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We provide an analysis of measurements for the cross-cutting activity (CCA) V52 at the Risø test site, in which a SpinnerLidar was mounted on the nacelle of the V52 wind turbine to characterize the inflow of the turbine. Measurements from cup and sonic anemometers at a meteorological mast deployed at about 2.3 rotor diameters from the turbine are used as reference for evaluation of the SpinnerLidar-derived inflow conditions. We find a very good agreement between the mean wind speeds derived from the measurements of the SpinnerLidar and those of the meteorological mast but a bias in the mean wind shear. We also find that we can accurately estimate the components of the Reynolds stress tensor using the SpinnerLidar measurements when compared to estimates using sonic anemometer measurements. The variation with height of the along-wind velocity variance using the SpinnerLidar measurements shows the opposite behavior as that observed using the sonic anemometer measurements. We also describe the output tables in which the SpinnerLidar post processed measurements are stored.

In this report we present how to estimate turbulence measures and unfiltered radial velocity variances from long-range WindScanners, which are pulsed scanning lidars. We also show how the radial velocity spectrum, and thus the radial velocity variance, are a function of the turbulence structure and the misalignment of the lidar beam with the mean wind. Moreover, we show how to optimize scanning strategies for scanning lidars in order to measure turbulence assuming that we are able to estimate the unfiltered radial velocity variance; we illustrate a method to estimate the relative error in turbulence estimates for a given configuration.Further, we show how to estimate the velocity component variances, which are those needed for site assessment, by combining second-order statistics of the radial velocities of multiple scanning lidars. Results of second-order statistics of radial velocities and velocity components performed at an experimental campaign carried out at the Høvsøre test station, where two WindScanners pointed close to a sonic anemometer during about one month, are illustrated and compared to theoretical computations.

Wind turbine design using calibrated wind models have been proposed to be used in conjunction with load cases which lead to reduced uncertainties in the design of wind turbines with hub heights above 60m. These recommended wind profiles have been made for shear, wind directional change and turbulence. The wind turbulence models used in the loads simulations have been calibrated so that their model parameters reflect the atmospheric stability conditions and the quantile of turbulence intensity considered. Consequently large multi megawatt turbines being designed today can benefit from these more advanced wind inflow models. A revision of the IEC 61400-1standard is being developed and has incorporated some of the recommendations made from this project.This project demonstrated the impact of wind models by simulating wind turbine loads based on high frequency wind measurements taken between 100m and 200m altitude performed at Høvsøre in Denmark. The project also demonstrated the impact of the new wind models on load cases and the certification envelope of turbines. Further the project provided a detailed assessment of safety factors for IEC 61400-1 load cases using reliability-based procedures incorporating the new models and this has been made as an Annex to the new standard that is due to be issued.

The project has created a new basis for further development and optimization of WT’s designed for WF operation. This has been accomplished through developing of more realistic modelling of WF flow fields as well as of such fields interactions with WT’s under non-neutral ABL stability conditions. On this basis a verified model complex for prediction of structural loads as well as production losses for wind turbines operating in wind farm conditions, which takes into account the effects from ABL stability conditions, is established. Thereby the way to increased reliability and cost efficiency of future wind turbines as well as to more precise prediction of the WF power output is paved.

The Remote Sensing in Wind Energy report provides a description of several topics and it is our hope that students and others interested will learn from it. The idea behind it began in year 2008 at DTU Wind Energy (formerly Risø) during the first PhD Summer School: Remote Sensing in Wind Energy. Thus it is closely linked to the PhD Summer Schools where state-of-the-art is presented during the lecture sessions. The advantage of the report is to supplement with in-depth, article style information. Thus we strive to provide link from the lectures, field demonstrations, and hands-on exercises to theory. The report will allow alumni to trace back details after the course and benefit from the collection of information. This is the fourth edition of the report and we warmly acknowledge all the contributing authors for their work in the writing of the chapters, and we also acknowledge all our colleagues in the Meteorology and Test and Measurements Sections from DTU Wind Energy in the PhD Summer Schools. We hope to continue adding more topics in future editions and to update and improve as necessary, to provide a truly state-of-the-art ‘guideline’ available for people involved in Remote Sensing in Wind Energy.

Kohærent detektion lidars (light detection and ranging) har efterhånden udviklet sig betydeligt og er nu de facto standarden for måling af vinde i det atmosfæriske grænselæg. De tidligere versioner af disse lidars var voluminøse, dyre og sårbare over for eksterne påvirkninger såsom temperaturvariationer og vibrationer. Men imidlertid har fremskridt indenfor fiberoptisk kommunikation resulteret i en række stabile, kosteffektive, vedligeholdelsesfrie optiske komponenter, som kan anvendes af lidar konstruktører. Kohærent detektion lidars deler nemlig mange ligheder med højhastigheds fiberoptisk kommunikation. Som følge heraf er den nye fiberoptiske teknologi hurtigt blevet anvendt i opbygningen af lidars. På trods af dette halter brugen af disse kommunikations komponenter stadig bagud i anvendelsen til lidars. I denne afhandling har jeg fremlagt nogle af de fremskridt inden for fiberoptiske transceivere, der oprindeligt er udviklet til high-speed data transmission, og vist, hvordan de kan integreres i pulsede og kontinuerlige fiberbaserede kohærent detektion lidars. Teknologierne har ikke alene muliggjort præstationsforbedringer i eksisterende lidarsystemer, men har også banet vejen for anvendelse i nye områder, hvor det ikke før har synes muligt. Denne afhandling, der består af en indledning, fire videnskabelige artikler og en artikel under udarbejdelse, præsenterer anvendelsen af nogle af de moderne fiberoptiske kommunikations-transceiver arkitekturer i kohærent detektions lidars. I artikel I er en ny kortrækkende fiber-baseret Doppler lidar, der anvender "image-reject" homodyn detektion, beskrevet og demonstreret. I artikel II diskuteres to forskellige måder at behandle signaler fra denne type lidar for at estimere vindhastigheder. Fordele og ulemper såsom signal støjforhold og effektivitet analyseres. Det foreslåede lidar system i artikel I bliver testet i en feltkampagne, hvis resultater er diskuteret i artikel III. I artikel IV præsenteres en patentanmeldt langtrækkende "polarization diversity" kohærent Doppler lidar. Systemets fordele er blandt andet en forbedret sendeeffekt (takket være tilgængeligheden af to erbiumdoterede fiberforstærkere med ortogonal polarisering) og samtidig evnen til at måle det depolariserede back-scatter. Graden af depolarisering muliggør karakteriseringen af aerosol typer som funktion af afstanden. Til sidst er det vist i artikel V, som er under udarbejdelse, at ved at anvende en "image-reject" homodyn modtager i en fiberbaseret kohærent lidar, kan spektret af den spontane Rayleigh-Brillouin spredning måles.Systemet bruger en 1,5 μm laser, som har den fordel, at den ikke skader det menneskelige øje, og kan i princippet give sammenhørende målinger af temperatur, tryk og vind. Fokus i artikel V er temperaturmålingen, som gennem numeriske simuleringer er vist muligt. Coherent detection lidars have evolved over time and gradually become the de facto instruments for high resolution measurement of atmospheric boundary layer winds. The earlier versions of these lidars were bulky, expensive, and suffered from vulnerability to environmental effects such as temperature and vibrations. However, with the advent of fiber-optic communications a new class of stable, cost-effective, and low-maintenance optical components became available to the lidar community. Coherent detection lidars share many similarities with the high-speed fiber-optic communications. As a result, the new fiber-optic technology was quickly adopted in these lidars. Although coherent detection lidars, especially all-fiber coherent detection lidars, have benefited from the technology available in coherent fiber-optic communications, a considerable gap (in both research and technology) seems to exist between the two. In this thesis, I have presented some of the advances in fiber-optic transceivers, originally developed for high-speed data transmission, and shown how they can be integrated in micropulse and continuous-wave all-fiber coherent detection lidars. The presented technologies not only enable the possibility for performance improvements in existing lidars but also pave the way for the application of coherent detection lidars in areas where their presence was neither plausible nor easy to realize. This thesis, composed of an introduction and four scientific paper and one manuscript, specifically presents the adoption of some of the contemporary fiber-opticcommunications transceiver architectures in coherent detection lidars. In paper I a new short-range all-fiber coherent Doppler lidar employing an image-reject homodyne receiver is described and demonstrated. In Paper II two different approaches to signal processing, necessary for the estimation of mean velocity from the spectra, are discussed and the associated advantages and disadvantages such as the signal to noise ratio and signal processing overhead are discussed. The performance of the system proposed paper I is put to test in a real measurement campaign the results of which are discussed in Paper III. In Paper IV a patent-pending long-range polarization-diversity coherent Doppler lidar is presented. The system benefits from an improved transmit power (thanks to theavailability of two erbium-doped fiber amplifiers separated in polarization) while having the ability to detect the depolarized backscatter signals. The ability to detect the degree of depolarization enables the characterization of aerosol types associated with each measurement range. Eventually, it is shown in Paper V that by adopting the image-reject homodyne receiver in an all-fiber coherent detection lidar, the spectrum of the Rayleigh or the spontaneous Rayleigh-Brillouin scattering (depending on the operating conditions) can be resolved. The system benefits from an eye-safe 1:5μm laser and can provide simultaneous measurements of temperature, pressure, and wind. The focus of the paper in Paper V is the temperature measurement capability of the system, provided as the proofof concept through numerical simulations.

Prevision of the wind field by remote sensing wind lidars has the potential to improve the performance of wind turbines. The functionality of a WindEye lidar developed by Windar Photonics A/S (Denmark) for the wind energy market was tested in a two months long field experiment. The WindEye sensor measures the wind speed along two beams to determine the wind direction of the incoming wind field. The field experiment utilized two sonic anemometers located in the two centers of the measurement volumes of the WindEye as reference instruments. It was found that the WindEye measured the wind direction with a high accuracy during the whole campaign.

The Remote Sensing in Wind Energy report provides a description of several topics and it is our hope that students and others interested will learn from it. The idea behind it began in year 2008 at DTU Wind Energy (formerly Risø) during the first PhD Summer School: Remote Sensing in Wind Energy. Thus it is closely linked to the PhD Summer Schools where state-of-the-art is presented during the lecture sessions. The advantage of the report is to supplement with in-depth, article style information. Thus we strive to provide link from the lectures, field demonstrations, and hands-on exercises to theory. The report will allow alumni to trace back details after the course and benefit from the collection of information. This is the third edition of the report (first externally available), after very successful and demanded first two, and we warmly acknowledge all the contributing authors for their work in the writing of the chapters, and we also acknowledge all our colleagues in the Meteorology and Test and Measurements Sections from DTU Wind Energy in the PhD Summer Schools. We hope to continue adding more topics in future editions and to update and improve as necessary, to provide a trulystate-of-the-art ‘guideline’ available for people involved in Remote Sensing in Wind Energy.