHz] config.
[µm] [m]/[m s −1 ] [s] length energy
[m] [ns]/[µJ]
Leosphere 1.54 40–200/0.1 1/10 alt 20 175/10 30 Five
WindCube7 beams DBS
WindCube 1.54 100–6000/0.3 1 75 400/100 10 LOS
200S mapping
WindCube 1.54 200–12000/0.5 1 150 800/200 10 LOS
400S mapping
LMCT 1.6 400–15000/1 0.1 80 300/2000 0.75 LOS
Windtracer mapping
Mitsubishi 1.5 100–1500/NA 1 90 600/6.5 1 Scanning
head
Sgurr 1.5 40–250/0.1 0.1–30 24 150/10 20 LOS
Gallion G250 mapping
G4000 1.5 80–4000/NA NA 30 NA NA LOS
mapping
5.3.7 Validation of measurements
Sincetheinstrumentalsourcesofuncertaintyarenowwellidentifiedandtherangeofdeviation
theymightincurin the wind speedmeasurement are wellestimated,it is necessaryto compare
the measurement ofanew lidarunit againstatall mast equippedwith traditionalanemometry
or against a well-known and validated lidar in a double phase verification/validation.
Validationisthe processofensuingthataWINDCUBE measureswindspeed characteristics
in conformity with what a reference instrument would give. Today, validation is done against
well-known traditional anemometry, like a mast equipped with calibrated cup anemometers.
This instrument comparison introduces additional uncertainties, not related to the inner performances
of each individual instrument but related to the differences in the measurement
process between the two instruments. These differences in the measurement process might
incur differences in measured values, which will be site and time specific. Even if these are
small,itis importantto closelydefinetherangeofvariationthat mightoccuronthevalidation
site.
With more than 140 field deployments worldwide for the past 4 years, the Windcube has
beenextensivelytestedindifferentconditionsandunderadiversityofclimates.Severalauthors
have reported very goodmeasurement accuracywith reference to calibratedcup anemometers
in good operating conditions (Oldroyd et al., 2009; Faghani et al., 2009; Jaynes, 2009).
DTU Wind Energy-E-Report-0029(EN) 117