Wind power becomes one of the most promising energy sources in the electricity generation sector in Texas over the past decade by declining levelized cost of wind energy. However, recent studies show that the wind farms in Texas are relatively less productive. Hence, this study aims to find out reasons of inefficiencies by constructing a two-stage performance assessment of wind farms in Texas. In the first stage of analysis, comprehensive input- and output-oriented Data Envelopment Analysis (DEA) models are applied to evaluate productive efficiencies of the 95 large utility-scale wind farms by using pre-determined three input and two output variables. The sensitivity analysis is provided for the robustness of the DEA models with different combinations of input and output variables of the original model. The slack analysis and projection data are obtained for inefficient wind farms to find out optimal input-output variables. Tobit regression models are conducted for the second stage of the analysis to investigate the reasons of inefficiencies. DEA results indicate that half of the wind farms were operated efficiently in Texas during 2016. 13 wind farms were performed at the most productive scale size, ten wind farms should reduce their operational size to improve production efficiency, and 72 wind farms have the notable potential to increase their production efficiency by expanding operational sizes with modern wind turbine technologies. The sensitivity analysis shows the importance of each input-output variables. Tobit regression models indicate that elevation of the site, rotor diameter, hub height, and brand of the turbine have significant contributions to the relative efficiency scores of the wind farms, and the age of turbine has a negative impact on the productive efficiency of the wind farms.

Der mittlere Wind in der atmospärischen Grenzschicht über den deutschen Nord- und Ostseegebieten unterscheidet sich gegenüber Landflächen durch höhere Windgeschwindigkeiten, eine stärkere Zunahme mit der Höhe und schwache Tages- sowie ausgeprägte Jahresgänge der Windgeschwindigkeit in Bodennähe. Neben diesen Vorteilen ergeben sich auch Nachteile im Hinblick auf die Windenergienutzung offshore. Das betrifft die Anforderungen an die Technik der Windstromerzeugung sowie wie die Messung und Prognose der relevanten meteorologischen Parameter. Nach Abschätzungen möglicher Flächen für die Windnutzung offshore und anlagentechnischer Möglichkeiten ist von einem enormen technischen Angebotspotenzial an Elektroenergie auszugehen, dem jedoch auch Beschränkungen seitens der Netzstruktur und Nachfrage entgegenstehen. Um das große Potenzial zur Stromerzeugung und Umweltentlastung nutzen zu können, sollte die Entwicklung in den kommenden Jahren im Bereich Windprognose, Anlagenbau, Regelungstechnik und Energiespeicherung zu weiteren Verbesserungen führen. / The averaged wind in the Planetary Boundary Layer over the german North Sea and Baltic Sea areas shows some differences to the wind over land areas. There are higher wind speeds, a stronger increasing with height and slight daily and more distinctive annual variations of the near surface winds. Thats why the utilization of wind energy offshore has advantages. But also exists certain drawbacks in reference to technical requirements and the measurement and prediction of meteorological parameters. Estimations of suitable areas and technical prospects indicate a large technical offer potential of electric energy offshore, though additional restrictions must be considered. To make this potential of electric energy and environmental protection usable todays knowledge of systems and control engineering, energy storage and wind prediction should be improved in the coming years.

Large Scale Wind Turbines (LSWTs) have been extensively examined for decades but very few studies have been conducted on the small scale wind turbines (SSWTs) especially for the applications near ground level where wind speed is of order of few meters per second. This study provides the first systematic effort towards design and development of SSWTs (rotor diameter<50 cm) targeted to operate at low wind speeds (<5 m/s). An inverse design and optimization tool based on Blade Element Momentum theory is proposed. The utility and efficacy of the tool was validated by demonstrating a 40 cm diameter small-scale wind energy portable turbine (SWEPT) operating in very low wind speed range of 1 m/s-5 m/s with extremely high power coefficient. In comparison to the published literature, SWEPT is one of the most efficient wind turbines at the small scale and very low wind speeds with the power coefficient of 32% and overall efficiency of 21% at its rated wind speed of 4.0 m/s. It has very low cut-in speed of 1.7 m/s. Wind tunnel experiments revealed that SWEPT has rated power output of 1 W at 4.0 m/s, and it is capable of producing power output up to 9.3 W at wind speed of 10 m/s. The study was further extended to develop a piezoelectric wind turbine which operates below 2.0 m/s wind speed. The piezoelectric wind turbine of overall dimension of 100mm x 78mm x 65mm is capable of producing peak electric power of about 450 microwatt at the rated wind speed of 1.9 m/s. / Master of Science

Saudi Arabia has been trying to change its long tradition of relying on fossil fuels and seek renewable energy sources such as wind power. In this thesis, I firstly provide a comprehensive assessment of wind energy resources and associated spatio-temporal patterns over Saudi Arabia in both current and future climate conditions, based on a Regional Climate Model output. A high wind energy potential exists and is likely to persist at least until 2050 over a vast area ofWestern Saudi Arabia, particularly in the region between Medina and the Red Sea coast and during Summer months. Since an accurate assessment of wind extremes is crucial for risk management purposes, I then present the first high-resolution risk assessment of wind extremes over Saudi Arabia. Under the Bayesian framework, I measure the uncertainty of return levels and produce risk maps of wind extremes, which show that locations in the South of Saudi Arabia and near the Red Sea and the Persian Gulf are at very high risk of disruption of wind turbine operations. In order to perform spatial predictions of the bivariate wind random field for efficient turbine control, I propose parametric variogram matrix (function) models for cokriging, which have the advantage of allowing for a smooth transition between a joint second-order and intrinsically stationary vector random field. Under Gaussianity, the covariance function is central to spatio-temporal modeling, which is useful to understand the dynamics of winds in space and time. I review the various space-time covariance structures and models, some of which are visualized with animations, and associated tests. I also discuss inference issues and a case study based on a high-resolution wind-speed dataset. The Gaussian assumption commonly made in statistics needs to be validated, and I show that tests for independently and identically distributed data cannot be used directly for spatial data. I then propose a new multivariate test for spatial data by accounting for the spatial dependence. The new test is easy to compute, has a chi-square null distribution, and has a good control of the type I error and a high empirical power.

The Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus; CSTG) has experienced range-wide population declines, primarily as a result of habitat loss or degradation, and currently occupies <10% of its historic range. Expansion of wind energy developments across the remaining occupied CSTG range has been identified as a potential threat to the species. To assess the potential influence of wind energy development on CSTG breeding season ecology, I captured and radio-marked 135 female CSTG during 2014-2015 at leks located between 0.1-13.8 km from wind turbines in restored grassland habitats. I subsequently monitored 147 nests and 68 broods and used an information-theoretic model selection approach to assess the potential influence of wind energy distance and density variables, multi-scale habitat features, temporal factors, and precipitation on CSTG nest site selection, daily nest survival, brood success, and chick survival. The best nest site selection model suggested a positive functional response to the amount of restored grassland habitat with >30% forb cover at the nesting core use (60 ha) scale. Daily nest survival was positively associated with visual obstruction readings at the nest and the amount of restored grassland habitat containing >30% forb cover at the core use (60 ha) scale. Nest site selection and daily nest survival were not influenced by proximity to turbines or turbine density at the core use or breeding season home range (1385 ha) scales. Early (14-day) brood success was positively influenced by post-hatch precipitation and late (42-day) brood success was positively influenced by earlier hatch dates. Chick survival to 42 days post hatch was positively influenced by post-hatch precipitation and earlier hatch dates and negatively influenced by increasing densities of wind turbines at the breeding season home range scale. The probability of an individual chick surviving to 42 days decreased by 50% when there were ≥10 turbines within 2.1 km of the nest. In restored grassland habitats, such as Conservation Reserve Program fields, I recommend plantings and management practices that will result in diverse, bunchgrass-dominated nesting habitat with residual grass cover and >30% forb canopy cover during the nesting season. My results suggest that wind turbines occurring within 2.1 km of nesting habitats (i.e., 4.8 km of occupied leks) may negatively affect CSTG recruitment.

A wind turbine array was constructed in the wind tunnel at Portland State University in a standard Cartesian arrangement. Configurations of the turbine array were tested with rotor blades set to rotate in either a clockwise or counter-clockwise sense. Measurements of velocity were made with stereo particle-image velocimetry. Mean statistics of velocities and Reynolds stresses clearly show the effect of direction of rotation of rotor blades for both entrance and exit row turbines. Rotational sense of the turbine blades is visible in the mean spanwise velocity W and the Reynolds shear stress -[macron over vw]. The normalized anisotropy tensor was decomposed yielding invariants [lowercase eta] and [lowercase xi], which are plotted onto the Lumley triangle. Invariants of the normalized Reynolds stress anisotropy tensor indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids are composed with the eigenvalues from the decomposition yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates streamwise trends, especially trailing the top rotor tip and below the hub of the rotors. Direction of rotation of rotor blades is evidenced in the orientation of characteristic spheroids according to principle axes. The characteristic spheroids of the anisotropy tensor and their relate alignments varies between cases clearly seen in the inflows to exit row turbines. There the normalized Reynolds stress anisotropy tensor shows cumulative effects of the rotational sense of upstream turbines. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean mechanical energy equation indicate a correlation between the degree of anisotropy and the regions of the wind turbine wakes where turbulence kinetic energy is produced. The flux of kinetic energy into the momentum-deficit area of the wake from above the canopy is associated with prolate characteristic spheroids. Flux upward into the wake from below the rotor area is associate with oblate characteristic spheroids. Turbulence in the region of the flow directly following the nacelle of the wind turbines demonstrates more isotropy compared to the regions following the rotor blades. The power and power coefficients for wind turbines indicate that flow structures on the order of magnitude of the spanwise turbine spacing that increase turbine efficiency depending on particular array configuration.

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Die Effekte des Klimawandels sind spürbar und es sind Maßnahmen erforderlich, diese schwerwiegenden Auswirkungen zu kontrollieren oder zu verringern. Diese Maßnahmen beinhalten die Vermeidung von Treibhausgasemissionen oder die Reduktion der atmosphärischen Konzentration sowie eine Anpassung an das vorhandene Klima und seine Auswirkungen. Erneuerbare Energiequellen tragen zur Eindämmung des Klimawandels durch die Reduzierung von Treibhausgasen konventioneller Energiequellen bei. Wie auch alle anderen sauberen Energiequellen spielt die Windenergie durch Reduzierung des CO2-Ausstoßes eine entscheidende Rolle bei der Bekämpfung des Klimawandels. Deutschland und Schottland sind beide Vorreiter bei der Entwicklung und Gewinnung landgebundener Onshore-Windenergie. Beide Staaten haben Im Rahmen ihrer Planungspolitik ehrgeizige Zielsetzungen durch Reduzierung von Treibhausgasemissionen die Auswirkungen des Klimawandels in Grenzen zu halten. In Deutschland und Schottland werden die Entwicklungen der Onshore-Windenergie durch Raumordnungsverfahren gesteuert, nach denen in der Regel Umweltverträglichkeitsprüfungen durchgeführt werden. In der Tat werden Umweltverträglichkeitsbewertungen als Mittel zur Umsetzung des Klimaschutzes in den Raumordnungsverfahren benutzt. Diese Forschungsarbeit soll zu einem strategischen Ansatz für die Entwicklung der Onshore-Windenergie in Deutschland und Schottland beitragen, wobei das Ausmaß der durch den Klimawandel verursachten Probleme und die klimatischen Faktoren der SEA in Raumordnungsverfahren auf regionaler und lokaler Ebene bei der Onshore-Windenergieplanung berücksichtigt werden. Diese Untersuchung hilft, die Beziehung zwischen SEAs prozessualer Wirksamkeit und den Herausforderungen bei der Umsetzung in Hinblick auf die Auswirkungen des Klimawandels in Deutschland und Schottland für die Onshore-Windenergiebranche besser verständlich zu machen. Der methodische Rahmen basiert auf der Auswertung relevanter Gesetze und Vorschriften, Grundsatzdokumenten und wissenschaftlicher Literatur bezüglich der Umweltbewertung von Onshore-Windplanungen. Zusätzlich wurden Experten befragt und Fallstudienanalysen deutscher und schottischer Onshore-Windenergiepläne durchgeführt. Ein Vergleich der Ergebnisse beider Länder zeigt, dass sowohl Deutschland als auch Schottland die SEAs auf politischer Ebene verbessern müssen, um die Auswirkungen des Klimawandels auf verschiedenen räumlichen Ebenen angehen zu können. Die Studie zeigt ferner, dass es gleichermaßen wichtig ist, aktuelle und zukünftige Trends des Klimawandels und des Windverhaltens mithilfe von Klimamodellen zu verfolgen, da diese Informationen dazu beitragen, das komplexe Phänomen des Klimawandels und dessen Auswirkungen effizient anzugehen. Die Studienergebnisse zeigen auch den Einfluss der SEA auf die Onshore-Windenergieplanung in Deutschland und Schottland in Hinblick auf Abschwächung und Anpassung der Auswirkungen des Klimawandels mit der Betonung der Notwendigkeit eines hohen Maßes an politischer Unterstützung, um die Belange des Klimawandels in die Onshore-Windenergie Planungsaktivitäten integrieren zu können. Auf dieser Grundlage wird empfohlen, in der Raumplanung der Onshore-Windenergieentwicklung die Auswirkungen des Klimawandels als ein kritisches Thema zu erkennen und auf den verschiedenen Planungsebenen wirksam zu berücksichtigen. Darüber hinaus sind für die Onshore-Windenergieplanungen starke politische Zielsetzungen erforderlich, um die Entscheidungsfindungen im Bereich des Klimawandels zu unterstützen.

Wind energy as renewable energy will be crucial in ensuring future energy supply. Foundation for agood implementation of wind power output in the electrical grid are wind forecasts. Especially windpower ramp forecasting is important for an effective generation of wind power energy by wind parks.Wind power ramps are large changes in wind power output over a relative short amount of time. Thiswork compares two statistical definitions for four Swedish wind parks using 15 years of data from theNew European Wind Atlas data. This model provides, among other variables, the wind speed and direction at for wind power relevant height with a temporal solution of 30 min. Compared to absolutedefinitions, commonly used to define wind power ramps, a statistical definition is beneficial since it considers each site’s climatology. Based on this definition, a random forest classifier identifies wind speedand direction as the most important variables when forecasting wind power ramps. When fine-tuned, therandom forest classifier could become a valuable tool for forecasting wind power ramps.