Wind energy explained : theory, design, and application
18 Dec 2009-Iss: 1
TL;DR: In this article, a simplified HAWT rotor performance calculation procedure was proposed to evaluate the effect of drag and blade number on the optimum performance of wind turbine rotor performance, considering the Betz limit and the ideal horizontal axis wind turbine with wake rotation.
Abstract: Preface Acknowledgements Introduction: Modern wind energy and its origins Modern wind turbines History of wind energy Wind characteristics and resources Introduction General characteristics of the wind resource Characteristics of the atmospheric boundary layer Wind data analysis and resource estimation Wind turbine energy production estimates using statistical techniques Overview of available resource assessment data Wind measurements and instrumentation Advanced topics Aerodynamics of wind turbines General overview One-dimensional momentum theory and the Betz limit Ideal horizontal axis wind turbing with wake rotation' Airfoils and general concepts of aerodynamics Momentum theory and blade element theory Blade shape for ideal rotor without wake rotation General rotor blade shape performance prediction Blade shape for optimum rotor with wake rotation Generalized rotor design procedure Simplified HAWT rotor performance calculation procedure Effect of drag and blade number on optimum performance Advanced aerodynamic topics Mechanics and dynamics Wind turbine rotor dynamics Detailed and specialized dynamic models Electrical aspects of wind turbines Basic concepts of electric power Power transformers Electrical machines Power converters Ancillary electrical equipment Wind turbine design Design procedure Wind turbine topologies Materials Machine elements Wind turbine loads Wind turbine subsystems and components Design evaluation Power curve prediction Wind turbine loads Wind turbine subsystems and components Design evaluation Power curve prediction Wind turbine control Overview of wind turbine control systems Typical grid-connected turbine operation Supervisory control overview and implementation Dynamic control theory and implementation Wind turbine siting, system design and integration Wind turbine siting Installation and operation issues Wind farms Wind turbines and wind farms in electric grids Offshore wind farms Operation in severe climates Hybrid electrical systems Wind energy system economics Overview of economic assessment of wind energy systems Capital costs of wind energy systems Operation and maintenance costs Value of wind energy Economic analysis methods Wind energy market considerations Wind energy systems: environmental aspects and impacts Avian interaction with wind trubines Visual impact of wind turbines Wind turbine noise Electromagnetic interference effects Land-use environmental impacts Other environmental considerations Nomenclature Problems Index
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01 Jan 2015
TL;DR: The results suggest that the LJQ is a reliable and valid instrument for evaluating LJ.
Abstract: Objectives: Lao Juan (LJ, 劳倦) is a syndrome described in Chinese medicine (CM) that manifests with : Lao Juan (LJ, 劳倦) is a syndrome described in Chinese medicine (CM) that manifests with fatigue, fever, spontaneous sweating, indigestion, work-induced pain, weakness of the limbs, and shortness of breath. fatigue, fever, spontaneous sweating, indigestion, work-induced pain, weakness of the limbs, and shortness of breath. The present study was conducted to examine the reliability and validity of a Lao Juan Questionnaire (LJQ). The present study was conducted to examine the reliability and validity of a Lao Juan Questionnaire (LJQ). Methods: A total of 151 outpatients and 73 normal subjects were asked to complete the LJQ. Seventy-three normal subjects A total of 151 outpatients and 73 normal subjects were asked to complete the LJQ. Seventy-three normal subjects were additionally asked to complete the Chalder Fatigue Scale (CFS). Twelve clinicians determined whether the were additionally asked to complete the Chalder Fatigue Scale (CFS). Twelve clinicians determined whether the 151 outpatients exhibited LJ or not. The internal consistency and construct validity for the LJQ were estimated using 151 outpatients exhibited LJ or not. The internal consistency and construct validity for the LJQ were estimated using data from the outpatient subjects. The CFS data were used to examine the concurrent validity of the LJQ. Total LJQ data from the outpatient subjects. The CFS data were used to examine the concurrent validity of the LJQ. Total LJQ scores and the clinicians' diagnoses of the outpatients were used to perform receiver operating characteristics (ROC) scores and the clinicians' diagnoses of the outpatients were used to perform receiver operating characteristics (ROC) curve analyses and to defi ne an optimum cut-off score for the LJQ. curve analyses and to defi ne an optimum cut-off score for the LJQ. Results: The 19-item LJQ had satisfactory internal : The 19-item LJQ had satisfactory internal consistency (α=0.828) and concurrent validity, with signifi cant correlations between the LJQ and the CFS subscales. consistency (α=0.828) and concurrent validity, with signifi cant correlations between the LJQ and the CFS subscales. In the test of construct validity using principal component analysis, a total of six factors were extracted, and the overall In the test of construct validity using principal component analysis, a total of six factors were extracted, and the overall variance explained by all factors was 59.5%. In ROC curve analyses, the sensitivity, specifi city, and area under the variance explained by all factors was 59.5%. In ROC curve analyses, the sensitivity, specifi city, and area under the curve were 76.0%, 59.2%, and 0.709, respectively. The optimum cut-off score was defi ned as six points. curve were 76.0%, 59.2%, and 0.709, respectively. The optimum cut-off score was defi ned as six points. Conclusions: Our results suggest that the LJQ is a reliable and valid instrument for evaluating LJ. Our results suggest that the LJQ is a reliable and valid instrument for evaluating LJ. KEYWORDS Chinese medicine, chronic fatigue syndrome, Chinese medicine-pattern Chinese medicine, chronic fatigue syndrome, Chinese medicine-pattern
3,787 citations
TL;DR: In this article, the authors examine the systems and processes needed to tap energy in vehicles and implement V2G and quantitatively compare today's light vehicle fleet with the electric power system.
2,022 citations
TL;DR: In this paper, the authors reviewed the opportunities associated with renewable energy sources which include: Energy Security, Energy Access, Social and Economic development, Climate Change Mitigation, and reduction of environmental and health impacts.
Abstract: The world is fast becoming a global village due to the increasing daily requirement of energy by all population across the world while the earth in its form cannot change. The need for energy and its related services to satisfy human social and economic development, welfare and health is increasing. Returning to renewables to help mitigate climate change is an excellent approach which needs to be sustainable in order to meet energy demand of future generations. The study reviewed the opportunities associated with renewable energy sources which includes: Energy Security, Energy Access, Social and Economic development, Climate Change Mitigation, and reduction of environmental and health impacts. Despite these opportunities, there are challenges that hinder the sustainability of renewable energy sources towards climate change mitigation. These challenges include Market failures, lack of information, access to raw materials for future renewable resource deployment, and our daily carbon footprint. The ...
1,545 citations
18 May 2015
TL;DR: The most successful generator-converter configurations are addressed along with few promising topologies available in the literature from the market based survey, and the past, present and future trends in megawatt WECS are reviewed in terms of mechanical and electrical technologies, integration to power systems, and control theory.
Abstract: This paper presents a comprehensive study on the state-of-the-art and emerging wind energy technologies from the electrical engineering perspective. In an attempt to decrease cost of energy, increase the wind energy conversion efficiency, reliability, power density, and comply with the stringent grid codes, the electric generators and power electronic converters have emerged in a rigorous manner. From the market based survey, the most successful generator-converter configurations are addressed along with few promising topologies available in the literature. The back-to-back connected converters, passive generator-side converters, converters for multiphase generators, and converters without intermediate dc-link are investigated for high-power wind energy conversion systems (WECS), and presented in low and medium voltage category. The onshore and offshore wind farm configurations are analyzed with respect to the series/parallel connection of wind turbine ac/dc output terminals, and high voltage ac/dc transmission. The fault-ride through compliance methods used in the induction and synchronous generator based WECS are also discussed. The past, present and future trends in megawatt WECS are reviewed in terms of mechanical and electrical technologies, integration to power systems, and control theory. The important survey results, and technical merits and demerits of various WECS electrical systems are summarized by tables. The list of current and future wind turbines are also provided along with technical details.
694 citations
01 Jan 2005
TL;DR: AeroDyn as discussed by the authors is a set of routines used in conjunction with an aeroelastic simulation code to predict the aerodynamics of horizontal axis wind turbines, including the effect of wind turbine wakes.
Abstract: AeroDyn is a set of routines used in conjunction with an aeroelastic simulation code to predict the aerodynamics of horizontal axis wind turbines. These subroutines provide several different models whose theoretical bases are described in this manual. AeroDyn contains two models for calculating the effect of wind turbine wakes: the blade element momentum theory and the generalized dynamic-wake theory. Blade element momentum theory is the classical standard used by many wind turbine designers and generalized dynamic wake theory is a more recent model useful for modeling skewed and unsteady wake dynamics. When using the blade element momentum theory, various corrections are available for the user, such as incorporating the aerodynamic effects of tip losses, hub losses, and skewed wakes. With the generalized dynamic wake, all of these effects are automatically included. Both of these methods are used to calculate the axial induced velocities from the wake in the rotor plane. The user also has the option of calculating the rotational induced velocity. In addition, AeroDyn contains an important model for dynamic stall based on the semi-empirical Beddoes-Leishman model. This model is particularly important for yawed wind turbines. Another aerodynamic model in AeroDyn is a tower shadow model based on potentialmore » flow around a cylinder and an expanding wake. Finally, AeroDyn has the ability to read several different formats of wind input, including single-point hub-height wind files or multiple-point turbulent winds.« less
625 citations
References
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Book•
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01 Jan 1972
TL;DR: In this article, the authors investigate five major trends of global concern: accelerating industrialization, rapid population growth, widespread malnutrition, depletion of nonrenewable resources, and a deteriorating environment.
Abstract: Every person approaches problems with the help of models. A model is simply an ordered set of assumptions about a complex system. Our world model was built specifically to investigate five major trends of global concern—accelerating industrialization, rapid population growth, widespread malnutrition, depletion of nonrenewable resources, and a deteriorating environment. It is possible to alter the growth trends and to establish a condition of ecological and economic stability that is sustainable far into the future. The state of global equilibrium could be designed so that the basic material needs of each person on earth are satisfied and each person has an equal opportunity to realize his individual human potential. Although the history of human effort contains numerous incidents of mankind's failure to live within physical limits, it is success in overcoming limits that forms the cultural tradition of many dominant people in today's world.
5,312 citations
01 Jan 1959
TL;DR: Chang et al. as discussed by the authors proposed a new geometric analysis procedure for wing sections based on the normal mode analysis for continuous functions, which can be used to calculate the section length.
Abstract: The thin airfoil theory for calculation of section ... http://charles-oneill.com/projects/iaf.pdf Thin Airfoil Theory Charles R. O’Neill ... The objective is to review the thin airfoil theory and to apply the theory to three wing sections. THEORY OF WINGS AND WIND TUNNEL TESTING OF A NACA 2415 AIRFOIL http://www.ewp.rpi.edu/hartford/~ernesto/F2011/EP/MaterialsforStudents/Ferrari/Ghods2001.PDF 2.0 STRUCTURE AND THEORY OF WINGS Wing is an aerodynamic structure that generates lift when comes into contact with moving air molecules i.e. wind. tbausyd.wikispaces.com http://tbausyd.wikispaces.com/file/view/aerodynamics_report1.3.doc Abbot & von Doenhoff, 1959, 'Theory of Wing Sections – including a summary of airfoil data', Dover Edition, Dover Publications, New York. Geometric Analysis of Wing Sections RITA | National ... http://ntl.bts.gov/lib/1000/1200/1265/950049_chang.pdf GEOMETRIC ANALYSIS OF WING SECTIONS I-Chung Chang, Francisco J. Torres, and Chee Tung? Ames Research Center SUMMARY This paper describes a new geometric analysis ... Geometric Analysis of Wing Sections NASA http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950018209_1995118209.pdf This paper describes a new geometric analysis procedure for wing sections. This procedure is based on the normal mode analysis for continuous functions. 4. Incompressible Potential Flow Virginia Tech http://www.dept.aoe.vt.edu/~mason/Mason_f/C4WHMPanels.doc
1,956 citations
TL;DR: In this article, the authors presented an efficient method for digital simulation of general homogeneous processes as a series of cosine functions with weighted amplitudes, almost evenly spaced frequencies, and random phase angles.
1,460 citations
Book•
01 Jan 1916
TL;DR: The preface to the first edition of Symbols and ABBREVIATIONS outlines the aims and objectives of the second edition, which aims to provide a “robust” discussion of the history and future prospects of dynamical engineering.
Abstract: CONTRIBUTORS THE EDITORS PREFACE TO THE ELEVENTH EDITION PREFACE TO THE FIRST EDITION SYMBOLS AND ABBREVIATIONS Chapter 1: Mathematical Tables and Measuring Units Chapter 2: Mathematics Chapter 3: Mechanics of Solids and Fluids Chapter 4: Heat Chapter 5: Strength of Materials Chapter 6: Materials of Engineering Chapter 7: Fuels and Furnaces Chapter 8: Machine Elements Chapter 9: Power Generation Chapter 10: Materials Handling Chapter 11: Transportation Chapter 12: Building Construction and Equipment Chapter 13: Manufacturing Processes Chapter 14: Fans, Pumps, and Compressors Chapter 15: Electrical and Electronics Engineering Chapter 16: Instruments and Controls Chapter 17: Industrial Engineering Chapter 18: The Regulatory Environment Chapter 19: Refrigeration, Cryogenics, and Optics Chapter 20: Emerging Technologies INDEX
1,292 citations
Book•
01 Jan 1974TL;DR: In this article, Stokes' potential flow is used to describe the potential potential of a fluid flow in the presence of a single source and a single sink, and the potential can be expressed as a function of the velocity potential of the potential flow.
Abstract: GOVERNING EQUATIONS Basic Conservation Laws . Statistical and Continuum Methods . Eulerian and Lagrangian Coordinates . Material Derivative . Control Volumes . Reynolds' Transport Theorem . Conservation of Mass . Conservation of Momentum . Conservation of Energy . Discussion of Conservation Equations . Rotation and Rate of Shear . Constitutive Equations . Viscosity Coefficients . Navier-Stokes Equations . Energy Equation . Governing Equations for Newtonian Fluids . Boundary Conditions Flow Kinematics . Flow Lines . Circulation and Vorticity . Stream Tubes and Vortex Tubes . Kinematics of Vortex Lines Special Forms of the Governing Equations . Kelvin's Theorem . Bernoulli Equation . Crocco's Equation . Vorticity Equation IDEAL-FLUID FLOW Two-Dimensional Potential Flows . Stream Function . Complex Potential and Complex Velocity . Uniform Flows . Source, Sink, and Vortex Flows . Flow in a Sector . Flow Around a Sharp Edge . Flow Due to a Doublet . Circular Cylinder Without Circulation . Circular Cylinder With Circulation . Blasius' Integral Law . Force and Moment on a Circular Cylinder . Conformal Transformations . Joukowski Transformation . Flow Around Ellipses . Kutta Condition and the Flat-Plate Airfoil . Symmetrical Joukowski Airfoil . Circular-Arc Airfoil . Joukowski Airfoil . Schwarz-Christoffel Transformation . Source in a Channel . Flow Through an Aperture . Flow Past a Vertical Flat Plate Three-Dimensional Potential Flows . Velocity Potential . Stokes' Stream Function . Solution of the Potential Equation . Uniform Flow . Source and Sink . Flow Due to a Doublet . Flow Near a Blunt Nose . Flow Around a Sphere . Line-Distributed Source . Sphere in the Flow Field of a Source . Rankine Solids . D'Alembert's Paradox . Forces Induced by Singularities . Kinetic Energy of a Moving Fluid . Apparent Mass Surface Waves . The General Surface-Wave Problem . Small-Amplitude Plane Waves . Propagation of Surface Waves . Effect of Surface Tension . Shallow-Liquid Waves of Arbitrary Form . Complex Potential for Traveling Waves . Particle Paths for Traveling Waves . Standing Waves . Particle Paths for Standing Waves . Waves in Rectangular Vessels . Waves in Cylindrical Vessels . Propagation of Waves at an Interface VISCOUS FLOWS OF INCOMPRESSIBLE FLUIDS Exact Solutions . Couette Flow . Poiseuille Flow . Flow Between Rotating Cylinders . Stokes' First Problem . Stokes' Second Problem . Pulsating Flow Between Parallel Surfaces . Stagnation-Point Flow . Flow in Convergent and Divergent Channels . Flow Over a Porous Wall Low-Reynolds-Number Solutions . The Stokes Approximation . Uniform Flow . Doublet . Rotlet . Stokeslet . Rotating Sphere in a Fluid . Uniform Flow Past a Sphere . Uniform Flow Past a Circular Cylinder . The Oseen Approximation Boundary Layers . Boundary-Layer Thickness . The Boundary-Layer Equations . Blasius Solution . Falkner-Skan Solutions . Flow Over a Wedge . Stagnation-Point Flow . Flow in a Convergent Channel . Approximate Solution for a Flat Surface . General Momentum Integral . Karman-Pohlhausen Approximation . Boundary-Layer Separation . Stability of Boundary Layers Buoyancy-Driven Flows . The Boussinesq Approximation . Thermal Convection . Boundary-Layer Approximations . Vertical Isothermal Surface . Line Source of Heat . Point Source of Heat . Stability of Horizontal Layers COMPRESSIBLE FLOW OF INVISCID FLUIDS Shock Waves . Propagation of Infinitesimal Disturbances . Propagation of Finite Disturbances . Rankine-Hugoniot Equations . Conditions for Normal Shock Waves . Normal Shock-Wave Equations . Oblique Shock Waves One-Dimensional Flows . Weak Waves . Weak Shock Tubes . Wall Reflection of Waves . Reflection and Refraction at an Interface . Piston Problem . Finite-Strength Shock Tubes . Nonadiabatic Flows . Isentropic-Flow Relations . Flow Through Nozzles Multi-Dimensional Flows . Irrotational Motion . Janzen-Rayleigh Expansion . Small-Perturbation Theory . Pressure Coefficient . Flow Over a Wave-Shaped Wall . Pandtl-Glauert Rule for Subsonic Flow . Ackert's Theory for Supersonic Flows . Prandtl-Meyer Flow Appendix A. Vector Analysis Appendix B. Tensors Appendix C. Governing Equations Appendix D. Complex Variables Appendix E. Thermodynamics Index
732 citations