Wind Energy Meteorology

This book offers an introduction to the meteorological boundary conditions for power generation from wind - both onshore and offshore, and provides meteorological information for the planning and running of this important renewable energy source. It includes the derivation of wind laws and wind-profile descriptions, especially those above the logarithmic surface layer, and discusses winds over complex terrains and nocturnal low-level jets. This updated and expanded second edition features new chapters devoted to the efficiency of large wind parks and their wakes and to offshore wind energy.

Autorentext

Stefan Emeis is a meteorologist. He received his PhD at the University of Bonn, Germany in 1985 and his habilitation at the University of Karlsruhe, Germany in 1994. He is currently a senior scientist and research group leader at the Institute of Meteorology and Climate Research at the Karlsruhe Institute of Technology in Garmisch-Partenkirchen, Germany and adjunct professor of meteorology at the University of Cologne, Germany. His research interests are the structure and turbulence of the atmospheric boundary layers, surface-based remote sensing of the atmosphere, the meteorological prerequisites for the usage of wind energy and all aspects of climate change.

He is the editor-in-chief of the scientific journal Meteorologische Zeitschrift and (co)author of more than 80 scientific papers and of several books.

Inhalt

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Scope of the Book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Overview of Existing Literature . . . . . . . . . . . . . . . . . . . . . . . 3

1.3 History of Wind Energy Generation. . . . . . . . . . . . . . . . . . . . . 3

1.4 Potential of Wind Energy Generation. . . . . . . . . . . . . . . . . . . . 4

1.5 Present Status of Wind Energy Generation . . . . . . . . . . . . . . . . 5

1.6 Structure of This Book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 Wind Regimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1 Global Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 Driving Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2.1 Hydrostatic Equation . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2.2 Momentum Budget Equations for the Wind . . . . . . . . . . 12

2.3 Geostrophic Winds and Gradient Winds. . . . . . . . . . . . . . . . . . 14

2.4 Thermal Winds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5 Boundary Layer Winds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.6 Thunderstorm Gusts and Tornados. . . . . . . . . . . . . . . . . . . . . . 18

2.7 Air Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.8 Thermal stratification of the air

2.8.1 The geostrophic drag law

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3 Vertical Profiles Over Flat Terrain. . . . . . . . . . . . . . . . . . . . . . . . 23

3.1 Surface Layer (Prandtl Layer) . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.1.1 Logarithmic Wind Profile . . . . . . . . . . . . . . . . . . . . . . 28

3.1.2 Power Law. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.1.3 Comparison Between Logarithmic and Power Law . . . . . 33

3.1.4 Vertical Wind Profile with Large Wind Speeds . . . . . . . 40

3.2 Profile Laws Above the Surface Layer. . . . . . . . . . . . . . . . . . . 40

3.2.1 Ekman Layer Equations . . . . . . . . . . . . . . . . . . . . . . . . 41

3.2.2 Inertial Oscillations in the Ekman Layer . . . . . . . . . . . . 42

3.2.3 Vertical Wind Profiles in the Ekman Layer . . . . . . . . . . 42

3.2.4 Unified Description of the Wind Profile for the Boundary Layer . . . . 43

3.3 Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3.4 Diurnal Variations of the Wind Profile . . . . . . . . . . . . . . . . . . . 50

3.4.1 Vertical Profiles of the Weibull Parameters . . . . . . . . . . 51

3.4.2 Low Level Jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

3.5 Internal Boundary Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

3.6 Wind and Turbulence Profiles Over Forests . . . . . . . . . . . . . . . 61

3.7 Winds in Cities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

3.7.1 Characteristics of Urban Boundary Layers . . . . . . . . . . . 63 3.7.2 Vertical Profiles of Wind and Turbulence . . . . . . . . . . . 65

3.7.3 Special Flow Phenomena in Urban Canopy Layers . . . . . 67

3.8 Summary for Flat Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

4 Winds in Complex Terrain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

4.1 Characteristics of Boundary Layers Over Complex Terrain . . . . 76

4.1.1 Mountain and Valley Winds. . . . . . . . . . . . . . . . . . . . . 78 4.1.2 Katabatic Winds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

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