Browsing by Subject "Wind power"
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Item A variable speed single phase wind generator(Texas Tech University, 1977-12) Tsai, Yue-guoNot availableItem A vortex model of the Darrieus turbine(Texas Tech University, 1978-12) Nguyen, Thong V.An aerodynamic performance prediction model for the Darrieus turbine has been constructed. The primary purpose was to allow reasonable prediction of aerodynamic blade forces and moments to be made. Previous aerodynamic models based on simple momentum principles are inadequate for predicting blade loading. In addition, accurate overall performance predictions for large tip to wind speed ratios cannot be made with the simple momentum models. Detailed prediction of the near wake structure is also within the capability of the present model. Results were obtained from the present vortex model for the one-, two- and three-bladed rotors operating at various tip to wind speed ratios to study the effect of number of blades and tip to wind speed ratios on the rotor performance. Power coefficients predicted by the present vortex model were compared to the vortex model due to Fanucci and the simple momentum or "strip theory". In addition, experimental results were used to compare with predictions obtained from the analytical model in an attempt to validate the analytical model.Item Analysis of the correlation between wind power generation and system response characteristics following unit trips on the ERCOT grid(2010-05) Lovelace, William Edward; Grady, W. M.; Santoso, SuryaElectric power generation using wind turbines is on the rise in not only the United States but the entire globe. While the benefits from such methods of generation include clean and renewable energy, wind turbines may pose a potential risk to the stability of grid operation. Wind turbine generators are similar to conventional generators; however, the manner with which the wind turbine is coupled to the grid may reduce system inertia and increase the magnitude of transient stability problems. This study empirically examines the effect of wind generation on ERCOT system response characteristics following unit trips such as frequency drop, and phasor oscillation frequency and damping. It is shown with a high degree of certainty that an increase in wind generation is leading to a greater phasor oscillation frequency and lesser system inertia. Wind generation may also be leading to less system damping and smaller power frequency drops.Item Competitive renewable energy zones in Texas : suggestions for the case of Turkey(2012-05) Ogunlu, Bilal; Baldick, Ross; Rai, VarunAs an energy-importing developing country, Turkey depends heavily on imported petroleum and natural gas. The increase in the global petroleum price has affected the Turkish economy adversely in the last decade. Renewable energy is an important alternative in reducing Turkey’s energy dependency. Turkey’s strategies are improving domestic production and diversifying energy sources for the security of supply. New investments, especially in renewables, have been chosen to achieve these objectives. As a model for Turkey, Texas is the leader in non-hydroelectric renewable energy production in the U.S. and has one of the world’s most competitive electricity markets. However, wind generation creates unique challenges for the Electric Reliability Council of Texas (ERCOT), the transmission system operator of Texas. The market environment has forced the Public Utility Commission of Texas (PUCT) to develop unique deregulated energy markets. In 2005, the Texas Legislature passed Senate Bill 20, in part to break the deadlock between transmission and wind generation development. This legislation instructed the PUCT to establish Competitive Renewable Energy Zones (CREZs) throughout the State, and to designate new transmission projects to serve these zones. In this context, first of all, the electricity market development in Turkey is introduced in terms of renewable energy, especially wind power. Next, considering wind power, the progress in the Texas electricity market is investigated. Subsequently, we examine the development of CREZs in Texas from a regulatory perspective and discuss Texas’ policy initiatives, including the designation of CREZs. Finally, we review the impact of wind power on the primary electricity market of Texas and evaluate market conditions and barriers to renewable energy use in Turkey in order to extract suggestions. This experience may be particularly instructive to Turkey, which has a similar market structure on the supply and transmission sides. This study suggests ways that Turkey might handle renewable applications in combination with existing transmission constraints.Item Design and control of an integrated wind-water desalination system for an inland municipality(Texas Tech University, 2008-08) Noll, Dennis D.; Ewing, Bradley T.; Song, Lianfa; Swift, Andrew H. P.; Chapman, Jamie C.Current water pricing standards do not take economic responsibility for dwindling potable water aquifer resources. By only incorporating financial, but not true economic costs of these scarce resources, serious depletion of these often slow-recharging groundwater resources has occurred in many areas in the United States. Aquifer depletion for some areas looms on a 50-year or closer horizon, and many municipalities in the Southwest and elsewhere face potential distress due to lack of sustainable fresh water availability. In order for these cities to remain economically and physically viable, alternative water resources must be found. An affected West Texas inland municipality will become the subject of research to evaluate the technology and economics of a full-scale, integrated, wind-powered reverse osmosis water purification system. The integrated system will be applied to produce potable water from a brackish aquifer using renewable energy to reduce the energy costs of the system. An adaptive and intelligent control algorithm will control the integrated wind-water system. The algorithm will process streaming real-time water use and electrical demand data in combination with wind speed measurements in order to determine the best use of the energy produced by a turbine array: either for water purification or for displacing conventional power on other municipal loads. The end product of this system is a water purification process that will utilize a brackish water aquifer for all of the city‘s potable water needs, and wind energy for all associated pumping, reverse osmosis, distribution and other electrical loads.Item The energy water nexus : increasing water supply by desalination integrated with renewable power and reducing water demand by corporate water footprinting(2013-08) Clayton, Mary Elizabeth; Webber, Michael E., 1971-Growing populations and periodic drought conditions have exacerbated water stress in many areas worldwide. Consequently, it would be valuable to manage both supply and demand of water to fully address water sustainability. Additionally, the inextricable link of water and energy -- energy is required to pump, treat, and distribute water and water is often used in the production of energy -- creates the need to study the use of these resources together. In response to water stress, some municipalities have considered desalination of saline water as a freshwater supply. Unfortunately, desalination requires a sizeable energy investment and causes significant carbon emissions with conventional approaches. However, renewable energy technologies can be paired with desalination to mitigate concern over the environmental impacts of increased energy use. At the same time, desalination can be operated in an intermittent way to match the variable availability of renewable resources. Both wind and brackish groundwater resources are plentiful in the Panhandle region of West Texas, making an integrated wind-powered desalination facility an option for meeting increasing water demands. Integrating wind power and brackish groundwater desalination generates a high-value product (drinking water) from two low-value resources (saline water and wind power without storage). This thesis presents a thermoeconomic, geographic, and operational analysis of an integrated wind-powered reverse osmosis facility treating brackish groundwater in West Texas. The results demonstrate the favorability of the integrated facility under certain economic, geographic, and operating conditions. Also in response to water stress, corporations are becoming increasingly interested in identifying water vulnerabilities in their operational portfolios to minimize physical, reputational, regulatory, and financial risks associated with potential water shortages. The water footprint is one tool available to assess water use, identify vulnerabilities, and guide mitigation strategies. This thesis provides an accounting methodology for water reporting that includes direct water uses and indirect (embedded in energy, services, and products) water uses in the operations. Further, a case study is considered to illustrate the methodology by assessing the water impact of a mixed-use facility in Palo Alto, California. The results demonstrate the importance of considering the indirect water uses, which requires a more exhaustive analysis.Item Forecasting congestion in transmission line and voltage stability with wind integration(2011-08) Kang, Han; Baldick, Ross; Grady, William M.Due to growth of wind power, system operators are being challenged by the integration of large wind farms into their electrical power systems. Large scale wind farm integration has adverse effects on the power system due to its variable characteristic. These effects include two main aspects: voltage stability and active line flow. In this thesis, a novel techniques to forecast active line flow and select pilot bus are introduced with wind power integration. First, this thesis introduces a methodology to forecast congestion in the transmission line with high wind penetration. Since most wind resources tend to be located far away form the load center, the active line flow is one of the most significant aspects when wind farm is connected to electrical grid. By providing the information about the line flow which can contribute to transmission line congestion, the system operators would be able to respond such as by requesting wind power or load reduction. The second objective of this thesis is to select the weakest bus, called pilot bus, among all load buses. System reliability, especially voltage stability, can be adversely affected by wind variability. In order to ensure reliable operation of power systems with wind power integration, the index to select the pilot bus is developed, and further prediction of voltage profile at the pilot bus is fulfilled. The objective function to select the pilot bus takes account of the N-1 contingency analysis, loading margin, and reactive power sensitivity. Through on the objective function, the pilot bus is representative of all load buses as well as controllable by reactive power regulation. Predicting the voltage profile at the pilot bus is also useful for system operators to determine wind power output.Item Hybrid powertrain performance analysis for naval and commercial ocean-going vessels(2012-08) Gully, Benjamin Houston; Seepersad, Carolyn C.; Webber, Michael E., 1971-; Hebner, Robert E.; Kiehne, Thomas M.; Chen, DongmeiThe need for a reduced dependence on fossil fuels is motivated by a wide range of factors: from increasing fuel costs, to national security implications of supply, to rising concern for environmental impact. Although much focus is given to terrestrial systems, over 90% of the world's freight is transported by ship. Likewise, naval warfighting systems are critical in supporting U.S. national interests abroad. Yet the vast majority of these vessels rely on fossil fuels for operation. The results of this thesis illustrate a common theme that hybrid mechanical-electrical marine propulsion systems produce substantially better fuel efficiency than other technologies that are typically emphasized to reduce fuel consumption. Naval and commercial powertrains in the 60-70 MW range are shown to benefit substantially from the utilization of mechanical drive for high speed propulsion; complemented by an efficient electric drive system for low speed operations. This hybrid architecture proves to be able to best meet the wide range of performance requirements for each of these systems, while also being the most easily integrated technology option. Naval analyses evaluate powertrain options for the DDG-51 Flight III. Simulation results using actual operational profile data show a CODLAG system produces a net fuel savings of up to 12% more than a comparable all-electric system, corresponding to a savings of 37% relative the existing DDG-51 powertrain. These results prove that a mechanical linkage for the main propulsion engine greatly reduces fuel consumption and that for power generation systems requiring redundancy, diesel generators represent a vastly superior option to gas turbines. For the commercial application it is shown that an augmented PTO/PTI hybrid system can better reduce cruise fuel consumption than modern sail systems, while also producing significant benefit with regard to CO2 emissions. In addition, using such a shaft mounted hybrid system for low speed electric drive in ports reduces NOx emissions by 29-43%, while CO is reduced 57-66% and PM may be reduced up to 25%, depending on the specific operating mode. As an added benefit, fuel consumption rates under these conditions are reduced 20-29%.Item Space-time forecasting and evaluation of wind speed with statistical tests for comparing accuracy of spatial predictions(2010-10-12) Hering, Amanda S.High-quality short-term forecasts of wind speed are vital to making wind power a more reliable energy source. Gneiting et al. (2006) have introduced a model for the average wind speed two hours ahead based on both spatial and temporal information. The forecasts produced by this model are accurate, and subject to accuracy, the predictive distribution is sharp, i.e., highly concentrated around its center. However, this model is split into nonunique regimes based on the wind direction at an off-site location. This work both generalizes and improves upon this model by treating wind direction as a circular variable and including it in the model. It is robust in many experiments, such as predicting at new locations. This is compared with the more common approach of modeling wind speeds and directions in the Cartesian space and use a skew-t distribution for the errors. The quality of the predictions from all of these models can be more realistically assessed with a loss measure that depends upon the power curve relating wind speed to power output. This proposed loss measure yields more insight into the true value of each model's predictions. One method of evaluating time series forecasts, such as wind speed forecasts, is to test the null hypothesis of no difference in the accuracy of two competing sets of forecasts. Diebold and Mariano (1995) proposed a test in this setting that has been extended and widely applied. It allows the researcher to specify a wide variety of loss functions, and the forecast errors can be non-Gaussian, nonzero mean, serially correlated, and contemporaneously correlated. In this work, a similar unconditional test of forecast accuracy for spatial data is proposed. The forecast errors are no longer potentially serially correlated but spatially correlated. Simulations will illustrate the properties of this test, and an example with daily average wind speeds measured at over 100 locations in Oklahoma will demonstrate its use. This test is compared with a wavelet-based method introduced by Shen et al. (2002) in which the presence of a spatial signal at each location in the dataset is tested.Item The technical potential of renewable natural gas (RNG) in the United States, and the economic potential of methanation-derived RNG in Texas(2014-12) Ólafsson, Brynjólfur Víðir; Webber, Michael E., 1971-Renewable Natural Gas (RNG) is a low-carbon fuel source that is derived from the anaerobic digestion (AD) or thermal gasification (TG) of biomass, or produced using renewable electricity through the methanation of carbon dioxide. This thesis uses a thermodynamic balance to determine the total technical potential of RNG in the United States, as well as the future technical potential of methanation-derived RNG based on growth curves for renewable electricity. Furthermore, this work establishes an analytic decision-making framework for determining on a rolling basis, from an economic standpoint, whether to sell electricity directly to the grid, or produce and sell methanation-derived RNG. This framework is used to establish the economic potential of RNG, based on Texas wind resources. This work details the formulation of a model that determines which production option generates more marginal profit, based on fluctuating electricity and gas prices. The model also aggregates the total amount of electricity and RNG sold, assuming that the main objective is to maximize the marginal profit of integrated wind- and methanation facilities. This work concludes that the annual technical potential of methanation-derived RNG nationally was 1.03 Quads in 2011. The technical potential of biomass-derived RNG was 9.5 Quads. Thus, the total 2011 technical potential of RNG in the United States was 10.5 Quads, or equal to roughly 43% of the total US consumption of natural gas that year. Assuming a constant, 80% electrolyser efficiency, the technical potential of methanation-derived RNG is expected to rise at an average rate of 1.4% per year, following growth curves for renewable power, until the year 2040, when it will be 1.54 Quads. The 2011 economic potential of methanation-derived RNG in Texas was between 2.06×10⁷ MMBTU and 3.19×10⁷ MMBTU, or between 19.4% and 30.1% of the corresponding annual technical potential. Furthermore, the total marginal profit increase from introducing the option of producing and selling methanation-derived RNG was around $366 million, given a ‘best case scenario’ for the state of Texas.Item The Darrieus Wind Turbine: An Analytical Performance Study(Texas Tech University, 1976-05) Reddy, Gopal BThe purpose of this thesis is to analyze and predict the performance of the Darrieus Wind Turbine. The analysis employs a multiple stream tube concept. The standard blade element theory is applied to each of the stream tubes to calculate the induced flow velocity which is then used to estimate the force on each of the rotor blade elements. A computer model, which can predict the rotor performance with reasonable accuracy, was constructed. This model can be used to study the effects of rotor geometry variations such as blade solidity and rotor height to diameter ratios. In addition, the transient behavior of the Darrieus rotor is studied for a step change in wind speed and a step change in torque output.Item The Effect of Blade Roughness on Wind Turbine Performance(Texas Tech University, 1982-12) Thompson, Douglas EIn this study, the effect of various degrees of blade roughness on the performance of horizontal axis wind turbines is investigated analytically. The roughness effects are analyzed in terms of the annual energy output and cost effectiveness. A computer model has been developed to quantify the effects of roughness. The model incorporates a correlation of experimental airfoil data for any degree of roughness and Reynold's number. Additionally, procedures for reducing surface roughness effects based on blade pitch variations have been evaluated. Three turbines, with rated power outputs of 25, 400, and 2000 kW, are cited as case studies to illustrate surface effects.Item Vertical axis wind turbine wake velocity measurements and comparison with analysis(Texas Tech University, 1981-05) Sun, HuanmingMean velocity measurements were performed in the wake behind a Darrieus Turbine. In this experiment the turbine was towed through a tank filled with water. Reynolds' number scaling was used to relate the operation in water to that in air. The results were compared with predictions from the momentum and vortex models developed by previous workers. In addition, some data from a full scale rotor obtained by other workers are presented and compared with analytical results.Item Wind Farm Diversification and Its Impact on Power System Reliability(2010-10-12) Degeilh, YannickAs wind exploitation gains prominence in the power industry, the extensive use of this intermittent source of power may heavily rely on our ability to select the best combination of wind farming sites that yields maximal reliability of power systems at minimal cost. This research proposes a general method to minimize the wind park global power output variance by optimally distributing a predetermined number of wind turbines over a preselected number of potential wind farming sites for which the wind patterns are statistically known. The objective is to demonstrate the benefits of diversification for the reliability of wind-sustained systems through the search for steadier overall power outputs. Three years of wind data from the recent NREL/3TIER study in the western US provides the statistics for evaluating each site for their mean power output, variance and correlation with each other so that the best allocations can be determined. Some traditional reliability indices such as the LOLP are computed by using sequential Monte Carlo simulations to emulate the behavior of a power system uniquely composed of wind turbines and a load modeled from the 1996 IEEE RTS. It is shown that configurations featuring minimal global power output variances generally prove the most reliable for moderate load cases, provided the sites are not significantly correlated with the modeled load. Under these conditions, the choice of uncorrelated/negatively correlated sites is favored. The correlations between the optimized global wind power outputs and the modeled load are studied as well.Item Wind power systems in the stable nocturnal boundary layer(Texas Tech University, 2007-08) Walter, Kevin RobertHourly-averaged tall-tower data from a 200m tower located near Lubbock, Texas are used to examine static atmospheric stability as a governor of speed and direction shear in the atmospheric boundary layer. Meteorological forcing mechanisms for such shears include the thermal wind, inertial oscillation, Ekman spiral, and others. The inertial oscillation is highlighted as an atmospheric mechanism capable of generating discernable diurnal variations in average speed shear data in regions void of low-level jet association. Theoretical aerodynamic treatment shows the case of direction shear to differ from the case of turbine operation in yawed flow, and has therefore not been studied in wind power systems. Numerical simulations of power production in steady non-turbulent flow fields containing speed and direction shear show instantaneous power gain as great as 0.5% and depletion as great as 6% relative to a no shear baseline. Coupled with joint-probability distributions of speed and direction shear measured at Lubbock, instantaneous losses as great as 3% and gains as great as 0.5% are expected, while the average power change relative to the zero shear case is estimated to be -0.5%. Over the 20 year lifetime of a 100 MW wind power plant this finding translates to a $2.1 million loss in project revenue. Observational evidence shows the correlation coefficient between the average diurnal variation in static stability and power law shear exponent is 1.00. The correlation coefficient between the average diurnal variation in static stability and direction shear magnitude is found to be 0.93. The influence of static stability on speed and direction shear is hypothesized to be globally applicable. Observations from a second data platform in northwest Indiana support the magnitudes of direction shear found at Lubbock, and further suggest that the presence of direction shear is a more general result. Large magnitudes of wind direction shear are found to occur concurrently with large magnitudes of power law shear exponent at hub-height wind speeds greater than 8 m/s, making them present in a critical operating region where wind turbine control transitions from speed control to power regulation.Item