14:30 - 16:00 LIDARs - the zapping competition
Resource assessment
Room: Hall G2
In this highly interactive quick-fire session, participants will scan through 14 LIDAR-related presentations and vote to select the three contributions they would like to hear in full. Presentations will cover a wide range of possible LIDAR applications, both offshore and onshore, such as power-curve validation, resource assessment in complex terrain, turbulence intensity measurements, and more.
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Learning objectives
Get a wide overview of the latest research and field work involving LIDARs, both onshore and offshore.
This session will be chaired by:
Presenter
Co-authors:
Harald Mueller (1) F Michael Eggert (1) Christian Gutsmuths (1) Axel Albers (2) Klaus Franke (2) Ailt-Wiard Janssen (2)
(1) Physikalisch-Technische Bundesanstalt, Braunschweig, Germany (2) Deutsche WindGuard Consulting GmbH, Varel, Germany
Presenter's biography
Biographies are supplied directly by presenters at WindEurope Summit 2016 and are published here uneditedHarald Müller studied physics at the Philipps-University Marburg in Germany, received his diploma in 1983 and his PhD in applied physics in 1986. From 1986 until 1991 he was staff member and chief engineer at the Institute of Metrology for Mechanical Engineering at the Leibnitz University Hannover. Since 1991 he is staff member of the PTB, the national metrology institute of Germany and since 1994 head of the working group fluid flow measuring techniques, responsible for air speed measurements and appointed as an assessor for the anemometer calibration laboratories in the framework of DAkkS, Germany's National Accreditation Body.
Abstract
A novel LIDAR system – first results of highly resolved wind vector measurements
Introduction
Wind lidar systems currently used in the wind energy industry are based on the monostatic lidar principle by tilting one laser beam into different directions to determine a wind vector. These systems have been established and provide reliable measurement results especially for flat terrain with almost homogeneous wind fields. But with increasing inhomogeneity in the wind fields to be investigated, wind vector measurements and their traceability become problematical. The newly developed bistatic wind lidar allows traceable wind vector measurements by determining the velocity vector of single aerosols in a highly resolved measurement volume in heights from 5 m up to 250 m.
Approach
By applying one transmitting module and three receiving modules with beams focused into a well-defined measurement volume it is for the first time possible to perform traceable lidar measurements of the wind vector with a high local resolution and a resolution of 0.1 m/s for the wind speed represented by the velocity of single aerosols without any assumptions concerning the homogeneity of the wind field as conventionally required.
In contrast to conventional wind lidar systems the newly developed bistatic wind lidar system measures wind vectors by determining the velocity vector of single scattering particles, so that inhomogeneous wind fields caused by the environmental conditions have no influence on the measurement uncertainty and the traceability of wind vector measurements with high local and temporal resolution.
Main body of abstract
The bistatic system designed by PTB comprises a narrow-bandwidth master laser and a high power erbium doped fiber amplifier to generate the transmitted light. While monostatic systems typically use combined transmitting/receiving optics and an optical circulator to separate the received light scattered by particles, the bistatic system is based on discrete optical paths for the transmitting and receiving optics. In order to focus the beams of the transmitting and the receiving optics into a small measurement volume, all four optics are motor controlled. An optical time of flight measurement is used to superimpose all three receiving beams with the transmitting beam in a selected measuring distance between 5 m and 250 m. Correlation techniques between the three detection channels are applied to ensure wind vector measurements based on single particles in the measurement volume.
The resulting measuring volume has a high local resolution depending on the measuring distance. In a measuring height of 100 m the measuring volume typically has a diameter of 6 mm and a length of 0.6 m whereas in a height of 200 m the dimensions increase to 12 mm in diameter and to 2.4 m in length.
The prototype of the PTB bistatic wind lidar is mounted on a trailer to perform measurements in the field. First validation tests have already been performed. Bilateral comparison measurements with met mast measurements on the wind energy test field of Deutsche WindGuard show a comparability of the traceable calibrated cup anemometer data and the PTB-Lidar data within a few per mill.
Conclusion
First validation tests of the novel PTB bistatic lidar system for wind vector measurements by comparison measurements with a met mast already show a comparability of the measurement results within a few per mill. Based on the well-defined geometry, the known wavelength and precise frequency evaluation, the novel system has the potential for traceable wind speed measurements in flat as well as in complex terrain.
Learning objectives
Due to its unique characteristics the novel bistatic lidar system is predestined to be applied in current research and development activities to improve the measurement capability and accuracy for site and wind resource assessment, power curve measurement, flow modelling as well as classification and calibration of conventional lidar systems.
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