Browsing by Subject "wind energy"
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Item Quantification and reduction of uncertainty of model predictions of wind turbines and plants via high-fidelity simulations(2016-12) Foti, DanielWith increasing energy demands renewable energy sources are continuing to receive attention and investment to become a larger source for electricity production. Today, wind generated power through wind turbines creates 4% of the electricity in the United States. The wind energy share of the electricity market is expected to grow rapidly as the United States Department of Energy goal is to reach 20% wind generated electricity by 2030. Computational models for wind plants can be used to predict wind plant performance and optimize the turbine placement and controls. However, uncertainties associated with such models, due to, among others, the computationally expedient simplifications need to be carefully assessed, quantified and reduced. A numerical investigation of model wind turbines employing large-eddy simulation and the curvilinear immersed boundary method to resolve the geometrical details of the turbine is undertaken revealing that the unstable hub vortex interacts with the turbine tip shear layer. Using a spatio-temporal filtering technique, wake meandering, a large scale displacement of the wake, is reconstructed into three-dimensional helical meander profiles. Statistics of the amplitudes and wavelengths corresponding to the intensity and streamwise elongation of the periodic wake meandering indicate complex coherent structures. Similar simulations are performed using the computationally expedient wind turbine actuator surface models with and without a nacelle model to parameterize the turbine. All simulations are validated against substantial experimental measurements. The simulations with the nacelle model are able to accurately capture the geometry dependent near wake and the dynamics in the far wake. The simulations without the nacelle model predict a stable, columnar hub vortex which does not interact with the turbine tip shear layer. Moreover, the amplitude of the meandering profiles is shown to be larger in the immersed boundary method simulations and simulations with a nacelle model compared to the simulation without the nacelle model proving that the nacelle and unstable hub vortex augment the meandering intensity in wind turbines. Due to the exceptional performance of the computationally efficient actuator surface with nacelle model, several turbine designs are simulated with diameters ranging from the laboratory scale (0.1 meters) to the utility scale (96 meters). Despite significant geometrical differences, a characteristic velocity based on the turbine thrust collapses the profile of both the wake turbulence kinetic energy and the amplitude of wake meandering based on the meandering profile for all turbine sizes. This result suggests that the turbulence levels and wake meandering intensity are explicitly linked. The wavelengths of wake meandering are properly scaled by the diameter of the turbine. In agreement with numerous measurements, the wake meandering and hub vortex Strouhal number based on the incoming hub height velocity and diameter is found to be approximately 0.3 and 0.7, respectively, for all turbines. Dynamic mode decomposition of the velocity field indicates that the modes related to these frequencies contain a majority of the energy in the meandering wake and confirms that an unstable hub vortex is a necessary requirement for simulating wind turbine wakes. The Horn Rev offshore wind plant is investigated showing conclusive evidence that the nacelle and hub vortex are important in large arrays of wind turbines. The consistency across scales and wind plant rows of the stochastic distributions of the wake meandering amplitudes and wavelengths allows for the development of a reduced-order kinematic wake model with statistic-based wake meandering inputs. Finally, uncertainties in the model parameters or model inadequacy are investigated using a framework of non-intrusive polynomial chaos. The feasibility of using a kinematic wake model is determined by investigating the parameter uncertainty of surface roughness and induction factor. The parameter uncertainty of the nacelle model is considered in a series of large-eddy simulations. The aleatoric uncertainty of the surface friction on the model and the epistemic nacelle geometry uncertainty propagate downstream in the inner wake and have implications on the uncertainty of the turbulence levels in the entire far wake.Item Responsible, Renewable, and Redesigned: How the Renewable Energy Movement Can Make Peace with the Endangered Species Act(Minnesota Journal of Law, Science and Technology, 2014-02-20) Robbins, KalyaniOne of the most promising routes to a sustainable energy future, as well as climate change mitigation, is the development of renewable energy sources such as wind, solar energy, and hydropower. Indeed, scientists have proposed plans to move completely (100 percent!) to these energy sources within a couple of decades. Mark Z. Jacobson and M.A. Delucchi, scientists from Stanford and U.C. Davis, have outlined a plan to achieve this goal, thereby “eliminating all fossil fuels.” Hydroelectric power already provides almost one-fifth of the world’s electricity, and wind and solar development is rapidly picking up as well. However, before we leave our worries behind and celebrate, we must resolve one potentially difficult issue for renewable energy, especially these three favored brands. They conflict with another important goal, that of protecting biodiversity. Wind, solar, and hydro energy all have one thing in common: they destroy habitat as well as directly kill wildlife, including listed endangered species and their habitat. Can these problems be reconciled with the movement toward renewable energy, allowing us to partake of its many benefits? At least for now, we regularly see renewable energy progress impeded by the need for Endangered Species Act compliance. The ESA has presented itself as a potentially catastrophic obstacle to renewable energy development. The time has come to think about how we might maximize our access to renewable energy while minimizing its impacts on vulnerable species. This Essay will first review the existing conflicts between endangered species and these three sources of renewable energy. This will be followed by analysis of the potential for harmonizing each energy source with the dictates of the Endangered Species Act, concluding with specific proposals for redesigning our methods of harvesting these forms of renewable energy. As one example, innovators have designed impressive new wind-harvesting technologies that are less dangerous to birds and bats without sacrificing efficiency. I propose that the U.S. Fish & Wildlife Service incorporate a preference for wildlife-protective technologies into the regional incidental take permitting requirements, at least for certain higher-risk landscapes. The ultimate goal of the piece is to analyze the extent to which it is possible to use each form of renewable energy without significant ecosystem impacts, to generate somewhat of a ranking of preferred modes of development, and to seek the best path (in relation to wildlife) to a renewable energy future. Such a future is itself essential to biodiversity, so the interests must be harmonized.Item Sustainable Communities and Wind Energy Project Acceptance in Massachusetts(Minnesota Journal of Law, Science and Technology, 2014-02-20) Petrova, Maria A.o The State of Massachusetts is one of the most progressive U.S. states in advancing sustainability through energy conservation and renewable energy. The Green Communities Act, signed into law by Governor Deval Patrick in 2008, has awarded 110 communities with the title “Green Communities” in the last five years. The title is earned after communities achieve “five clean energy benchmarks,” two of which are the provision of “as-of-right” siting for renewable/alternative energy generation and the adoption of an expedited application and permitting process for “as-of-right” energy facilities. The expedited “as-of-right” siting is one of the policy tools designed to encourage communities to speed up the siting of renewable energy projects—particularly wind and solar—as the State has a goal of obtaining 20% of its electricity capacity from renewable energy projects by 2020. Despite the fact that high-ranking energy officials in the State are of the opinion that Massachusetts is able to continue on the path of a “‘clean energy revolution . . . in large part because of leadership at the local level,’” the State has had many difficulties implementing renewable energy projects locally, and many projects have met with strong public resistance. This paper examines the relationship between the “Green Community” designation and the level of acceptance of wind energy projects in the State. Results from surveys conducted in Spring 2012 in three Massachusetts towns—one of which is a designated “Green Community”—are used to show how residents’ perceptions of the siting process, project familiarity, and opportunities to participate in the siting decision affect project support. The paper also discusses the policy implications for renewable energy facilities.Item Wind in the Upper Midwest: Assessing Wind Resource Variability and Representation in Reanalyses(2020-08) Coburn, JacobWind has become an important element of climate for consideration due to the its growing presence as a renewable source of energy. Variations in wind create uncertainty which adversely impacts investment and planning decisions and can lead to structural damage to equipment when extreme events occur which are not able to be adequately planned for. Long-term wind variations are related to climate variability over periods ranging from months to years, with the so-called teleconnections possibly driving significant changes in power output. The goal of this study was to assess the potential impacts of modes of variability within the climate system on wind energy output in the Upper Midwest (UMW: 40-52°N, 87-105°W), a North American region rich in wind resources and experiencing rapid turbine deployment. First, to facilitate this goal, the representation of wind resources by reanalysis models was tested, as were methods of extrapolating 10-meter wind speeds to heights more common of wind turbines (hub-height, often around 80-100 meters). Reanalyzed wind fields were found to capture many of the mean, variational and distributional characteristics of wind speeds at 10-meters as measured by weather stations, though declining trends in the observations were not found to be accurately replicated in the reanalysis models. Next, four methods of wind speed extrapolation commonly used in the literature were tested for their capacity to capture the mean and variations in wind speeds from tall towers measuring at heights ranging from 39-100 meters above ground level. Each method was applied to four reanalyses and results compared against tall tower data. All of the method-reanalysis combinations produced wind speeds which were too slow than observed and less variable than those measured at the tall towers, though the variable exponent power rule applied to MERRA was able to achieve relatively close results with small mean biases. 80-meter wind fields were generated from MERRA using the variable exponent power rule for application in the final section of this study. The 80-meter wind fields were utilized to derive wind energy output. This power output data was then used in a multiple linear regression model to assess the influence of several teleconnections important to the UMW, as well as potential effects of solar forcing variations. This model was applied to each grid cell and season, allowing for spatial and temporal variations in the relationships between the modes of variability and power production to manifest. The magnitude and significance of the teleconnections and solar forcing vary throughout the year and across the region. These influences are shown to fit with expectations of flow set by sea level pressure anomaly patterns. Extreme monthly wind energy anomalies are explored, with the strongest extremes affecting most of the region simultaneously and negative power anomalies found to persist for periods of several months to a year. Negative power output episodes are shown to follow from a combination of synoptic and teleconnection-driven factors while strong, positive output episodes are mostly short-lived and the result of synoptic factors (favorable positions of high and low pressure and strong pressure gradients). These findings have important implications for long-term energy planning and have the potential to improve seasonal and interannual predictions for the industry.Item Wind turbine wake flow visualization data from experiments conducted at UMore park on March 5-6, 2018 and April 8-9, 2018(2020-05-20) Abraham, Aliza; Hong, Jiarong; jhong@umn.edu; Hong, Jiarong; University of Minnesota Flow Field Imaging LabThis data includes flow visualization videos using natural snowfall in the wake of a utility-scale (2.5 MW) wind turbine. In addition, the meteorological and SCADA data from the same time periods are included. These datasets are used to analyze the interaction between the wind turbine wake and the ground surface, which has important implications for understanding the impact of wind farms on their surroundings, particularly in the area of agriculture.