scholarly journals High-resolution Bistatic Wind Lidar

2021 ◽  
Author(s):  
Paul Wilhelm ◽  
Michael Eggert ◽  
Julia Hornig ◽  
Stefan Oertel
Keyword(s):  
High Resolution ◽  
Measurement Uncertainty ◽  
Wind Velocity ◽  
Coherent Detection ◽  
Velocity Measurements ◽  
Measurement Volume ◽  
Optical Transmitter ◽  
Large Measurement ◽  
Inhomogeneous Flow ◽  
Wind Lidar

The high-resolution bistatic lidar developed at the Physikalisch-Technische Bundesanstalt (PTB) aims to overcome the limitations of conventional monostatic lidar technology which is widely used for wind velocity measurements in wind energy and meteorology applications. Due to the large measurement volume of a combined optical transmitter and receiver tilting in multiple directions, monostatic lidar generally has poor spatial and temporal resolution. It also exhibits large measurement uncertainty when operated in inhomogeneous flow, for instance, over complex terrain. In contrast, PTB’s bistatic lidar uses three dedicated receivers arranged around a central transmitter, resulting in an exceptionally small measurement volume. The coherent detection and modulation schemes used allow the detection of backscattered, Doppler shifted light down to the scale of single aerosols, realising the simultaneous measurement of all three wind velocity components. This paper outlines design details and the theory of operation of PTB’s bistatic lidar and provides an overview of selected comparative measurements. The results of these measurements have shown that the measurement uncertainty of PTB’s bistatic lidar is well within the measurement uncertainty of traditional cup anemometers, while being fully independent of its site and traceable to the SI units. This allows its use as a transfer standard for the calibration of other remote sensing devices. Overall, PTB’s bistatic lidar shows great potential to universally improve the capability and accuracy of wind velocity measurements, such as for the investigation of highly dynamic flow processes upstream and in the wake of wind turbines.

scholarly journals High Spatial and Temporal Resolution Bistatic Wind Lidar

2021 ◽  
Vol 11 (16) ◽  
pp. 7602
Author(s):  
Paul Wilhelm ◽  
Michael Eggert ◽  
Julia Hornig ◽  
Stefan Oertel
Keyword(s):  
Measurement Uncertainty ◽  
Wind Velocity ◽  
Temporal Resolution ◽  
Coherent Detection ◽  
Velocity Measurements ◽  
Measurement Volume ◽  
Optical Transmitter ◽  
Large Measurement ◽  
Inhomogeneous Flow ◽  
Wind Lidar

The high-resolution bistatic lidar developed at the Physikalisch-Technische Bundesanstalt (PTB) aims to overcome the limitations of conventional monostatic lidar technology, which is widely used for wind velocity measurements in wind energy and meteorology applications. Due to the large measurement volume of a combined optical transmitter and receiver tilting in multiple directions, monostatic lidar generally has poor spatial and temporal resolution. It also exhibits large measurement uncertainty when operated in inhomogeneous flow; for instance, over complex terrain. In contrast, PTB’s bistatic lidar uses three dedicated receivers arranged around a central transmitter, resulting in an exceptionally small measurement volume. The coherent detection and modulation schemes used allow the detection of backscattered, Doppler shifted light down to the scale of single aerosols, realising the simultaneous measurement of all three wind velocity components. This paper outlines the design details and theory of operation of PTB’s bistatic lidar and provides an overview of selected comparative measurements. The results of these measurements show that the measurement uncertainty of PTB’s bistatic lidar is well within the measurement uncertainty of traditional cup anemometers while being fully independent of its site and traceable to the SI units. This allows its use as a transfer standard for the calibration of other remote sensing devices. Overall, PTB’s bistatic lidar shows great potential to improve the capability and accuracy of wind velocity measurements, such as for the investigation of highly dynamic flow processes upstream and in the wake of wind turbines.

scholarly journals Performance and Technique of Coherent 2-μm Differential Absorption and Wind Lidar for Wind Measurement

2013 ◽  
Vol 30 (3) ◽  
pp. 429-449 ◽  
Author(s):  
Hironori Iwai ◽  
Shoken Ishii ◽  
Ryoko Oda ◽  
Kohei Mizutani ◽  
Shinya Sekizawa ◽  
...  
Keyword(s):  
Wind Velocity ◽  
Signal To Noise Ratio ◽  
Sonic Anemometer ◽  
Correlation Coefficients ◽  
Co2 Concentration ◽  
Horizontal Wind ◽  
Doppler Lidar ◽  
Differential Absorption ◽  
Velocity Measurements ◽  
Wind Lidar

Abstract A coherent 2-μm differential absorption and wind lidar (Co2DiaWiL) has been built with a high-power Q-switched Tm,Hm:YLF laser to measure CO2 concentration and radial wind speed. The performance of the Co2DiaWiL is described and analyzed, with a view to demonstrating system capabilities for remote measurements of wind velocities in the atmospheric boundary layer and free troposphere. Bias in the velocity measurements was estimated at −0.0069 m s−1 using measurements from a stationary hard target. The Co2DiaWiL achieved a velocity precision of 0.12 m s−1, derived from the magnitude of random error in radial wind velocity measurements. These measurements were made for ranges out to 20–25 km by using a horizontally fixed beam mode for average times of 1 min. Quantitative intercomparisons of 1-min averages between the Co2DiaWiL and a sonic anemometer revealed a correlation coefficient of 0.99. This study demonstrated measurements of horizontal wind profiles, by making radial wind velocity measurements with the Co2DiaWiL using conical scanning. Profile differences at higher levels could be attributed to probable large horizontal separations of the radiosondes and the low signal-to-noise ratio of the Co2DiaWiL. A pseudo-dual-Doppler technique was developed to retrieve horizontal wind components with a single-Doppler lidar and a steering mirror. Intercomparisons of the 1-min-averaged u and υ components from the pseudo-dual-Doppler lidar measurements with those from the sonic anemometer revealed correlation coefficients of 0.84 and 0.83, respectively.

ALADIN: an atmospheric laser Doppler wind lidar instrument for wind velocity measurements from space

1996 ◽  
Author(s):  
Rodolphe Krawczyk ◽  
Jean-Bernard Ghibaudo ◽  
Jean-Yves Labandibar ◽  
David V. Willetts ◽  
M. Vaughan ◽  
...  
Keyword(s):  
Wind Velocity ◽  
Laser Doppler ◽  
Velocity Measurements ◽  
Wind Lidar ◽  
Doppler Wind Lidar

ALADIN: an atmosphere laser Doppler wind lidar instrument for wind velocity measurements from space

1995 ◽  
Author(s):  
Rodolphe Krawczyk ◽  
Jean-Bernard Ghibaudo ◽  
Jean-Yves Labandibar ◽  
David V. Willetts ◽  
M. Vaughan ◽  
...  
Keyword(s):  
Wind Velocity ◽  
Laser Doppler ◽  
Velocity Measurements ◽  
Wind Lidar ◽  
Doppler Wind Lidar

scholarly journals Validation of three-component wind lidar sensor for traceable highly resolved wind vector measurements

2019 ◽  
Vol 8 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Stefan Oertel ◽  
Michael Eggert ◽  
Christian Gutsmuths ◽  
Paul Wilhelm ◽  
Harald Müller ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Wind Tunnel ◽  
Measurement Uncertainty ◽  
Test Section ◽  
Wind Tunnel Test ◽  
Wind Vector ◽  
Wind Fields ◽  
Lidar System ◽  
Measurement Volume ◽  
Wind Lidar

Abstract. Conventional monostatic wind lidar (light detection and ranging) systems are well-established wind speed remote sensing devices in the field of wind energy that provide reliable measurement results for flat terrain and homogeneous wind fields. These conventional wind lidar systems use a common transmitting and receiving unit and become unacceptably inaccurate as the wind fields become increasingly inhomogeneous due to their spatial and temporal averaging procedure (large measurement volume) that is inherent to the monostatic measurement principle. The new three-component fiber laser-based wind lidar sensor developed by the Physikalisch-Technische Bundesanstalt (PTB) uses one transmitting unit (fiber laser) and three receiving units to measure the velocity vector of single aerosols in a spatially highly resolved measurement volume (with diameter d and length l) in heights from 5 m (d=300 µm, l=2 mm) to 250 m (d=14 mm, l=4 m) with a resolution of about 0.1 m s−1. Detailed comparison measurements with a 135 m high wind met mast and a conventional lidar system have proven that the high spatial and temporal resolution of the new, so-called bistatic lidar leads to a reduced measurement uncertainty compared to conventional lidar systems. Furthermore, the comparison demonstrates that the deviation between the bistatic lidar and the wind met mast lies well within the measurement uncertainty of the cup anemometers of the wind met mast for both homogeneous and inhomogeneous wind fields. At PTB, the aim is to use the bistatic wind lidar as a traceable reference standard to calibrate other remote sensing devices, necessitating an in-depth validation of the bistatic lidar system and its measurement uncertainty. To this end, a new, specially designed wind tunnel with a laser Doppler anemometer (LDA) as flow velocity reference has been erected on a platform at a height of 8 m; this allows the new wind lidar to be positioned below the wind tunnel test section to be validated for wind vector measurements that are traceable to the SI units. A first validation measurement within the wind tunnel test section is presented, showing a deviation between the bistatic lidar system and the LDA clearly below 0.1 %.

scholarly journals Measurement Uncertainty of Radiated Electromagnetic Emissions in In Situ Tests of Wind Energy Conversion Systems

2018 ◽  
Vol 16 ◽  
pp. 13-22 ◽  
Author(s):  
Sebastian Koj ◽  
Axel Hoffmann ◽  
Heyno Garbe
Keyword(s):  
Wind Energy ◽  
Measurement Uncertainty ◽  
Energy Conversion ◽  
Wind Velocity ◽  
Standard Procedure ◽  
In Situ Tests ◽  
Wind Energy Conversion ◽  
Wind Energy Conversion Systems ◽  
Energy Conversion Systems

Abstract. The electromagnetic (EM) emissions of wind energy conversion systems (WECS) are evaluated in situ. Results of in situ tests, however, are only valid for the examined equipment under test (EUT) and cannot be applied to series production as samples, as the measurement uncertainty for in situ environment is not characterized. Currently measurements must be performed on each WECS separately, this is associated with significant costs and time requirement to complete. Therefore, in this work, based on the standard procedure according to the “Guide to the Expression of Uncertainty” (GUM, 2008) the measurement uncertainty is characterized. From current normative situation obtained influences on the measurement uncertainty: wind velocity and undefined ground are evaluated. The influence of increased wind velocity on the measurement uncertainty is evaluated with an analytical approach making use of the dipole characteristic. A numerically evaluated model provides information about the expected uncertainty due to reflection on different textures and varying values of relative ground moisture. Using a classical reflection law based approach, the simulation results are validated. Thanks to the presented methods, it is possible to successfully characterize the measurement uncertainty of in situ measurements of WECS's EM emissions.

The Doppler Aerosol Wind (DAWN) Airborne, Wind-Profiling Coherent-Detection Lidar System: Overview and Preliminary Flight Results

2014 ◽  
Vol 31 (4) ◽  
pp. 826-842 ◽  
Author(s):  
Michael J. Kavaya ◽  
Jeffrey Y. Beyon ◽  
Grady J. Koch ◽  
Mulugeta Petros ◽  
Paul J. Petzar ◽  
...  
Keyword(s):  
Laser Pulse ◽  
High Energy ◽  
Coherent Detection ◽  
Lidar System ◽  
Airborne Measurements ◽  
Secondary Mirror ◽  
Wind Measurements ◽  
Wind Lidar ◽  
Aerosol Backscatter ◽  
Flight Measurements

Abstract The first airborne wind measurements of a pulsed, 2-μm solid-state, high-energy, wind-profiling lidar system for airborne measurements are presented. The laser pulse energy is the highest to date in an eye-safe airborne wind lidar system. This energy, the 10-Hz laser pulse rate, the 15-cm receiver diameter, and dual-balanced coherent detection together have the potential to provide much-improved lidar sensitivity to low aerosol backscatter levels compared to earlier airborne-pulsed coherent lidar wind systems. Problems with a laser-burned telescope secondary mirror prevented a full demonstration of the lidar’s capability, but the hardware, algorithms, and software were nevertheless all validated. A lidar description, relevant theory, and preliminary results of flight measurements are presented.

Photogrammetric Investigation of the Flying Shape of Spinnakers in a Twisted Flow Wind Tunnel

2009 ◽  
Author(s):  
Kai Graf ◽  
Olaf Müller
Keyword(s):  
Image Processing ◽  
Pattern Recognition ◽  
High Resolution ◽  
Wind Tunnel ◽  
Wind Velocity ◽  
Digital Cameras ◽  
Pattern Recognition Methods ◽  
Twisted Flow ◽  
High Resolution Images ◽  
The Impact

This paper describes a method for the acquisition of the flying shape of spinnakers in a twisted flow wind tunnel. The method is based on photogrammetry. A set of digital cameras is used to obtain high resolution images of the spinnaker from different viewing angles. The images are post-processed using image-processing tools, pattern recognition methods and finally the photogrammetry algorithm. Results are shown comparing design versus flying shape of the spinnaker and the impact of wind velocity and wind twist on the flying shape. Finally some common rules for optimum spinnaker trimming are investigated and examined.

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